In this listing, I am offering the latest version of my classic premium headphone amplifier.
Section 1: Development Background
Section 2: Independent Reviews
Section 3: Unique Features
Section 4: Technical Details
Section 5: Customer Opinions
Section 6: How to design and buy your amp (just go to the end of this listing for all the info you need to "buyitnow")
Development Background
I am a Ph.D. level scientist, an audio enthusiast and an audiophile. Back in the 1980's I used to eagerly inhale articles in Stereophile or Audio Review about Matthew Polk's or Bob Carver's current advances in audio engineering.
While I have always dabbled in audio electronics, this business was conceived almost 11 years ago with me designing and building an amplifier for a friend (his wife wouldn't let him buy the $500 headphone amplifier he "needed" for his Ety's). That effort turned into a fledgling hobby, and I turned to Ebay to "get rid of" my prototypes. It evolved into a weekend business that has continued for 10 years. During this time, I have continually updated and improved my amplifier design to ensure it remains the most refined example of audio purity in the cmoy class. With true audiophile intent, I avoid unnecessary circuitry, or "features" which artificially color the true sound, instead focusing on identifying components which provide the most neutral, faithful, and detailed sound quality possible at this price point. "Biosciencegeek" is my registered business, though it is not how I support myself: it is an outlet for my audio passion. And although I have less and less time for this side project (my real job is being an industrial scientist), I love to invest my free time into developing better and better sounding amplifiers for myself and for my thousands of customers worldwide who appreciate great sound...by HAND, and in small numbers to maintain the quality and service my customers deserve.
As you browse other amplifier offerings, you may notice that over the years, many others have copied my ebay listing style, mimicked my descriptions (sometimes reproducing my anecdotal side stories as their own), and even incorporated some of my features into their amps including auto-power on/off headphone jacks and dual gain. Well, imitation is the most sincere form of flattery. Good luck to them as they try to turn a profit in their business endeavors. However, I was the first to offer customized tuning of my amp to suit your headphones and your audio source. And although other amp builders now try to follow suit, those businessmen are highly restricted by the design of their circuit boards in what they can do for you. Only my hand-built amp is truly customizable.
Perhaps the most telling praise for my amps are in reviews and writeups which were totally unsolicited by me. They were not generated by paid partners or friends but by impartial audio/technical review organizations and individuals who I don't even know. Follow the links below to the reviews:
Independent Reviews:
What sets my amp apart from the rest?:
Flexibility: There are many reviews of my amps detailing how well my amps work with a wide variety of gear. I originally designed this amp to work well with my 32 ohm Grado SR225's and 300 ohm Sennheiser HD-600's. I have made recent mods to optimize performance and bass support with characteristically power-demanding low impedance gear like Grados, ATH-M50's, and AKG701's and 702's. My customers have reported favorable results using my amp with their 600 ohm, difficult-to-drive Beyerdynamics, AKG's and even low impedance/high sensitivity earphones like ER6's and SE530's. The unique flexibility to tailor my amp to suit your headphones makes this range of compatibility possible. In addition, a beefed up high current power supply is now a standard feature. This means my amp is now even more capable of supporting these users' needs and their gear as well as or better than any amp in this class. Coupled with my adapter, this high current amp can now drive AKG701s and other demanding headphones cleanly, without distortion, and to their limits.
My amplifier is hand-built from scratch to order and is tailored to suit YOUR headphones, source and application. It is optimized for gain and hiss reduction. I don't simply populate a premade circuit board with predetermined parts and slap it in a case. This actually makes my job harder not easier, but it's worth it for you.
An 8-pin opamp socket means you can tailor the sound of your amp by pulling the existing chip and swapping in new chips. I designed my amp with stability and tolerance to support a wide variety of opamp chips.
You get to "build your own amp" by having it optimized for your gear (you have a choice of chip, current output, case, LED color, knob style and even how the battery option is configured).
My amp was the first to incorporate a variety of features including auto power on/off and dual gain support. Some may be offering these now, but I've had 8 years of experience perfecting these and other features.
