I'm building the 'Improved Hum Free A/B/Y' off Geofex.
Schematic: http://www.geofex.com/FX_images/humfree2.gif (http://www.geofex.com/FX_images/humfree2.gif)
I've done a stripboard layout for the design, however wasn't quite sure how to read the charge pump converter section in the bottom left hand part of the schematic (I assume it illustrates a MAX1044). I read the Geofex article on the charge pump (http://www.geofex.com/circuits/+9_to_-9.htm (http://www.geofex.com/circuits/+9_to_-9.htm)) which uses 2 10uF capacitors, however the ABY schematic uses a couple of 22uF and 0.1uF capacitors.
I found the GGG A/B/Y project here:
http://www.generalguitargadgets.com/pdf/ggg_amp_aby.pdf (http://www.generalguitargadgets.com/pdf/ggg_amp_aby.pdf)
which uses all three capacitors and cobbled together a stripboard layout following the traces from the GGG PCB:
(http://farm8.staticflickr.com/7422/10511574864_639f88c3aa_o.jpg)
I don't need the stereo jack switching, so have omitted the 2N3906 transistor, 1K and 6.8K resistors. The above is a partial layout featuring only the MA1044 section, so is incomplete (+9V and -9V will connect to the op-amps, footswitch obviously just to illustrate the LEDs). Could anyone tell me if my stripboard combined will work (when combined with the rest of the schematic)? I'm been sort of guessing so far; it matches the GGG layout (I hope), but my incompetence at reading the Geofex schematic means I'm a bit unsure.
Also I've only been able to get hold of a MAX1044 CPA; does the 'CPA' part still make it OK to use for the pedal? Thanks.
> http://www.geofex.com/FX_images/humfree2.gif
> wasn't quite sure how to read the charge pump converter section in the bottom left hand part of the schematic
I don't see a pump. I see two 9V batteries.
The GGG plan does use a charge-pump.
OK, thanks. That makes sense, I was assuming it must have been a charge pump (shows what I know). So presumably I can use the separate Geofex charge pump schematic (that uses just the 10uF caps and the MAX1044) and put it in place of the two battery set-up on the ABY schematic to get +9V and -9V with one DC jack (don't need a battery).