Vox - Repeat Percussion (V 809)  [schematic]

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

Duckman wrote:Hey, Calambres, no le saquen el pie del acelerador a Pisotones!
VOX Repeat Percussion at pisotones.com

In spanish, of course, but do a google translate if you wish :wink:

Hope you enjoy it.

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Calambres
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Post by Calambres »

In crappy googlenglish

The funniest part is translating my nick me as "cramps"... :D :D :D

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Calambres
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Post by Calambres »

Oops.. there were a couple of omisions and a wrong capacitor value :oops:
I think it is OK now

VOX Repeat Percussion

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Calambres
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Post by Calambres »

Some scope shots.
Original signal is channel 1 (above) and the processed is channel 2 (below):

Image
The whole LFO action showing how abruptly starts and how slowly it fades.


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The shape of the pulse.

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An average of the pulse. It is lower in amplitude to the original signal but the peaks make the illusion of being more or less on par with the bypassed signal.

I love this circuit :mrgreen:

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tabbycat
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Post by tabbycat »

Calambres wrote:Some scope shots.
The whole LFO action showing how abruptly starts and how slowly it fades.
I love this circuit :mrgreen:
many thanks for the scope shots. it's a luxury for we scopeless people to be able to see as well as hear how the magic happens.
if this appeals to you maybe look at the vicovibe, another fairly unconventional (non-opto) vintage trem circuit. it reminds me of the tremolo circuit in the fender rhodes piano, being as much a liquid shiver as a tremolo. interesting.

fsb link and schematic here https://www.freestompboxes.org/viewtopic ... ibe#p34690
gfx link here http://tagboardeffects.blogspot.co.uk/2 ... -vibe.html

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Calambres
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Post by Calambres »

One interesting point about this circuit is that the resistor from the 2N2646 Emitter and lugs 1-2 of the rate pot, 4K7 in the the schematic by Gottfried Divos (first post in this thread), is 5K6 in the original JEN Repeat Percussion portrayed in my web. The higher the value in this resistor, the slower the LFO.

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The cited resistor is the rightmost of the bottom pair.

The rate pot value here is 100K but it seems to be too much as the first third is almost useless. It behaves better with a value of 50K Lin as in Divos' schematic..

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Lani
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Post by Lani »

Does anybody know if the 2N2418B would work as a replacement for the UJT? I have a bag of 20 that I can't figure out what to do with. Looking at the datasheet for both they look similar . Current is a lot more if I'm reading it right but that's about it....
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