Earth Sound Research - Graphic Fuzz  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
Sickle
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Post by Sickle »

Here ya go, guys:

https://www.stompboxes.co.uk/forum/viewt ... f=6&t=1676

Pretty cool fucking pedal.

Broken, though..

:|

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alteredsounds
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Post by alteredsounds »

New one on me that. Looks bloody nice though. Any idea on those cap values?

Sickle
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Post by Sickle »

No clue, but the seller said he had a manual for it he was sending me a copy of. If I'm lucky, there'll be a schematic in there.

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Post by drbob1 »

There're now two commercial releases of this pedal:

http://fencedinarea.com/SHTI/?page_id=431

http://www.jimmybehanfx.net/custom/eart ... aphic-fuzz

Both for roughly $130 shipped to America. It's a decent price for a fuzz, until I realize that there's only 9 components in there! It's an op-amp fuzz, with no clipping diodes, so is it causing fuzz by pushing the op-amp to the rails? There's also a very simple resonant filter before the op-amp that gets some almost wah like effects.

fldrvr
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Post by fldrvr »

https://www.freestompboxes.org/viewtopic ... zz+#p52145

I've seen the gut shot and the pics of the components, but as a noob I find it pretty hard to figure out what's what.

I came across this thread elsewhere: http://music-electronics-forum.com/t29348/

Any thoughts on getting the schematic in line with the original pedal? Thanks
Good deals: (TGP) leray1, Electroman, bigEbeer; (HC) StratsRule07, lfrz93, Firebrand, caeman, bluesthug; (Talkbass) jazzyitalian, MicG, bufert57, marineman227; (DIYstompboxes) LucifersTrip, (ILF) Monkey Boy, julius_deane, oldangelmidnight, K2000

fldrvr
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Post by fldrvr »

Also got this:
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Good deals: (TGP) leray1, Electroman, bigEbeer; (HC) StratsRule07, lfrz93, Firebrand, caeman, bluesthug; (Talkbass) jazzyitalian, MicG, bufert57, marineman227; (DIYstompboxes) LucifersTrip, (ILF) Monkey Boy, julius_deane, oldangelmidnight, K2000

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Post by peepsthecat »

Greetings. I did some R&D, traced this beast, and slapped together a vero layout. It works like the clips.
Lm741 and TL061 work the best in terms of taming the whine. UA741 works okay, though the squeal is always present. I suppose one could add a series resistor to the frequency pot. This is my 1st layout using the DIY software- I typically work from a hand-scribbled notebook...
Cheers,
Peeps
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agoldoor
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Post by agoldoor »

Wow, that's so interesting... weird timing. I know mirosol and IvIark were pulling their hair out over this one... In the meantime I had been looking at it separately. Thanks for finally getting something working!

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Nocentelli
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Post by Nocentelli »

Thanks for this. I have a couple of questions - Did you research and tracing involve an original unit, or is the information from the DIYSB thread? Secondly, I tried breadboarding it from the schem at DIYSB but had no luck getting any sound at all. On the layout, where it says "ground", should this be connected to the normal ground connections (i.e. Input+output sleeve, power supply negative and battery negative), OR the battery negative ONLY. I understood from the DIYSB thread that the "ground" for this circuit needs to be isolated from all other ground connections, since it is actually at a different reference voltage, meaning it cannot be daisychained with other pedals to a common power supply. However, I may be be totally confused - Hopefully you can help.
brownwhopping wrote:How can I learn by reading threads an making circuits, when some day I can see a lawsuit or somebody beat me in the face for that?

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Intripped
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Post by Intripped »

this should be the schematic - I've done the R.E. again, starting from the pics you can find on the net
the schem is coherent with the veroboard layout posted by peepsthecat
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ESR-GF.png
ESR-GF.png (2.58 KiB) Viewed 2688 times

peepsthecat
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Post by peepsthecat »

Nocentelli wrote:Thanks for this. I have a couple of questions - Did you research and tracing involve an original unit, or is the information from the DIYSB thread?
I traced the original circuit by comparing every picture of the board I could find- component and solder sides. I used no schematic, though I read somewhere the 9V- went directly to the board. It was the last wire to figure out, then it worked like the sound in available clips. The degree of squeal can be controlled by choice of op amp or a little series resistance with the Filter pot (which I labeled "freq" in the layout). Other omissions: Vol is 10k log, Filter is 1M lin, and output is from Vol 2.
Now, can we improve this circuit?

