eBay

* Please contact me BEFORE BUYING so that I can determine your exact needs. *

** This listing is for Parts AND Installation. **

*** Parts price increases is unfortunately here in 2024. Unfortunately, parts have become more and more difficult to find and, in some cases, have quadrupled in price! The specific Power Supply Capacitors I have been using have reached their 'end of life' from the manufacturer. Finding ANY in-stock, reasonably priced, quality substitutes is posing a real problem. Many parts have seen a 100-400% increase because of supply chain shortages and increased tariffs. Even with the increase, you will find that these upgrades are a great value when you consider the increased performance & reliability of these upgraded Hafler Amplifiers. ***

Turn-around time for this Upgrade is typically 1-2 weeks once I begin your project. However, because of the popularity of my upgrades, I currently have 6 projects lined up. So if you are willing to wait your turn in line, I would be happy to put you on my 'Wait List'. As I move through the list, I will let you know when to ship me your amp so I can begin work on your amp. I also will send you regular progress updates so you can see how things are coming along. I will also advise you if anything unexpected reveals itself. I ALWAYS open, and inspect your amp when I first receive it BEFORE doing anything. I check all fuses, then power it up. I check the Power Supply voltages 'as-is' before I run some music through it to make sure there are no other issues. I will notify you if I find anything that we don't already know about.

The wait may be long, but it is SOOO worth it- just read my testimonials below!

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If you want to revitalize your 30+ year old Hafler Amp, but don't have the technical knowledge or skills to do your own installation, let me professionally rebuild your Power Supply for you. This is one of the FIRST things that should be done on these vintage amplifiers. This alone will improve the sound of your amp. I have been an Engineer in the Broadcast industry for 30+ years and have worked as a Studio Recording Engineer as well. I take great pride in the quality of my work. Being an Audiophile has been a life-long passion of mine.

Here's what you will get:

You will get your DH-500 Amplifier Power Supply rebuilt with (2) new 24,000uF 100V Nippon Filter Capacitors, a new, higher current 35 Amp Rectifier Bridge and a new higher current 16 Amp Lighted Power Switch with a fresh 1KV Disc Capacitor. If your 500 is a very early version, it may not have an Inrush Limiter as do the later versions. I will also add that if yours does not have one. I will also calibrate the DC-Offset and Bias to original factory specifications. I will also make sure your amp's grounding system is done properly & install a 12-gauge, Solid Copper Main Ground and rewire the 'Star Grounding System' as needed to reduce the possibility of noise induction. I HIGHLY recommend having this PS rebuild done if you still have the original 30+ year old caps installed. If your Power Supply is not solid, not balanced or sagging, your sound quality will suffer and may even cause premature failure of the output MOSFETS! If you plan on doing any upgrades and plan on keeping your amp running properly for the next 30 years and sounding its best, do the Power Supply rebuild.

As part of my upgrade service, I will clean your Input and Output Connectors, Frame & Heat Sink. Once completed, I put each amplifier through 4 hours of rigorous 'in-system' testing to make sure everything sounds just right. I will also make sure you have the correct Speaker Fuses installed for the specific speakers you are driving at no additional cost. 2A-3A Speaker Fuses are usually adequate for most speaker systems and provide a safe level of protection. I will also include a Speaker Fuse Selection Chart if you should elect to change the rating to better suit your listening habits. Only make 1/2 amp increases at a time to avoid damaging your speakers. The DH-500 is capable of a 30 Amp output which would destroy almost any speaker, so choose wisely.

Want more from your amp? See my other Audiophile Upgrade listings!

Here's what you COULD get:

If you have a DH-500 Hafler Amplifier that has become old and tired, but still works and needs some new life breathed into it or you are still searching for true high-end Audiophile quality sound without the high-end price tag, then let me install QUA-CO Audio's Ultimate upgrade kit to get you to that next level. I exclusively install their upgrade parts and kits. I have had nothing but FANTASTIC results using their upgrade kits. These upgraded Hafler Amplifiers have NEVER sounded better! See my other listings for Installation of the QUA-CO Audio PC-1 Driver Board Upgrade Kit or Complete Ultimate High-End Audiophile Upgrade ( https://www.ebay.com/itm/273769134625 ) if you really want a major amplifier upgrade. After listening to my first fully modified DH-500 I did for a friend who worked many years for several 'high-end' audio equipment companies, we were BOTH immediately convinced that Ed, the designer at QUA-CO had truly designed something really special. Ed spent many years working at Hafler as the Amplifier Project Manager, but his own PC-1 Driver Boards that he designed to work specifically in Hafler amps are a culmination of his years of experience. Your fully modified amp will go head-to-head with amps costing several thousand dollars. Find out why the #1 comment from my customers is:

"I'm hearing things I've never heard before!"

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Other Upgrade Available: NOTE: CURRENTLY NOT AVAILABLE: Due to a change in manufacturing, we have not been able to get reliable MOSFET devices for this upgrade. Fantasia Audio is trying to resolve this issue with the supplier. I do have a very limited supply of the original 'matched' Hitachi MOSFET's should your amp need them. These are good used devices. If I have the same series and batch 'matching' number as those in your amp. There are $20 each.

I can also install a new set of 12 (6 'matched' pairs on the DH500) for $240. I only use the Exicon MOSFETS also available from Fantasia Audio. All 6 pairs of MOSFETS are closely 'matched' and sound every bit as good, if not slightly better, than the originals (NLA) as they are slightly faster offering better transient response.

If you decide to have my complete set of upgrades: Power Supply & PC-1 Boards ( see my High-End Audiophile Upgrade listing: https://www.ebay.com/itm/273769134625 ), you will have one of the finest sounding stereo amplifiers one can own! Your fully upgraded DH-500 will complete with amplifiers costing several thousand dollars. Take the time to read the new and improved specs provided by the PC-1 Upgrade Kit:

PC-1 DESIGN GOAL REALIZATION:

A. Precise PC board layout with no track crossover.

B. First stage single ended JFET/bipolar cascode differential amplifier with CCS regulation. JFETS incorporated are genuine Toshiba 2SK170BL devices with IDSS closely matched. If you know anything about this JFET, I need not say anything else. High input impedance, high gain, tube like presence, and eerie low noise in listening tests makes it a no brainer. Cascode configuration reduces Miller effect, drastically increasing bandwidth and lowering distortion. This all important first stage configuration eliminates the need for massive gain and feedback used in many amps to cover up distortions and design flaws.

C. Second stage also uses SE bipolar cascode amplifier with CCS regulation. Again, Miller effect is reduced and bandwidth is not compromised.

D. Simple bias control and emitter follower circuit to drive output stage is added and all that is needed to complete the design goal.

DH-500: Clipping now occurs at 335 watts into 8 ohms instead of the 270 watts from original PC-10 or PC-19.

DH-220, DH-200, P-220 & P-230: Clipping now occurs at 150-160 watts into 8 ohms instead of the 110-115 watts from original PC-6 or PC-19.

