Dr Boogey - Squeel Remedy?

[mydementia]

Guys, I think Xavier might have found the answer to our squeeling high-gain pedal troubles... the power regulator.
(ref: http://www.diystompboxes.com/smfforum/index.php?topic=50776.msg380245#msg380245)

I put the regulator into my wildly squeeling Dr. Boogey, biased the drains to ~4V (power regulator puts out ~9V out of the unconnected circuit, but only about 7.4V in the Boogey - still don't get this), and plugged in...  The squeeling was GONE!!  I have J201's in all five positions and can crank ALL the pots to max without inducing squeel!!!  The only thing maxing the pots add is hiss (totally understandable in this circuit). 

Also - here's a snapshot of my 'rats-nest' circuit... After this discovery, I'm not really buying the 'keep it short and tidy' and 'use shielded wire for all I/O' edicts for high gain circuits...I might change my tune when I try to put a 3PDT in the mix...


I'd love to hear from anyone else who tries this fix.  Hopefully, running these circuits around 7.5V is a fix - not a fluke!!

Thoughts?
Mike

[Bucksears]

I had squealing using all J201's, but all is well using an MPF102 in Q1, as I've been saying. It has hiss as this thing has so much gain, but there IS something TO parts location/wiring proximity when you start to increase the gain that much. That's why I have recently tried to allow for a LITTLE bit of increased space between traces/parts in the (new) Dr. Boogey and Plexizer PCBs.

If you don't buy into the 'short wires' & 'shielded I/O's', that's cool. But A LOT of people say that it has worked for them (including myself) which is probably why they have suggested it.
I'll read up more on the power regulator (I'm not ruling it out, mind you), but I would personally be a little leary over the lesser headroom (however minimal) in using less than 9v on these circuits. Maybe using higher voltage might be another fix?

- Buck

[rtill]

so where is this schematic/layout for the regulator deal you're talking about???

[rtill]

nevermind ....found it  THANKS!

[Xavier]

Glad to hear it worked for you !!

I have to say I used the same regulator in the Flipster and I had the same issue (6 volt at the output).

Well that wasn't exactly the problem. I used a different multimeter for that one and gave me this reading, but as soon as I used the "good one" I have at the service department, the reading was correct . Maybe the battery on the first multimeter was wasted.

Check your multimeter as well !!

[Paul Marossy]

Hmm... I wonder if that is why I generally never have problems with squealing pedals? 
I use a regulated wall wart that puts out right at 9V with up to 1 amp of load on it...

[mydementia]

Actually, slacker explained the voltage drop in the Plexiser thread... I haven't gone back and swapped out my resistors in my Boogie or Plexiser...but probably will next time I tear them open... any one else tried this regulated PS idea on squeelers?

I built another regulator (using another 1N4739A 9.1V Zener and a 1.2k resistor - I'm out of 1k!!) and get just under 9V.  Cool...  When I added the circuit to my multi-box - the output dropped to 3.4V... WTF?

The reason the voltage drops is probably because the resistor is too big. The current through the resistor will be the same as the circuit it's attached to and with a 1K resistor each milliamp that the circuit draws will drop the voltage by 1 volt. If you're getting a 5.6 volt drop across the resistor then that means your multi box is pulling about 5.6 milliamps which sounds reasonable.
Try changing the resistor to about 100ohm that should reduce the voltage drop to about half a volt.

[rtill]

does anybody have a .pcb file they could send me of the dr. Boogey?  I'd like to have a real board manufacturer make the board rather than myself as my boards for some reason seem a little iffy to me.  Or, if someone would make a dr. boogey etched board for me I'd gladly pay them.

Thx,
Rich

[rtill]

I totally redid my circuit, still had squealing, I tried the power regulater with a 9.1v zener, shielded wires, max length 2inches, still squealing like a pig.  Tried a 5.1 zener just to see what would happen cuz I had one laying around, still squealed like crazy. Anymore ideas?

[MartyMart]

I totally redid my circuit, still had squealing, I tried the power regulater with a 9.1v zener, shielded wires, max length 2inches, still squealing like a pig.  Tried a 5.1 zener just to see what would happen cuz I had one laying around, still squealed like crazy. Anymore ideas?

Well I just had "horrific" squealing on my Meteor ( Doug H's huge gain circuit ) and after a total "clean" of all
traces - removing flux etc, it's stopped !
May well have been some voltage/audio bleeding across where it shouldn't have.
Give it all a good scrub and re-heat any "dull" solder points.

MM.

[rtill]

Well, I used the verified perf layout....solder joints look good, didn't use flux.  Any ideas on what would happen if I increased the value of the 1M resistor from the input? or how bout the 1.8k resistor or 1uf cap in the first stage...would changing these values slightly  possibly cause it to stop squealing?

[MartyMart]

It's a tough one, squealing and motorboating can happen just because of "lead dress" and a
number of other reasons !
Not only did I clean my circuit up, I added 33pf caps across a few drain/gates and more PS filtering
( 2 x 220uf & 100n caps ! )
You may just have a couple of sections of the circuit too close to each other ... nightmare !
Any high gain circuit that's a bit "cramped" is asking for trouble ...

