The META42 Headphone Amplifier
The META42 was the first headphone amplifier I built on a pre-made PCB. I remember following the design phase on head-fi with great interest through the spring of 2002 and when version 2 of the amplifier PCB came out I just had to order a few PCB's and try it for myself. It was the first time I bought something from the US via the internet so I was a bit nervous but everything worked out fine. I sometimes think of all the money I could have saved if that first experience had scared me away rather than lure me in ;-)
The Hammond enclosure is quite "bog-standard" as far as headphone amps go, but still looks good if you ask me :-)
Space on the front panel is a little tight, but there's always room for an LED...
...especially if it's blue and bright ;-)
Nothing fancy back here, just RCA inputs, an isolated DC-socket and a power switch.
Picture of the inside. Note the AD8620-opamp on its adapter (from Browndog) and the brass coupling for the shaft extension on the potentiometer.
A little more detail of the insides. The input caps in the center are 0,33 uF Wima MKP's. The gain resistors are socketed because this was my "lab-amp" or quite a long time. I used it for testing and trouble shooting other audio equipment and for comparing opamps etc. It was only recently I finally took the time to complete it and put it in a proper enclosure.
When I first built this amp, I didn't really think it would be that much better than my previous build, the miniamp, but I was pleasantly surprised. If it hadn't been for this amp I probably would have sold my AKG K501 headphones because this was actually the first time I heard them at anything approaching their full potential. It was also the first time I heard the differences between different opamps (which scared me at first - you're not supposed to hear these things :-)). This is one amp I'll always keep :-)
©Uffe Nisbeth 2002-2004 Last update: Sept. 28, 2004