E. High Quality Polypropylene Capacitors throughout with all HE electrolytic caps bypassed with Polypropylene's.

F. Vital 'Star Grounding' realized with pictorial showing proper wiring arrangement"

IMPROVED SPECIFICATIONS:

Signal to Noise Ratio, unweighted:

Exceeds 100 db referred to 100 watts into 8 ohms - 103 dB Typical

Typical THD at 100 watts into 8 ohms:

20 Hz: 0.0025%

1 kHz: 0.0025%

20 kHz: 0.008%

Input Impedance: 33,000 ohms.

Frequency Response into 8 ohms: - 3 db, 4.8 Hz to 225 kHz at 1 watt.

And if all those specs are a little too technical for you, your ears will tell you the rest of the story! I was blown away the very first time I heard an upgraded DH-500 and you will be too. You will have a deeper, wider sound stage, better dynamics, better sound articulation and a cleaner, quieter, much more 'musical' sounding amp. QUA-CO uses only the highest quality components and closely 'matches' all semiconductors to ensure that the best specifications are achieved.

Better Architecture + Better Components = Better Sound.

Add professional, hand-build construction, custom installation and you've got a truly High-End Audiophile grade amplifier!

I have been working directly with Ed, the designer at QUA-CO/Fantasia Audio and exclusively use his Hafler upgrade kits and parts. Message me with any questions about the other available upgrades.

Shipping: (Please Read Carefully)

You MUST make sure that your amplifier is packaged properly as they can weight upwards of 50 lbs.! I suggest having it double boxed. It would be a shame to have it damaged in shipping. I will be using YOUR packaging to return ship your amp once completed. Buyer assumes all responsibility.

Please include a PREPAID UPS GROUND RETURN SHIPPING LABEL in the box along with your amp so that there is no delay in returning your amp to you once completed.

Buyer pays ALL Shipping Costs, to and from me and will specify shipping method if other than UPS Ground. Estimated shipping cost each way: $28 - $75 (cost varies by buyer's location).

Thanks for looking.

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Customer Testimonials:

Hello Jim. Just got my Hafler. It sounds like never before. Lows have more warmth, highs more crispy and mids have a beautiful presence too. The frequency spectrum is much wider. Great job!

Thanks again!

Mario

Hi Jim,

Your work is impeccable. So clean and sanitary looking. I have had a few weeks to listen to the DH500 after the rebuild process. Before I delivered the amp to you, it had a lifeless, almost flat sound. The bass was weak, and the mids/highs were muddy-sounding—typical for a 40-year-old amp, I suppose.

The sound now- defined, clear, authoritative bass, very musical is what I would describe it as. If the recording is good, wow! If the recording is less than ideal, it shows. I attribute that to the amp letting all the detail through. I am using a very nice tube pre-amp. The system just sounds incredible. It was worth every penny! I would put this amp up against any Bryston, Krell or McIntosh; it's that good. What a powerhouse. I don't always listen to Steely Dan, but when I do so do the neighbors!

Best regards,

Kurt D. Ristow

Jim,

Got the amp set up last night. One word: Magnificent! More thoughts to come...

Don B.

Don B's follow-up thoughts:

I am extremely pleased with the work done. I was hesitant at first because of the price, but then found out what it would cost to replace with a similarly powerful amp of the same quality. I went from hesitancy to no-brainer. The sound quality is like nothing else I've heard from ANY system. Visitors to my rec room are blown away by it. Most say the same couple things: 1) That they are hearing subtleties of the music they've never heard before, and 2) It sounds like they are in the recording studio, as if the band is right in front of them. Best $1000 I've ever spent on my system. Thank you very much.

Don B.

Music lovers. Champagne ear on a beer budget? Anyone looking to upgrade a legendary David Hafler vintage power amp should strongly consider a Jim Settecase rebuild. (200, 220, 500) High quality improved circuit boards designed by former Hafler amp guru Ed Fantasia. Outstanding build workmanship quite reasonably priced. Jim provided precise progress notes and photos during the rebuild. Post build documentation too. In summation; I sent Jim a glass of tap water. He sent back a bottle of San Pelligrino. Superb sounding amp with effortless power. (Power rating upped from 220 to 280 watts) Highly musical. Brought my already very good system up to outstanding.

Chris MorehouseHouston TX

Jim,

After having plenty of time to do some serious listening I have concluded that there is a dramatic improvement in the sound of my Hafler 500 after the audiophile upgrade. I hear detail like never before. The vocals jump out with such presence I am able to clearly hear the lyrics where before the upgrade on some recordings the vocals would get lost and muddled. I never thought my speakers were capable of producing the sound I am hearing. A perfect example of this are recordings in Dolby Atmos. Prior to the upgrade Dolby Atmos recordings had virtually no difference in sound. I now hear depth, clarity, detail, separation unlike anything I have heard. I have no doubt the investment was well worth it.

My experience with the process is not the first time having Jim work on my Hafler 500. About three years ago he did a PCB upgrade and I thought there was no way to improve on the sound until I had the Audiophile upgrade. There is no-one else I would trust to work on my 40+ year old amp. He is a true professional that takes pride in his work. His detailed updates along the process is unusual in today’s world. I highly recommend the upgrade for anyone who would want to make a major improvement in the sound of their system.

Stephen G.

Hi Jim:

Just a note to say that Hafler #2 arrived in perfect condition last week. Thanks for the expert packing to insure safe travels for the return trip. Alway appreciated!

I also wanted to say thanks again for all your hard work on both of my Hafler amps. I've set one QC-600 up in a dedicated media room and the other in the main livingroom. Both are performing flawlessly and sound awesome paired with my Benchmark DAC3 HGC Ref. DACs.

Happy Thanksgiving Jim.

Jim, January is on it's way out the door but my Hafler amp is staying put! It sounds great. I have it driving a pair of Vandersteen 2Ce speakers using a Rotel CD11 Tribute, Everything sounds so good, friends just can't believe the clean signal, the separations and the sheer quality of the entire system. I have played several types of music ranging from the Acid Rock of my youth to the quieter sounds of wooden guitar music and all sound superb. I have put this amp thru several days of intense listening and I have not heard a flaw in any of the tunes I have played. Separation between instruments has been spot on and each sound as I believe they should. Most importantly the program being played is smooth and not in your face (that's the Mosfet system at work I believe).

This now brings me to a crossroad. Do I go back to collecting vinyl and buy a good turn table or buy a good used reel to reel for extended listening time when socializing? Either way my wife will think I'm nuts!!!

Thank you again for doing a wonderful job in restoring this amp. It makes it impossible to NOT listen to the system, it's a real joy.

I really hope you enjoy the great work you do.

David L.

What an amp!! Music is my first love – listening, playing, and performing. To me, the best quality home stereo equipment reproduces the original signal as accurately and invisibly as possible, i.e. without adding or subtracting anything. A straight piece of wire with gain, as the saying goes. My Hafler sounded excellent before shipping it to you, and sounds stellar after receiving your upgrades. I’m using an Emotiva pre, with the QC-280 driving a pair of 1978 vintage Klipsch Cornwall's and couldn’t be happier with the sound at all volume levels – warm, punchy, dynamic, detailed, revealing, deeply enjoyable without fatigue.

