Dr. Boogie Detective [Why some boogie and others sqeal?]

[aloupos]

Just finsihed assembling Dr. Boogie.  Some really great tones are possible with this pedal;  Excellant Circuit!!! 

Like many others on this board, my circuit functions (almost) flawlessly outside of a box, but when enclosed, it squeels with gain or mid turned up.   

I started thinking this morning what might be the cause.  Everyone is building the same circuit, using the same PCB layouts and the same components.   The quality of some components may differ slightly, but I don't think it's enough for such night and day differences. 

There real variables here are:
-     the size of enclosure
-     the layout of the potentiometers; how far they are apart, and which ones are ajacent others. 
-     location /pcb/led/stop switch


I suspect that this positioning is what causes some to sqeel and others to boggie once enclosed.  In the interest of Science, can I ask those of you who have built one of these to briefly describe how you've enclosed it?  I'll start with my example: 

Performance:   Squeels with gain or mid above 10. 
Power Supply:  Voodoo Labs pedal power
Layout:  Bucks
Potentiometers:   MID-BASE-TREBLE
                          GAIN-PRES-VOL
These are pretty much butted against each other in two rows. 

True Bypass / LED

I bet we see a trend where those who's boogie doesn't squeel have their pots in a certain order.  Would be very interesting to see. 

[Pushtone]

Potentiometers:   MID-BASE-TREBLE
                          GAIN-PRES-VOL
These are pretty much butted against each other in two rows. 

With that description I take it your using a 159B enclosure.

[Paul Marossy]

I do not think that the order of the pots has anything to do with it. Check your wiring. You want all of your wires to be as short and direct as possible. In high gain circuits like this, you can not have wires eight inches long all stuffed in a box - that makes a perfect environment for parasitic capacitance to have a field day, and hence, a lot of squealing noises.

EDIT: Just an FYI - I have my controls laid out like this -
Top row, left to right - LEVEL, GAIN, PRESENCE
Bottom row, left to right - LOW, MID, HIGH

Thinking anout it some more, I guess the order of the pots might matter if the wires going to them aren't routed properly.

[aloupos]

I'm using the Taiwanese 'C' Size boxes from small bear.  Definately, my wiring is direct and painfully cut to size.  Paul, have you built this circuit?  If so, I'd be interested to know your layout of components in the enclosure, and weather you have any squeeling/oscilating at all? 

I realize this approach is different from the other approaches towards troubleshooting this problem on this board.  The reason for this is I've yet to see (a)someone actually have the problem[squeeling/oscillating] (b) re-wire their pots more directly/ (c) then have the squeeling go away.  Also, some members admit to having messy wiring and they have no squeeling. 

Please help by posting your encolsure layouts ... I think the results will be very interesting !!   

[aloupos]

Thanks so much, Paul.  I'll try this configuration tonight and post the results.  I assume you can crank your gain with no oscillation?  Also, are you using all J201's?

A

[WGTP]

answer:  They are like girls!!!

Are there 4 or 5 stages.  If 4 the output is in phase with the input, it is more likely to squeal.  If 3 or 5, it would be out of phase and less likely to squeal and more likely to boogie. 

[MetalUpYerEye]

Looking at my Dr. Boogie from the front of the pedal the setup looks like this...

VOL. BASS. TREB. MID.

GAIN       LED      PRES.
INPUT             OUTPUT

     STOMPSWITCH (3pdt)

All of the controls are on the front of the box but the input/output are on the sides. I just put the LED indicator on there maybe a week ago and it worked perfectly without it and still works perfectly with it. After having a second look at it, I noticed that the wiring isn't terribly long, just mildly messy. It's in an enclosure from a former DOD Death Metal pedal and everything was a bit cramped when I assembled it. The only unusual noise i've heard coming from it is a very faint garbly sound if I leave the guitar plugged in and everything running while I got to get a drink or something. I also biased the jfets by ear, no multimeter. I used an MPF102 in the first position, though I am considering trying a J201 just to see what will happen. Then again with all you guys having so much trouble with your Dr's, i'm hesitant to remove mine from the enclosure so long as its working great.

[mojotron]

Squealing like a pig here in 2 4x4" electrical box using the cover as the top.

                        Elec box 1                           Elec box 2

out                PWR             in           |
                                                      |
Gain     Bass          Mid       Treb       |  Pres    Vol
                                                      |
                      LED                          |
                      3pDt                         |

Have not tried it with a battery or extra Pwr filtering.

