[sdiy] spring reverb and pots

[Marc Bareille]

Hello

Nicholas Pelkey a écrit :

> Two quickies.
>
> I was about to order pots for my ASM-1 faceplate.  I'm either ordering through Radio Shacks or Mouser.. and will probably be using 100k linear.... one thing that the Radio Shack guy stumped me with was he had asked "how many amps?"  I never see much mentioned assides from 100k and linear.  So my question is what are the other recommended specs for pots asides from 100k, linear (or multi-turn)?
>

I have builded an  ASM- 1 , so this is what  i have used :

- cermet 100k linear pot for CV attenuators and controls (VCF cutoff...)
- plastic 100k log for all attenuators on audio path

- for VCO tune  : 10 turns 100K lin pots, it is a personnal choice and you can also use a coarse and a fine tune knobs...( suggest 100k lin...).
- for ADSR  attack, decay sustain, i feel it better with log pots but.... 100K give  a quite short duration time. Use a  bigger value as 500k or 1M if   you can, esle you can increase by 2 or 3 the value of the capacitor  who define time constant in ADSRs ... ( on the pcb border near adsr's wires)
- same remark for Glide pot ...

>
> Second
> This should be easy because people have been discussing reverbs lately.  I was on a link from Magnus' ASM-1 site and spotted the use of a spring reverb tank in one of them.  I have one that comes with an amplifier from a Hammond M100 organ.  There is the main amp, an amp for the reverb speaker and the tank (it currently patches into the "reverb amp").  Any tips on how to use the reverb tank without the amp would be great.  Theres no way I'm sticking a tube amp in the housing I have in mind for my ASM-1.

My first idea was to put a little spring reverb in my ASM-1. As i didn't find any around me ( i didn't search a lot) i have implemented a little
CV crossfader mixing the direct signal you send with an external effect ... A kind of effect insert loop with CV mix control... This methods have 2 advantages finaly: you avoid the big Clang that spring reverb can produce when moving the synth...and it allow to plug any external effect (chain) in that place...

A simplest method for your needs could be to add a "big"  voltage divider with 2 resitors at the output of  amps. Resistor should be sized according to the power of  the output amplifier and temperature dissipation....May be power resistors, i don't know Hammond 's tubes amps but i imagine they are close for guitar power amps designs ....This last tip is not a very good method, it is the "Mc Gyver's way"  on my idea but it should  work ...

For driving the tank separatly you will need a little preamp/ driving stage. You can make a search for guitar effects diyers... I have already seen schematics on this subject ... Guitarists are  main users of spring reverbs...

Regards

Marc Bareille

email : mailto:m.bareille.free.fr
web: http://m.bareille.free.fr

>
> Thanks,
> Nick P
>
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