Need help with first build... Dist +

[cabowabo]

hi, I'm new to DIY effects building and have decided to go with the Distortion + for my first build.  I just finished assembling it last night but can't get it to work right.  Its the tonepad.com version that uses the 4558 dual op amp. Couldn't find any 1M reverse log pot for the gain so I used a 100k linear pot for gain and a 10k log pot for the volume.  I used 1N4148 diodes.

It works somewhat because when I plug in my guitar, it sort of boosts the signal and I can adjust the volume with the pot, but when I adjust the gain pot, there is hardly any distortion. Its very faint sounding, you have to hit the strings hard to hear even the slightest distortion. Its currently working as a clean boost.. not as a distortion pedal :cry:

I double-checked all the connections,  the polarity of caps and the pin orientation of the IC and made sure they were correct.  What could be wrong with it? Maybe I fried the diodes, IC or something when soldering, not sure...


Any help appreciated!!

[Mark Hammer]

Typically, when I need to slam the strings to get the sound to break through, the problem can be identified in a polarized cap pointing the wrong way.

Since you are using a 4558, there is also a possibility that you have the IC stuck in wrong or that a pin is bent under during chip insertion (assuming you uised a socket...obviously you'd notice if there was no pin sticking out on the copper side for soldering).

The 100k distortion pot is not a problem whatsoever.  The 1meg pot is actually needed for reducing the gain enough to deliver minimal clipping.  A 100k pot just means that the lowest possible obtainable gain is somewhere around x10.  Using germanium diodes, this should allow there to always be some dirt in the signal.  Worst case scenario is that you wouldn't have as much contrast between lowest andhighest distortion settings as you might like.

If the diodes were damaged, then I would think they would behave like they were open circuit, which would mean negligible clipping from the diodes, but a little bit of clipping from the chip.