CMoy Based Portable Headphone Amplifier
I am in the extremely privileged position to have access to a high quality studio with an SSL desk and monitoring provided by Meyer and Klein & Hummel. Because of this, I’ve not really needed top notch monitors at home, and instead listen to music on a decent hi-fi system. My room acoustics aren’t great either, and as I do a lot of editing work with my laptop I use a pair of Sennheiser HD 600 headphones which are able to provide quality and resolution equivalent to some pretty decent studio monitors. But the Senneheisers (as do all other top end headphones) have one major requirement, and that’s a good headphone amplifier. Unfortunately, headphone amps tend to be rather expensive. Hi-fi headphone amps start at around £200, and one of the best pro headphone amps around, the Grace Design m902, will set you back £1000. Admittedly, it is bundled with an excellent DA converter, but that’s rather overkill if all you want is a good headphone amp. To solve this problem, enter the CMoy headphone amp. This hobbyist project which is sold by a number of sellers on eBay and promises good, high quality, loud headphone amplification on a budget.
The Home Made Touch
The basic design for this amplifier was devised by Chu Moy (original schematics), and has been built, tweaked and sold on by a number of eBay sellers, mostly in the USA. The amplifier I’ve purchased is from the seller juice2214, whose amplifier is reasonably similar to the original design with a few enhancements. Instead of the original Burr Brown OPA134, mine has a Burr Brown OPA2227 and the capacitors have been beefed up in the hope of better bass response. It also includes a Panasonic 10k potentiometer for volume control.
The unit itself is built on a protoboard and fits nicely inside a penguin peppermints tin. We don’t seem to have these tins over in the UK (or if we do, they’ve passed me by), but it makes a cute and slightly quirky case for the CMoy amp. It’s also small and light, so very practical for taking around with my laptop. You may also be interested to know that penguin peppermints are both sugar and fat free, and contain just 5 calories!
External layout is simple enough. One side contains the input and output on 3.5mm jacks and a volume knob with a nice smooth action. The front holds a blue power LED and little toggle on/off switch. It would have been nice if the input/output jacks were labelled, but it shouldn’t be hard to remember which is which. On the whole, the device feels pretty decent and although you wouldn’t want to play football with it, this device should survive pretty well if looked after.
In use, this headphone amp serves a pleasant surprise. The sound is clean and loud, and a definite upgrade on the headphone amplifiers built into most audio equipment. The tracking on the pot is pretty good (better than I expected given the price of the potentiometer) and at reasonable listening levels noise is very low. Obviously this is not the greatest headphone amplifier ever conceived by man, it was never going to be. But at the price this is a lot better than it should be. Taking advantage of a favourable $-£ exchange rate, this cost me just £17 (ish), and for that amount this is top draw. If you spend any time at all listening to headphones this is by far the most cost effective to upgrade your listening.
Pimp My Headphone Amp
The unit I bought is reasonably straightforward but some eBay sellers have added a number of modifications and enhancements to the basic CMoy design. Features such as AC adaptor inputs, automatic switch-off when headphones are unplugged, better Opamps, printed circuitboards and various methods for boosting the bass level are available. One seller who provides such amps is biosciencegeek and at some point I hope to test out one of his enhanced amps as well.
Pros
- Better quality headphone output than you would find on most audio equipment
- Very compact
- Battery powered
- Quirky casing
Cons
- None at this price!
Summary
A cheap way to improve the headphone output on your audio equipment
