Quote:
Originally Posted by
Willakan 
The O2 isn't meant to be silent on power on - there's a small and certainly audible turn-on transient, but nothing even close to headphone damaging. If it is particularly loud, it's kinda difficult to diagnose assuming that you are using non-stock opamps and the like - the DC transients they produce on power-on were measured as part of the regimen of tests run on the chosen opamps to determine their suitability for the amplifier.
Personally, I prefer it to be silent on power on, if I can figure out why it isn't silent on power on why not fix it? The issue for me is that it was silent on power on until I added the off board jack. So the goal is to return it to how it was, swapping out the voltage regulator solved that issue for the time being. We'll see what happens when I get my next (and final O2 related) parts shipment from Mouser, which includes as few fixer parts for my current O2 (v-reg, other op amps), and parts for my second O2, which will be like a "gold edition" with upgraded parts. Total parts cost for the "gold edition" is about $55 vs $32 for the stock O2. In almost all cases it was possible to spend only a few more cents per part for objectively better specs.
I'll set up my measurement mic and test the FR of both amps driving HD448's and HD650's of course.
Edited by cheapskateaudio - 11/14/11 at 12:44am
