Switchable TS808 Op-Amp?

[chieljan]

Just tested my homemade TS808, and heck, it worked! It has a sym-asy clipping switch (the two don't really seem to make much of a difference to the sound, barely audible) and a bass/mid switch (fried the bass .22uF cap by accidentaly touching it with the soldering iron, stupid, but whatever, the normal side works. I'll replace it some day)

But then came the problem: which op-amp do I like most? I bought a JRC4558, TI 4558P and a TLC 2272CP. 4558P wasn't quite impressing, but I just can't choose between the JRC and the 2272...

So I wondered, could I make them switchable? I remember that a long time ago I read a website about a guy who had the same problem, and he "stacked" his op-amps, and left the 9v+ pins stick out, so he could connect them with a switch to 9v+ choose which op-amp gets 9v and so, which op-amp wil work... couldn't find the site again now.

because I am not sure, maybe someone here can tell me if this really works? all other pins of the chips are still connected to one another, so I thought maybe the two chips would interfere with one another, changing the sound... Hope you can tell me more about this, would be superb if this works!

[Seljer]

I believe this here would be the project you're thinking about:
http://www.beavisaudio.com/Projects/ScreamerLab/index.htm

[KerryF]

What does Op-Amp/IC stacking accomplish?  If I did it to my BluesBreaker, what would it do?  Would it give more gain?  Clearer sound?  What?

Also, Seljer, check your thread in the Selling Sub-Forum...

[bancika]

IC stacking only gives you ability to switch between two or more ICs, it doesn't combine them or something...at least I think so...

[markm]

Actually, I think the idea is to give it a different tone and less noise perhaps.
Here's what David Barber says;

http://www.barberelectronics.com/parallelopamps.htm

[chieljan]

Cool! Thank you very much!!!
Beavis audio research was the site I saw... But still, I don't really understand what he says, but if I do get it well:

Making pin 1 and 7 switchable with a DPDT (like shown on the website) will give me the oppurtunity to switch between the JRC and the 2272, with no interference or whatsoever between both chips?

Maybe there is someone on the forum with experience in this op-amp stacking, I'll change the title a little

[mjones99]

I would try to make sure that if you can switch between opamps try to wire it so that if the switch fails at least one opamp will continue to function.  Myself, I like the RC4558P better than anything, so go figure, it sounds more like the raytheon part but then I am kinda old school...

[Seljer]

use just one DPDT on-on-on to switch pins 1 and 7 on the opamps and you'll be able to select either opamps or both of them at once

Code Select Expand

                 _____
opamp #2 pin 7 - |o o| - opamp #2 pin 1
  socket pin 7 - |o o| - socket pin 1
opamp #1 pin 5 - |o o| - opamp #1 pin 1




I don't think you have to bother with switching the inputs? try PMing Dano on here and ask him on specifics if he got his project working yet

[Paul Marossy]

Wouldn't you get a loud pop when switching opamps?