I almost posted that reply myself as I suspected your opinion was exactly that. Obviously I caught myself before answering in your place. When using a good OP-amp the "sound" is defined by the circuit itself (everything else equal) and not the OP-amp as such. Fitting a socket is highly undesirable and I can't really see the point. Desoldering and fitting another one is better. IMHO.
Excellent job P-A. If this works out well with my headphones then I'll probably try the BUF634 one as well.
Excellent job P-A. If this works out well with my headphones then I'll probably try the BUF634 one as well.
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Do me a favour: Build two identical devices with a 2way switch so you can swap back and forth between them. Then you might let go your "placebo-effect difference".
I think P-A likes to take his designs as far as he can, or wishes, in terms of professional and scientific design. He designs for "extreme performance" i.e. that being one of his design goals. That is the reason. Remember, P-A is a professional not a person who believes in "day-and-night" sonic differences between two different resistors.
I believe that once you have designed something well enough in a circuit with low enough intrinsic colouration (distortion if you will) then the difference between different OP-amps is not audible. This in my opinion as is both logical and reasonable.
I believe that once you have designed something well enough in a circuit with low enough intrinsic colouration (distortion if you will) then the difference between different OP-amps is not audible. This in my opinion as is both logical and reasonable.
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"Do me a favour: Build two identical devices with a 2way switch so you can swap back and forth between them. Then you might let go your "placebo-effect difference".
With op-amps at a similar performance level, I think this will be extremely difficult . . .
If you switch between op-amps with disimilar performance, then yes, this is posible. And when I talk about dissimilar, I mean really dissimilar.
This is a good design, so just trust the designer and build it.
With op-amps at a similar performance level, I think this will be extremely difficult . . .
If you switch between op-amps with disimilar performance, then yes, this is posible. And when I talk about dissimilar, I mean really dissimilar.
This is a good design, so just trust the designer and build it.
as a good example of "what I mean", read this please Ganz böser Fake-Test! | Hifi Aktiv – David Messinger GmbH (babelfish or google_translator should help those less skilled in deutsch).
unless the test is double-blind there's always a risk of a placebo (or psychoacoustic, depending on preferred terminology) effect.
You will add inductance since you will have a longer way down to the pcb. This can be crucial if you are trying fast opamps.
Received the Hahn transformers today. Hopefully I'll get round to testing it this weekend.
Some of the soldering on my PCB is really bad as for some reason I couldn't get the amount of solder small enough in many places. Still, for a first attempt I'm quite satisfied. The really thin solder I had was Multicore tin/silver which I couldn't use so I had to go with my usual 0.7 mm Multicore 60/40.
Some of the soldering on my PCB is really bad as for some reason I couldn't get the amount of solder small enough in many places. Still, for a first attempt I'm quite satisfied. The really thin solder I had was Multicore tin/silver which I couldn't use so I had to go with my usual 0.7 mm Multicore 60/40.
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My QRV09 is tested and found to be working perfectly on BOTH channels so I'll get stereo (!). The bandwidth seems a bit lower than the specified 700 kHz with AD8610 but obviously far away from anything audible (I'd say around 550 kHz on mine). I'll do more testing as the frequency roll-off that interests me is in the low end.
Excellent job P-A, so far this is a success and I hope I won't be able to mess it up by putting it in a box...
Excellent job P-A, so far this is a success and I hope I won't be able to mess it up by putting it in a box...
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Finished mine off this afternoon. For it being my first soldering effort (other than a 10 component pin-based PCB kit from Maplin to practice) I must say that I've made a right mess of it (that was kinda the plan; ruin the first one and build two more that would actually work). 
It took me a long while to figure out that I should wet the bit and hold the component in place with the tweezers to tack it down which is why my first few SMDs are such a mess (the flux boiling off would send them flying across the table).
Will test it on the weekend, when I've had the opportunity to buy a 2.5mm jack and connector (they're not on the BOM and it just never occurred to me) and a mains cable that I don't mind cutting the end off.
My back hurts, my eyes are crossed and I'm sure that I have lead poisoning from the solder but, hot damn, was that fun.
I can't wait to plug it in and find that it's not working and then debug it.
It took me a long while to figure out that I should wet the bit and hold the component in place with the tweezers to tack it down which is why my first few SMDs are such a mess (the flux boiling off would send them flying across the table).
Will test it on the weekend, when I've had the opportunity to buy a 2.5mm jack and connector (they're not on the BOM and it just never occurred to me) and a mains cable that I don't mind cutting the end off.
My back hurts, my eyes are crossed and I'm sure that I have lead poisoning from the solder but, hot damn, was that fun.
I can't wait to plug it in and find that it's not working and then debug it.
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The fuse holders that you list from Farnell don't come with covers. Hmm... and that's another thing I forgot to order; a fuse.
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