Distortion + mod - signal chain question

[silent_k]

Hi everyone,

I should preface this by saying it's my first post, and that I've just started experimenting with effects and electronics, so forgive the newbie-ness.  After attending a circuit bending workshop recently, I decided to experiment with an old 80's/early 90's-era MXR Distortion + that my brother gave me.  I had my own older model with the script text, so this one was extra, and it wasn't working.  After discovering the source of the problem (a frayed battery connection) and fixing it, I decided to mimic a mod I'd see for a Boss distortion pedal by adding a feedback loop with the addition of a transistor.  After a few hours of mucking about with test leads, I found some points that made it sound weird and great (to my ears, anyway).  It's definitely in the tone-destruction category – notes break up into a kind of pulsating mess, and it oscillates like crazy when the distortion knob is turned up, but I can't help liking the sound.

The problem I'm having is that when I put anything in front of the modded pedal, even a volume pedal, the oscillation goes away and the effect is reduced.  The more other pedals are in front of it, the greater the reduction.  I've preserved the original Distortion + circuit with the original switch and everything, and that works fine by itself (the loop can be switched in and out), but the only way it appears that I can hang on to the crazy oscillating madness is by having the modded Distortion + in front of everything else in my set-up, including my volume pedal, which isn't very convenient. 

If anyone has any ideas about why this might be happening and some suggestions for fixing it, that would be great.  I know this might be too vague, so if I can provide additional info, please let me know.

Thanks a lot!

Kieran

[earthtonesaudio]

I don't really have any suggestions for you, but some others might, and they might want to know: is your volume pedal active or passive (does it require batteries)?  Another thing that might help you get this sorted out is, does the same thing happen when you lower the volume on the guitar? 

For example, say your modded Dist+ is first in the chain, right after the guitar.  Does messing with the controls on the guitar do anything?

I'm having sort of the opposite problem with some of my builds... I want to get rid of the weird noises!

[silent_k]

Thanks for writing back!  First, the volume pedal is passive (an old Ernie Ball).  Second, the controls on the guitar do, in fact, affect the sound, though in weird ways.  When the tone control is all the way up, the oscillation goes nuts -- rolling it back to 7 or 8 cuts off the oscillation, and as it does so, the oscillation's frequency lowers a bit.  The volume control on the guitar tends to cut the oscillation out completely, even if it's turned down from full by only a little bit.  But lowering the guitar's volume control seems to have a less dramatic reduction of the pedal's weird characteristics than putting a volume pedal in front of it, though it's subtle.

I'm going to keep experimenting (adding true bypass, LEDs, external power, etc) and I'd really appreciate any suggestions of things to add/take out of the circuit to solve this problem.  Thanks again!

[earthtonesaudio]

Well from a pure curiosity point of view, I'd like to know what your modification is exactly.  If you have a link or picture of a schematic, that would help a lot.

My perspective is that the weird noises are a problem, and in my case they can be traced to long, unshielded wires on the breadboard.  You actually want the noises but it seems your mod needs to be more robust (and not care what pedals come before).  You say you added feedback via a transistor, but have you tried feedback via a potentiometer?  That just might be less susceptible to unwanted interactions.  However, without knowing the details of your mod, it's hard to make very useful recommendations. 

P.S. There are threads and schematics for "feedbacker" type of mods on this forum, with diagrams.  Use the "search" function.
Good luck, and welcome to the forum!

[AL]

Ok so you've added an extra transistor which should add some gain and then a feedback loop = more gain. So that = crazy noises.

Any pedal added? Even True Bypass?

Possible impedance issues?

Maybe a buffered pedal is toning things down a bit? Or other pedals may be dragging the signal down just enough to control the craziness. Then again... maybe I'm stupid and completely off but that's all I've got until the coffee kicks in.

AL