proposed dr. boogey layout -- seeking comments

[Victor]

I agree with John. We should care about all, simplified signal path, star-grounding, and pots connections...... they all matter, in my opinion...... maybe tube amps need those techniques more because they work with "larger" signals, higher voltages, longer wiring and signal paths...... but we shouln't make this an "excuse" (please, don't read this as an offensive word, I don't mean that    ) to not to worry about it, no matter how small and "potentiometer-less" are our pedals..... my 2 cents 

[Victor]

on second thought, maybe the signal path routing has made a difference.  as john points out, we can protect ourselves from oscillation by careful routing of the signal path.  also, pushtone said that he didn't use any shielded wires for his hookups.  so doesn't that suggest that we should stop worrying about pot wiring? 

My Buck Boogey has a major problem. It goes into oscillation just by moving tonestack pots side by side, or close to each other. Maybe those tonestack-only wires, that connects Bass to Treble and others should be in the board, so we can solder wires directy and straight to each pot ....... I believe that will make some difference..... 

[gaussmarkov]

on second thought, maybe the signal path routing has made a difference.  as john points out, we can protect ourselves from oscillation by careful routing of the signal path.  also, pushtone said that he didn't use any shielded wires for his hookups.  so doesn't that suggest that we should stop worrying about pot wiring? 

My Buck Boogey has a major problem. It goes into oscillation just by moving tonestack pots side by side, or close to each other. Maybe those tonestack-only wires, that connects Bass to Treble and others should be in the board, so we can solder wires directy and straight to each pot ....... I believe that will make some difference..... 

right.  but with the layout that we have been working on in this thread, pushtone had no problems:

I'm finished with the build. Fired up great.

100% No squeals at all, even with all unshielded wire, even with all controls maxed.

so maybe we should just move on to incorporating your output buffer, as john suggests?

all the best, gm

[Victor]

gm,

That's ok for me. Please proceed. 

[George Giblet]

>Instead of messing with the tone stack why not just add to the layout a simple buffer /switchable?/ after the TS like the one found in Randall's preamp?

With the scaling idea you aren't "messing" with the behaviour of the tone stack, it behaves the same.   Unfortunately people are brainwashed by the "standard" tone control pot values because they don't really understand how tone stacks work.   The buffer will work course but it adds circuit, which is probably unnecessary.

[John Lyons]

Ok, Lets go with George's scaling idea. Seems simpler. Less craming on parts on the already cramped layout.
The buffer is doing what the scaling will do so let's keep it simple and go with the scaling.

Here is what george sugested:

Slope Resistor:        was 47k    now 4k7
Treble Cap:             was 680p  now 6n8
Mid Cap:                 was 22n    now 220n
Bass Cap                 was 22n    now 220n
Treble Pot:              was 250k  now 25k
Mid Pot:                  was 25k    now 2k5
Bass Pot:                was  1M   now 100k
Volume Pot             was  1M   now 100k
Presence Resistor    was 22k   now 2k2
Presence Pot           was 100K now 10k
Presence Cap          was 3n   now 30n

A 2k5 pot might be harder to find but you could go for say a scaling factor of 5 instead of 10 in the example.

The mid pot could be 5k and still be ok, Or else just add a resistor across the outside lugs to make it 2K5.

The layout remains the same, Just plug in these values and we should be set.

Waddaya think!

John

[Victor]

If Pushtone is willing to try the tone-stack scaling...... 

[Pushtone]

If Pushtone is willing to try the tone-stack scaling...... 

Having built two I would prefer to leave the Gauss version as a reference so I could come back and compare.
I have another etched Gauss board. If I had the parts, which I don't, I would put it into the Buck version enclosure.

I prefer the scaling option to the buffer as an immediate path of experimentation in order to document a final outcome to the output impedance issue.
And George gave anyone all the info needed to start experimenting back on page three I think.

[Pushtone]

I've had a nice long morning rockin' out with BOTH Dr Boogey's. They definitely have different characters.
Sometime the Buck (100k VOL) sounded better while at other times the Gauss ( 1m VOL) sounded best.

Overall I'm leaning to the Gauss version because of better midrange response.
Remember, other than the PCB layout and the VOL pot these two builds use EXACTLY the same components.
The EQ controls go a long way in getting a good sound.

I hope to get around to replacing the VOLUME pot in the Buck version tonight. To see if they can be made to sound the same.
However, the 500k GAIN pot option still seems to make sense.



