Why would anybody want to do that, save in case of instability? Is it because, if used normally, most 8 legged critters produce distortion well below the threshold of audibility? And increasing noise gain brings out the good stuff?
Nelson has advocated the technique of increasing noise gain for better subjective performance. This was quite some time ago though, and we have better devices today. Post #18 here,
http://www.diyaudio.com/forums/solid-state/6558-opamp-inverting-input-sounds-better.html#post67880
This is an old example of mine where R6 alters the noise gain and R7 allows gain above unity... all text book stuff.
Wow, thanks Mooly.
This is from Nelson:
"As a result, whenever I use op amps in an audio circuit, which
is not often, I make sure that I either use up or throw away
about 20 dB of open loop gain. If the circuit has a gain of
10 or greater, this is automatically achieved.
If the circuit has less than 20 dB gain, I toss some away.
With an inverting amp, a resistor from the - input to ground
will do it. If not, then resistance from both + and - to
ground is used."
So I will try inverting first, as I think it is a better way to do this.
Anything you can do, I can do better, I can do anything better than you.
http://www.diyaudio.com/forums/solid-state/20591-adcom-gfa-585-dc-servo-opamp.html#post240784
http://www.diyaudio.com/forums/solid-state/20591-adcom-gfa-585-dc-servo-opamp.html#post240784
> so it is indeed about allowing some distortion in.
That may be a by-product , but not the purpose .
The excess gain afforded by op-amps , when turned
into excess feedback gives music a constrained , blanketed
sound compared to a more open loop situation where
dynamics are more freely manifested .
That may be a by-product , but not the purpose .
The excess gain afforded by op-amps , when turned
into excess feedback gives music a constrained , blanketed
sound compared to a more open loop situation where
dynamics are more freely manifested .
Best personal experience :
phono preamps using 5534's
1) RIAA stage with 30db @ 1kHz and 30db line amp .
............vs..................
2) RIAA stage with 60db @ 1kHz .
You should try it : )
No, the noise/distortion is just byproduct (like hitsware said). Nelson mentioned that most opamp needed this, but he said he didn't use opamps often.
In my case, I just want to do this with 4562. It has superior electrical characteristics so may be sacrificing a little will bring good trade-off.
By ears I observed that the performance of 4562 is better with higher gain (when I said better, it is compared to other opamps, not to itself). Actually, anything that theoretically increases stability will improve its performance.
And remember, I will be comparing the 4562, in its best implementation, with other JFET OPAMP in its own best implementation. So it is like reducing performance in one part in hope of gaining performance in other part.
To do yourself in with food and beverages, there are two ways which are equally effective :
- don't eat or drink at all
- wine and dine yourself into a coffin
Eating and drinking half, but pass on the other half to someone else, doesn't cut it.
Is that a quote or did you make it up? You could frequent forums where folks like me, Waly, and SY are simply banned. BTW I don't care who says it it's nonsense.
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Of course you discount the issues of gain structure and overload margin at each stage out of hand.
The gain of the opamp section is standard opamp theory where G= (R9/R7)+1 Altering R6 doesn't materially alter the closed loop gain.
The filter network in front of the opamp adds a miniscule amount of attenuation of course.
Here is the file if anyone wants a play.
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