The sound of concatenated opamps.

[Circlotron]

There seems to be a certain religious fervour attached to the opinion of whether or not opamps sound ok for audio. I have vaccilated back and forth about whether I should use one or not, and currently in my setup the only one is inside the DVD player right after the D/A converter; some 8 pin thing made by JRC.

Anyway, what I decided to do was make an opamp buffer cct and have a changeover relay so I could listen through it or bypass it completely, and have a long wire so I could switch it from my normal listening position. I chose a Texas Instruments TLC2274 quad fet opamp simply because I had a few. Also, the distortion as a buffer is only 0.0008%. Naturally as with all stuff diy, things got out of control and before I knew it I had no less than 12 opamps wired in series as unity gain buffers in each channel. I wired it between the DVD player and the power amp.

Well, what did it sound like??? I was expecting the worst, BTW.
Hiss - Only the tiniest, tiniest, weeniest increase in hiss.
Distortion - no obvious change.
Frequency response - no obvious change.
Overall clarity - no obvious change.
Left to right soundstage - again, no obvious change.
Front to back soundstage - aha! Instead of extending off into the distance somewhat, it only sounded as if it was about a foot deep. Not objectionable, just different.

It took me about 10 minutes of listening to actually pick this difference - it was simply not a black and white thing like some people have claimed. Also, if someone else was operating the switch I have some doubts that I would have picked the difference.

Now I know that all kinds of people may jump in and tell me this and that, and how some wonderful opamp magically improved their system, or how completely junky my system must be, but that's not what I am talking about for indeed there are good, bad and ugly opamps for sure. What I am saying to the *anti opamp brigade* is that I don't think opamps are all that bad per se. Some people just say 'all opamps are no good' and don't investigate the matter any further. The result of my experiment is - I for one can't hear what all the fuss is about.

[janneman]

That is an interesting experiment. I haven't done something like that, but am aware that mixing and other consoles used in producing some of those fine sounding LPs and CDs must contain also many, sometimes 100's of opamps. Of course, it's not the same, but makes one wonder why a single opamp on replay would have much more influence than say 10 or 20 on the recording side.

Jan Didden

PS Like your choice of words - like to concatenate or not is the vacillating question. (Yes, it's one c and two l's ).

[AKSA]

Graham, I love it!

The last frontier - sound stage. No other effect. Ahem.....

Cheers,

Hugh

[Frank Berry]

Jan,

I was going to say the same thing.
I work with a Euphonix mixing console. It's state of the art with great specs.
Guess what it's stuffed with?
You guessed it.

[Pjotr]

Great experiment !

Not many people realize that their beloved recorded music went through a long chain of op-amps already, in the mixing console for instance.

But it is not the op-amp by itself that makes sense but the right op-amp in the right place. The so much discussed I/V converter here on the board is one of the trickiest applications for an op-amp.

Cheers

[Circlotron]

Originally posted by janneman
makes one wonder why a single opamp on replay would have much more influence than say 10 or 20 on the recording side.

Oh, it's the synergy between the local opamp and the magic power cord. Don't you know anything?

Hugh, with such good ears, you surely must be irritated / disappointed with sound more often than I.

[Tube_Dude]

Originally posted by Circlotron


Well, what did it sound like??? I was expecting the worst, BTW.
Hiss - Only the tiniest, tiniest, weeniest increase in hiss.
Distortion - no obvious change.
Frequency response - no obvious change.
Overall clarity - no obvious change.
Left to right soundstage - again, no obvious change.
Front to back soundstage - aha! Instead of extending off into the distance somewhat, it only sounded as if it was about a foot deep. Not objectionable, just different.

All the quote above can be resumed in two words:
-Input equal to output.!!!

That i have learned many moons ago but with my favorite null test...and more... i haven't yet measured a op amp that make a deepest null, than the "old trusty" NE 5534...

[Circlotron]

Null test. Of course!! I'll definitely try that. Thanks Tube_Dude.

[Tube_Dude]

Originally posted by Circlotron
Null test. Of course!! I'll definitely try that. Thanks Tube_Dude.

Do it!!...see post in post #8 in :

Null Difference Testing

[Eva]

That's why I love double blind tests

It's a pity you hadn't placed sockets on the test boards, It would be funny idea to test more crappy things like LM324 or TL074


Tube_Dude :

The funniest thing about nulling is that you can connect the resulting signal from the substraction to an amplifier and a speaker to be actually able to *hear* the *difference*