# Duocast noob question



## Markus Kersius (Apr 21, 2021)

How essential is it to have all electrolytic caps in the Duocast rated at 35+ volts?
Are there any that don't require that rating?
Especially the 330uf.
And is it possible to modify the charge pump to 18v?
By removal of a 5817 ?
Noob.. i know..


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## slowpogo (Apr 21, 2021)

Those caps need to be 35V to account for the voltage switch -- which goes between 9V and 27V. The next lowest cap voltage is 25V which is not enough, obviously.
You could jumper the switch to always be at 9V, then you could get away with smaller caps. But I wouldn't recommend it, you will want to at least try 27V and see if you like it.
C100 does not need to be 35V, according to the build doc. Looks like a filter cap.


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## Markus Kersius (Apr 21, 2021)

Thnx, i think I'll just leave out the 1054 ic out first then, got no more 35v or 50v lying around but i really want to finish it and hear it.
I figure when switching with no voltage doubler present in the circuit, but  the 5817 diodes all present might give some interesting results as well 😅


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## Mcknib (Apr 21, 2021)

I'd try leaving C12 out don't jumper it just leave it out @Chuck D. Bones posted somewhere how to calculate a rough voltage doubler output can't find it at the moment, but afaik you count the number of caps coming off IC1 pin 2 and add 1 then multiply by the voltage in and subtract the voltage drop across each diode

So as it stands 2 + 1 = 3 x 9 = 27 - 2 = 25v
(According to the datasheet a 1N5817 drops 0.45v so say 0.50v x 4 = 2v) you'd also get a wee bit of voltage loss from the 1054

Take away a cap and

2 x 9 = 18 - 2 = 16v

Now I don't know if it'll work so I'd try it with the switch left in the 9v position then check what voltage you get on the cathode of D4 before you switch it over and let it loose on the circuit

The analog devices datasheet does show you building blocks etc if you want to have a look

Mind you might be fun watching a few caps blow

Maybe Chuck will come in and tell me I'm an idiot talking a pile of u know what

Just in case....   tell me something new Chuck I already know I'm a chancer but I'm an idiot that likes to learn

Found it scroll down a bit 






						Triangulum problem
					

I’ve just recently built the Triangulum build. It’s a working build but something sounds off. When I turn the level up to a decent level or about half way up I get a really bassy heavily saturated sound that starts to cut out and break apart when heavy power chords are hit. Like it’s being...



					forum.pedalpcb.com


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## giovanni (Apr 22, 2021)

I’m not sure that will work. You basically want to take the voltage across C13 (~18V) instead of C15 (~27V). You could remove C14 and C15 and jumper D3 and D4 and that will definitely do it. Not sure what happens if you just remove C12: it’s a configuration that’s a bit different from the recommendation in the data sheet and I’m not familiar enough with the chip to understand what it will do.


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## Mcknib (Apr 22, 2021)

Yeah as I said I don't know if it would work but easy enough to try without any adverse affects as long as you don't switch it in until you know what the effect on that SW positions voltage would be 

I never read the datasheet but thought the diodes may have some effect on the caps charging and discharging hence saying maybe have a look at the datasheet

I'm a bit of a mad experimenter when it comes to stuff like this haha as long has there's zilch damage potential and what's a wee cap between friends


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## giovanni (Apr 22, 2021)

Yeah looking at the schematic again I think removing C12 would work. In that case I would also remove C13. The only catch is that you will still get 4 diode drops so it’ll be ~16V output.


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## Markus Kersius (May 1, 2021)

Got the 35v caps.
This is a great pedal and I seem to dig it most at 24v as a boost on low mode.
It brings a presence to my sound with a bit of grit that's usable with clean or overdrive sound.
Still experimenting with the gain trimmers and my stash of telefunken/rca/Phillips and mullard transistors.
Had a AC125 /AC128 / AC188 / 2n1309 / OC 304/ OC72 / OC76 /GC511 and a TFK AF101 in it.
No OC71 unfortunately. 
Really like the AC188, AF101and 2n1309 so far.


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## nickquack (Apr 2, 2022)

Markus Kersius said:


> How essential is it to have all electrolytic caps in the Duocast rated at 35+ volts?
> Are there any that don't require that rating?
> Especially the 330uf.
> And is it possible to modify the charge pump to 18v?
> ...


a follow up to this, does it need to be 330uf? thats the only part im missing, wondering if i could get away with 220uf


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