Welcome
In this auction, I am offering an optimized, feature-packed headphone amplifier, improved as of June 2011 (see power specs section below). This amp is hand-built to order by me, a Ph.D.-level scientist, in the U.S.A. My amp is not a standard cMoy, but contains several upgrades and enhancements including a new circuit layout, premium components, and many performance and convenience features that I've incorporated over the years. My current amps bear little resemblance to those first ones I sold 3000 amps ago.

I have always focused my attention and resources on optimizing sound quality. I don't add unnecessary parts or superfluous circuitry that may impede a neutral, clean, crisp response across the entire audible frequency range. I don't try to artificially enhance any particular frequency band.

And because I personally build your amp when you order it (2-3 day build time), you can communicate with the builder, ask questions and have your amp tuned to suit the impedance and performance characteristics of your headphones. I also provide impeccable support down the road no matter how long ago you bought your amp from me. All of the above are now, and have always been, standard features of the service I provide.
 
Many others have 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.   However, I was the first to offer customized tuning for headphone impedance and I still offer dual gain and a wide range of other complimentary features and user-selectable options, all supported unconditionally by personal customer service. I realize there are many other quality amps available to you, and I appreciate your taking the time to review mine. My amps may not be the cheapest, but that's the point.
 
UPDATES:.

  • An independent technology review organization inspected and reviewed my amp back in July09 and now another site did so on July 15th ! I didn't know I had sold an amp to a reviewer nor did they inform me of their article (another customer saw it and informed me of it ). These are great reviews on techy sites. They don't sell anything there; they just review cool new hardware that catches their eyes. If you are interested in reading an unsolicited third party's opinion of my amp in this auction (including great pictures of the rectangular silver tin version with the crosshatched knob), you can see it at:  


 http://the-gadgeteer.com/review/cmoy_headphone_amp

and now a second review at

http://gadgetsteria.com/2010/07/15/review-cmoy-headphone-amp-by-biosciencegeek/

A recent customer has also reviewed my amp on the headfi forums here:


Why do you need a headphone amp? Because most portable devices (even fruit-branded ones costing $399) have weak internal amplifiers which sound only 'ok' with demanding (high impedance) audiophile headphones and earphones. You need amplification to get your phones to reveal the most detail in your music and to experience effortless, robust sound. Tell me what headphones you use so I may adjust the amp to suit them.

Who buys my amps? My amps are aimed at the user who needs to boost weak output from an MP3 player, computer, laptop, or CD player. Like me, they generally own one or more pairs of high quality or high end headphones or earphones and need a versatile yet inexpensive amp that can handle them all with ease.  I originally designed and optimized this amp to work well with my 32 ohm Grado SR225's and 300 ohm Sennheiser HD-600's. My customers have reported favorable results with their 600 ohm Beyerdynamics and AKG's as well.   Surprisingly, after I posted this information, a number of ebay ads now 'coincidentally' quote this exact range of impedances and headphones in their amp specs.  the reality is that most well-built cMoy amps will work with a wide range of phones if properly designed and optimized. In addition to robust circuitry and careful component choices, I make this range possible by including dual gain as a standard feature. This means my amp is capable of supporting both low and high impedances as well as low and high sensitivity head and ear phones.  



The specialized features bundled into this amp give you broad flexibility to:
  • boost the output of your computer or laptop (a fine input volume control on the amp is essential as computer software controls are relatively crude and can overload any headphone amp's input)
  • amplify and regulate a line-level signal ( from an ipod docking port connection or line-out on a portable).  Tell me if this is something you plan on doing.
  • use the amp with a variety of head and earphones each of which has very different impedance, sensitivity and performance characteristics thanks to the unique dual gain control in my amp.
  • regulate volume right on the amp.
  • use the same amp with a wide variety of headphones.
  • power your amp using batteries or a DC adapter (I provide the DC jack on your amp and you purchase your own wall wart).




What sets my amps apart from the rest?
  • The OPA2227 OpAmp chip which comes standard with my amp is a significant upgrade over the more commonplace OPA2134. Additionally, my amp is qualified and tested to be stable and robust enough to accept a number of other highly regarded OpAmp chips, offering a range of audio characteristics from lush and warm to bright and detailed. See below or ask about them if you're interested in experimenting.
  • The OpAmp is installed in a gold-plated 8-pin DIP socket making it easy to replace.
  • Auto power on: My amp powers up automatically when you plug in headphones. No cheap toggle, slide or scratchy dial switch to accidentally get flipped on or break.
  • Your amp is hand-built to order and will be optimized (for gain and hiss reduction) to suit YOUR phones
  • You get to "build your own amp" by having it optimized for your gear and by selecting the case, LED color, and knob style of your amp.
  • All my amps come with a satisfaction or return guarantee. I am always there to answer questions and offer support even years after the purchase.
  • Please note: I do not offer options for graphic equalization or mechanisms to artifically distort specific frequencies (ex. bass enhancement). While these features have their place, I have found the majority of customers are more interested in purity of sound and place more value on faithful, accurate sound reproduction rather than distortion or manipulation. My amps are desiged to reproduce sound as accurately as possible. And if you really want powerful sound (at all frequencies), this amp will do just that.
Standard Features
Case:
Choice of tin. I often have a limited selection of alternate tins available at no extra charge. Altoids has discontinued their round sours tins, however, please ask if you have an interest in something different, as I just might have it.  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 using electron microscopy-grade Helvetica lettering. A  solid aluminum knob completes the high quality finish. I currently have either a brush-finished knob with dual rubber O-rings or a knob with a crosshatch textured barrel surface. You can choose which one you prefer on your amp (see pics below). The default selection will be the one with dual O-rings.

