Op-Amp Big Muff with Dying battery simulator

[zosotone]

Has anyone tried using the Dying battery simulator with the IC Big Muff? I use the typical 10KB pot but when I turn a little bit the pot the sound it's very gated, like this model works only with +/-9V.

With a normal transistors muff works well but with the IC i have this issue.

Cheers.

[Frank_NH]

I'm assuming you're using the "dying battery" simulator to reduce the supply voltage to the circuit.  If that's the case, then your question has become very interesting to me!  After doing a little internet research, I realized that most of our bread and butter op amps (e.g. TL072, RC4558) have a *minimum* supply voltage around +/-5V.   Single supply, this means we need a minimum of 10V - yet we use 9V supplies!  Well, it turns out that you can still operate your op amp at slightly below minimum recommended voltage, but the performance may (and I stress *may*) be negatively impacted.  We may not hear it, given the way the op amp is used in something like an overdrive.  But it seems to me that designs which use soft clipping (like the tube screamer) would probably work OK, while others which run the op amp output voltage to rails and clip afterwards (like the RAT and your op amp muff) may not, and thus would be more sensitive to the op amp type.

So, how does all this affect your op amp muff?  I think going well below the rated supply voltage may degrade the performance too much for proper operation of the circuit.  I don't know what op amp you're using, but if you substitute a rail-to-rail op amp (many of which can operate at low supply voltages), maybe it will sound better.

[zosotone]

I'm using the layout from Mirosol http://tagboardeffects.blogspot.com.es/search?q=ic+big+muff
with IC1 RC4558NB and IC2 UA741.

I've tried some IC's and i has the same issue, also with a FET opamp on IC2 TL071. I will continue experimenting with the IC's...

It's curious, but in the kitrae page http://www.kitrae.net/music/big_muff_op_amp_history.html i've read about Billy Corgan used this muff with a dying battery on the studio. Maybe with another IC's?

Also, with my Earth Sound Research Graphic Fuzz (UA741) i have the same issue. Great fuzz!

[Frank_NH]

Probably the best way to understand this effect would be to simulate a dying battery in LTSpice.  I may try that if get some time in the next few days.  I suspect that the signal is becoming mis-biased due to low voltages somewhere in the audio path.

[zosotone]

Thanks a lot Frank!