Re: Decadence Preamp Elec Caps

[k3yPr0gg3r]

Hi,

I really want to build the Decadence Preamp correctly. On the build guide front page it notes 35V for the 7 Electrolytic caps. I'm having a hard time finding 2U2s and 22Us in 35V. Is this just a minimum volts needed type of thing and one can use 50V, or do all caps need to be 35V in order for the circuit to fire?

Thank you...

 

[fydo]

The ratings on the capacitors are a maximum rating, so you can safely use 50V when a 35V is called for. Just keep in mind that sometimes the higher rated caps are physically bigger, so it's a good idea to check the size in the specs/datasheet.

Enjoy the build!

 

[k3yPr0gg3r]

Thank you! I use low profile elec caps. I also have a bunch of 25V 2U2s and 22Us, so I guess it's ok to use those if I'm reading things correctly.

 

[fydo]

The PCB for Decadence Preamp calls for all 7 of the electrolytic caps to be rated at least 35V, so I wouldn't use 25V caps for this build. Hope that helps to clear things up!

 

[jesuscrisp]

In all seriousness, there's no reason the circuit would need anything more than 16V rated caps unless you plan to run it from higher voltage power supplies than 9V.

 

[jwin615]

I see no mention in the build guide of voltage requirements for caps.(on the pcb)

https://docs.pedalpcb.com/project/Decadence-PedalPCB.pdf

There's no boost converter but I don't see any reason that you couldn't run it at 18v if you wanted.
(I'd opt for a 1n5818 though)
If you wanted to do that, 35v caps would be recommended.
It's good practice to overrate your caps 2x the supply voltage or VCC. 16v caps will work just fine, but not ideal. One connection to an 18v supply and the party is over. Over rateing them can extend their working lifetime as well. 25v would be the minimum rating I'd recommend, 35v is ideal, 50v won't hurt if they fit.
You can mix and match voltage ratings without issue.

 

[jesuscrisp]

16v caps will work just fine, but not ideal. One connection to an 18v supply and the party is over.

What I'm saying is, when you run it at 9V only, there's no reason to have 35V rated caps specifically. I've read varying benefits in terms of lifetime when overrating caps a whole lot, but definitely helps with caveman guitar players plugging in whatever fits the hole.

In general though, 25V rating is usually absolutely fine for 18V usage.

 

[hamerfan]

When we were young and stupid, my friend used to crack up old electrolytic caps. Just a lab transformer and a long cable to the garden fence. I tell you that these caps can eat some more voltage than printed on the can.

 

[jwin615]

What I'm saying is, when you run it at 9V only, there's no reason to have 35V rated caps specifically. I've read varying benefits in terms of lifetime when overrating caps a whole lot, but definitely helps with caveman guitar players plugging in whatever fits the hole.

In general though, 25V rating is usually absolutely fine for 18V usage.

I hope to leave my pedals to my grandchildren one day so it helps me sleep better at night.
Funny story. A few months ago I bought a PV dual clock chorus, dsc-2 if I remember correctly. It's hot pink and manufactured around 88 to 1990. I popped it open just to see cuz, you know, you have to. It was actually 98% SMD surprisingly. Not bad for the boys down in Meridian back in that day. The filter cap and BBD were through hole. The filter cap was only rated for 9v, and while swollen, was still working. Seemed like a planned service fee, but it worked 25 years later.

 

[Robert]

The similar pedals (Ten Years is a Decade and Acorn Solid State) can both be powered at 9 - 18V.

35V caps were spec'd on the PCB just to be safe, 16V would work perfectly fine for straight 9V operation.