Amp Camp Pre+Headphone Amp - ACP+

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Here's the case I put together. Made some dumb mistakes (like making the power switch hole in the wrong place so I had to make it again), and there's a bunch more tweaks I want to do (I replaced the input caps (again) with Nichocon caps which are even better (though the difference is small), but now I'm going to move back to the power supply, which was delayed because I accidentally blew up the transformer and had to buy another one. However, I have it all set and the case drilled and so it should be ready soon.
 
Revised as suggested by Dennis.

I was editing post #324 and I ran out of time. So this is part of post #324.
Hi, I have built the ACP+ incorporating additional DPDT switch into the chassis as shown in the photos attched as I am planning of having a selectable high/low impedance switch while not affecting the line out net Rout value.

I have drafted out the wiring diagram as shown in the attached for your reference. Does it looks correct?

Wil
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Just wanted to do a follow up post that adding the dpdt (on-on) switch as per my earlier wiring diagram doesn’t really work the way i wanted it to be.

Switching to low R actually added all the resistors in series together at the line out to ground. No problem switching to high R so I’ll just leave it as it is until i find another switching solution to do that.

Reason to do this mod is that both my HD600/650 are 300ohm. The bass will sound boomy when cranked up on the original 32ohm output. This mod result in a more articulated bass.

I compared the modded ACP+ to my other opt tube amp and i can confirm that they are quite close in terms of sound quality. The ACP+ is definitely more clean and accurate. Both have the transparency that works very well with the Sennheiser.

I would like to thanks Nelson Pass and the community for creating this opportunity for me to experience building this wonderful HPA. Oh ya and it did paired very well with my bridged ACA on my desktop setup.
 

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