FS: Ugly PPA v1.1 *price reduced*
Sep 8, 2009 at 5:31 PM Thread Starter Post #1 of 5

Sycraft

100+ Head-Fier
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Jul 6, 2004
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Since it is a really ugly amp, I'll knock some off the price. $190 now.

This is a PPA I built for myself some time ago. It is not pretty, at least not by most standards. I like looking at the circuit so I put it in a box with no top. However, it is a properly built PPA and works well, I just don't use headphones anymore at home.

It is based on the 1.1 design so no discreet output stage. You could put diamond buffers on it, as the buffers are socketed, but I've not done so. Has OPA637APs on the left and right channels, an OPA627AP on the ground channel, all socketed. 4 5002 buffers per channel. Caps are Elna Cerafine. Resistors are all Vishay Dale 1% or better. It does NOT have a bass boost. Only component left out was C3, since the ones I ordered were the wrong size, however it is stable without them so no need.

Currently the amp has a gain of 10, so it is designed for high impedance phones (I used it with Sennheisers). If you have low impedance phones, you might find it necessary to adjust the gain, which would require replacing resistors (not socketed). I've biased all the channels in to class A, and the resistors are vairable so you can increase or decrease the bias as you like.

Low DC offset, less than 3mV across any channel combination last time I measured it (I'll take a new measurement if you like). No oscillation I can see on a scope. FR is flat from DC out to 1.5MHz.

Comes with a 24v Elpac PSU.

Asking $190 OBO

ppa1.jpg


ppa2.jpg


ppa3.jpg


NO DOA Guarantee: I will guarantee that if you buy this, it'll get to you working. It'll power up, and amplify sound. If it doesn't, ship it back within 10 days and I'll give you your money back. However I make no specific performance guarantees. I will not refund your money if it works, but doesn't sound how you want.
 

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