Subbing film cap for an electrolytic bypass cap

[turtle441]

Crazy question... I've been messing around building a Plexi SE using the pcb sold here:  https://www.gapcb.com/products/plexi-se-pcb

C7 in their schematic is a standard cathode bypass cap, looks pretty electrolytic to me.   https://www.gapcb.com/documents/Plexi-SE-PCB-Schematic-v11.pdf

Interestingly, their BOM lists it as a 100V film cap.  Haven't ever seen a non-electrolytic used as a cathode bypass cap before.  Does that work??

[sluckey]

C7 in their schematic is a standard cathode bypass cap, looks pretty electrolytic to me.

What looks electrolytic about it?

You will have a hard time finding an electrolytic that is less than 1µF. All the old plexi amps used a .68µF cap in that position. Works very well.

[PRR]

> What looks electrolytic about it?

On *that* drawing, the filter caps have a curved line, the tonestack caps are straight lines.

The 0.68u has a curved line.

OTOH, on the PCB, the known-electrolytic parts have + and - signs on the printing. The 0.68u does not.

We should also know that the difference Fender to Marshall is that Jim had boomier speakers and down-sized Leo's 10u-22u caps to under 1uFd, finding happiness around 0.68u. While you "can" get 0.68u in an e-cap it is very odd. And a film cap is better (won't rot in a decade). And Hoffmann stocks 0.68u film in lowest-available voltage *for* this purpose.

[92Volts]

You can "always" use a film cap in place of an electrolytic, if voltage and capacitance ratings are right.

You will have a hard time finding an electrolytic that is less than 1µF. All the old plexi amps used a .68µF cap in that position. Works very well.

I actually have 0.68uf electrolytics on hand but I don't remember exactly why or what I used them for. I assume I bought them because it was cheaper than a film cap at that size/voltage, but I doubt I saved more than $0.10 each.