Skreddy - Mayo

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
kismet78
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Post by kismet78 »

Marc has set the bar really high for BM clones.

Omar Bagh Dad-A
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Post by Omar Bagh Dad-A »

:secret: The Skreddy Ernie is farking amazing. It seems to be beyond what I thought a Big Muff could be.

Zero
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Post by Zero »

Here are some guts shots from the pedal that was used to trace the schematic that you can see in page 1: http://www.mediafire.com/?bizddxltpok

And here are the voltages of each transistor:
Q1 :
e : 28.9 mV
b : 0.613 V
c : 3.96 V

Q2 :
e : 26.3 mV
b : 0.627 V
c : 6.37 V

Q3 :
e : 28.3 mV
b : ? (==> unable to reach the lug with my DMM)
c : 3.79 mV

Q4 :
e : 1.090 V
b : 1.668 V
c : 4.68 V

Enjoy :wink:

PS: I traced the schematic and took the pictures a long time ago, but I never wanted to make them public for respect to Marc Ahlfs as I think he is doing a great job. I happened to give the schematic to ech0es and he posted it. Now that the Mayo ain't in sale anymore, I can post the gut shots without doing any harm to Marc (I hope so).

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Greg
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Post by Greg »

Omar Bagh Dad-A wrote::secret: The Skreddy Ernie is farking amazing. It seems to be beyond what I thought a Big Muff could be.
So is the Zero !
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Post by stefcuypers »

Thanks for the package zero!

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Post by nokaster »

i for one would be very interested in schematics and detailed component list for the ernie and the zero...
if i'm allowed to say so.

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Post by Skreddy »

nokaster wrote:i for one would be very interested in schematics and detailed component list for the ernie and the zero...
if i'm allowed to say so.
Same layout. Transistors are 2N5088 (NOS circa 1980?). All original "triangle knob" specs otherwise, except that the input cap is a .1uf tropical fish, the coupling cap between stage 2 and 3 is also a tropical fish .1 (and there's that 100uf power-supply filter and polarity diode and tbp and led).
Image

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Post by nokaster »

thx marc! you are very kind!!!

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Post by Skreddy »

Seen any of these?
Image
I don't know if they're made by Central or by CDIL...

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The Rotagilla
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Post by The Rotagilla »

Skreddy wrote:Seen any of these?
Image
I don't know if they're made by Central or by CDIL...
Where were you when I tossed a load of these about a year ago? :slap:
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Post by seniorLoco »

Skreddy wrote:Seen any of these?
Image
I don't know if they're made by Central or by CDIL...
I have been using those on my muff builds for the last three years :thumbsup
...guess that 'C' is for China :mrgreen:
"Curiosity may have killed the cat, but it saved the mice, who ate the cheese."

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Post by Skreddy »

Anyone have a bunch with gains ranging from 600 to 800 for sale? I like 'em.

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Post by seniorLoco »

Skreeedddy ... you got PM :D
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Post by alteredsounds »

sorry for butting in here but transistor's on my rams head clone, I've used 4 old can bc109's that all measure between 350 and 370, i notice that ur asking for 600 - 800, interesting how would that affect the sound?

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Post by analogguru »

....interesting how would that affect the sound?
that´s a real good question since in every gain stage is current AND voltage feedback..... AND the gain of each stage is far below the ß of every si-transistor.

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Post by Skreddy »

alteredsounds wrote:sorry for butting in here but transistor's on my rams head clone, I've used 4 old can bc109's that all measure between 350 and 370, i notice that ur asking for 600 - 800, interesting how would that affect the sound?
Higher gain transistors result in a more "biting" sound (more aggressive attack, more sensitivity to high frequencies, boosted mids/upper mids content), all other things being equal, in the BMP. Lower hfe's render a mellower sound, more natural attack, a bit darker response, all other things being equal. But the nature of the transistors themselves, owing to the maker, the process, the materials, etc., is more significant usually than the gains. E.g.; old, circa 1970, 2N5133's with gains in the 500's sound smoother, creamier, more dynamic, and sweeter than newer versions of the same with gains in the 300's.

Certainly all the nice biasing and feedback built into the gain stages of the BMP ensure that nearly any BJT will work; but that doesn't mean they'll all sound alike.

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alteredsounds
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Post by alteredsounds »

Thanks, I'm gonna throw a load of different ones at it over the w/e, see what I come up with.

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Post by noelgrassy »

Great zip file! Thanks Zero (the Hero).
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Post by noelgrassy »

Big thanks to Skreddy for sharing your hard work. :thumbsup
I enjoy reading your observations in the various threads around here. Your posts evidence a gentleman &
mature personality sporting an obviously skilled pair of ears. I really liked some of your comments on the
"Fuzz" movie I just bought. You never appear as self absorbed as some of the other interviewed builders.
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Post by nokaster »

i wanted to and succeeded in understanding the big muff circuit. knowing what each component does etc...
making a vero layout thought me a lot.

but on the mayo i still have a few questions...
- why a higher collector voltage on Q2?
- why split the collector resistor on Q4 in 2 resistors with the output at their joint?
- i guess the 47pF after the tone section filters some highs?

i love the sound of my clone A LOT!
AB'd it with a little big muff last week... LBM s*cks...

8)

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