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I'm beginning to plan for features for a "dream" amp. Could be long, long off but here I am wondering - I'd like a decent bit of switching capability. I'm gonna keep it short.

What is the best way to perform switching at high voltage like seen on an amp with a minimal footprint? Is it relays?
Say I wanted many smaller options - would 100v/1amp or 50v/1.5amp DIP switches such as these or these work?



Do I need a vDC250 switch for pretty much all switches or mostly just ones with Plate voltage? Are signal path (such as passive RC filter) components going to need it? What about grid/cathode?

Short answer is no. What do you want to switch and what do you mean by switching capability?

i tell you this,i am restoring an old Binson hifi 60w,mid 60s amp,original tubes and caps,600V on plates and 390 on screens.
The one and only switch in this is a plastic case 1P1T,with copper tabs,so just one pole switching the main transformer on.
It works perfect like this,all these years.

+1 to depends on what you're switching...
For things like channel switching, relays work great. They don't have to be large or heavy duty. There shouldn't be any high DC voltages present on them because you would ideally have the switching happen after the coupling capacitors. For other things, like selecting different value cathode bypass caps and the like, it's a similar situation of there generally not being any high voltages or significant currents happening in those parts of the circuit. Light duty mini toggle switches work fine there too. Alot of commercial amps have used LDRs for channel switching, which are nice because the switching is noise free without any popping sound, but they have the problem of often going bad after 20+ years and needing replacement. Relays will eventually wear out too, but a high quality one may well last longer than the LDRs seem to.

The place where you really need to consider the high voltages and currents is if you're doing any switching in the power amp circuit. Like if you're doing a triode/pentode switch. But even then, it seems you don't need anything particularly special, just recommend a heavier switch with thicker insulation. I use the same switch for both the mains power and the standby (which is switching the B+ high voltage), and it has been fine. Alot of this depends on how powerful the amp is.

I honestly haven't decided if I want to make my own included power amp or just run it as a preamp yet.

As for what the switches do, they're all kinds of voicing switches, such as bright switches, crunch switches, coupling/filter caps, etc...
Cathode bypass switches are definitely planned for at least some stages, but also cathode resistor shorts (may have up to 3 resistors on some stages and bypass some via shorting on a switch). I'm guessing it's the same as the caps since its they're parallel so that's good to hear.
But I would also like them to perform similar bypasses in the signal path on coupling capacitors (always with one in line still) to control the voicing more, as well as plate-power and grid-gnd resistors.

So right now my assumption is this:
As far as over-voltage/ampage, almost any switch will be fine. Maybe one exception is at the plate to voltage? But I suppose I could probably get most or all of this effect by just having more switches on the cathode.
But popping could be bad on a loud amp. So for anything that can be assumed will be messed with when the volume/gain up, generic physical switches could be an issue for pops.

I've been confused about LDR switching a little bit - LDR switching is where you use the photoresistor to control a relay for the switching, isn't it? Why not just use a relay? And what do you really gain by controlling the relay with a transistor rather than just straight from power? These questions have alluded me on the relevant resources I've been able to find...

If I'm not making sense, I've attached a copy of the schematic so far, though its a mess and I want to say most of those switches are probably going to be removed as well as maybe some later stages. My idea came from heavy switching amps but also from the Carvin Quad X (11 stages in one channel, 8 preamp tubes), but wanted to include architecture from the Peavey 5150/SLO and something more classic (Univox 1086). And so I basically put everything I saw as a choice the designer took for the voicing specifically and turned it into a switch for now to see how many it could possibly be at max and I'll make it reasonable from there. Maybe put the Quad X stages somewhere more in the middle but maybe that should be a switch too...

So sounds like most of this would be technically safe with DIP switches, though I know they may not last the longest. Maybe socketting them all would be a good idea. Also maybe not buying these switches from Tayda for once. DIP switches would just be perfect because they're so small, seems like the closest analog equivalent to the level of control a micro-controller can provide.

Thank you all!

EDIT: Attachment failed probably due to my resolution. Uploaded to Imgur

Check out the schematic for the Peavey VTM-60 to see an example of a DIP switch used successfully.

Regarding LDRs for the channel switching. The SLO and Ampeg VL-1002 are examples you can look at. How it works is that it uses the variable resistor as the switch. When the channel is "off" the resistance is very high and mutes the channel. There is usually also at least a second one that turns on to give a low resistance to ground, to further aid in muting that channel. The big problem that often happens as they age is that the resistances drift too far off to effectively mute the channel and you get a problem where you hear the muted channel bleeding through in the background.

Using a transistor to switch a relay makes it easier to do things like having logic circuits controlling the switching. These days, I can see it being entirely feasible for a DIYer to do a crazy midi-controlled multi-switching amp (with stored presets!) using an Arduino or the like. Transistors switching relays would make this possible, since a microcontroller or logic circuit isn't able to switch a relay's coil on its own.

Thanks for all the explanation. Makes sense why an LDR could work well for things like channel switching, or anything that can be done by pure resistance, and less so for maybe coupling and cathode caps. It would be sweet to do some Arduino stuff with this project but programming may be above my grade!