High Supply Voltage Op Amp

[Minion]

The OPA2604 will handle +/-24v and it is a good opamp ....

http://focus.ti.com/lit/ds/symlink/opa2604.pdf

[oddist]

Hello,
You say the application is gain "recovery", but are you actually putting the gain before the tonestack?  Otherwise,
why the need for so much headroom?  If it is truly gain recovery, you would be taking in a small signal and
amplifying it up to a useable level (2 Vpp would seem more than sufficient for a pedal). 
Anyhow, just trying to understand the application here.
Good luck.

[Ripthorn]

Hello,
You say the application is gain "recovery", but are you actually putting the gain before the tonestack?  Otherwise,
why the need for so much headroom?  If it is truly gain recovery, you would be taking in a small signal and
amplifying it up to a useable level (2 Vpp would seem more than sufficient for a pedal). 
Anyhow, just trying to understand the application here.
Good luck.

The opamp is after the tonestack in a preamp, so I want to get the gain back up to the pre-tonestack level and still have the eq effects of the tonestack.  My preamp prior to the tonestack is pretty loud, thus the desire for high headroom.  I think the dual supply voltage might get me there if I can get +/-16 or 17V (+/-12V got me somewhat close).

[snap]

My dad was working at a (now defunct) power company working on some digitally-programmable power chip. He was telling me about an all discrete op amp that he got to play with that did some ungodly numbers (I'll ask him later to get the specs and model). I think they were somewhere above $1k a unit though..

That 990 is very cool as well!

I got to play with some Air Force surplus Philbrick opamps back at school about 6,000 years ago. They used two 12AX7s per opamps, one for a diffamp and the other for a pushpull output stage. Neat stuff. They ran from about +/-100V as I remember it. We had to get a double integrator sine-cosine generator to work as a homework assignment.

Of course, modern audio power amp practice is simply to build a discrete opamp without a lot of concern for DC accuracy. The standard Linn-format power amp works well as an opamp if the designer didn't play games with the compensation to get good test numbers. Some of them are only stable above a certain gain. Maybe the simplest single chip solution is an LM3886 at +/- 40V or a TA7293 at +/- 50V.

Looks like it was more like +/-300V  Philbrick

[liquids]

The op-amp is after the tonestack in a preamp, so I want to get the gain back up to the pre-tonestack level and still have the eq effects of the tonestack.  My preamp prior to the tonestack is pretty loud, thus the desire for high headroom.  I think the dual supply voltage might get me there if I can get +/-16 or 17V (+/-12V got me somewhat close).

How did this work out for you?  I'm experimenting with something similar and curious about your findings.

[Ripthorn]

I ended up going with an NE5532 running it at +/-21V.  It gets me about unity on the clean channel, but when boosted, there is still a very noticeable level difference.  I was actually looking at maybe doing one that goes +/- 24V or so as those are still relatively cheap.

[davidallancole]

This link shows how to bootstrap a op-amp to get swings of up to +-100V.

http://www.edn.com/contents/images/45890.pdf

[kurtlives]

I ended up going with an NE5532 running it at +/-21V.  It gets me about unity on the clean channel, but when boosted, there is still a very noticeable level difference.  I was actually looking at maybe doing one that goes +/- 24V or so as those are still relatively cheap.

Just wondering (don't know much about op-amps)...

Could you have 42V and 0V?

[davidallancole]

It should work.  Hook it up and give it a try.

[Cliff Schecht]

The OPA547 does 60 V and the OPA454 does 100V. Both are about $6.00 an op amp though..

[Ripthorn]

I ended up going with an NE5532 running it at +/-21V.  It gets me about unity on the clean channel, but when boosted, there is still a very noticeable level difference.  I was actually looking at maybe doing one that goes +/- 24V or so as those are still relatively cheap.

Just wondering (don't know much about op-amps)...

Could you have 42V and 0V?

yes, you can do this, you just have to make sure you have a Vref that is 21V.  I did it the way I did because I could take in my 12V into a TC1044 and get out +/-21V from a single chip, a few diodes and a few capacitors. That way my Vref was ground.

Cliff, thanks for the heads up.  For the kind of thing I am doing, $6 wouldn't be too much to make sure that I have the flexibility with the amp I want.  But I am actually now on to thinking about the next amp(s).

I also thought about bootstrapping, I just wasn't confident in my self enough to be sticking 80V on the thing.