Additionally, your customer service is second to none – the amount of communication and the detail therein along with all the documentation provided, is truly exceptional. It is very clear that you love what you do, which is immediately evident from your level of workmanship. Being the electromechanical systems technician and lifetime nerd that I am, I was obligated to open the case and have a look – inside I observed some of the most perfect wiring and soldering that I have ever seen performed by human hands. Meticulous, careful, patient. I am confident that this now heirloom quality audio component will function flawlessly for at least another 40 years.

Lastly, I don’t think there is a power amp out there anywhere close to the price point of the QC-280 that can come within a country mile of its performance. Thank you Jim, I am very pleased with my investment!

Jesse

Stunning, phenomenal, accurate, precise, I could go on describing the sound!!!! Top notch impeccable build quality. Parts quality spot on . Jim stayed in touch with me every step of the way. Phone, email, text message every method was used. This was an awesome experience all the way around. If you are on the fence about doing this to your amp. I can't stress enough DO IT !!!! You will be glad you did. Sonic purity !!!! You will hear things that you didn't before.

Capt. Mark L.

Hey Jim,

Well, I've been having a marvelous time with my QC-280, and so have a friend or two. We've thrown a variety of speakers at it, both bookshelf and floor-standing, as well as different amps and preamps. I've gotten to know its sound pretty well and am convinced of its long-term reliability. So here goes the testimonial I promised. I hope it isn't too corny as I tend to wax. When referencing you and your service, I just used the name "Jim". Here goes…

I'm a repeat customer of Jim's Hafler Amp upgrade service on eBay. So, I think I can speak with some authority on Jim's overall professionalism, reliability, timeliness, and quality of the upgrades he offers. If you appreciate true high-end sound and can do without the boutique looks and exorbitant prices of today's new amps, then I urge you to get in touch with Jim on eBay. I'll explain why.

Jim's first upgrade for me was a complete recap of a Hafler DH-120 that I built from a kit in the mid 1980's. Along with some new hardware for more solid connections, this upgrade also included a new switch, surge protection and higher value power supply filter capacitors. I was completely stunned at the improvement in smoothness, bass slam and overall musicality Jim brought to this little medium power amplifier.

While no circuit mods were performed on my DH-120, the overall improvement in sound quality whetted my appetite for what Jim could do with his "audiophile upgrades" to Hafler's higher power amplifiers. So, I patiently waited and watched on eBay for a used DH-220, that was still in working condition, had the cosmetics I was willing to live with and at a price I was willing to pay. I didn't have to wait long and snagged my 220. I immediately contacted Jim. He went over the upgrade options and prices with me, and I didn't hesitate to opt for the full audiophile circuit upgrade, speaker protection circuit and the other hardware component upgrades to transform my amp.

Jim supplies instructions on how to safely pack your amp for shipment to his location. So, I sent Jim the agreed upon down payment and shipped him my amp with no consternation at all. These upgrades are getting pretty popular, so Jim let me know my place in his working queue and the approximate time it would take to complete the upgrades on my amp. Once that started, Jim provided me with an overall assessment of my stock amp, made a few adjustments to bring it within spec and started the upgrades. He sent me photos each step of the way so I could see exactly what he was doing. He also sent me a link where I could download the new circuit schematic and a description of the new circuit's operation as well as other useful technical information. My amp was completed within a couple of weeks of Jim starting work on it, tested in Jim's own listening environment, and promptly shipped back to me.

I've been listening for a few weeks to the upgraded 220, now called the QC-280, as these upgrades add an additional 20 watts of power to each channel and wanted to provide a few thoughts on its sound. I'm not a professional reviewer, but I'll use the power of 3 and summarize my thoughts into 3 categories. I'll call these Slam, Space and Soul.

SLAM: Jim advised me beforehand that I might no longer need to use a subwoofer in my listening setup as the QC-280 could provide all the bass power, slam, and testicles that anyone could want. He was so right! I've already reassigned my subwoofer to home theater duties. The difference the upgraded 280 makes is actually startling. And that's not all - bass notes now have quality and texture - something I had not heard before out of my Nola Contender speakers.

SPACE: With a good preamp, in my case a Benchmark LA4, the QC-280 will reveal all of the spacial queues that are captured on your recordings or streaming services. Individual instruments are precisely located in space and provide separation from other instruments in that recorded space. The stereo image is 3D with great front to back depth and lateral spread. I think this is a hallmark of the new circuit design and a quality usually only heard in very expensive amps. It really puts the high in high-end and creates a listening experience that you wouldn't think possible at this price-point.

SOUL: Ok, so this is the hardest part to describe in words, but you will certainly know it when you hear it. I like to go to a lot of live performances of Jazz, choral, orchestral, and small ensembles around where I live. This helps keep my ears attuned to what live instruments and voices really sound like. Real, live music has texture, tones, overtones, and ambiances that help make a live musical performance such an emotional experience. We want that in our home music systems too, but it's hard to obtain. The QC-280 gets you a long way there. You can hear the husky growl and sexiness in Diana Krall's voice, the sweet and lush string tones of the Vienna Philharmonic, the hall ambiance of Severance Hall and the Cleveland orchestra, the bite of Coltrane's horn, and all the percussive effects of Fourplay and today's modern music.

Needless to say, I'm completely happy with my upgraded QC-280. It has provided me with much musical value and happiness at a price I never imagined possible. I urge you to contact Jim soon.

Jim,I’ve been letting your upgrade of the DH-200 soak into my musical brain for a few weeks now. Wow! I never imagined how profound an improvement it could make in my system! It’s hard to stop listening and yes, I’m rediscovering my music collection all over again!! I’m driving a pair of DefTech BP-10s and it’s handling the 6 ohm nominal very well. Everything sounds so tight, so much more detailed with a good soundstage even for the bipolar speakers. As an acoustic guitar and banjo playing nutter, I’m especially impressed with how “real” acoustic instruments appear…the attack, decay and resonance are amazing. Also, the transients and percussives are so tight! High quality recordings like my re-mastered Miles Davis will lock me in my chair and I can’t stop smiling!! Thanks again for your guidance, your outstanding workmanship and the value you built into this amp!! I’ve got several musical instruments and this amp may be the best one I’ve got! Highly recommend!Dave

Hi Jim,

First, all I can say for now is the results of your efforts are "Simply Unbelievable". I have never had my Hafler perform like it is now even when it was new. The clarity and crispness have blown me away. The amp is really fantastic!

Thanks, Tom

Hi Jim,

It's Cam here from Nelson BC , Canada.

I have to commend you and Ed's for your combined work contributing to the rebirth of my DH 200.

I am delighted with the outcome and couldn't be happier!

The words that sum up my listening to the rebuilt amp for the first time is simply WOW! I can't thank you enough for your support to my friend Jim S. who did the install of the boards.

It was so worth the wait, the additional power from the upgrade has made my Kef 105.2's sing to new highs!

Many many thanks!

Kind regards ,

Cam (another happy customer)

Hello - my name is Denny. If you're an audiophile and music lover like me, you're on a constant quest for better sonics and musical enjoyment. But the cost of high-end audio gear continues to soar, perhaps putting our goals out of budgetary reach. But, there might be another way forward, just as musically satisfying, and well within your budget.

Why not refurbish or completely upgrade your existing Hafler amp? Replacing worn out parts components with those made from modern materials or completely upgrading circuit cards with modern designs, can dramatically transform the sound of your Hafler amplifier. And all this can be done in the existing chassis, so you're not spending money on new metal work or cosmetics that do nothing to improve the sound of your amp.

