Pédale de Vibrato et de Super-Aigues  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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Rambozo96
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Post by Rambozo96 »

Hello all I have stumbled upon a schematic with a treble booster and a tremolo effect from a French DIY magazine. What strikes me as very odd is how the aforementioned treble booster uses 2 transistors. They kinda look like 2 identical gain stages running in series. I got the circuit built on PCB and ready for final assembly since curiosity got the better of me. A schematic is provided for those also curious about this or anyone that can shed light on how this circuit works as a treble booster.
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Schematic

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idy
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Post by idy »

The first transistor is a booster. Then there is a "T" filter that cuts bass. The second transistor is a gain recovery stage. So your signal is super hot and super aigue.

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modman
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Post by modman »

Posting this partial page from the French electronics magazine Le Haut-Parleur on Facebook turned up the missing page.
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Rambozo96
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Post by Rambozo96 »

I finally got around to building this, used MP11A NPN Russian germanium so I don’t need a charge pump for the circuit. It’s very thin sounding and almost unusable with how much high end it pumps out. Maybe the T filter can be tweaked to tame the ice pick highs? Probably doesn’t help that I used a Danelectro in the demo.


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modman
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Post by modman »

Thanks for that clip - I don't think anybody has an excuse for demo clips anymore :D
Did you build this part of the circuit or the whole thing?
Screen Shot 2019-12-20 at 13.19.17.png
It may be the transistors, if not start jumpering the filtering between the two transistors. Dropping first 1n5 and the 10k resistor...
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Rambozo96
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Post by Rambozo96 »

Just the treble booster side. I attempted the whole thing last year and couldn’t get either to work BUT my laying out schematics to PCB skilled were fairly weak then. I guess I’ll try different transistors first and see what happens from there.

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mictester
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Post by mictester »

It's NOT a vibrato - it's a badly designed germanium TREMOLO. It might (sort of) work, but there are LOTS of better circuits around to do this. The treble booster is also poorly designed and will have more hiss than signal!
"Why is it humming?" "Because it doesn't know the words!"

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