Guarantee/Warranty: All my amps come with a satisfaction or repair or return guarantee: YOU get to choose how you're satisfied. I am always there to answer questions and offer support (including the rare repair) even years after the purchase often for just the cost of parts. You will not find this level and quality of support elsewhere. Still uncertain? Ask my customers on Headfi.org.
Technical Details:
Case:
Choose your tin from the selection offered in the "Tin Choices" picture. Tins may vary slightly in appearance as the mint manufacturers occasionally change their designs. In addition, I often have a limited selection of alternate tins available at no extra charge. I can even use a tin you provide providing is has the same dimensions as a standard Altoids or Penguin mints 1.7oz tin.
Metal cases like these shield the amp from any stray RF signals or interference from other electronic devices. The jacks are clearly and neatly labelled in professional Helvetica lettering.
A solid aluminum knob completes the high quality finish. You can select either a brush-finished knob with dual rubber O-rings or a knob with a crosshatch textured barrel surface.
Power supply:
To provide long battery life and stable amplifier performance, the power subsystem uses either one or two (depending on your headphones) high performance TLE2426 voltage rail splitters to precisely balance and buffer the supply voltage. Lesser amps use a simple resistor divider, often without resistance-matched components resulting in slightly imbalanced power channels. The power supply includes a high grade, audio-qualified Nichicon capacitor of the same type used in high end audio gear costing thousands of dollars. I have just upgraded this component to a superior unit as part of a new, beefier power subsystem. What this means to you is that if you want to drive the opamp chip with a higher voltage to get closer to its performance sweet spot, you may now do so. To plug your amp into the wall, all amps come with a DC jack for use with a power adapter (see my adapter listing or provide your own). Using my adapter provides HIGH CURRENT to support even demanding headphones without distortion. You can now drive your gear to their limits.
Your amp can also be powered by batteries. You choose which of the following 2 types of internal battery options you want with your amp when you order: (batteries not included)
Option 9V: You only need one battery to run your amp, but this option gives you a slot for inserting a second battery to double your run time if desired. You can still drive the amp at higher voltages using an external adapter if you desire higher voltage operation at your desk.
Option 18V: Two 9v batteries are required to run this amp. 18VDC operation offers optimal chip performance in a portable device. You must have 2 batteries installed to run the amp on battery power with this option. Again, you can still run the amp using an adapter at your desk if desired.
The OpAmps:
When I first launched my amp all those years ago, the older OPA2227 (with it's ultra low-noise and lush, warm sound) was one of the best sounding amplifier chips made by Burr-Brown (Texas Instruments). It still is an easy "go to" choice for many amateur builders.
Today, there are many chips which offer higher levels of detail and clarity with total harmonic distortion levels below 0.01% over the audible spectrum. I now ship my amps with the JRC4556 chip used in the famous Grado RA-1 amp. But I have others you may choose from. I don't stock all of them in bulk however, I do try to stock a few, so I can offer you a choice when you order your amp: OPA2227 (for a warm, lush, bassy sound), or the LM4562 (for overall greater definition and detail) ...or the AD712 for an optimal, blend of warmth and detail across the entire audible spectrum ...or the TLE2082 for sonic clarity and definition.
Several people have asked me which chip is an upgrade over the OPA2227. My answer is that at this level of audio quality, one is not necessarily "better" than another; they ALL sound great.
I recommend the JRC4556 for clarity and solid bass and for demanding headphones. I recommend the AD712 or TLE2082 for those who prefer a more neutral chip. And I recommend the LM4562 for those who crave high frequency detail. Your choice!
Take this as an opportunity for you to play around with the amp and to fine-tune the sound to suit your listening tastes. Ask about ordering additional chips. The choice of which chip sounds better to your ears is best made by you.
High Quality signal-processing resistors and capacitors:
Resistors in the audio path are the highest quality metal film resistors. Resistance of paired (left and right channel) components is hand matched ensuring that the audio signals in the left and right channels are processed identically for balanced output. It takes a bit of extra time to do this, but it's worth it! The polypropylene film box capacitors were chosen specifically for their great audio characteristics (polypropylene box caps are one of the best types to use in audio applications). They protect the amp and your headphones from voltage spikes without interfering with sound quality.
