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Hi everyone,

I´m working on an Ibanez GE10 and apart from several attempts to improve its sound, I´d like to run it at 12-18V for more headroom. I use BB OPA2134 as OP´s. Two Problems so far:

- When I ran it at 12V (Voodoo-Lab PP+2) which the parts allow for, I noticed humming which isn´t there at 9V. It´s audible and increases with sliders all up. Any Ideas on its origins? Filtering? OP-amps?
- There is a 16V rated 22uF nonpolar electrolythic in the level-path. Do I have to change that too? Its value is rather exotic and if I have to upgrade that, what can I do?

Thanks for any Ideas on that matter...

Ok, I swapped the OP´s for JRC4558DD´s. The Hum is gone, so I would have to find out what the problem with the OP2134 is.
Any Ideas?

Cheers from over the pond!

Please change C29 and C30 to a higher voltage rating before connecting it to a higer supply voltage again.

If you want to try, how it sounds on higher voltage you can apply voltage up to 15 volts for short time. It allows one characteristic for aluminium electrolytic capacitor called surge voltage. It means that you can apply 15 percent higher voltage over the rating for short time (few minutes).

Dirk_Hendrik wrote:Please change C29 and C30 to a higher voltage rating before connecting it to a higer supply voltage again.

Already did that. How about C10 and C22? They´re both rated for 16V...

Any Ideas to prevent the hum caused by the OPA2134?

... my bad C23 (22uF/16V)...

FloPoeKo wrote:

Dirk_Hendrik wrote:Please change C29 and C30 to a higher voltage rating before connecting it to a higer supply voltage again.

Already did that. How about C10 and C22? They´re both rated for 16V...

Any Ideas to prevent the hum caused by the OPA2134?

You switched back to the 4558's didn't you?
Is the hum gone when powering these at 18 volts? This question for the simple reason I do not believe the hum can be caused by the opamp type used.

Dirk_Hendrik wrote:

FloPoeKo wrote:

Dirk_Hendrik wrote:Please change C29 and C30 to a higher voltage rating before connecting it to a higer supply voltage again.

Already did that. How about C10 and C22? They´re both rated for 16V...

Any Ideas to prevent the hum caused by the OPA2134?

You switched back to the 4558's didn't you?
Is the hum gone when powering these at 18 volts? This question for the simple reason I do not believe the hum can be caused by the opamp type used.

I´m currently running them at 12V until I have replaced all 16V-rated electrolytics (Do I really have to upgrade C10 and C23 for running the effect at 18V as well?).
I have the hum with OPA2134 and NE5532P, but not JRC4558DD.

Maybe it's related to op amp's speed. Try to put a 100u capacitor directly on the op amp's supply pins (8 and 4) and see if the "hum" is affected for OPA2134 and NE5532.

ggedamed wrote:Maybe it's related to op amp's speed. Try to put a 100u capacitor directly on the op amp's supply pins (8 and 4) and see if the "hum" is affected for OPA2134 and NE5532.

Already tried that too... It maybe has something to do with power consumption and the circuit as a whole... NE5532 and OPA2134 seem to draw more current than a JRC4558DD...
Ah, its a drag...The OPA have a nice quality to them, but I find more and more pedals that seem to prohibit their use... I hope I´m profoundly missing something here...

Any help is greatly appreciated!

Ok, I´ve changed the last capacitor to a higher voltage rating and fired it up at 18V (2x9V via summing-adapter). It works without any hum. My suspicion is that the PP+2 gave unregulated power at 12V and regulated at 9V.
Next Problem: The flipflop works just fine at 9V, but at 18V there is a dropout of the signal when switching. When you hit the footswitch the signal drops out for about half a second until it reaches the other state, whereas in 9V it´s immediate with no perceivable latency.
Any ideas on that?