Skreddy - P19  [traced]

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mojah63
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Post by mojah63 »

I've had a few muff's and sold them all on Ebay. Made a few bucks and I thought they all sounded quite crappy to be honest. I picked up a workalike p19 on MB's forum and it does sound really, really good. I just lowered the 1st tranny's emmitter resistor a tad to compensate for my low output strat pickups. Does the Pink Floyd and other mid heavy strat tones in spades. I guess I'll have to build one now and try my hand at a diode recipe, 1n4148 + 1n4149.

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Post by 1oldsidewinder »

Skreddy wrote:
Seiche wrote:
Skreddy wrote:Interesting. Did not even know this. Wikipedia entry on 1N4001:... "Many of the diodes in this family exhibit a change in capacitance with reverse bias and can thus be used by experimenters as makeshift varicap diodes."
not sure what the application of varicap diodes would be?
I imagine that their capacitance would increase with voltage? So you could conceivably use smaller nfb aka "miller" caps and let the diode's variable capacitance smooth off at stronger signals. This would fix one of the Big Muff's issues: the high harmonics are created by virtue of the clipping; and so with constant filters, lower-intensity signals, which are not clipped, naturally sound dark and muddy.
It looks like the issue may have been addressed on the P19 with the .002uf cap across the sustain control. Adds some highs at lower settings, right?

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Post by Skreddy »

1oldsidewinder wrote:
Skreddy wrote:
Seiche wrote:
Skreddy wrote:Interesting. Did not even know this. Wikipedia entry on 1N4001:... "Many of the diodes in this family exhibit a change in capacitance with reverse bias and can thus be used by experimenters as makeshift varicap diodes."
not sure what the application of varicap diodes would be?
I imagine that their capacitance would increase with voltage? So you could conceivably use smaller nfb aka "miller" caps and let the diode's variable capacitance smooth off at stronger signals. This would fix one of the Big Muff's issues: the high harmonics are created by virtue of the clipping; and so with constant filters, lower-intensity signals, which are not clipped, naturally sound dark and muddy.
It looks like the issue may have been addressed on the P19 with the .002uf cap across the sustain control. Adds some highs at lower settings, right?
Yeah, that definitely makes the lower-gain settings useful.

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Post by 1oldsidewinder »

Thanks for the reply. I added the cap to my Russian Muff last night and it sounds much better. Best of all, I'm no longer pushing the tone control up near the top of it's range at low-gain settings and I'm hearing stronger mids. BTW, the clips of the P19 sound fantastic! Can't wait to play one.

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Post by fretzburner »

I used 1N914 paired with 1N60 on my P19 build based on Skreddy's schematic and sounds good to my ears.Tried all 1N60 and it lower the over all output a bit.Will try other diode combinations soon.Thanks Skreddy for the schematic,it keeps me busy tinkering.

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Skreddy
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Post by Skreddy »

fretzburner wrote:I used 1N914 paired with 1N60 on my P19 build based on Skreddy's schematic and sounds good to my ears.Tried all 1N60 and it lower the over all output a bit.Will try other diode combinations soon.Thanks Skreddy for the schematic,it keeps me busy tinkering.
I still haven't found a good use for germanium clipping diodes, personally. Maybe try two of them in series opposite the one silicon and see how that sounds? I'm sure just one ge paired with one si will have a pretty prominent asymmetric rasp to it. Also, if you're doing that same thing on both clipping sections, it makes a huge difference whether you flip-flop the pairs (reverse the polarity of the ge and si diodes in Q2's section relative to Q3's section) or run both sections the same way. The signal is inverting, so if you match them, you're really flip-flopping them electrically (I think) and vice versa. But play with it and see. To get the sound of my build, you'd want to mis-match your clipping diode pairs by only a small fraction of a volt. Doesn't sound assymetrical at all, really, unless you compare it to symmetrical; then you can tell that mine has just a touch more depth to the sound and the symmetrical version is a little "flatter" and less interesting. You can just barely feel it, though; it's not something you can put a simple descriptive term to (and it isn't to say the symmetrical version will sound "bad" either).

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Post by fretzburner »

Thanks Skreddy for some hints.Will try those and check the results.Will check BAT41 too

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Post by Cub »

My next build may borrow some sections from the P19. To see if the tone control and mid-switch would be part of it, I loaded some values in Duncan's TSC to see what it does.
Nice and subtle, seems like it will let you cut just a bit better while preserving the Muff's characteristic dip.
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Post by Cub »

mojah63 wrote:I guess I'll have to build one now and try my hand at a diode recipe, 1n4148 + 1n4149.
fretzburner wrote:I used 1N914 paired with 1N60 on my P19 build based on Skreddy's schematic and sounds good to my ears.Tried all 1N60 and it lower the over all output a bit.Will try other diode combinations soon.Thanks Skreddy for the schematic,it keeps me busy tinkering.
Gentlemen, how did your diode experiments turn out ?
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Post by ik6gpy »

Cub wrote:My next build may borrow some sections from the P19. To see if the tone control and mid-switch would be part of it, I loaded some values in Duncan's TSC to see what it does.
Nice and subtle, seems like it will let you cut just a bit better while preserving the Muff's characteristic dip.
There's a major mistake in you simulation. The capacitor on the low pass filter side must be 10nF not 100nF, otherwise you'll have uber scooped mids! The P-19 doesn't have any mid scoop at all.