But I was skeptical. Do I really want to ship my amp off to a person completely unknown to me? Would I get it back? Will it get damaged in shipping? Would it take forever and a day for the upgrades to be completed? Would I be happy with the results?

With these questions in mind I began looking for upgrade resources on the internet to get answers. Among others I found Jim (7houses) out on eBay. Jim was patient and took the time to explain his upgrade process, detailing exactly how everything would work along the way. He also explained different upgrade options, at different price points, that were available to me. Jim also described the sonic benefits of each upgrade and even made a suggestion for the biggest sonic bang for my buck for my particular Hafler amp. Jim's been doing these upgrades for years and knows how to coax the best performance from these amps, rivaling just about any new products you can buy today. Jim also sent me detailed instructions on how to pack my amp to prevent any damage during shipping and the approximate time-frame it would take him to perform the upgrade. As a result of these communications I got real comfortable with Jim, decided to move forward with his recommendation and price and shipped my amp off to him.

Was it worth it? The answer is a resounding YES. Jim communicated with me during the entire upgrade process, even sending photos along the way with his comments. I got my amp back within the specified time-frame too. Jim's upgrades not only improved the long-term reliability of my

amp but completely transformed its sound in just about every way. These sonic improvements aren't trivial, and I'm just delighted with the sound

of my amp, knowing that Jim saved me hundreds or even thousands of dollars over a new amp. I'd do it again in a heartbeat.

Thanks.... Denny

Jim,

It's been around 6 yrs+. since you upgraded my amp. It still sounds absolutely fantastic every time we listen to it. Being an old-time audiophile, I have yet to hear a cleaner, attention to detail and clearer sounding amp. I've rep'd Adcom, JBL, Hammond and retailed McIntosh, B&0, NAD, Carver/Phase Linear, & Linn along with several others and chose Hafler for the realistic strong sound it offers (even met David Hafler @ a CES back in the day). Your mods make a difference and I strongly recommend anyone who owns a Hafler Amp to invest in your talents.

Good Job & thanks!

- lexovet

Jim,

Got my amp back last night and all I can say is WOW!! Stayed up till 3 AM listening to things on tracks that I’ve never heard before. Stereo separation, soundstage and clarity are vastly improved. Thank you so much Jim!

Mike

Mike's follow-up comments:

Hi Jim........My name is Mike and you did a Hafler DH-500/QC-600 upgrade last year for me....and it is flawless.... I have hundreds of hours on it now and you may use me as a reference anytime......any prospective clients can come to listen to my Lancaster, PA. system anytime. It will be a lifetime relationship with this amp!

Jim,

The amp sounds terrific, and your electronic workmanship is top-notch!

Thank you!

Doug A.

Jim,

As I promised, I’ll share my impressions and thoughts about the QC600 upgrade that I’ve been listening to for the past couple of weeks. I plugged the amp in and listened as the amp seemed to start opening up after an hour or two of on time. It did sound pretty good, but it really got better after being on for 24 hours or so. Improvements after a day or so are subtle, but noticeable. What I’ve heard is an expansion of the perceived stage. The image is both deeper and wider (more 3-D) than any of the other amps I have that I’ve recently listened to. For me, I’ve discovered that the leading edges of a note, chord or a voice also seem much cleaner. To me, that leading edge reveals a lot about the amp in its ability to direct current in the proper direction in the proper amount of time to make the music sound as I think it should. The amp isn’t “mushy”, nor is it giving a crystalline quality. It just sounds right to me.

On well recorded sources, the image can expand beyond the outside edges of the speakers. It’s funny, as in my old house, this phenomenon more often occurred in the right channel, and in the house I’m in now, it happens mostly in the left channel. It’s got to have something to do with speaker/room interactions and how the speaker is situated with room boundaries and listener position. The QC600 is good at presenting a stable image, wide, tall and deep, and you will hear room artifacts if the music was recorded in a larger space or was injected post-recording. I prefer the real stuff, but if it’s there, you’ll notice it.

The amp is very good and quite honestly, has exceeded my expectations. It is quiet, clean and has plenty of power to keep the Magnepans singing. This amp really is a quality upgrade.

Good job! Thanks for spending the time and energy to get this thing working so well!

Regards,

Steve

Hi Jim,

I hope all is well with you and your family.

Now that I’ve listened to my upgraded Hafler 500, I just wanted to let you know that I’m super happy with it. It’s more than I imagined! The thing that really sets it apart for me is the way it drives my 1.7 Maggie’s. I was previously using a Hafler 220, and while the sound was good, I noticed that some recordings were lacking in bass. With the upgraded 500 driving them, that issue is long gone. The 500 drives them wonderfully, and there is plenty of bass!

I will likely send you a Hafler 220 next. 😊 Thank you Jim, I’m very appreciative!!

Rick

Hi Jim,

I unpacked and plugged in the amp today and it does sound fantastic! Incredibly crisp and clear, with easy power.

After more listening:

I've really been enjoying the QC-280. It sounds great with all kinds of music. It's nuanced and precise playing The Nutcracker (my 2-year-old daughter's current favorite), with easy separation of instruments and a wide sound stage. It handles the dynamic range very well, with barely any loss of detail in the quiet parts. The controlled power of the guitar riff on Dire Straits' "Money for Nothing" was enough for my Infinity CS-3008's to knock a picture off the wall--with the volume at 1:00. Ella Fitzgerald and Count Basie sound like they're playing "Honeysuckle Rose" right in the room with you. I wish I could say more, but I'm more of a music lover than an audiophile.

Joe

It sounds fantastic! The day my reworked amp arrived, I spent the entire evening listening to a wide variety of music and loved every minute of it - straight out of the box. No fiddling with the controls on my preamp, no acclimating my ears to the sound - just sonic bliss. To describe this upgraded amp as "musical" falls short. It lends liveliness and presence to songs that I've heard a million times previously but had never ‘experienced’ them like this before. I love it! You can listen to music for hours with this amp, without the fatigue that was an a facet of the character of the original DH-220.

Its also important that I mention the communication by the seller was top notch every step of the way. I got daily updates via email on the progress of the upgrade and prompt replies to my email queries before, during, and after the sale. If I owned another Hafler amp, I wouldn’t hesitate to upgrade it.

-Jon G.

If you own a vintage Hafler amplifier do not hesitate to get the full PC1 upgrade Jim is offering. I’ll break this down into two parts. First is the work and Jim himself. At every step of the upgrade Jim kept me informed including photos of my amplifier as he transformed it. Every picture showed me that this man is meticulous and conscientious in the work he does. Craftsmanship is rare these days and Jim is truly a craftsman. Now how does the amplifier sound. Is this hyperbole or the real deal? To remove any variables I kept my audio system the same as it was, the only difference is I connected my new QC280 amplifier Jim built to the pre-out on my NAD C368 BluOs and reconnected my KEF XQ10's to the new amp leaving my KEF 400b subwoofer on the sub out. My source material was CD’s ripped with Exact Audio Copy and 32/192 kHz streaming through the BluOs. This amplifier was a revelation! The soundstage was massive, both wide and deep and truly holographic in its’ imaging. Dynamics were crisp and instantaneous. I put on Steve Reich’s Music for 18 Musicians and every instrument was clearly defined and organic in timbre. Next up was Miles Davis In a Silent Way. Again, from Miles’s trumpet to Shorter’s sax to DeJohnette’s brush work on drums and cymbals and McLaughlin’s guitar runs all seemed to be in the room with me. I stayed up until dawn going through every genre, classical, jazz, rock and roll, Afro-Pop, and all of it was like I was truly hearing it for the first time. This amplifier upgrade is the best value I have found in a very long time and Jim himself is a gem. I am currently building myself a pair of CSS 1TD speakers and I can’t wait to hook them up to this amazing amp.

