guitar preamp to drive headphones and/or powered speakers

[wgrea3]

Hi all,

I'm thinking of building a <1 Watt tube amp / preamp for guitar, that I can use to drive both a pair of headphones, or a powered speaker / studio monitor. I live in an apartment building, so I'm looking for something quiet, but something that will allow me to overdrive the tubes.

I've been searching for a while to find info on such a project, but I'm not having much luck. Could any of you point me in the right diretion?

So far, I'm thinking I just need to build a preamp stage, and then a power output stage that is essentially unity gain, but I'm not too clear on whether that signal would be able to drive both a pair of headphones (~600 Omhs, 90 dB/mW) and my studio monitors (~10 kOhms).

Thoughts? Thanks for your help.

[wgrea3]

So after some further reading, I think I've figured out what must be done. Please correct me if I am wrong.

For headphones, I need to use a guitar preamp stage, followed by the power output stage from a headphone amp.

For powered speakers / monitors, I guess I would simply bypass the power output stage, and put the preamp signal directly into the input of the monitors.

Anyone see a problem with that solution?

Thanks.

[Hotsauce]

Headphones will require 2 channel amp, most guitar amp are mono. Maybe a design than can be summed to mono?

John C.

[EWBrown]

The headphone left and right (ring and tip) can be connected in parallel, at the jack, then they will effectively be half the nominal operating impedance.

Or the alternative scheme si to run a two channel guitar preamp, if the pickups can be brought out separately, and then go with stereo, though it might sound kinda strange that way

/ed B

[wgrea3]

Yeah, that's what I was thinking. I could either run the two earphones in parallel or in series. Not sure what the audio difference would be. Anyone know?

[EWBrown]

If you are using standard stereo headphones, (as opposed to ear-buds), then the best would be to connect them in parallel, as a series connection (if the cable has three conductors) would put the drivers out of phase.

Even with ear-buds, I'd choose parallel conncetion, the resulting lower impedance would be easier to deal with.

I never really liked ear-buds, I just see them as an open invitation to ear infections, even if they are never "shared" with anyone else.

Remember that old warning about "never stick anything sharper than your elbow into your ears"...

/ed B

[Bishvajit75]

If you are using standard stereo headphones, (as opposed to ear-buds), then the best would be to connect them in parallel, as a series connection (if the cable has three conductors) would put the drivers out of phase.
...

Is it possible to use the standard headphone by a series connection? I cannot figure my amp here with my headphone because I do not know how to connect it by a parallel connection. I was wondering if connecting it by series won’t damage my headphone.