I have no "objections" what so ever with the performance of QRV-03. Pure and clean sound, more or less identical with QRV-04. I'll guess some guys here and at Head-Fi would hear a huge difference but I don't have that sharp hearing.yejun said:
I'm thinking now to upgrade the QRV-03 so I don't have to deal with the patent guys at Analog Devices. Maybe I get some permit, but when?
Hey peranders I just wanted to say your amplifier has a very nice look. Clean layout and very nice construction. I especially like "Made with a Macintosh". Maybe I'll start printign "Made with a Macintosh running Linux" on my boards 
Do you have any pictures of the whole amplifier assembled? Inquiring minds want to know...
Do you have any pictures of the whole amplifier assembled? Inquiring minds want to know...
Thanks, jwb. Not many people in the world can really put "Made with a Mac" on the pcb 
because the only good PCB CAD is now dead since a couple of years. I used the german RUN Electronic Design System which uses a dongle
Does anybody know if someone out there is developing for Max OSX?
The amp is cute, I agree. I think so myself too.
and no, sorry, no pictures of a "boxed" pcb because the pcb has never been put in a case. Later maybe.
because the only good PCB CAD is now dead since a couple of years. I used the german RUN Electronic Design System which uses a dongle Does anybody know if someone out there is developing for Max OSX?
The amp is cute, I agree. I think so myself too.
and no, sorry, no pictures of a "boxed" pcb because the pcb has never been put in a case. Later maybe.peranders said:
This is something I find very interesting. The 100 ohm resistor in series with the headphone seems to be some sort of de-facto industry standard. Does anyone know where this idea comes from?
As far as I can tell it only makes the amp work more as a current output, especially into low impedance headphones (Grado=32 ohm). I thought an amplifier was supposed to have as high damping factor as possible? Is there a difference between headphones and loudspeakers that make the headphones more suitable for current drive?
Lots of questions, maybe someone here could give some insight.
PS: Very nice work P-A!
There's a couple of reasons, but with long cables it could make things worse removing it.
Think cable capacitance and the effect on the amp output.
It's also how most headphones are designed, tested and measured so the 100R defines the correct source impedance.
I used to do without, but now have it in place and it sounds better.
Andy.
ALW said:
I have two options (or three). If I compare the sound with my headphones HD545, the differnce between low output impedance plus 100 ohms is series or 100 ohms inside the feedback loop, the difference is none, according to my ears but I suspect that low ohmish headphones can sound different.
Driving capacitive load with 100 ohms inside the feedback loop is no problem. Works like clockwork.
I think this is a typical testing thing. No religion in this, just go testing!ALW said:
Hi, are you still using AD8610 supplied on 15v?
I would like to try it in my preamp which is also 15V, but maximum voltage of AD8610 is 13V only.
Regards
Hey P-A, I didn't know you had a OPA627 amp in your collection! I was actually thinking of using the BUF634 at one point for this ODA thing I'm working on but then figured parallel NJM4556As would be more in keeping with the O2. Good thing I didn't use BUF634s, I would have just re-created the wheel for no reason. That looks like a good amp you have there. I know that a thread from a few years ago by Maxhawk with a OPA627 and BUF634 came to life again a week or two ago. That also looked like a pretty good design.
I'm making no claims whatsoever on performance for my OPA627 + NJM4556A thing, just done for fun. A beefed up CMOY. Your amp there on the other hand probably delivers some pretty well-measuring sound.
I just took a look at the schematic on your site and see you have the trim added. I did wind up stuffing those PC holes after all on mine. The first channel I built up didn't need it, but the second did when I got the chips in. Using the trimmer I was able to zero most of about 100uV of offset.
I was actually thinking of using the BUF634 at one point for this ODA thing I'm working on but then figured parallel NJM4556As would be more in keeping with the O2. Good thing I didn't use BUF634s, I would have just re-created the wheel for no reason. That looks like a good amp you have there. I know that a thread from a few years ago by Maxhawk with a OPA627 and BUF634 came to life again a week or two ago. That also looked like a pretty good design.I'm making no claims whatsoever on performance for my OPA627 + NJM4556A thing, just done for fun. A beefed up CMOY.
Your amp there on the other hand probably delivers some pretty well-measuring sound.I just took a look at the schematic on your site and see you have the trim added. I did wind up stuffing those PC holes after all on mine. The first channel I built up didn't need it, but the second did when I got the chips in. Using the trimmer I was able to zero most of about 100uV of offset.
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