JMI Vox - Grey Wah c. 1967

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

This thing making me hard on! I have a couple of internal picts, but no shots under the board. Since it's not so complicated this should be easy to make an exact clone.

Here's some info about components used http://wah-wah.co.uk/greyvox.html

And the picts

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Post by analogguru »

sinner wrote:This thing making me hard on! I have a couple of internal picts, but no shots under the board.
There is nothing important under the board - the connections are all made left and right of the board and visible.

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Post by Electric Warrior »

It's a clyde without the resistor in parallel with the inductor. The inductur supposedly measures 250mH.

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Post by sinner »

analogguru wrote:
sinner wrote:This thing making me hard on! I have a couple of internal picts, but no shots under the board.
There is nothing important under the board - the connections are all made left and right of the board and visible.

analogguru
Electric Warrior wrote:It's a clyde without the resistor in parallel with the inductor. The inductur supposedly measures 250mH.
So this will be simple to draw, I'll do it when I'll back to work, now 3 days of

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Post by Solidhex »

You'll find its identical to this schematic... Image
Also know that the Texas Instruments 2n3707 have a ECB pinout instead of the usual EBC.

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Post by Bernardduur »

Now does it sound? For example compared to a standard Vox / Dunlop wah????
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Post by phibes »

Paco, who did the refab board in the very top picture? I was expecting to see JMI doing a reissue of these since that's been there jig but I'm glad to see that's not the case. I always kinda wanted to build one of these up in the vintage fashion. Did you draw a layout yet or you want me to?

...I bet someone at JMI is drawing up plans as we speak.
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Post by Geoffrey Teese »

I'm amazed by all the hullabaloo on TGP about this series wah. I've had a number of these through my hands and was never impressed by their sound. A thin whine just doesn't do it for me. Then again, I'm not the favored dog in that race anymore...

Nice work doing the repro layout.

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Post by leeyoungun »

Bernardduur wrote:Now does it sound? For example compared to a standard Vox / Dunlop wah????
Tighter, thinner sweep. A lot less low end, more emphasis on high end and upper midrange. Page used one in The Yardbirds and the first couple Zeppelin albums. Also featured in the RAH '70 DVD.

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Post by leeyoungun »

phibes wrote:Paco, who did the refab board in the very top picture?
That's Stuart Castledine's work. www.wah-wah.co.uk
Brad/Creepy Fingers built me a mean clone! "Thin whine" is a good description. lol. I really dig the wah tones Page got and I believe The Pretty Things used one on the S.F. Sorrow album.

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Post by sinner »

phibes wrote:Paco, who did the refab board in the very top picture?
No idea, my buddy send me those picts by email, it comes from DAM's forum AFAIR, I can't find this topic out there, I have to ask Johnny where to look
phibes wrote:Did you draw a layout yet or you want me to?

...I bet someone at JMI is drawing up plans as we speak.
Don't you dare, live it to Paco. Paco turned 30 today, and since his old he need to have a brain exercises. I'll do it day after tomorrow, as I've lost my head some ware yesterday and I'll lose it again today :mrgreen:
Geoffrey Teese wrote:I'm amazed by all the hullabaloo on TGP about this series wah. I've had a number of these through my hands and was never impressed by their sound. A thin whine just doesn't do it for me. Then again, I'm not the favored dog in that race anymore...
Sir, it's not about the sound it does, it's for education, and I mean really :) I've find out that while I was doing R&D of my FF builds, I'm almost ready with 5 clones from different era, with a lot of care to details. Great fun, I need it with wahwahs now, I will repro every fucking classic out there :mrgreen:

I'll understand if you don't, as its your bread, but can you post some more details of the components used there? Brand, type, any differences between units you had in your hands? what is the pot value, anything you will to share?

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Post by Dan N »

The Thomas Organ part # for a 250mh inductor is 80-5044-7. Organ Service Corp. ( http://www.organservice.com/ ) have them on their stock list for $8.00. I don't know exactly what OSC stocks, but they replace a brown TDK in a Fasel style package.

Maybe email them for more info? You can tell them you want to replace a #44 from a rhythm unit. That should get you the right thing.
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Post by theehman »

Dan N wrote:The Thomas Organ part # for a 250mh inductor is 80-5044-7. Organ Service Corp. ( http://www.organservice.com/ ) have them on their stock list for $8.00. I don't know exactly what OSC stocks, but they replace a brown TDK in a Fasel style package.

Maybe email them for more info? You can tell them you want to replace a #44 from a rhythm unit. That should get you the right thing.
Order several and I'll take a couple.
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Post by Geoffrey Teese »

The wah pot is a simple 100K audio taper, nothing sexy or made with unobtainium in the whole piece.

BTW-A lot of the "Icar Taper" 100K pots on the market are actually audio taper, at least according to CTS (who makes 99% of them).

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Post by sinner »

Dan N wrote:The Thomas Organ part # for a 250mh inductor is 80-5044-7. Organ Service Corp. ( http://www.organservice.com/ ) have them on their stock list for $8.00. I don't know exactly what OSC stocks, but they replace a brown TDK in a Fasel style package.

Maybe email them for more info? You can tell them you want to replace a #44 from a rhythm unit. That should get you the right thing.

Thanks for the info, but fuckem, I'll wind my own, It's also education process and should be fun :)
Geoffrey Teese wrote:The wah pot is a simple 100K audio taper, nothing sexy or made with unobtainium in the whole piece.

BTW-A lot of the "Icar Taper" 100K pots on the market are actually audio taper, at least according to CTS (who makes 99% of them).
Thanks Geoffrey! Any idea what range of transistor hfe should work best?

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Post by phibes »

Nice on the inductor info! I'll have to order one. Might as well add another wah to the family.
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Post by mictester »

Solidhex wrote: Also know that the Texas Instruments 2n3707 have a ECB pinout instead of the usual EBC.
... and a good equivalent for the 3707 is a BC184L - same pin out, same gain range.
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Post by sinner »

Is the schematics from Fuzz Central is correct?

I see no jumper or wire connection between 22k resistor and 470k resistor coming from Q2 base on photos...

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Post by sinner »

This is what I have already, also you'll find DIY Layout Creator project file attached just in case if you can correct it. It doesn't have connection mentioned by me in my previous post, so it might be wrong

As per transistors Hfe - datasheet shows that 2n3707 is in range of 100-400, so I suspect it should be in middle of this
mod wrote:file removed - see updated revision below

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Post by sinner »

I believe its correct now, don't thank - it's my duty

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