Voltage and Signal question?

[Dan0h]

I need help. Dumb questing but I really don’t know.

If you have two circuits that you wish to combine but they both operate on different voltages can their audio paths be intertwined in the same circuit? Is the audio portion of the circuit separate from the power section? I know this is a dumb question but it’s got me all tied in knots.

What I am trying to bread board is a tube preamp with a delay circuit in the “effects loop” of the tube preamp circuit. Coming from the first stage of a 12ax7 into the delay circuit and then out and into the second stage of the 12ax7 with a blend pot to mix in the wet signal. In my head it can work but because the delay and the preamp circuits are running at different voltages will this cause an issue? It shouldn’t right? Pedals of all sorts of voltages are mixed and matched all the time, but can they be wired together?

My last bits of parts should arrive soon from Tayda, then I can wrap up the breadboarding just thought I would ask before I zap myself or the circuit.

The photo is not the values I intend to use but the path is.


Or am I wasting my time trying to surgically insert a delay between the two stages of a tube and would be better served just having the two circuits tided from out to in like everyone else does for two in one builds?

Thanks in advance.

 

[swyse]

I would think this should be fine as long as you use capacitors of the appropriate voltage rating to block the DC as appropriate and your tubes aren't sending a massive AC signal that clips the delay's input.

 

[vigilante398]

Sorry I didn't see this sooner, but I'm pleased to inform you that you're overthinking it.

Take a look at the Klon schematic: the first opamp runs off 9V, but the second runs off 27V(-ish). Running a high-voltage tube circuit into a low-voltage digital device like a PT2399 would be no different. Naturally you want to make sure you have coupling caps on the tube side so you aren't feeding a 200V DC offset into your signal and frying the PT2399 input, but if you follow the general signal path laid out in that picture you would be good to go.

That's basically how I did mine, and unfortunately my schematic isn't on this computer, so I'll try to remember to post it when I get home. but basically as long as you're removing DC offset with coupling caps and you're minding audio levels so you aren't clipping inputs, you should be good to go.

 

[vigilante398]

I remembered to pull the schematic Looks like I lied though, I used a gainstage before the PT2399, not a cathode follower.

 

[Dan0h]

I remembered to pull the schematic Looks like I lied though, I used a gainstage before the PT2399, not a cathode follower.

View attachment 33012

Cool. I’ll breadboard this out and see how it sounds. Currently wrapping up two different mn3005 delays. It’s been delay month for me.

 

[vigilante398]

Cool. I’ll breadboard this out and see how it sounds. Currently wrapping up two different mn3005 delays. It’s been delay month for me.

Oh make sure you ignore the pin numbers on the tube, those correspond to the daughter board I mount my tube on, not the pins of the tube itself.