oscillations in Dr. Boogie...

[Connoisseur of Distortion]

i boxed it up today, and it sounds spectacular. EXCEPT that it oscillates when i dampen my strings. AND that i pick up 101 KUFO when my guitar is off. also, interestingly enough, i can change the pitch of and eventually stop the oscillations, and also tune the radio, by lowering my tone on my guitar... but eventually i end up with a very flat tone...  

i have been getting the impression that long wires might be to blame for this... but i need to know which wires are suspect for this particular circuit! please, if you can point me in the right direction, it would be very much appreciated.

[electrictabs]

well i didn't have any problems with Dr. Boogey even when it was out of the box.it is pretty quiet for the gain it has.
so you have to check all of your board and wiring again.
one cause could be input close to output,signal too close to supply,bad solder joints,there also many other things to check
you can also use shielded wires
look at aron's FAQ or geofex FAQ and i'm pretty sure you'll find the answer

[nuttmeg1]

When I first built this circuit it worked as is but did oscillate when the gain was dimed out. So, knowing that the DR and Soldano SLO100 are VERY similiar, I thought I'd play with some vales. I removed the 1n cap on the gain control. It is the equivalent to the Warren Haynes mod on an SLO100. Oscillation problem solved, at the expense of the higher/fizzier frequencies that I don't care for out of a real DR anyway. I also swapped out the 47k slope resistor and the 680pf in the tonestack for  Marshall values of 33k and 470pf. Finally, I lowered the gain pot value to 250k. This decreased some gain and made it more usable to my ear. For me the pedal now is warmer and more Soldano-ish. This thing rules! Being the dork I am, I'll continue to futz with it. Thanks electrictabs and bucksears for all of the work on this one! I hope this helps your problem and gets some other ideas going.

[electrictabs]

When I first built this circuit it worked as is but did oscillate when the gain was dimed out. So, knowing that the DR and Soldano SLO100 are VERY similiar, I thought I'd play with some vales. I removed the 1n cap on the gain control. It is the equivalent to the Warren Haynes mod on an SLO100. Oscillation problem solved, at the expense of the higher/fizzier frequencies that I don't care for out of a real DR anyway. I also swapped out the 47k slope resistor and the 680pf in the tonestack for  Marshall values of 33k and 470pf. Finally, I lowered the gain pot value to 250k. This decreased some gain and made it more usable to my ear. For me the pedal now is warmer and more Soldano-ish. This thing rules! Being the dork I am, I'll continue to futz with it. Thanks electrictabs and bucksears for all of the work on this one! I hope this helps your problem and gets some other ideas going.

well yes lowering the gain pot's value will make the circuit better at least to my ears as i stated in another thread.
once again thanks for the kind words nuttmeg1

[Davide]

I've often read this jewel has a lot of gain.. but how much ? Cause i'd like to have a stomp box wit a metal roaring distortion (not fuzzy..) like dual/triple rectifiers at max gain.. i think i'll build the Dr. anyway.. but i'm asking too much from it ^_^ ?

[Connoisseur of Distortion]

update:

i pulled out the mentioned capacitor, i shortened and braided all of my hookup wire, i put shielded wire on my input and output, and it is STILL oscillating. the radio reception is annoyingly clear, too. It comes through when my guitar is turned off, and is about as loud (probably louder) as my distorted signal. how can i get so much damn reception in an aluminum box??

[Connoisseur of Distortion]

anyone have any ideas?

[nuttmeg1]

Okay. I thought I had the oscillation problem worked out. I didn't. It does go away with an output buffered pedal in front of it. I'm going to build another one from scratch ( because I'm sick of looking at this one) with some different parts suppliers to see if that works. If it worked for electrictabs and bucksears, then it works. With the oputput buffered pedal (Maxon CP101 and Boss OC-2) it KILLS!!! I've had it on the road already with two different amps. 2-'59 Bassman reissues on Saturday in Florence, AZ, (15,000 people, not that I'm bragging) and Sunday into a Triple Recto at Anahiem Stadium in Anahiem, CA (45,000 people, okay I'm bragging)
You'll also be able to hear it on Nashville Star on 4-26-05 with Cowboy Troy.

Thanks,

[electrictabs]

damn i wish i could get there to hear my creation in front of so many people but it ain't easy being in a different country.
nuttmeg1 i'd love to hear an audio-recording of your live concert.

[Ivan]

I breadboarded Dr. Boogey this weekend with 95% specified parts sans tonestack. Love the sound, finally some fat distortion on my single coil strat, however I too have the oscillation problem. It behaves almost identically to the one Connoisseur of Distortion made, if I change the tone on my guitar it goes away at the expense of treble... also if gain is set further back it goes away. Now I realize it's on the breadboard and it is far from being shielded or perfect however I've breadboarded Eighteen and Thunderchief among others without any oscillation issues. Any clues to why this might be?

[Connoisseur of Distortion]

one thing for sure: putting it into a box will not save you! beware!  :x

[Bucksears]

Ok. I finished building my Dr Boogey this weekend, although it's not boxed up yet.
Yes, mine squeals too. But........it has IN-SANE distortion. Very 'metal' and hard rock, not at all a low-gain, crunchy or bluesy pedal.
I pulled the 1n cap and that didn't do much.
I'm going to give my MPF102's a try and hear how they sound; might swap the gain pot for a 500k.
If the squealing would stop, this would definitely be my metal riffing box.

[AmpliFuzz]

Please slap me around a bit with a large trout if I'm about to say yet another clueless bestiality, but if putting a buffered pedal before it is indeed the cure, you could try adding the wah output buffer circuitry that's useful for driving fuzzes right at the circuit's start.

[Ivan]

Bucksears, I have same sentiment about the sound, it definitivelly rocks! Plenty of distortion to go around, that's why I want to get to the bottom of this and have a working pedal that sounds great!

[Bucksears]

Dear God.....I hope it's not a problem with my layout!!!?

[Connoisseur of Distortion]

i think amplifuzz may be on to something...!

but, as i am far too lazy to actually work on the doctor ever again, i am going to put my whammy in front of it. case closed.

[Bucksears]

Ok. I put my Boss TU-2 Tuner in front of it, and the squealing went away; however I still get a 60-cycle hum, but nothing like the whine I used to get.
Man, this thing was made JUST for metal/hard rock.

I'm still going to work up an alternate layout for this thing; per Conossieur's suggestion, I'm going to put all off-board controls on one side of the PCB. Almost all of GGG's layouts are like that and I never had a problem. Even though the 'buffer pedal in front' method works, that's kind of a pain, especially if you wanted to let someone else borrow it.
Still, I'll never buy a Metal Zone again.

[Davide]

i've just built it... no oscillations at all .

[electrictabs]

Davide did you perf it or use the pcb layout?

[Davide]

i've used Bucksears' pcb.
All jfet are J201, i'm using an ESP MH300 guitar..