[Paul Marossy]

Paul, have you built this circuit?  If so, I'd be interested to know your layout of components in the enclosure, and weather you have any squeeling/oscilating at all?

Yep, I've built it. No squealing. I used an MPF102 for the first stage and J201s for the rest of the stages. BTW, mine's on a wall wart only power supply. Maybe the oscillation demons decided to leave me alone when I built mine? 

Here's a few pics of mine:

[MetalGod]

Paul, thats an incredibly tidy build - I officially hate you now   

[MetalGuy]

Mine is an all J201 version and is housed in a 125 type taiwanese box and looks like this:



When turning the volume past 10 o'clock it starts to squeal. I added a resistor to decrease the output level to ~250mV. Tried a MPF102 without improvement. Added 150pF miller caps - no change /as far as squealing is concerned/. I'm using a 3PDT footswitch. Pot caps and the box are connected to ground.

[Paul Marossy]

Paul, thats an incredibly tidy build - I officially hate you now

Imagine hearing a big raspberry right now. 

When turning the volume past 10 o'clock it starts to squeal.

I never turn my volume up that high on most of my distortion pedals. Maybe that's why it's not a problem for me? 

[aloupos]

Interesting ... I systematically isolated every pot from the others, by moving it outside the case and closing the cover (just draping the leads over the side).  None of them made any improvement.  Then I remember someone recommending keeping the input and output jack as seperate as possible.  So, I moved the input jack outside the case and closed the cover.  No squeel!!  I moved it close to the circuit while it was active, squeel!  Hmm...

I'm going to build a small alluminum shield around the input jack and report my results.

[John Lyons]

Why not just use shielded wire on the input and from the foot switch to the circuit? 

[aloupos]

I could do, but it doesn't seem to be the wire as much as the jack itself. 
- The squeel only occurs when the jack is moved near the other components.  The wire can sit on top of them with no problem.  Maybe I'm missing something here? 

[Paul Marossy]

Hmm... that's an interesting finding. I think a shielded wire from the input jack would probably suffice. And maybe a shielded wire from the bypass switch to the circuit board.

[MartyMart]

I had similar problems with a Thunder Chief and some other "high gain thing" of my own.
Shortening the wires and using the outside lugs on the 3PDT ( Led in centre ) sorted it out
I guess shielded cable would be a very good idea on high gain builds too - perhaps we
should make it a "standard" on such circuits ??

Marty.

[aloupos]

OK, so the good doctor sits at the end of my effects chain (with an Ibanez delay, boss delay stage tuner).  It's a little noisey (hiss), but no longer oscillates/squeels.  I can max gain / mid with no additional noises. 

I'm extremely happy with this circuit.  I added the miller caps at the other gain stages, and the pedal is very amp like.  It reminds me of the mesa's I use at the studio.   The 3 weeks I spent on building / troubleshooting were well worth it.   This is the first project I've built, and I've learned TONS!!  Thanks to everyone who helped and joined in this thread. 

A couple of things that are noteworthy: 

- DEFINATELY (really) the proximity of the input jack to the pots is where the interference takes place, causing the oscillation and squeels.  I'll likely rebuild in a larger enclosure and space the input / pots / output and board further apart. 

- Something really interesting occured while I was troubleshooting the board, before I had the squeel problem.  I had very low gain, which would change periodically while I was testing it.  I heard a lot of pops and scratches using the audio probe.  I spent a lot of time trying re-soldering, changing components out.  No appreciable difference, no matter what I did.  There was, however, a lot of flux residue.  I know this is not conductive, but after cleaning the board with a toothbrush and acetone, the board fired right up and functioned perfectly.  It went from no sound, or scratchey pops, to perfect wth only that cleaning. 

- Baking with a dark t-shirt iron on turns the iron on yellow and brown, and gives the pedal a vintage look.  Interesting, but not what I was hoping for

Looking forward to building my next project.  Maybe BSIAB II! 

Anthony

[Paul Marossy]

No appreciable difference, no matter what I did.  There was, however, a lot of flux residue.  I know this is not conductive, but after cleaning the board with a toothbrush and acetone, the board fired right up and functioned perfectly.

Believe it or not, this appears to have been responsible for weird behaviour in at least a few of my builds, and even an amp footswitch malfunctioning! Anyhow, glad you got the bugs worked out of it. Persistance + patience = results! 

[boogietube]

I added the miller caps at the other gain stages, and the pedal is very amp like.

I have seen this mentioned a few times, but I am unable to find a reference -
1. Where do I get them ?
2. What are the benefits?
3. Why in the gain stages?