CMoy Headphone Amp Review

Do you listen to your audio player through your car’s stereo? Then I would wager that you have probably run into the same problem with volume levels that I have. Quite often, in order to hear the music, I will have to turn the volume on the player all the way to maximum and then do the same with the car stereo. This in itself isn’t the real issue though… The problem is that after I disconnect my player from the car’s stereo, I’ll almost always forget that I left the volume turned to the max. Then later when I go to listen to the car stereo or player, I’ll be blasted with extremely loud music that makes me jump out of my skin. This happened to me three times last week, so I went looking for a solution and learned about CMoy headphone amps.

According to Wikipedia, the CMoy headphone amp was originally invented by Chu Moy. He created a simple design that can be powered by a 9V battery and stuffed inside a small container like an Altoids tin, making it a popular DIY project. Since I didn’t want to make the the time to order the parts, and build one myself, I did a quick search on eBay and found quite a few entrepreneurs selling their handmade CMoy amps.

CMoy headphone amp

I settled on one from a seller named Biosciencegeek because he offered customization options that the other sellers did not. I liked being able to pick the LED color, knob style and tin type. I went with a plain tin so that I can decorate it myself later.

CMoy headphone amp

The left side of the amp has a power status LED and a 3.5mm DC in jack. The amp is powered by one 9V battery that can run for 20+ hours. You can use rechargeables, or you can get an AC adapter that can supply 9-15 volts.

CMoy headphone amp

On the opposite side there is a line level input 3.5mm jack that is attenuated for strong signal sources.

CMoy headphone amp

On the top edge, you’ll find the audio jacks for input and output, as well as the volume knob. This knob doubles as the master power switch.

As you can see from these images, the installation of the various jacks looks really professional. They are even labeled for easy identification. I was very impressed with the workmanship.

CMoy headphone amp

Opening the lid of the tin will let you see the actual circuit of the CMoy amplifier. Everything is neat and tidy, with silicon around contact points and foam padding around the sides. The amplifier chip is socketed so that you can replace it if needed.

To use this amp with your audio player, you plug your headphones into the output jack and plug a 3.5mm patch cable from the input jack on the amp into headphone jack of your audio player. Unfortunately, you’ll have to supply your own patch cord as one is not included.

CMoy headphone amp

These headphone amps were designed to be used with headphones, but I’ve been using mine to boost the output of my Slacker Portable Radio with my car stereo and even with my Audioengine A5 speakers. Now I don’t have to turn up the volume on the player and car stereo or A5 speakers anymore than I normally would. If I need the audio to be a bit louder, I just turn the knob on the amp. I’ve found that the CMoy doesn’t just boost the sound, it makes the audio sound crisper and more colorful.

One of the nicer features of this particular amp (not sure if other amps do this too…) is that it will automatically power down if you turn it off using the volume knob, or when you disconnect the headphones from the jack on the amp. It also won’t power on unless you have headphones connected to it. Nice!

This amp was priced at $49.99 which was a little pricier than other sellers, but I’m very happy with my purchase and can recommend CMoy amps (at least the ones that Biosciencegeek builds). Now I need to figure out how I want to decorate this thing :o)

 

Product Information

Price:49.99
Pros:
  • Boosts the volume of audio players
  • Improves audio quality
  • Easy to use
  • Auto power off
Cons:
  • A patch cable to connect audio player to amp is not included
Posted in: Audio, Video, TV Gear

12 comments… add one

  • Eric July 20, 2008, 10:07 am

    Thanks for the review. I’ve considered building a CMoy and this pretty much seals the deal.

    If you are looking for decorating ideas, try Mod Podge and some magazine pages or photos.

    It goes on like white glue, but dries to a water resistant seal. The tins make less noise when they bang into things.

    Some finished projects here:

    (http://www.ericsprojects.com/cpg/displayimage.php?album=12&pos=12)

    1
  • Julie July 20, 2008, 10:37 am

    Eric:

    Thanks for the tip on Mod Podge. I think I’ll probably use stickers, but then put a coat of the Mod Podge over it to keep them stuck down for good :o)

    2
  • Tyler Puckett July 24, 2008, 11:37 am

    Wow, is it just me or does the Mod Podge logo remind you of the Price is Right? “And to the winner of this Os-Cal goes a years’ supply of Mod Podge decoupage and glue! Use as directed.”

    3
  • Julie July 24, 2008, 11:58 am

    Tyler:

    Hahahahah ;o)

    4
  • Leo Boivin July 27, 2008, 3:47 pm

    Based on this review I ordered one from Biosciencegeek on eBay. Right after the article ran there were none listed as available, but within a couple days the auction was back up.

    The order was easy, fast e-mail response, and it arrived much quicker than I anticipated. I ordered a similar model to the one Julie reviewed.

    I wanted to use it from my mp3 player (Sansa e280) to boost the signal to the AUX jack on my car stereo head. Some podcasts and mp3 files pulled off YouTube on the Sansa do not play very loudly on the stereo, even with both volume controls cranked up.

    Works great. I also think it improves the sound quality.

    5
  • Julie July 27, 2008, 4:59 pm

    Leo:

    Glad you also like yours! :o)

    6
  • William Perez May 17, 2009, 11:49 pm

    I bought a CMOYfrom bioscience geek three years ago and I have not been disspointed. I even replaced the opamp chips..never had a problem.

    You will not be dissapointed.

    7
  • Hayden November 17, 2009, 9:44 am

    Thanks Gadgeteer for the excellent review! I am planning to make my own CMOY amp! May I just ask, what MP3 player is that in the photo? Thanks!

    8
  • Julie November 17, 2009, 10:45 am

    @Hayden That was the first version of the Slacker Radio: http://the-gadgeteer.com/2008/07/11/slacker_portable_radio/

    9
  • Bob De Angelis September 5, 2011, 6:50 pm

    I have a Fiio E5 for my Waqlkman but I am thinking of buying the CMOY for my home stereo system. I only need bass boost for my JVC HA DXi headpnones no problem with volume. Does anyone know or could venture an educated guess as to db bass boost on the cmoy? Thanks.

    10
  • Petes August 26, 2013, 7:03 pm

    What is the circuit for using a 9v battery and dc-in 15v at the same time without making the battery blow up?

    11
  • Petes September 3, 2013, 12:26 am

    Figured it out, the coaxial input comes with a switch incorporated, that’s what the third pin is for. Just in case someone is interested too.

    12

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