The amp is finally "complete". Just have to add one more ceramic in the regulator board when the order gets here, but it isn't required for operation. This baby started singing a little while ago. Driven from the y2 and going into the K1000's
Front:
Back:
Inside:
Another angle:
Case is from eBay, I engraved the panels in my DIY CNC machine so this was quite cheap to do (although a massive PITA). Transformer is a 50VA 2x15VAC (series connected) AntekInc toroid, with a steel case. The IEC module includes the switch + fuse + line filter inside of it. A ToliRegV3 regulator (obviously
) set to 30VDC with a current limit of 1.5A. There is an amplified zener set to 35V as a protection in case something goes wrong with the supply voltage. There's a ground loop breaker bolted to the case, I went for the one with the diode bridge mainly because its easier to mount
M3 with 2.5" high heatsinks set to 140mA bias, OPA627 for all 3 channels. Gain is set to 5, a compromise between driving the K1000 to sufficient volume and using it with my other headphones. I was pleased to see that with this gain I get sufficient listening volume with the K1000's even when playing a quite recording from my Sansa Fuse player (used it for testing since it has a low output level). When using the y2 I'm mostly around the 1-2 o'clock position.
e12 mounted on the center aluminum plate I've added to the case. It was slightly too sensitive when playing music with lots of bass at high volume levels, so I've replaced R5-R8 with 33K to lower the gain at low frequencies.
Since all the input wires are shielded, and the transformer (which is itself a shielded transformer) is placed inside a steel case, there's no hum. Plugged in a pair of PX100 and rotated the volume knob from minimum to maximum position, no hum/noise anywhere.