Marshall - Supa Wah  [schematic]

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

Right on, I've change my mind. I'm going to give it a go. I'm going to pick up my laptop after uber quick fix and some layouts (vero, and tagboard) should be up later tonite

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Post by sinner »

tagboard is up, vero on the way. I don't care about PCB, so you're free to go

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Post by Chugs »

I take it your laptop is up and running again! :applause:

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Post by RnFR »

Chugs wrote:Attempt three!

I am going to try and make one of these. I'm not going to try and track down some of the 2G374 transistors though, probably try a few different Russian germanium's and see what sounds best. Might try and throw a Marshall Supa fuzz in the wah case too! :mrgreen:
FYI- I deleted your older schematics. just a note to remember- those transistors are PNP.
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Post by sinner »

Yep, my faithful piece of shit is up and running again :)

I was searching datasheet for those trannies and in the one I have tha hfe range is 75-265 so no that much low gain Timm. It looks like they was chosen with gain range in mind. NKT257 or OC81D for example are much lower hfe-wise in the datasheet, way lower than popular gain recommendation are. I have a couple higain low leakage unknow germaniums I'm going to use here

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Post by phibes »

Yeah I got the same datasheet downloaded. It's really hard to say how much they might measure out as Germanium's differ so much from transistor to transistor. I'm sure there are some that spike way over the gain range on the datasheet and some that fall under. Give the ones you got a go. Personally, I'd just skip the trouble and use PNP silicon since it's a wah. No need to waste the mojo!
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Post by RnFR »

I think it might be fun to intentionally up the gain on the Ge gain stages to get a bit of growl with your wah. I wonder how it would sound? I might have to try that!
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Post by sinner »

To be honest the only reason I'm going to build it is the use of germaniums, odd thing, unusual, worth to try. I can always scrap the board and put something different into the shell.

As per trannie selection. I'm quite sure that the Marshall picked this set not because of sonic abilities, but because of what datasheet showed in the gain region. Look on the other popular trannies sheets of this era.

Texas Instrument 2N3707. Data sheet from 1967 shows 100-400hfe (those I have are between 280-403) so the middle of it is 200hfe. Middle range of Supa Fuzz trannies is something around of 175hfe. Close to typical gain range of the silicon ones picked for grey wah
RnFR wrote:I think it might be fun to intentionally up the gain on the Ge gain stages to get a bit of growl with your wah. I wonder how it would sound? I might have to try that!
Sounds like fun isn't? :)

BTW - I think we can move it from the requests ;)

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Post by sinner »

2N3707 datasheet

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Post by Chugs »

Yeah, it might be interesting to try some high gain germanium's. I popped some low gain germanium's into one of my wah's today and it was ok but nothing stellar. Seemed like there was potential there though. 2N1309's are quite often around 150-200 hfe with low leakage. Might be a good choice if you are looking for a bit more growl.

Thanks for deleting the old schematics RnFR.

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Post by RnFR »

I've got some 2n1307s that are similarly hi gain/low leakage that I was thinking of using. you could definitely tweak Q1's values for more gain as well. I think that's where the distortions going to be coming from.
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Post by sinner »

Here's promised vero.

I took a lot of care to match mojo component selection to small vero (IC friendly).

Components I had in mind as fallows:
- IC friendly vero board
- 1/2w Bredley CC's
- axial Philips 10uf 25v (small and sexy)
- axial 0.1uF's are Mustard Cap like in original unit, standing on the layout. Takes less space, and looks Marshall'ish They did it like that in several units I've seen
- 0.01uF are Erie ceramics. Distance between legs is around of 7mm. Fit nice into vero Supa Fuzz, as well as in here. You can find them on ebay UK - seller valvesetc - £0.99/one I'm using that in my builds quite frequently.
- Whipple halo replica. I'll check how Arteffect's SoD looks on it (if I remember right, SoD is smaller), I just need to get home, I don't have one here with me

I took much care to rout out close enough to grounding point to use shielding output wire

Surly you can use other component types, like 1/4w resistors, whatever - layout can be even smaller. It was drawn with my favorite part selection in mind, with something I'm using and I have

Everything fits nicely with the parts I've listed, like seen on the pictures of my proto board (it's not the actual circuit I'm building, so the resistor values are wrong, I did it just to see how parts lay down). Only one Mustard cap shown, as only one I have on hand at work.

Also, some pictures of the masta during drawing process attached to show how frustrating it is sometimes for a simple paramedic on the shift.

Pictures are shitty - laptop camera was used here

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Post by RnFR »

:lol: :) :lol: :lol: :) :lol: ....

haaaahh!!!!!

oh god.... that is some funny shit! :slap:
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Post by drewl »

Interesting.....anyone else ever build a wah using germaniums?
That could sound pretty freakin' cool....theoretically.

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Post by sinner »

RnFR wrote::lol: :) :lol: :lol: :) :lol: ....

haaaahh!!!!!

oh god.... that is some funny shit! :slap:

You haven't seen the last foto :D It's just two legs with the sock on one only
drewl wrote:Interesting.....anyone else ever build a wah using germaniums?
That could sound pretty freakin' cool....theoretically.
Or like shit :mrgreen: But it's worth to try. I think I'll do what topic author said. I'll put the supa fuzz circuit to combine those two with 3 way switch fuzz/wah->fuzz/wah only. Founds like fun.

I'm still looking around the boxes for SoD inductor. I'm always finding shit when I'm looking for something specific. I'll end up finding this inductor by accident looking for something like light bulb :slap:

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Post by Geoffrey Teese »

I can't find my schematic or any Supa-Wah files (too many hard drive crashes ago I guess) but I'm pretty sure the inductor is more towards 1.5H and not 500mH.

Sorry I can't be of more help right now. If I can find any real paper I'll update.

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Post by sinner »

Geoffrey Teese wrote:I can't find my schematic or any Supa-Wah files (too many hard drive crashes ago I guess) but I'm pretty sure the inductor is more towards 1.5H and not 500mH.

Sorry I can't be of more help right now. If I can find any real paper I'll update.

Thanks Geoffrey, that would be nice of you :) Can you sort one thing ones for ever and tell us is that makes much tonal difference if we'll use 250/500/higher inductor?

As per SoD thing. Naturally I didn't find any fucking single light bulb, but the inductor is found. It's Arteffect Stack Of Dimes replica. I think it's 500mH, but I'm not sure, I must to email them. Like I've said, the body is smaller, but the base takes almost the same space like Whipple so no moving around of layout will be done.

Now, I need to put the order to the factory for paxolin IC'ish vero, and I'll give it a born

I'll keep you guys updated

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Post by Chugs »

The vero is looking mojo-tastic Sinner! Looking forward to hearing how it sounds.

I would love to put those photo's of you into a flick book! I think the sequence would work quite well. Remember those?

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Post by sinner »

Thanks :) Don't do it ;) I don't want to see my ugly face on all forums around the world ...anyway I've deleted them

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Post by Geoffrey Teese »

Yes, the inductor value matters. 1.5H is very deep sounding and the rest of the circuit is tuned for that value. Any value inductor will make the circuit work but the 1.5H will get Marshall's sound right. Throw on 3x500mH inductors and you'll hear the difference. Similar to the difference with a 250mH versus 500mH in the Vox circuit. One part makes a big change in frequency response. Even the difference between 500mH and 600mH is audible.

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