Yours in the love of music and high fidelity, Jeff Young

Jim,

I have had a chance to put the amp through a wide range of my musical tastes and can only come to one noticeable difference - EVERYTHING!!!

I have been able to listen for a long period of time at a high level without any listening ‘fatigue'. I am hearing things on recordings I have been listening to for may years that I never heard before. Especially subtle differences as a song I’ve known for many years now hearing there is some reverb and delay in the recording I never heard. I can clearly hear the differences in how recordings are produced, some very minimally (clean instruments and vocals) and others that sound ‘over produced‘. My wife who is not an audiophile says everything sounds so much more clear with defined presence. I hear complete silence through the speakers where before I would hear a hum at high levels. I thought my speakers were past their prime and ready to replace, but now its like I’m listening to new speakers.

I installed a few more cooling fans in the cabinet that my stereo components are in because before your upgrade the amp fan would usually kick on to the high speed. Now the cabinet temperature is at around 10 -15 º cooler and I have yet to hear the fan go to high, and can’t hear it on low because it is so quiet.

I have had this amp for over 40 years and about 10 years ago began looking for someone who could diagnose and replace/upgrade what it needed so I wouldn’t have to part with it. It basically has been idle for that time until I came across your ad on eBay. My only regret is not packing the amp as you suggested by double boxing. I believe I had enough cushioning but another box around it with more insulation would have protected it on the way home. The dent it suffered is hidden by the cabinet, so the fact that it works flawlessly is what I care about. The wait time to send the amp and get it back was well worth it. Your attention to detail and meticulous workmanship is hard to find today. It really shows how much you care and love what you do. You have definitely made a big impact on my love and appreciation for a good sound system. I can’t thank you enough. I would recommend you to anyone looking to upgrade a Hafler amp needing some TLC.

P.S. The first album I played was Lyle Lovett ‘Step inside this House‘ double album all the way through. It was a good first test because the album although recorded in 1998 is one of my favorite quality recordings of great musicians and well produced. Turn it up loud for ‘Rolin By'. Another favorite is Dire Straits ‘Brothers in Arms’, I was blown away listening to the remastered recording.

Thank you.

Stephen Grzeszkiewicz

OH MY GOODNESS!!

Is it working? Is? It? Working? IS IT WORKING?????

Never in my life have I heard anything like this! Audio nirvana! My Polk RTi A9's have always been super thirsty, which is why I bi-amp them—till now it’s been the only way to get decent bass. Their sensitivity is garbage. Well, once I finally had time to hook up the amp, I fired up a test song from one of my favorite playlists. I had only intended to verify the amp was working, but an hour later, I realized that the speakers had disappeared and I had just sat there enjoying songs I’ve heard a hundred times like they were brand new. Expansive soundstage—it was just me and the music.

Bass was deep and tight, not boomy or loose in any way, but still powerful and commanding. The mids, my god the mids! They stood out on their own with a clarity and smoothness that was astonishing. The highs were so clean and airy—I had not even a HINT of listening fatigue after the hour session—in fact, I had to tear myself away from the music to get some work done. Another awesome thing was that the music sounded fantastic at all levels—even quiet, it still had powerful presence and compelling clarity.

Before I quit though, I did an A-B with my Adcom 555SE (a not inconsequential $1400 amp), and a heavily modded Yaquin tube amp I had nearby. The Adcom had great mids, but nowhere NEAR the commanding presence and incredible bass of the QC600. It sounded shrill, hollow and empty, flat and disappointing. (It actually sounded great, but after the QC…well now I am officially SPOILED!!) The tube amp was nice and warm, but just didn’t have the power that the Polks needed. It too, while sounding really great, was greatly disappointing after hearing the QC600.

This amp has been one of the most expensive investments I’ve ever made, because now my other amps are all worthless, hahaha!

But seriously, NEVER in all my years of audio have I gotten so much value from my investment. This was worth the wait and the money 100x over. Thank you so, so much for sharing your gift with the world, and with me. I can tell you with absolute certainty that I will be back for more in the future! It was an absolute joy working with you. I will remember in the future also your advice about double-boxing, it was an eye-opener just how close I came to having something bad happen to this absolute treasure!

With the quality I see inside this amp, I would expect it to play faithfully for maybe 20-30 years with no problems. I’d love to pass it on to my son someday :)

Thank you, Jim. I wish you and yours a wonderful year, filled with happiness, health, laughter, family, smiles, friends, and MUSIC.

Sincerely,

Cisco

Hi Jim: I bought my Hafler in the late 1970’s along with a Luxman tube pre-amp. At the time this was a big step up in affordable quality. Eventually I put my gear in storage, which ended up being for 25 years. I decided to resurrect this equipment last January. I happened upon your eBay offering and after giving you a call, decided to move forward with it. I was expecting maybe marginal improvement in performance but I was looking to at least to have an evaluation and replace any aged parts. During this time I also re-tubed my preamp and cleaned it up in anticipation of the audition of 21st century electronics. Your communication was excellent during this process. You provided very affordable recommendations. Just a note, anybody out there, if Jim makes a recommendation for parts - don’t go cheap. Follow his direction. When I received the amp, I hooked up the Luxman, and I was off to the races. The initial impression was the surfacing of music in the tracks that were never clearly audible before. Separation in stereo was markedly improved. The new N.O.S. stock tubes in the pre-amp brought a sound stage to this amplifier that was nothing short of profound. THIS AMPLIFIER IS MADE FOR TUBES. This prompted me to look in the marketplace for new technology in a tube pre-amp. I settled upon a PrimaLuna Dialogue pre-amp. Outstanding performance and build quality. After rolling some N.O.S. tubes, this turned out to be superior to the Luxman. Now I’m hearing vocal back tracks in Jan and Dean that I never heard before. The Doobie Brothers tracks I thought were out-takes because there is so much more music that I never heard before. Jim’s efforts are one of the great open secrets in audio. This quality in sound is the biggest bargain I’ve run across. Thanks again Jim

Hi Jim,

I can tell you that the original 500 you reconstructed sounds incredible! (more 3D than my other older one, but with the same perfect frequency balance). In fact, the 3D enhanced 500, due to the increased depth of the sound, provides more space between sounds and instruments. I will have you do the same reconstruction to my other 500 at a later date.