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Post by Cub »

Whoops, I see. I mistook the .01 in Skreddy's schematic for 0,1µF
I'll ask a mod to delete the misinformation.
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Post by jalmonsalmon »

Anyone know where to find those cool type of aluminum knobs? I have some pedals that can use an upgrade!~

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Post by jalmonsalmon »

Nevermind... searched Google and wholla, he gets them from Jameco
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Post by flood »

Hi there from Bombay, India. First off, kudos to Marc/Skreddy for being as down to earth and open as he is. About a month ago, I announced a little giveaway of a one-off etched pedal for the first two people to give to this fantastic organization on a donations-matched day: http://www.kranti-india.org/ They're doing an extremely difficult job in the red light districts of Bombay, educating the daughters of sex workers and keeping them out of the trade, countering trafficking etc.

The donor requested a gilmourish muff, but smoother than a regular BMP. I had built the pinkmour for myself a couple of years ago, was veering towards that but decided to try this design instead. My component values are almost identical with the skreddy version, except for a couple of places on the board. Probably the biggest difference being that I use 470nF going into the final gain stage. Almost all my resistors are 0.6W or 1/4W metal film, caps are a mix of poly and ceramic.

I'd like to make clear that I am not making any money on this transaction at all - the funds are going directly to the organization. The offer was the first person to give $100 or more (which would be matched to 50% by a globalgiving.org sponsor) would get a free pedal from me, as long at it was an overdrive or fuzz of my choice with a maximum of three knobs and one switch (i'm throwing in two more switches in addition to the Mids switch because the winner is an awesome guy, who tried to drum up more funds of his own volition). a second 3PDT switch will go between the stock 200 ohm value to 100 ohms in the diode clipping stages, and an on-off-on toggle will flip between the clipping diodes - 1N4148+1N60 (symmetrical), 1N4148 only or no clipping at all in stage 2.

Anyway, I felt it appropriate to share my "version" here. It's not verified yet, but since I based it off an old Eagle layout, it should be all right. Will verify this after testing tonight. I'd also like to state that I haven't advertised this to the donor as a skreddy clone, because of the deviations from the original circuit and it would be bad form in general, but I'd like to thank Marc nonetheless - irrespective of what Muff I would have built, I think I've learned a lot from poring over your schematics here.

Cheers and keep your shit loud.
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AFA - Numb and Number - Schematic
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Skreddy
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Post by Skreddy »

Try using a 50k pot for the tone control instead of 100k. Less separation between high and low, so the middle ground is fuller.

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Post by flood »

Skreddy wrote:Try using a 50k pot for the tone control instead of 100k. Less separation between high and low, so the middle ground is fuller.
Thanks Marc, I did end up using a 50kB pot in the final build. I think I've screwed up somewhere else because the circuit works great as a very mild overdrive/boost, there's practically no clipping happening anywhere. time to cross-check the board with the layout. i have a feeling my batch of 470k resistors is actually a mislabeled batch of 47k.
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Post by Skreddy »

flood wrote:
Skreddy wrote:Try using a 50k pot for the tone control instead of 100k. Less separation between high and low, so the middle ground is fuller.
Thanks Marc, I did end up using a 50kB pot in the final build. I think I've screwed up somewhere else because the circuit works great as a very mild overdrive/boost, there's practically no clipping happening anywhere. time to cross-check the board with the layout. i have a feeling my batch of 470k resistors is actually a mislabeled batch of 47k.
Well, that would do it. Simple thing to check, though.

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Post by flood »

The resistors were ok - I dun goof'd with the resistor going from the sustain knob into the 2nd gain stage though. Used 82k instead of 8k2. Interesting possibility for a future build - use a very small resistor, maybe 10E, on the first and second gain stages and a 100k "Less" knob to cut down the amount of fuzz and turn it into an OD of sorts! :)
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Post by Skreddy »

flood wrote:The resistors were ok - I dun goof'd with the resistor going from the sustain knob into the 2nd gain stage though. Used 82k instead of 8k2. Interesting possibility for a future build - use a very small resistor, maybe 10E, on the first and second gain stages and a 100k "Less" knob to cut down the amount of fuzz and turn it into an OD of sorts! :)
Look at the Cornish G2 for more ideas.

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Post by flood »

Thanks Marc. Something's up with my build, or my testing setup or both - the pedal just doesn't sound right on it's own, but sounds perfect when the input is hit hard with an overdrive. i'm guessing i've made a mistake in the first stage or there's a solder bridge, or a weak tranny (doubtful, all tested between hfe 500 and 560). probably a bad connection somewhere.

I did etch a second board from the same layout, so i'll see if that one works right and then post the verified transfer for this build.
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