Being a music nerd – I bought some sweet headphones about a year ago – Beyerdynamic DT770 Pro’s. Unfortunately I was borderline underpowering them, and within a few months what started as light buzzing in the left ear got so bad they were unlistenable. When the warranty check came I decided to get a pair of Sennheiser HD280’s (I’ll pay to get the DT770’s repaired). To avoid underpowering and wrecking these too, I decided to either buy or make a headphone amp. I wasn’t happy with what I was seeing to buy, and I just knew that in order to get something that would do what I wanted – I’d be spending at least $200-300, which I just can’t justify right now.
So I decided to rock the DIY ethic and build a CMoy amp – using the instructions on Tangentsoft’s Audiologica DIY Audio page, found here: http://tangentsoft.net/audio/cmoy-tutorial/. He lays out a comprehensive parts list, schematics, wiring diagrams, and lays out tweaks to make it your own. I opted to use bigger \ higher quality capacitors on both the power (470 uf vs 220) and audio circuits (.47 uf vs. 1) – since I tend to listen to a decent amount of hip hop, and rock that has a decent amount of bass \ deep drum hits that can tax smaller capacitors. I upgraded the OPAMP from the Burr Brown OPA2132PA to the OPA2227PA – to avoid the tubby lower-end while keeping the flaw friendly chip design. (I bought both just in case – but the 227 is a worthwhile upgrade) I also decided to run the amp at 18v rather than a single 9v. The bigger caps and 2x 9v batteries meant I couldn’t stuff the thing in an altoids tin – but I probably won’t be using this on the go too often.
Wiring took two nights, followed by a frustrating search for a proper enclosure. I wanted to go as small as I possibly could, but finding something that would fit everything without being the size of a shoebox ended up being next to impossible – at least without waiting for something to ship. I opted to go with two cases from Radioshack – drilling out the circuit board stand-offs, insulating the board and hot-gluing it to the bottom of the larger case. I re-wired things down to assembly size, but just as I was about to seal up the bottom compartment – the main power wire broke (sonofa!). I soldered that lead to the LED lead (overheating that and burning it out in the process), but at least had a working power circuit again.
After that fiasco I got everything back together, finished up the top half, and everything works! The amp sounds fantastic – with almost no noise (which considering its basically running at full power – with volume control at the source, due to not being able to find a proper volume control pot – not bad). The headphone connections got a little bit loose after desoldering and resoldering the connections, and I neglected to testfit the powerswitch with the headphone out jack in place, and had to move it. Lessons Lessons.
At some point I’ll replace the headphone jacks, fix the power led, fix the main power lead to the circuit board, and hopefully find a better sized enclosure. For now, I’m really happy with the outcome – This is the best my music has sounded in a while. I’d definitely recommend giving this project a go if you need a headphone amp, don’t want to pay a ton, and are at least semi comfortable with DIY wiring projects.