Power supply:
Power supply includes a high grade, audio-qualified Nichicon HE grade capacitor, in a larger capacitance than used by most others.  The HE is a low noise, high speed model that provides more than generous power reserves for superb, solid, fast response during demanding musical passages.  I have just upgraded this component as of June 2011 with a larger unit which provides more impactful sound (see pic at right of the old cap and the new one to its right).  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 using your DC adapter and the free DC jack I provide on the side of the amp. The new power supply will handle over 20VDC input, more than what most chips can use. The default OPA2227 can be driven up to 15VDC. This is like having 2 amps in one: a 9V portable plus a high powered desktop unit for when you want maximum performance.
 
To provide long battery life and stable amplifier performance, the power subsystem uses a high performance TLE2426 voltage rail splitter which precisely balances and buffers the supply voltage. Lesser amps use a standard resistor divider, often without resistance-matched components resulting in slightly imbalanced power channels.


The OpAmp(s):
The OPA2227 is one of the best sounding amplifier chips made by Burr-Brown (Texas Instruments). It is a dual channel, ultra low-noise amplifier with a lush, rich, warm but detailed sound; much higher quality and more refined-sounding  than second-tier chips like the LM386 and others found in cheaper or more basic amps. The OPA2227 is positioned as one of the BEST-sounding amplifier chips for a battery-powered headphone amplifier. From the graph you can see that the total harmonic distortion on this chip, at maximum, barely reaches 0.002% over the entire audible spectrum. (anything less than 0.1% is great by audiophile standards). This is what Burr-Brown has to say about the OPA227 series amps:
"The OPA227 and OPA228 series op amps are ideal for professional audio equipment.....ideal for portable applications requiring high precision." - Burr-Brown datasheet for OPA2227

The OpAmp chip is the heart of most headphone amplifiers, and changing it can significantly alter the personality or sonic characteristics of your amp. I consider the lush and warm-sounding 2227 to be my personal favorite (as do many other amp sellers). However, tastes vary.  There are a number of other highly regarded amplifier chips discussed on Headfi.org. I supply the 2227 as standard with this amp and can't make substitutions in this auction due to cost. However, I do have other chips (shown in the picture to the right).  

 

I have ranked them with regard to their audio characteristics. Several people have asked me which chip is an upgrade over the 2227. My answer is that  at this level of audio quality, they ALL sound great. This is really just an opportunity for you to play around with the amp and to fine-tune the sound to suit your listening tastes. The choice of which chip sounds better to your ears has to be made by you, but  for those who wish to invest in a second chip, the AD823 offers the most "change" from the 2227. It's very similar to and perhaps even cleaner than the popular LM4562.  For a more complete treatment of these chips, please refer to the chip manufacturers or check out the online forums like Headfi.org. I will defer to the wisdom and experience of those who post there and will not go into a detailed description of each chip here.


High Quality signal-processing resistors and capacitors:
Resistors in the audio path are the highest quality 1/4 watt 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. Interestingly, a few newcomers to the amp building world are now seeing the advantage of taking the extra time to do this too! 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). Their high value protects the amp from voltage spikes while providing solid bass and clear, detailed high frequencies. This amp sounds GREAT!


Auto Power ON/OFF:
NO ugly and inconvenient toggle switch to accidentally get turned on in your bag or break off. No cheap combo volume/switch. The high quality Alps control contains a main power switch. However, you can just leave it in the "on" position if you wish as my amp automatically powers up when you plug in your headphones and turns off when you remove them. This elegant and convenient solution offers safety as well since  you don't have to worry about a power switch accidentally turning on and running down the amp's batteries. If you are one who prefers to leave your phones plugged in all the time, simply use the Alps control as the main power cutoff.