Kind Regards,

Pierre

Jim,

Thank you for the work on my DH-200, now QC-280. I still can't fathom the difference that you've built into this amp, It's too much (in a good way)! I've only played the amp for an hour or so and am floored by the bass response. I could go on, but you know what you built for me, so I won't. Suffice to say, I am one very happy customer :)

Update:

Thank you again for the upgrade work on my 'QC-280', it's so clear. And seems to appear more transparent and more dynamic every day (maybe the speakers are finally getting run in too? who knows!). I'm having to weed out the 'not so well produced' sources, not necessarily a bad thing. This amp is deep (as in, way down the audiophile rabbit hole!!).

Regards, Mark.

Hi Jim,

I wanted to send you an update on how the Hafler 500 (QC 600) has been performing. It's been a couple of months since the upgrade and I am really enjoying the amp. The Solstice speakers are moderately efficient so it doesn't take much form the QC 600 to shake the house. What I have really noticed is the increase in sound stage, the clarity of the individual instruments, especially with Hi-Res sources. Bass response is fast and punchy way different than the Adcom amp I used to own. It has been a blast to listen to my collection of music and hear parts of the recordings that I was not able to discern before. The amp runs super quiet thanks to your work getting the fan to run correctly. I was really impressed with how fast you responded to questions I had and the level of detail to questions and to the repair process itself. I wanted to let you know how pleased I am with the process and the end result. Your attention to detail is tremendous and your fees are really reasonable!

Best Wishes,

Dave B.

Hi Jim,
Remember me? You did a total rebuild on my DH-500 amp just about a year ago. I happened to be going through my old email drafts & saw one to you that I didn't send. So I thought I'd contact you & let you know about my amp. It's still working great! Here's my old unsent email:

"The Hafler sounds great! I could hear the difference from what it was before & now immediately. The sound is super clear. The highs are much, much better, they probably stand out most but the overall sound is just tremendous! The whole system sounds great!

I also definitely noticed the increased power. I am very happy with the way it preforms now. Wow, last night, I listened to it for a couple hrs. When I listened to stereo (just the Hafler) not 7.1 multi-channel, I could especially hear the increased clarity & improvement in sound very easily.
I got it last Friday from FedEx. It survived shipment well. Excellent re-packaging by you, thank you! On Sunday, I took apart the body to put the face plate & handles.
The quality of your workmanship inside is just awesome! ...the pictures you sent me don't do it justice! Everything you did is very clean & neat.,, very well done. I know quality when I see it! I'm really happy with everything & glad I had you do the work."

Thank you for all the high-quality work & care you put forth on this project for me. It was well worth it & much appreciated!

Wishing you the best Jim, take care!
Sincerely, Bob

Hey Jim, been meaning to send you a line or two with my thoughts about the "new" DH200/QC280. 😁

I've been giving it some very serious listening sessions since discovering I'd wired the right speaker out of phase. 😝 In a way I'm glad I messed up, I can be confident I'm listening objectively and not hearing what I want to hear.

So what I'm hearing is nothing short of spectacular! The combination of the Hafler and Infinity's is incredible. As you pointed out these speakers have the reputation of being amp-killers. Paired with an amp that took measures to prevent speaker-killing and I think we have a thing of beauty. The amp has the balls to push the speakers and they have the balls to take all it can dish out. I haven't come close to pushing either but enjoy the pure, clean power while listening 'comfortably loud'. I have no doubt the sound will be just as pure at ear-splitting levels as well.

Like you said, some music is better produced than others and I find myself cringing a tad from time to time, but when you hit a well produced song it is absolutely thrilling. I listen to just the Infinity's on 2 channel most of the time, but occasionally I'll kick it into full 9 channel wall of sound and it's really something.

I'm totally happy that I went ahead and had you do the full mod on my amp. It was totally worth every cent not only to have an absolutely top notch power-amp, but the nostalgia factor of having the core of my 30 plus year old hi-fi system back can't be measured. I don't think a modern 2 channel amp can come close to the old Hafler's for the price of this upgrade. This is as close to the warm sound of a tube amp as anybody can possibly hope to come.

I look forward all week to my weekend listening sessions.

Thanks Jim!

Theo

Hi Jim,

I wanted to give a few impressions after having the amplifier on for over 200 hours. I want to first state that I have mainly used tube amps in my main system (Marantz 8B, Eico HF 81 Sam Kim mod, Dynaco St 70, Dynaco ST 35 power supply upgraded and others). With that said, I have a bias and a love for the midrange, especially vocals and strings, a good and properly working tube amp can bring. My favorite, the ST35 is only 16 or 17 watts, but the EL 84 tube is fast in the transients and has airy highs and a good foundation for bass. I have used my Hafler XL280 in my main system and my 2nd system uses an old NAD 3020 amplifier which had been serviced recently. My impressions will now focus only on the QC-280 with only a few comparisons to the other amps.

Associated Equipment: conrad johnson PV5 (Bill Thalmann mods) pre-amp; Sound Dynamics RTS 9 speakers, Linn Lingo turntable with Dynavector 10X4 cartridge, Thorens TD 147 turntable with Audio Technica AT33 mono cartridge, Marantz SA8001 CD player and a Yamaha T85 tuner.

Break in period observations: the amplifier did not ever get hot to touch throughout the burn in period. I could place my hand on the top and touch the cooling fins without any problems. A 40 watt light bulb gets hotter to touch than the amp. When the amp was first on for an hour and listening to the tuner, I could tell the sound was clean, dynamic and in control with orchestral music. The floor noise was clean. As time passed, at 50 hours I could hear a change in the soundstage getting wider and going outside the speakers with music I was familiar with. At 100 hours, using the same music, I felt the soundstage reached its potential and I could get a better sense of the front to back depth. I could easily hear the space of the recording venue. Likewise, it took the bass the same amount of time to sound its best in terms of detail and solidarity. I have found this with my tube amps when they haven't been played for long periods of time. Yes, IMHO, break in is important before judging an amp.

Impressions: after 150 hours of break in, I found this amp to be dynamic, able to resolve musical details and was in control of the music at all listening levels. Complex passages and the many instrumental soloists playing at the same time found in Decca's Gerhard "The Plague" by Antal Doriti or London's "Messiaen" by Antal Dorati proved to be no problem for this amp. Individual instruments were easily heard and no smearing of the instruments was evident. It was easy to hear a soloist in a choir as the choir harmonized in the background (evident in the soundtrack "Glory" with the Harlem Boy's choir). You can hear cello soloists breathing and in the case of Glenn Gould, hear his humming as he played the piano (sometimes annoyingly). Microdynamics are good when going from a soft to loud passages. Musical lines are easy to hear. The only area I found not as pleasing as my trusty ST 35 tube amp was getting the nth degree of musicality in the midrange. This is not a criticism, but maybe a bias. What I mean is that on unamplified music like Yo Yo Ma playing his cello or a violinist like Heifetz, I can hear and in a physical sense the bowing of the strings as they play. On piano music or hearing drum cymbals, the decay of the notes is more pleasing to my ear and realistic on a tube amp. The QC-280 gets to 90% of what I sense and enjoy. Is it more correct?, I don't know. But with the bass, there is no comparison. This amp brings a solidarity in the bass foundation that I have never heard. There is detail and a "correctness" of how it presents itself. It is my speaker that is the limitation as it only goes down to 35 Hz. Drum whacks are realistic and quick. No boomy bass here. My last point is that regardless of the listening level, this amplifier controls the music, whether it a singer and a guitar or a 100 piece orchestra. Usually when you play music loud (which I seldom do), it just breaks up and gets distorted. Not this amp.