This layout was verified at tagboard effects by JaviCAP.

Cheers,
Peeps

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Nocentelli
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Post by Nocentelli »

Many thanks to peeps and intripped for the advice, i've got it on the breadboard and i'm getting some fuzzy sounds but only at a very narrow window on the frequency/filter pot: Either side of that, it cuts out totally. It's late, i'm using headphones so it's hard to tell, but i'm pretty sure there's no sign of the extreme filtering effect, huge slabs of heavy fuzz, or oscillation as evidenced on this awesome video https://www.youtube.com/watch?v=h3VEA6ivC1M

I'll check all my connections, maybe swap the chip, and try again over the next few days. I'm pretty sure I understand the circuit, but I just want to check I have this right: On intripped's schem, all the ground symbol points should be connected together and can presumably also be connected to the guitar cable shield, the pedal chassis, and therefore the negative of the AC power supply of any other pedals in the chain; As long as this one circuit uses a battery connected at +9v and -9v on the schem (and is therefore separated from power supply of the other pedals), it should all work, right?
brownwhopping wrote:How can I learn by reading threads an making circuits, when some day I can see a lawsuit or somebody beat me in the face for that?

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Nocentelli
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Post by Nocentelli »

Simple/stupid mistake (pinout error), works now! Oscillation aplenty, tweaking begins tomorrow.
brownwhopping wrote:How can I learn by reading threads an making circuits, when some day I can see a lawsuit or somebody beat me in the face for that?

allesz
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Post by allesz »

:applause:

So is the schematic verified?
I don't like (or can :oops: ) work with ic, but this one it's very inspiring. Sadly I did not understand the schemo posted on diysb.... great work intripped., it goes on my to do list (very short recently).

btw... It seems that the filter is nothing but a feedback control, and so I understand the effect of it; but I don't understand the fuzz effect: is it just the chip being overdrived? On the video posted above I see no relationship between the clipped sound and the position of the feedback knob (guitar volume maybe?); If so it would be possible to build a very simple overdrive-disto-fuzz with very few components :hmmm: Not that I want to dismiss the fun factor of the filter control, only tring to understand the thing better.

btw n. 2... does jhon l. basicaudio posts here?

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John Lyons
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Post by John Lyons »

The Schematic has been verified for a year or more.
Granted the Schematic I posted was missing a ground and a 10k resistor. :oops: :lol:

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Post by allesz »

John Lyons wrote:The Schematic has been verified for a year or more.
Late to the party?

I just got to get me some single ic (only 4558 and tl072 on hand) and start breadboarding me too :horsey:

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Nocentelli
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Post by Nocentelli »

allesz wrote:On the video posted above I see no relationship between the clipped sound and the position of the feedback knob (guitar volume maybe?); If so it would be possible to build a very simple overdrive-disto-fuzz with very few
The filter knob really is just that - It visciously filters the fuzz sound (HPF?), and at the extreme maximum setting, it cuts the signal all together. The difference in fuzzy-ness levels in the video must be from adjusting the guitar's volume control.
brownwhopping wrote:How can I learn by reading threads an making circuits, when some day I can see a lawsuit or somebody beat me in the face for that?

allesz
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Post by allesz »

Thank you for the info... the feedback is funny, but it would be useful to control the distortion too: maybe an input pot?
I called John Lyons because it seems he has done a little bit of work and experimenting on the circui,t so maybe he could give some hints about it. It's a basic circuit so maybe I will find out by myself... since I have only double ic chips I could try to use only one, and maybe use the second one for something else (clipping, buffer, boost,mondo gain?).

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John Lyons
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Post by John Lyons »

When you use a buffer before the circuit it will help with bringing back some high end
and stabilizing the circuit a bit. The oscillation is the fun part of the circuit.
There are a lot of big fuzz sounding circuits but this one has some weirdness
which is neat.

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Post by peepsthecat »

Weirdness. Yes, that's the fun. For me the graphic fuzz takes a back seat to Escobedo's Bronx Cheer, which can get properly weird with a twist of a guitar knob or even a slight circuit tweak. I'm curious to see if anyone tweaks the graphic fuzz...

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