MM.

[rtill]

I'll try the caps across drain and gate- thanks!  Now what exactly do you mean when you say "lead dress"....I've seen this term a lot and figured it was just the connection to the board from the input.  As far as things too close together, my perf board is 4 1/2 x 3 - so it's pretty good size.  This is the 3rd time I've built this circuit with all the same problems so I thought that the components too close may be a problem so I used a larger board to space out the components.

[MartyMart]

"lead dress" comes from amp building and refers to all the connections to the board and transformers
how they are wired and what can cross over what.
Here I mean I/O and all off board pots etc
If you have tried keeping everything short, not crossing wires over and even using screened cable for
the I/O then there's not much more you can try, other than reducing the gain a bit.

You could built three of these and three amps using the exact same method , two could be fine and one
could be a pig , just because of a tiny change in layout etc
... very hard to spot what;s causing it I'm afraid ..

MM.

[rtill]

Is it possible to take the smash drive schematic (cause it's a hell of a pedal!!!) minus the tone controls ( http://www.diystompboxes.com/pedals/schems/smashdrive.gif ) and incorporate that as the first stage in the dr. boogey? If so, what changes would have to be made to the smash circuit? ...basically dropping this schematic before the 470k resistor in the dr. boogey.

I've tried the boogie circuit 3 times now and end up with the same result with squealing, tried perf and etched board, made the regulator and it did nothing, tried shielded 2 inch wires...,mpf102 tranisistor...tried a larger perf board for larger spacing....all seems to come down to the first stage in the boogey. Just wanna know if there is an alternative 1st stage I could try regardless if it is with a jfet, opamp, or regular transistor.

[ubersam]

...I've tried the boogie circuit 3 times now and end up with the same result with squealing...

Have you tried using small caps (150-200pf) from gate to ground? There was a thread a while back about this, search for "boogey" and "miller caps". IIRC, adding those caps helped some overcome the squeeling problem.

[RDV]

...I've tried the boogie circuit 3 times now and end up with the same result with squealing...

Have you tried using small caps (150-200pf) from gate to ground? There was a thread a while back about this, search for "boogey" and "miller caps". IIRC, adding those caps helped some overcome the squeeling problem.

That fixed mine along with taking wires in a straight line to the pots and not crossing any of them.

RDV

[aloupos]

I spent hours trying to de-squeel my boogie build using bucksears layout. [there's a thread, search boogie detective].   First off, mine didn't squeel until I enclosed it.  I found that, atleast in my case, the squeel problem was directly propotional to the proximity of the input jack to the pots/output jack. 

Try this:  unscrew the input jack from the enclosure, and drape it outside of the box.  Put the cover back on, and plug in your guitar and try it. 
Also, if you want to play around, with everything on, move the input jack really close to the pots, and you'll hear the squeeling get a lot worse. 

If this works, you have some options.  You can relocate the input jack as far as possible from the other components, try some shielding arangement around the input jack, or do what I did [lazy ].  Put a rubber graumout in the input jack hole in your enclosure.  I used a shielded wire/jack and ran it outside the box.  No squeel, even with the gain  /mid maxed out. 

Good luck !

Anthony

[rtill]

Thanks for all the advice, although, mine isn't in an enclosure yet.....I did some digging around on this site and found Gringo's layout found at http://www.diystompboxes.com/smfforum/index.php?topic=50549.0  wondering if anyone has had success with this layout?  Noticed there is a 5n cap missing from Q2 in the layout, is it important? I've tried all the things mentioned in this thread and some of the ideas made the squealing worse....hehe.  I really like the sound of this circuit, just want it to work correctly so I can use it for shows!!!

[John Lyons]

Rtill
The .005 (5n) is a cap to kill some Ultrasonic high end frequency stuff. You should add it just to be sure.

Here are the things I did to my Dr Boogie.

On Q1, Q2, Q4 I added 220pf caps from source to gate.
I upped the 20p cap to 150 pf. Kills off some of the high frequncies that there are a lot of already.

I changed the gain pot to 500K log (lowers gain)
I reduced the 1M to ground at the Q3 voltage divider to 470K (lowers gain)
I get a bit of oscillation when dimed but it's not so much a squeal as howling. Since the 220pf caps cut the high stuff out the frequrncy changes to more of a howl. There is a ton of gain anyway so I don't need to crank it at all!

I also shielded the gain, volume, jack in and outs, all the switch in and outs and the treble connections. Most high gain amps shield the volume and gain controls as routine.
I added a 68K resistor to the input in place of the jumper. This will lower the gain a bit as well as help with noise. I may raise the value more.

I used all J201s but I want to experiment with MPF102s in some places.

I plan to audio probe the circuit and find out where the gain really comes from.

This soundclip was recorded a little dark but there is plenty high end on tap.
http://www.mrdwab.com/john/Drboogie.mp3

There are more clips on my soundclips site below.

I was skeptical about this circuit but it really sounds nice. A very heavy and modern rock sound.

John