In closing, this amp has the 'WOW' factor. What I mean is when you are playing the stereo system and listening from a different room and either I or a friend says "Wow, that really sounds good", the amp has done its job. Jim, a job well done and a true bargain for having done this under $1,000 to boot. This isn't my Hafler XL280.

Thanks (and I'm sorry I babbled on too much.)

John H.

Jim,

I wanted to tell you your work is impeccable and nice to see those skills of yours. Thanks so much for all of your help. When I get customers wanting there Haflers upgraded, your the man and I'll send them to you.

Thanks again,

Alan

Jim and Ed ,

First thing, Thank You for a great design Ed, and Jim your expert work and grand service. The sound emitted from this upgrade is truly noticeable first track !! The clarity jumps front and center! Taj Mahal honestly could have been just across the room, so much “like you are there!” experience. I am just amazed how the instruments from front to back are clear, clean with no drop off for background passages, crisp not muddled. Silent passages are just that, dead silence, that stood out. The openness of the sound this puts out is truly a joy to experience! Seems even better as days go by😃. After listening to full compliment of Pink Floyd “Wish You Were Here”, I felt like my lower jaw needed pushed back up!!! That pretty well sums it up there!!!!

Could not be happier, Thank You both , Rob

Jim,

I'm writing to let you know that my new preamp reveals a lot of difference with the Hafler upgrades. It's an Apt Holman that has new capacitors courtesy of another fine Ebay seller. So in addition to testifying to your excellent service and all your help with my Hafler rebuild, I can now talk about the great sound - because I hear it. Your build of the PC-1 boards, combined with new filter capacitors from Qua-Co, made a major musical improvement in the sound of my Hafler DH-200, which dates from the very first year of that amp's production. To gauge the difference, I made recordings of several favorite pieces before and after the PC-1 upgrade: Bob Marley's Coming in from the Cold on vinyl, Bill Evans' My Romance at the Village Vanguard on Spotify's high quality setting and a track from the Heath Brothers' Family Jazz CD with both an extended bass melody line and a wonderful piano solo. All are well recorded. I used Audacity and a Blue Snowball USB mic. The difference, in a word, was definition - more of it. On low frequencies, the upgrade produced sweeter, clearer, crisper sound and tempered the lush, resonant and boomy qualities that existed before. All the richness remained, but the accuracy and detail improved and the sound became more spacious, less cluttered. Piano notes sound like wound steel strings vibrating and are more clearly distinguishable from notes in the same octave played on the upright bass. The middle- and upper-range tones gained similar clarity and precision. Like dead grass was raked from the lawn. The differences also are visible in the track waveforms in Audacity. These subtle changes are audible with careful listening, but they also build up when playing music casually in the background. After even a few minutes, I find myself saying, simply, "Wow. That *really* sounds good." I have been an audio enthusiast for 40+ years. This amp is fantastic. Now, about those speakers....I am sure a lot more detail will appear when those get upgraded next.

Your clear instructions, illustrations and responses to questions allowed me to install and correctly bias with confidence. It was a fun project with great results. Thanks, Jim!

Hello Jim:

The amp arrived yesterday about 7 pm without mishap. I waited about 30 minutes to let it warm up before I played a cd. Needless to say, I was in a state of expectation as to what I was going to hear after reading all the glowing reviews. To reiterate what speakers I am using, they are the Polk SDA-SRS 1.2TL, their flagship model, 12 speakers in each and weighing 180 pounds each. Their frequency response is 20 to 20,000Hz. So the music I was hearing with them before the upgrade was impressive. Settling down in my listening chair, I started a cd. My initial impression was not that startling. The piece that I was playing did not sound much different than when played through the Hafler SE240 that I was using as an interim amp. That initial impression was soon to change as I played another cd, and another, and so on until the realization came that the sound from symphony orchestras and from electronic music had no harshness or distortion in certain passages, where there was before the upgrade. The cymbals, chimes and bells were crystal clear. The deep bass notes could be felt in your body without any aural harshness. In fact, some pieces that I had previously marked as good but not worth listening to before the upgrade took on new life and were a pleasure to listen to. I listened to one piece after another until it became late and it was time to retire. So, to summarize, the impression of what I was hearing with this upgrade was a richness, or fullness in sound with no perceivable distortion or flatness, an improvement in stereo separation, with improved clarity at the far points, as well as the ability to hear the sound of instruments in the background move to the forefront with presence and clarity where I could barely hear them before. My listening pleasure has just been taken to a new level. I don’t know if what I now hear can be improved on to any extent, since I now think I have reached perfection. I would recommend this upgrade without any hesitation to anyone wanting to enhance their listening pleasure. You won’t be disappointed. Thanks Jim, for the great and passionate work you do to enhance the listening pleasure of music lovers and to Ed for the brilliant QC upgrade. The updates and photos of the work as you were performing it also kept me involved in the process.

Thanks again for opening a new adventure in listening pleasure.

Best regards, Kurt

Jim,

The amp arrived Wednesday with no damage. Unboxed and plugged it in last night and took it for a test drive. Unbelievable! This is THE sound that I thought I could never afford. I bought the Klipsch speakers a few years ago and was not overly impressed with them. They had deep bass but lacked punch (and the highs were a little harsh). That was apparently an amp issue and not a speaker issue. My apologies to Klipsch (I know there are plenty of Klipsch critics out there). I can now feel the snare drum in my chest. I could hear the change in the high hat sound as the drum stick hit different parts of it. And I thought the "let the amp warm up" thing was questionable. Nope, I could absolutely hear the difference 15 and 30 mins into it. I'm a Rock guy so last night I took it through Led Zep III, Iron Maiden, Mad Season, vintage Heart, Type O Neg, Skynyrd, and Fleetwood Mac - all vinyl. I now realize that the remastered Led Zep III could be better. Jim, thanks for the attention to every detail and the superior workmanship. I am also so thankful that my fuse blew last fall or else I don't know if I would have pulled the trigger on this upgrade. I saw your upgrade offer on Ebay a while ago but just did not think it was worth the hassle of the shipping and waiting....HA! Thank God for that fuse blowing.

-Dave

Jim,

I'd like to give you a heart-felt thanks for what you did for my DH500. It's taken some time to fully appreciate...

Right out of the box I noticed that the amp made my JBL 4412's sing, a strange word but that sums it up. Back in it's youth the DH500 sounded great, and I have no way to do a side by side between 1988 and 2018, but this made me very happy. Unfortunately this exacerbated problems I was having with poor room acoustics and lead to a major re-organization of my audio space- a big, time-consuming project. That finished, I brought my parametric EQ into my preamp EPL along with a new 31 band Graphic EQ and mostly fixed the problem.

I've spent many hours at this point sitting on the couch at the focal point of the 4412's, listening very carefully. I've concluded that the "imaging" of the soundstage in the 'reborn' DH500 is almost certainly better than it has ever been. I say this because I'm hearing things I've never heard before on CD's that I know well. Specifically, I can hear little tweaks on the board by the sound engineer changing the location of the musicians within both 3D image-space and sonic layers of frequency space ever so slightly to great musical effect. Of course this is both a blessing and a curse - some recording engineers have the gift and some don't. It's a whole new dimension to the music.

