September 17, 2020 at 3:16 am #14816larryayreParticipant
It took some fiddling, but I finally got my SWAH v4 pedal to work – and it sounds great!
After initial build the pedal did not work. I socketed the GE diode in D3 and discovered that if I manually connected and disconnected it, the wah sound was triggered. I read up on it and asked a bunch of questions (Thanks to those who helped me out!) I finally found some different TL074 chips in another pedal that I had semi-retired, and tried them out. That was the main problem – the output voltage on pin 14 was way too high; the new chip put the voltages right in specs and triggered the touch wah sound.
In the process I had socketed a number of components, and once I had solved the main problem couldn’t decide which diodes or caps to use in my final build. I had taken the thing pretty much apart and decided to put it in a different enclosure with a couple of options modded.
I mounted the bias pot externally. I have 5 different guitars and the external bias pot makes it much easier to get it tuned in.
I put in 2 mini switches. The top one toggles between a GE diode and a silicon diode in D3. The GE is a bit brighter and more touch sensitive – better for lead work. The silicon diode really gives the pedal the Crybaby sound – something about it is distinctly familiar and better for the funky quack.
The lower switch toggles between the stock 8.2n cap and a smaller (quicker) 5.6n cap in C8. The 2 caps increase the range of the Delay pot.
I also increased R17 to 47k, which makes the range of the Sensitivity pot more useful.
This and the cap mod are described on this page https://guitarpcb.webs.com/apps/forums/topics/show/8230458-swah-super-white
I was a bit worried that the board might have gotten a bit roughly used, but it all came together without problems. Now it quacks like crazy and is easy to tone down for subtler shading as well. I have a lot of control and can dial it in well with a distortion pedal. With my humbucker guitars compression can kill the quack if put before the autowah. But single coils are not so effected.
This is a really great and unique sound. Thanks Guitar PCB!September 17, 2020 at 4:37 am #14817BillyModerator
Nice! sounds like the mods are a good idea thanks for detailing how they sound etc
I’ll give some a go with the swah board I’ve got lying around
This was my 2nd ever build around 2011 which is still going strong great circuitSeptember 17, 2020 at 12:32 pm #14820BarryKeymaster
Thanks for reporting.
We had two previous SWAH troubleshoots that could not get a wah sound either so it is always nice to see reported success. Typically one would not expect the TL074 chip to be bad but it does happen. Way to stick with it and sort it out.
Thanks also for the build details.
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