GEOFex's Bipolar Power Circuit: can use DC adapter?

[Bucksears]

I too am building Anderton's tremolo and wanted to know if the GEOFex bipolar converter circuit can be used for a DC adapter as well as batteries.

Can this be done? Do the cap values in the converter circuit need to be different?

Thanks,
- Buck

[R.G.]

Within the converter limits, yes.

However - if you use the MAX1044, you have to be really certain that your DC supply never exceeds the absolute max voltage spec, which for that part is 10.0000V. Exceed that and it will likely self distruct. This isn't much of a problem with a battery, but DC supplies are notoriously fickle.

You could use an ICL7662, which has a higher Vmax; but it also runs at about 3-8kHz, well within audio, so your grounding and decoupling on both your positive and negative supplies had better be immaculate. The 1044 lets you run it at over audio by connecting two pins. You can overdrive the 7662 clock, but that gets into another chip, likely a CMOS hex inverter or CMOS 555.
You could also regulate  the external DC down to 9V with a low dropout regulator chip (not a 7809, which needs 2V between in and out to keep regulated).

If you do this, use the power setup from the "Neutron" filter, which has correct ground and power supply routing, most especially including not using the input jack ground trick on the battery lead to switch power. You need to remote this with a PNP transistor on board and switch the transistor's base to not have insufferably converter whine.

[Fret Wire]

However - if you use the MAX1044, you have to be really certain that your DC supply never exceeds the absolute max voltage spec, which for that part is 10.0000V. Exceed that and it will likely self distruct. This isn't much of a problem with a battery, but DC supplies are notoriously fickle.

Most regulated 9v power supplies run about 9.2 - 9.8v. An inline polarity protection diode between the dc jack and the 1044 should give you a .6v safety margin, corrrect?

Not related to the question, but it seems the regulated power supplies from fx companies like the boss psa-120 (9.6v), seem to go 9v plus to compensate for the inline polarity protection diodes they use in their ckts. The older aca is a different story, however.

[Bucksears]

Thanks, RG and Fretwire.
My Ibanez AC109 is running at 8.8v, but I'm not sure about the jacks on my Godlyke Power-All; haven't measured those yet.

But the Bipolar converter takes ONE 9v power source and converts it to TWO 9v outputs? one (+) and one (-)?