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Old 15th September 2011, 04:13 PM   #381
agdr is offline agdr  United States
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Ah - they may have sold it. It never occurred to me that either Mouser or Digikey would be making some "house brand" parts of their own, although it makes biz sense.
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Old 15th September 2011, 06:19 PM   #382
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Here's a shot of the final PCB in all its revised glory:

Click the image to open in full size.
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Old 15th September 2011, 06:26 PM   #383
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Looks nice. I wonder if desktop version would have some benefits from larger PCB, that looks really packed
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Old 15th September 2011, 07:01 PM   #384
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@Spacehead the O2 measurements speak for themselves. While I agree the PC board layout is cramped and less than optimal, I worked really hard to make it still perform well.

The desktop version will have a better layout and I expect it to measure even better in at least a few areas. But both amps are well beyond the point of diminishing returns in terms of performance. So, short of more the more optimal gain structure and perhaps a few other minor things, it's not likely the desktop amp will sound better than the O2. But it will be a more optimal design and should provide some additional "piece of mind" for audiophiles who want more than just great measurements.
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Old 15th September 2011, 07:50 PM   #385
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Quote:
Originally Posted by RocketScientist View Post
@Spacehead the O2 measurements speak for themselves. While I agree the PC board layout is cramped and less than optimal, I worked really hard to make it still perform well.

The desktop version will have a better layout and I expect it to measure even better in at least a few areas. But both amps are well beyond the point of diminishing returns in terms of performance. So, short of more the more optimal gain structure and perhaps a few other minor things, it's not likely the desktop amp will sound better than the O2. But it will be a more optimal design and should provide some additional "piece of mind" for audiophiles who want more than just great measurements.
Yeah, I look forward to listening to it. I have only Superlux HD668B but they have been praised everywhere. It is very good to have all connectors and switches on the PC board, I guess you will try to achieve that also in desktop version. I think you need to change the load sharing resistors in desktop version, or how much the power dissipation would be at max level , with 15V rails?
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Old 15th September 2011, 08:01 PM   #386
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@Spacehead, despite concerns raised about obsolete 600 ohm K240 headphones, I still believe 12 volt rails, and 7+ Vrms of output, is all 99% of us need. So I'm not planning on 15 volt default rails for the desktop amp. The load sharing resistors can safely stay at 1 ohm for a 0.5 ohm output impedance. I've run an O2 on AC power, pushed to clipping into a worst case 15 ohms with typically heavily compressed pop music, for hours and the 4556's were still within their max temp limits.

If someone into serious hearing damage, or with really unusual headphones, really needs more than 7 Vrms they can either modify the amp at their own risk, or simply use a different amp.
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Old 15th September 2011, 08:36 PM   #387
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You have now listened the amplifier. How you think it sounds, subjectively?
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Old 15th September 2011, 08:39 PM   #388
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@Spacehead, I assume that's addressed to me? I think it sounds great! To pick one word, the O2 is "effortless". With any headphones I own it doesn't come close to any of its limits, is dead silent, and delivers the best sound I've ever heard from any of those headphones. That said, my $1600 Benchmark DAC1 Pre sounds equally as good. As the O2 reviews by others have confirmed, the amp just disappears and lets you enjoy the music as the recording engineers intended. That's more than can be said for LOTS of popular amps that let their presence be known in one or more ways.
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Old 15th September 2011, 08:48 PM   #389
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Originally Posted by RocketScientist View Post
@Spacehead, I assume that's addressed to me? I think it sounds great! To pick one word, the O2 is "effortless". With any headphones I own it doesn't come close to any of its limits, is dead silent, and delivers the best sound I've ever heard from any of those headphones. That said, my $1600 Benchmark DAC1 Pre sounds equally as good. As the O2 reviews by others have confirmed, the amp just disappears and lets you enjoy the music as the recording engineers intended. That's more than can be said for LOTS of popular amps that let their presence be known in one or more ways.
Yeah, total transparency. Then some audible differences can be found and heard from different audio sources and of course changing headphones. Have you thought about designing a DAC ?

I have this amplifier here that is built on protoboard (don't laugh) and with NJM2068 buffered with BUF634 on each channel, and virtual ground (don't laugh) buffered with NJM4556 (parallel, 0.47 ohm load sharing resistor). It is quite effortless too and silent. Usually new amplifiers sound better , because the subjective experience changes.
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Old 15th September 2011, 09:01 PM   #390
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Originally Posted by RocketScientist View Post
If someone into serious hearing damage, or with really unusual headphones, really needs more than 7 Vrms they can either modify the amp at their own risk, or simply use a different amp.
Amen, brother.
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