Auto Power ON/OFF:
The Alps volume control pot incorporates a main power control: you can just leave it in the "on" position if you wish as my amp automatically powers up only when it senses you have plugged in your headphones. Or, if you are one who prefers to leave your headphones plugged in all the time, simply use the Alps control as the ON/OFF switch.
Board, Layout and Construction:
A signature hand-finished black custom board is manually assembled to ensure the highest quality construction. It has a slight irridescent cast to it that really looks nice permanently fixed in the case. There are no stray wires flopping around to pick up stray signals or degrade the signal path. Just as Bob Carver used to advertise that his amps were internally wired with Monster Cable, my amps use solid connections linking components for optimal signal transfer and reliability. Manually assembling the amp this way is much more difficult and labor intensive than simply populating a prefabricated printed circuit board. However, it represents a choice to build a solid amp with focus on sound quality rather than speed and ease of assembly.
A few years back, a customer who had bought one of my amps (to replace a broken cmoy made by another builder) asked me to inspect and repair his defective amp. The builder was one of those who claims to use the highest quality printed circuit boards. Inspecting the broken amp, I found solder traces had broken and separated from the board causing the amp to fail. I repaired the amp for the customer, though I believe the customer preferred to continue using my amp.
My circuitry and solder joints are sealed in soft rubbery shock-absorbing plastic. The foam surround is a feature which I originally implemented on the request of G.I.'s deploying to sandy environments in Iraq back in 2004/2005. Although most of you probably don't work in sandstorms, the gasket is still there to keep the amp looking neat and the battery snugly in place.
Gain Customization and Bass Response:
Having an amp tweaked to match your gear can make the difference between hiss/distortion and an enjoyable listening experience. The ultra-low noise characteristics of modern opamps means noise that normally accompanies high gain is not a major issue. However, using too low a gain for your gear means your headphones will sound weak; too high a gain setting and your phones may distort. Dual gain allows the user to select the "fold amplification" which provides the most robust sound and broadest soundstage regardless of impedance or sensitivity ratings.
The control is an easily-accessible jumper on the amp board. This option is useful for those who have a wide variety of headphones but don't want to buy an amp tailored for each. Best of all, having built thousands of these amps for almost every type of head or earphone, I can make any necessary tweaks for your gear or application.
Many customers have asked whether I can include a bass boost feature. The BSG amp offers higher gain than most other cmoys with bass support to match or exceed their performance. This is especially true with the high current mod for users of low impedance headphones. This makes for stronger frequency response and detail across all frequencies including those in the bass range. To demonstrate this, I compared a BSG standard amplifier to one of many competitors offering a BassBoost feature. From the figure at right, one can see that with BassBoost off, the competitor amp signal, overall, is far weaker than that of the BSG amp (compare waveform height in top vs. bottom graph). With BassBoost on (see middle graph), the competitor amp signal improves. However, the amplitude of five introductory "house-vibrating" bass pulses in the test track (labeled A-E) are still greater and maintain their amplitude longer with the standard BSG amp than with the BassBoost competitor. Also note the absolute magnitude of the sustained signal level with the BSG amp is still greater than that of the BassBoost competitor indicating more robust sound (compare the body of the waveforms in section F rather than the transient spikes).
Volume Control:
I selected the Alps (RK0971221Z05) volume control out of dozens of available Alps pots and special ordered it in bulk for Biosciencegeek from Japan. It is a velvety smooth dual channel level control with a solid feel and reliable operation, free of any static.
This model of Alps, generally used in professional audio applications reduces the noise floor of the amplifier, resulting in dead silence when the music isn't playing.
Some customers have expressed concern that the knob may break off in their backpacks. I explain to them that the Alps shaft is a quarter-of-an-inch thick solid metal rod and that they couldn't snap it off even if they tried.
To match the quality of the volume control, I now offer your choice of brush-finished solid aluminum knobs (see ordering section below).
