Evening all,
I've built a bugcrusher as per the bugbrand design (I cant link to the original picture, as his site has changed). It works fine with the 2 batteries or 1 ac adaptor and 1 battery, but I thought I'd be clever and use a Max1044 charge pump to supply the bipolar voltage.
Problem is, I've got a crackling at the output that I cant get rid of.
Things I've tried:
-running the charge pump output into the original voltage regulator circuit
-separating the chips grounds (1 to the adaptor ground and one to a vref from the 18volts)
-running all the grounds to a vref from 18 volts
-filter caps of varying values on +9v to gnd
-filter caps from -9v to gnd
-filter caps from +5v to gnd
-filter/bypass caps from the positive and negative supply pins in the AD781 to gnd
-pull up/down resistors on the audio input and output.
I've got rid of a lot of the problem, but it's still there. I know cloudscapes had a similar problem (http://www.diystompboxes.com/smfforum/index.php?topic=53633.0 (http://www.diystompboxes.com/smfforum/index.php?topic=53633.0)
The schematic for the best I've managed to do is here:
http://i28.tinypic.com/2cib5hf.jpg (http://i28.tinypic.com/2cib5hf.jpg)
Voltages +4.98v, +9.56V, -9.47v
I've recorded a sound clip if that's any use?
Starts off with the output from the 40106 swept up and down. Nice clear square wave with no noise. Then guitar bypassed (no noise). Finally with the bugcrusher on. The last few seconds of audio I'm not playing so you can hear the crackling more clearly, but it is noticeable when I'm picking notes.
http://www.filefreak.com/public/viewset/12475 (http://www.filefreak.com/public/viewset/12475)
I'd be really grateful for suggestions/help.
Thanks,
Michael.
i wish i'd seen your post before i tried the exact same thing-the simple bugcrusher with max1044 for bipolar power with the same resulting noise...since it's been over a year since you originally posted, i was wondering if you had any luck using the max1044, figured out another route, or just went back to batteries to avoid the crackling. anything to help.
thanks
If you're running two batteries in series you could try using a TLE2426 to set up nice +/-9v supply. Used them in many a headphone amp and they work great there. Available as a TO92 or DIP8.
datasheet http://focus.ti.com/lit/ds/symlink/tle2426.pdf
dave