Good replacment for BB OPA 2604/604

[moving_electron]

Originally posted by carlosfm


Would you trade those for some "hand-selected" JRC op-amps?

If anyone has any JRC 4558 op amps where the numbers stamped on them are 4 digits (rather than 5) I seriously would be interested in trading.

If you have a clock radio made in Japan in the 80's you can take it apart and look. There is a good chance there is one in there.

The application is recreating a vintage guitar effect box.

[moving_electron]

Originally posted by ericpeters
Hey Carlos,

I know it matters where to put the bypass, but how important is the quality/size of the cap used?

I just used what I had laying around, and it improved my project dramatically. I'm now wondering if a high quality/right size cap will even improve that.

http://www.diyaudio.com/forums/showt...ht=#post532582

[ericpeters]

Originally posted by carlosfm


It does.
Search this forum and you'll find my hundreds (thousands?) of posts about that.
I suppose it's easy to find.

Ok, one thread I knew (VSPS) and I found a few others (So thousands or even hundreds is a bit )

anyway between 22 and 100uf it should be according you (I have 470uF now). Cannot find a quick mentioning of quality so I'll get some decent but not extremely expensive.


Thanks moving elctron, I just found it at the same time you poste.

[carlosfm]

Originally posted by ericpeters
Ok, one thread I knew (VSPS) and I found a few others (So thousands or even hundreds is a bit )

And the ones you didn't find?
Ok, tens.
Check out what I say about the bass.
Doesn't matter, put the right caps on the right places and full speed ahead.

[Gaucho]

No it's not.
You just don't know how to use it.
And yes, I KNOW what you're talking about. You've hit the spot.
Hint: PSU bypass.

Sorry try again. I have the bypass caps right at the pins: 47uF electrolytics with 0.1uF films from the supply pins to ground. Perhaps you are influenced more by datasheets then by your own ears.

[moving_electron]

Originally posted by Gaucho




Sorry try again. I have the bypass caps right at the pins: 47uF electrolytics with 0.1uF films from the supply pins to ground. Perhaps you are influenced more by datasheets then by your own ears.

Anything between V+ and V- ?

[Gaucho]

Anything between V+ and V- ?

Yep, I put 27uF across the supply pins too.

Perhaps LM317/337 simply don't get along well with the 2132.

[carlosfm]

Originally posted by Gaucho
Perhaps you are influenced more by datasheets then by your own ears.

Quite the reverse, actually.
Most datasheets say the electrolythics can be shared between the op-amps and at some distance, with small caps on the pins. This is completely wrong, it sounds nasty.
You have a problem with the layout and/or the PSU and you think it's the op-amp.
The OPA2132 is quite demanding at that, as is the OPA627/37.
Try the LM6172 on that circuit.

[carlosfm]

Originally posted by Gaucho
Yep, I put 27uF across the supply pins too.

27uf?

[Gaucho]

Most datasheets say the electrolythics can be shared between the op-amps and at some distance, with small caps on the pins.

I agree the best sound is achieved by putting the electrolytic/film caps at the pins. I use bypassing on the in/out pins of the regulators too.