[Karlosak]

I would like to lower the gain of my PPA. So far I've been using standard gain value of 10. But with that configuration I use hardly the first third of the Alps' range with my Senns HD650 (listening at about 9 o' clock position). How low can I go with OPA637/627 combo? I know that OPA637 should be stable at the gain of 5 and higher. But is it safe to use the lowest value or should I go a bit higher (e.g. 6)? I would like to move the standard listening position of the pot from the 9 o' clock position to something about 12 o' clock. Is it even possible to approach this?

Thanks for any input!

 

[Glassman]

hmm that means 3 o'clock when Glassman's on the visit

 

[ppl]

gain of 10 is pushing stability as it is i would use the opa627 at any lower gain.

 

[tangent]

You may get away with a gain as low as 5. Try it and see what happens, but be prepared to bump the gain back up if stability suffers. A decrease in sonic quality is an indicator of partial instability.

You might consider increasing the value of R1, to form a significant voltage divider with R2. This will give you a lower overall gain while keeping the op-amp in a stable range. The disadvantage of this vs. lowering the op-amp gain is that it doesn't lower the noise floor.

 

[Karlosak]

Thanks for answers.
I will try some 6K resistors in R4 positions first and see what it does.

 

[Super-Gonzo]

How low can the gain be reliably set when using the AD8610?

I basically have the same volume setting issue as Karlosak, but w/ a different op-amp.

 

[Glassman]

AD8610 is unity gain stable, that means you can set whatever gain you like.. two or three for example..

 

[Super-Gonzo]

Quote:

Originally Posted by Glassman AD8610 is unity gain stable, that means you can set whatever gain you like.. two or three for example..

Thanks!

 

[tangent]

Quote:

AD8610 is unity gain stable

...as are most op-amps. (Just commenting for the archives.) Read the datasheet to see if your op-amp is one of the few exceptions.