I've been trying different pedals following the DB and I'm starting to wonder if all this tone stack and output impedance is a red herring.
I tried a couple of Boss pedals, a Digitech RP-80 and a GGG IC buffer built into it's own box. I did all the testing with the 1m VOL pot version.

Yes there is a slight decrease in high-end with the Boss and RP-80.
But with the DB this is not a bad thing and the TREBLE control can make up for it.

With the GGG IC buffer the level was reduced by half and slightly less high-end. I compensated with the DB VOL control to get the same level as without the buffer following. Volume pot ended up at 2 o'clock which worries me it might run out of travel before reaching unity gain on some amps.
The sound without the buffer is more raw and open. With buffer, a little more compressed but smoother top-end which is a good thing. But both sounded good.

SUGGESTION: PCB layout that allows you to have un-buffered AND buffered outputs so you have the choice.

Bottom Line: IMHO, the tone loss from the high output impedance is not significant to worry about modifying the values or layout. If your dying to build a DB then grab Gauss's layout and do it. Anymore work done will be a minor refinement that is the work of those dedicated to making it the best it can possible be from a technical standpoint.

It was my Honor to beta test a new layout. Great circuit.
Thanks to Electrictabs, Bucksears and Gaussmarkov for their work.
A challenge of a build and something to work up to.
Not as tough as one would think from the previous reports.
Sounds totally different from my other JFET distortions.

IT WORKS, GO BUILD ONE!

[Pushtone]

Anyone interested in pictures comparing the two builds ?

[$uperpuma]

absolutely!

[John Lyons]

Pics are always nice!

Thanks for the report Pustone. Interesting that the IM pot didn't change the sound more with pedals following it.
Theoretically th impedance should be low at the output so I say we should scale the tonestack and call it finished.
Either way will work. If you notice a problem with a dulled output with the 1M pot then you know what to do...

+1 Go build it!

John

[Victor]

Geez, I was gettting more confused anytime I saw this topic...... it's so many things we can improve and see...... maybe maintaining standart approach would be the best for me...... so I can get started to build another one..... 

I did some math with the circuit today and found out the "numerical explanation" for gain behave in boogey. I'll try to use a 220k log pot to see if I can explore more those nice "low gain almost crunch" sounds of it.... 

And thanks Pushtone, for your new impressions about it.   

[Victor]

What supply voltage are you guys using? I believe that 18V give Boogey more definition on notes and tighter bass..... and also trimpots resistances are increased, so gain is also increased, maybe (Zo got higher, Av too).......... makes sense?

[kissack101]

In terms of printing the layout onto PnP Blue and etching the PCB, how big should the circuit board be in millimeters/fractions of an inch?

Also, its really great to see folk working together like this, world needs more if it i think...

Adam.

[Pushtone]

Use Gaussmarkov's PDF project file to print it in scale.

http://gaussmarkov.net/index.php?page=layouts#drboo

http://gaussmarkov.net/

[kissack101]

Use Gaussmarkov's PDF project file to print it in scale.

http://gaussmarkov.net/index.php?page=layouts#drboo

http://gaussmarkov.net/

Yeah I was thinking about that, only when I print anything onto PnP Blue I usually put a bunch of layouts onto into a word document so as not to waste a whole sheet on one pedal, just wondered how big I had to re-scale it?...

Adam.

[gaussmarkov]

Use Gaussmarkov's PDF project file to print it in scale.

http://gaussmarkov.net/index.php?page=layouts#drboo

http://gaussmarkov.net/

Yeah I was thinking about that, only when I print anything onto PnP Blue I usually put a bunch of layouts onto into a word document so as not to waste a whole sheet on one pedal, just wondered how big I had to re-scale it?...

Adam.

on gaussmarkov.net, every project has a pcb.png file listed.  this is a graphics file with a 300dpi resolution.  if you "insert" this file into MS Word and do not rescale, the image will scale correctly.  at least it did for me. 

[gaussmarkov]

i just posted the latest consensus version:  rescaled tone section, no output cap (C22 removed), 24 mil pads   of course, with every new version there is always the chance that i introduced an error but i double checked.  so i'm confident we are o.k.    the only change to the pcb was moving a couple of components over at the output to take advantage of C22's departure.  i'm mostly thinking of errors in part values.  ah yes ... i also increased the pull-down resistor value at the input to 2M.

go crazy, gm

[gaussmarkov]

argh!!! i forgot to change the MID pot around.  one more try coming soon.