ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

Tube Screamer help!

 :

5/31/1997 6:29 PM

Paradiddle

Tube Screamer help! Hi,...I'm Back,....sorry i have been away for a few months because of My ISP an problems with their shit,...so anyway,.....i have built the best pedal in the world for my High School electronics project I have a DoD Overdrive a TS-808 tube screamer and a Big Muff Pi,....all in the same box,.....it rocks,.....but i have one problem,..but before i get into that i just want to say a couple thank-you's to the following people:     R.G Keen, Christian, and Most of all Mark Hammer thats alot guys for you time to help diagnose some of my Big Muff probs,........     Ok,.....I have built the TS-808 and i have a slight problem it seems like if i turn the gain past a quarter it squeals i think its some self oscillation but i have tryed changeing out the feedback Cap from 47pf to 600pf at about 150 Pf it cuts out the squeal but then i loose a hell of a lot of gain and distortion,.........I tryed different diodes,.....could a ground be off,.....   also i tryed diferent guitars from Fender to gibson some guitars are worse than others and when you frig around with the tone controls you can also change the squeal. What can i do???   Thanks alot guys,......   Jeff

 

6/1/1997 8:24 AM

CJ Landry

Jeff,   First, op-amps do not like to drive a capacitive load. this will cause oscillation and this could be the cause of your problem. The first thing i would do in this situation is to check the circuit carefully for miswiring. P ay close attention to the input stage of your circuit beacuse your Tone circuit is changing the frequency of your oscillation. This is a proven circuit and there should be no squel.   Hope this helps,   Christian

 

6/2/1997 8:13 AM

R.G. Keen

Stuffing several high gain distortion devices into the same box is a good recipe for squeals of various sorts. You can get all kinds of ugly things out of this, from the high gain, close spacing and lead dress.     I would try decoupling the power supplies first. From the main power source, instead of wires, take 100 ohm resistors to each separate section, and then a 100 to 1000uF 10V capacitor from the end of the 100 ohm to local ground.     You also need to scrupulously separate the grounds between sections They should each have a separate ground wire back to the mail power supply, and the input should too. Signal wires between sections should be shielded, and the shields star grounded as well.     Try the grounds/decoupling first.

 

Page 1 of 1