Reverb circuit FBJ / FHRD

[Apprentice]

Any ideas on this. Last year on the forum someone provided a rob robinette circuit for a reverb driver cct.
I have done the same as the poster and build a Hoffman BJ. and now want to add reverb. I've got a new Ruby BJ reverb pan and was wondering if I can drive it with the HR deluxe driver cct. The impedance of the pans for BJ and HRD are not too far different from each other and wondered if anyone had gone the Rob R route as its described as driver for "any" amp. Or do I need to use the BJ cct for the New BJ pan? The HRD is a more straightforward cct in my eyes and therefore an easier build.
Also on the BJ cct there is a 330pf at 1kv, can anyone tell me why it needs to be 1kv.
Thanks

[PRR]

> a 330pf at 1kv, can anyone tell me why it needs to be 1kv.

I see a 47pFd @ 1KV.

It does not have to be 1,000V. Since it could see full tube voltages, it probably should be 400V, though some figuring might lead to a 50V max stress.

The real thing is, before today's nano-electronics, it was not worth making very small pFd in very small voltages. About all <100pFd caps were 500V or 1,000V. If you look in *tube guitar amp* shops, that is what you will find. *Pedal* shops may list few-pFd 50V caps, though again they are likely to be 100V-1000V just because not worth making them lower-Voltage. If you design cell-phones, packing a super-computer and a super-radio into a wallet, then you may find 5V caps but they are too small to see or handle with my fat fingers.

[Apprentice]

I'm from the age when all these items were piled up as junk for scrap. It seems everything is now so valuable and has to be cost effective. If only I could have seen into the future. I'm probably going to source a 630v as they are reasonably easy to get hold of.
Thanks for the reply

[2deaf]

I see a 47pFd @ 1KV.

The Blues Jr. Rev. has a 330pf 1KV for the input filter to the TL072.  The DC has already been removed by a .0022uF coupling cap. at the plate.  I'm sure they just used a ceramic cap. that was rated at 1KV because that was the cheapest thing at the time.

[Apprentice]

Yes that's why I asked the question, in case I was missing something. Thanks for the reply