Build Quality:
All parts in this amp are neatly and tightly mounted for reliable and easy operation. The input and output jacks are high quality, well insulated, silver plated locking jacks which are extra snug and hold on tightly to your headphone and input cable plugs. Importantly, the parts on this amp are mounted neatly in perfectly sized, professionally formed openings. No crudely made oversized holes with jagged or sharp edges as I have found on sample purchases of competitor amps. And most importantly, my amps are built to last.
DC Jack
My amps now come with a more universal barrel style DC power jack to enable you to take advantage of a wider variety of commercially available external power sources. For convenience, I have sourced and sell one in a separate listing. The advantage of this adapter is that it allows you to take advantage of the high current design. On the adapter, the amp can drive even demanding headphones with ease where a battery powered amp may reveal distortion. The amp will run on 9-24 volts DC (max allowable voltage is dictated by the chip).
For safety reasons, I do not make my amp rechargeable. With the amp's incredibly long run time, the extra cost and burden on the system created by a recharging module simply did not make sense. Run time on a single high quality 9V battery (alkaline, NiMH, Li) can be 50-100 hours depending on the battery's mAh rating and your headphones (up to 200 hours with battery Option 3).
LED color choices:
Choose your color preference for the power LED. Bright Red, Blue, Amber, White and Green are the available choices. For your information, the brightest LEDs are the blue and white ones. The dimmest is green. All LED's are clear and light up to the specified color. The LED's and their brightness do not significantly affect the current drain or run time on the amp.
How to use this amp:
Plug your headphones into the amp's 3.5mm output jack. Use a standard interconnect cable (see manual for recommendations) to connect your portable player to the amp's input jack. Turn on your source and amp and you are ready to go! Caution: my amp's high gain setting can be a lot higher than most other cmoy gain settings. I'd recommend starting with your player's volume ON LOW. I'm not responsible for hearing damage due to irresponsible use of this amp at high volume levels. PLEASE USE COMMON SENSE WHEN USING THIS AMP!! By buying this amp and using it you agree that you know about hearing safety and take all responsibility for using the amp at listening levels that are safe for your ears.
Customer Feedback
This is a collage pasted together (in no particular order) of what a few of my customers have said about my amps (please excuse their typos). For a more complete view, simply check out my Ebay feedback.
"Best Cmoy on ebay! exelent service! super fast post! very very impressed! thanx" ---Buyer Marchandd123
"Listening to your little amp from the line out on my Denon DCP-30 portable with AKG-701 cans. To my ears it beats my headroom micro with upgrade, the C&C box+, and the iBasso T1. Better on vocals, better on strings, better on bass depth and accuracy, imaging, everything! I would never have believed before buying this amp this it was going to be such a giant killer!" ---buyer orcaaudio (email)
"My Westones are living in rapturous bliss! What a fantastic amp!"---buyer illumineering
"Hey how you doing? got my amp today and I am blown away! I've got a premium Cmoy from 'Juice' which is good, I've got a C&C Box+ which is really good but let me tell you your amp is more involving, warm yet detailed than either. I've only tried my SE530's so far but will be trying the 595's later. This is a superb amp & one day my friend you will be a household name! Many Thanks Nigel"---buyer nigel-hayley (ebay message)
How to design and order your amplifier
Note: the $49.99 amp price is a flat rate that includes your choices below. You will need to buy batteries, cables and, if desired, a wall wart power adapter (see my other listings for DC adapter and audio cables or message me for information).
Available Accessories in my other auctions:
What happens next? As soon as I receive your customization requests, I will begin building your amp. Build time is usually 3 working days. You will receive an automated email from Paypal or Ebay when I ship. Feel free to contact me at any time for updates.
I service and support my amps, so contact me if you need help.
Sales tax charged by Ebay to CA residents only.
Shipping Costs:
Standard Domestic (USA, ~5days): $2.95
Economy Worldwide Flat Rate (2wks or more): $9.95
Priority Standard Worldwide Flat Rate (6-10 days): $24.95 (more reliable for international shipments)
Apologies, but the USPS is going bankrupt and is charging heavy international rates these days. My shipping charges are just the cost of postage. Delivery times are estimates. Customs can delay international shipments. Please note: Italy, Spain, Malaysia, and Canada are notorious for delaying packages for long times in Customs. Please keep this in mind when ordering from those countries.