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 purple 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. Solid point-to-point wire joints (NOT the micron-thin traces used on mass-produced cheap commercial printed circuit boards) connect components for optimal signal transfer and reliability. Although it would have been easier for me to just have some inexpensive PCB's made (yes, I did experiment with that at one point; I'm a scientist :), my experience has shown those boards' reliability and conductivity are no match for hand-built quality. I was recently asked by a customer to inspect and repair a PCB amp built by a competitor and can say with total certainty that I vastly prefer the quality of my design and construction methods (and so do my customers). My circuitry and solder joints are sealed in soft rubbery plastic. A foam surround keeps everything snug, so it'll survive being tossed around when you're on the go. This is another feature which I implemented specifically for G.I.'s deploying to sandy environments in Iraq back in 2004/2005. A few of those early customers requested some sort of gasket to keep out sand, and the foam surround was born. Now, I've reduced its height as most of you don't work in sandstorms ;) and use it to keep the amp looking neat and the battery snugly in place. 


Gain Customization:
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 the OPA2227 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 user to boost "fold amplification" to obtain the most robust sound and broadest soundstage from high-impedance or difficult-to-drive headphones and then to drop gain down to accommodate high-sensitivity earphones. 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, with my amps, when you let me know what types of phones you'll be using, I can set up the dual gain feature of this amp to provide you with two gain settings suitable for your range of gear or applications.




Volume Control:
This amp features an expensive, velvety-smooth, quiet-operating, and tank-solid sealed ALPS volume control. This high quality control, generally used in professional  audio applications, represents a significant upgrade over cheaper variable potentiometers offered in some cmoy amps. Please note, this is a PROFESSIONAL GRADE unit, not a cheap control. I have tried many brands of volume controls in my test amps over the years, and found that many commonly available pots provide non-gradual volume regulation, audible static or at the very least, color the audio signal. This ALPS pot which I special order from the manufacturer does not suffer from any of these issues. To match the quality of the volume control, I now offer your choice of brush-finished solid aluminum knobs (see below).
 
A quality volume control is a convenience for those who may want a volume regulator on their amp as well as on their portable player. It is essential for those who intend using the amp with a "line-out" source signal (you can't control the volume from your player) or for those whose source is a desktop PC sound card (Windows' volume control puts too much signal out to the amp and it needs to be attenuated). Please note that placement of the volume control on your amp will depend on your amp configuration and the case and may vary from unit to unit.


Quality Jacks:
Even the input and output jacks are high quality, well insulated, silver plated locking jacks. They are extra snug and hold onto your phones and input cable plugs to avoid accidental unplugging. They are neatly and cleanly mounted in perfectly sized and professionally formed openings; not sharp-edged drilled or punched out holes (see pics to the right); This neat finish is yet another unique feature which my customers have told me set my amps apart from the others (besides the sound quality! :)


DC Jack:
I put in a standard 3.5mm jack for accepting an external power source and provide info on the type of power adapter you need. I do not provide the actual AC power brick, but the amp manual (last pic below) contains information on what you need and where you can buy one for $10-20. Basically you need a regulated, non-switching wall adapter with a 1/8" (or 3.5mm) power plug (same as the mini headphone plug) that can supply anything between 9-20 volts DC (max input voltage  is determined by the chip. The installed opa2227 has a max of 15vdc). You can see an example adapter and catalog number in the picture of the manual (see auction pics).


LED color choices:
Choose your color preference for the power LED. Bright Red, Blue, Amber, White and Green are the available choices.  All LED's are clear and light up to the specified color.

Additionally: Free 9V battery supplied
Foam case surround/seal
No stray wires
And all wiring contact points are sealed in rubbery shock-resisting insulating plastic


Simple to Use:
Plug your headphones into the amp's 3.5mm output jack, connect your portable player to the input jack and go! The amp can make your music sound tight and defined as if you had your headphones plugged into a high powered home stereo system. And that's the whole point of a headphone amp! 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.

Additional information?
See the Amp Manual in the last picture in the auction for more info on the DC adapter you might want to get, the cables, etc.


Reviews
80 characters aren't enough to describe what a great purchase this is! THANKS!!!
Buyer glass_kisser

Great little amp (my 2nd), better than other such amps, fast shipping, best A+
Buyer opalguy3

Genius!Highest quality engineering!gr8 service v helpful Recommend 2 all Thanks
Buyer Pinkez75

Quick service, excellent product. Amp drives HD600s excellently and sounds great
Buyer Jonny5ive

Best Cmoy on ebay! exelent service! super fast post! very very impressed! thanx
Buyer Marchandd123

This amp is amazing. It was a night and day difference on my Sennheiser HD 555s

Buyer illusionsz27

"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)

 


Help with ordering and shipping






Next, sit back and wait for your amp to arrive :)

Build time is usually about 3 days. I ship right after I build.


Sales Tax: I am a registered business in the state of California. 7.5% sales tax will be collected from California residents (determined by your Paypal or shipping address).


Shipping Information:

U.S. Domestic: $6.95 for U.S. First Class service (3-5 days)


International Shipping: Priority International Airmail:  $13.95  (about 6 days + any customs delay at your end)




Thanks, BSG.

 

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