I hate to admit this, but I was a bit hesitant to ship my amp off to a complete stranger. I am grateful that you took the time to get me on board. You, my friend, and the engineer that designed the driver boards, are the real deal, true afficionados pushing the audiophile envelope to new heights.

Thanks and God Bless you and yours,

Jerome S.

Here's what a recent customer had to say about Ed's PC-1 design and my installation work on his 2 Mono 500's:

Dear Jim and Ed,

I wanted to let both of you know how ecstatic I am with the sound and build quality of my two bridged Hafler DH500's. I am having the same feelings of wonder and awe I got 35 odd years ago when I first bought assembled and listened to them.
I've tried several different amps over the years including Carver, Proton, Adcom, Nakamichi, and a few others, but nothing came close to the power and clarity of my Hafler’s. They've been used exclusively with a pair of Polk rta12b speakers bought at the same time, and until recently, the only speakers I ever needed.
While Jim was rebuilding my amps, I had the good fortune to acquire a nice set of Infinity rs2b’s. An order of magnitude better than the Polk’s, they also quickly showed every flaw of any piece of equipment attached to them. The Nakamichi Stasis 7 did not sound good on them, a Proton AA-1150 sounded more musical and less harsh. I could tell that it just wasn't powerful enough, the infinities are serious power hogs.
So yesterday when my amps returned home from their visit with Jim, I spent the next 12 hours listening. Suddenly, all of the drivers in my speakers came alive, the emims got the power they needed to keep vocals and percussion separate and distinct. Where I once thought I might need a subwoofer, the speakers now extended way down to their bottom end, you could hear bass notes fade clearly as the strings vibrations lessened. Spatial imaging took on outstanding depth as well as breadth.
Like I said, it felt like the first time all over again.
Kudos to you for the board design Ed, and you've got a real treasure in Jim. He went above and beyond to make everything perfect. I'm really surprised he hadn't changed his phone number.
Jim, I can’t say enough about how great it was to do business with you! Thanks for answering ALL my questions and helping me with your advice.

Kind regards,
A very satisfied customer,
Russ Hunsberger

Jim,

My 4 Mono Hafler P505’s are exceptional! Between you and Ed at QUA-CO, I could not be happier.

Ed‘s design and your assembly of these boards have put together a remarkable product. The best thing I did was listen to you when you said I should replace the Power Supplies, when all four of these amps were on and running at normal volume they would draw about 5 or 6 Amps when looking at my power conditioners meter, now 3 amps if even.

As for sound quality they are remarkable. I am running a pair of Dahlquist DQ-10’s with the two matching Sub woofers and the Dahlquist DQ-LP1 Electronic Crossover. These speakers are known for their remarkable reproduction of sound, and I thought they were good before, but now, it is unbelievable. I am hearing instruments in songs that I have played for years and never heard.

I went to the Hafler line, because after a lot of searching and reviewing to find the closest sound to a vacuum tube amp, in a solid state, all roads lead to Hafler, I have never looked back. Now I have four brand new amps that could very easily go up against amps costing $5,000 dollars or more.

So thank you for an excellent job! Anyone out there thinking their Hafler amp is shot or too old, contact Jim and bring new life to your system, if you really appreciate high quality sound, and want a high end system do this upgrade, you won’t be sorry.

I love music and you and Ed have given me a great gift of sound. Thanks to the both of you.

Thanks again Jim

Gary S.

Jim;

The work you did on my Hafler DH500 EXCEEDED expectation! Between you and Ed at QUA-CO, I would put my amp up against ANY other in the $5,000+ price range.

The modifications designed by Ed and your technical expertise and commitment to quality assembly is well noted. The fact that you even went to the extent of rebuilding and balancing the power supply (something others might not check) is a show of your professionalism and commitment to the art of high-end audio.

I now have a brand new amp utilizing what was left of my old, limping DH500 and incorporating the newest technology and techniques that will stand the test of time for another 30 years!

As an audiophile that has always demanded the best sound possible, an Adcom Rep from the 1980's and a Hafler enthusiast since the mid 1970's, I can easily say, that your ability to perform such high quality work on mine, as well as many other high-end amps of that era, that I would not hesitate referring you to my closest friends. You've given me the sound I have spent a lifetime searching for! Many, Many Thanks.

Sincerely,

R. J. Case

Ashland, Ohio

Here's more satisfied customer feedback:

Hi Jim,

As you know, I’ve been developing speakers and assembling systems for my clients for over 20 years. I’ve dealt with many brands of amplifiers, preamplifiers, DAC, cables, etc.

The best sonic balance (not the depth or wideness of the sound-stage, just the sonic balance – the closest to a live performance) I have found in any amplifier at any price is in the original DH-500 (I’ve used amplifiers worth tens of thousands of dollars). I might also add that I’m a musician and that I’ve been going to live shows (pop. Jazz, classical, electronic, world music) for more than 40 years.

I won’t bother you with describing how this or that musical piece sounded in comparison to what I’ve heard before, but I will tell you that not only did your amplifier reproduce the original Hafler frequency balance, but somehow improved it to my total astonishment. But this is not all. I’ve heard many amplifiers with great depth and wideness of sound-stage (I have to mention that these criteria come second to the frequency balance for me), but I have to say I’ve simply never heard anything close to what your new DH-500 can produce in these regards. It is simply incredible. To give you just an example, it is possible to hear the first violin in a violin concerto clearly closer than the second and third violins and to hear all the other instruments of the orchestra just as they should sound vis-à-vis the others, exactly at their place sonically and physically. The same is true for jazz, rock, pop, electronic. (I simply never heard such beautiful deep bass frequencies, so detached from the rest of the sounds).

Jim and Ed, you know how important it is to us crazy sound and music lovers when we can improve our sound by even a fraction. With your amplifier, I’ve gone from the seventh sky to the 8th one, which I didn’t know existed!

So thank you so very much.

Pierre Murray

President

ArtVibes Audio

P.S.; If I may make a suggestion, you should sell this amplifier for at least $7,000. I don’t believe it is possible to find a comparable amplifier under $15,000, which is the level I stopped at in my searches (even dual monos and mono blocks). My favorite one is the Pass Lab 100.8, and I feel this new DH-500 is in the same class, even though I prefer the Hafler to the PLab.

"Absolutely professional! Perfectionistic! Great communication! Amp sounds great!"

"Excellent service! Jim goes out of his way to be helpful and meet your needs!"

"Holy SH*&! I can't get over how detailed this sounds! And the Bass is very deep and tight. I'm hearing things in songs that I've never heard before. Great work, Jim. Thanks!"

"Had a chance to test out the amp, and it sounds AMAZING! Thank you for all the work. Starting with great communication throughout with progress updates, the attention to detail and letting me know of unforeseen issues with advice on remedies, taking the time to repackage the amp for shipping just because it was in my best interest. And finally, the craftsmanship that went into putting it all together. Initially I was apprehensive about spending the money on an old piece of electronics, but after having had a chance to really listen to the results, it was the best money I've spent on audio gear in years!"