Basic layout question

[demonstratedspatulas]

I want to try doing an amp on a pcb. I've done a few turret amps, and once you start needing relays, things can get pretty annoying.

100 watt push pull.

I have my layout divided roughly into regions:



I'm worried about three separate things.

1. Region 1: This is where some power amp components come close to some first stage preamp components. For example, the first stage cathode resistor ground side is about 1/2 inch away from a screen resistor power supply side. I could scoot my power amp region a bit to the right, but I would end up with a bit of wasted pcb space. I've also been considering doing it in two boards, the preamp, and everything else.

2. Region 2: The presence and depth controls of the PI come pretty close to the reservoir caps. I'm guessing the presence and depth caps are less sensitive to noise than say, the preamp components, but I'm guessing also the reservoir caps are radiating noise like crazy due to the current pulses that charge them.

3. Long signal wires from the PI to the coupling caps of the power amp. These are really the only long signal traces on the board. Left side is about 4 inches, right side is about 3 inches. I could run these as shielded wire if necessary. I doubt they are too susceptible to noise as the signal is pretty high amplitude to drive the power tubes of course, but long traces I know aren't ideal.

I'm totally fine with just trying it and seeing how it goes, but if there are any obvious mistakes I'm making I could fix them now.

[thetragichero]

so I'm a guy who is now comfortable with building tube amps through older styles (i prefer terminal strip point-to-point because it's easier for my breeding to understand how it's supposed to work when troubleshooting) so for me I'd get my feet wet with the stuff that needs to be on pcbs on small daughter boards so that the majority of the amp can be laid out as I'd normally do it. obviously depends on the complexity of your switching system. frankly that's the kinds stuff that makes my head spin lol
I'm sure other folks will respond with more direct answers to your questions

[wpaulvogel]

Are your tube sockets going to be soldered to the board? I’d build the board in a different shape other than a pure rectangle, let the preamp section set over away from the power section.

[demonstratedspatulas]

Everything that can possibly be panel mount will be panel mount.

I think you are both right, doing a monolithic board design is definitely the wrong way to go. It does not lend itself well to experimentation or replacement of sections.

What if I want to replace just the preamp at some point? Etc.

Thank you for the advice here, I will certainly take it.

[demonstratedspatulas]

I have the pcb split up into several sections now.

Now I'm just concerned about one layout item: The proximity of the OT to the preamp tubes.

How close can it be? I know the OT radiates EMF like crazy, and the lamination edges are "pointing" directly at the preamp tubes. (ie, the end bells are pointing to the left and right sides of the amp looking at it from the front)

What's worse? The end bells or the laminations pointing at the preamp tubes?

How many inches away must the OT be from the preamp tubes?