Tiny tube amp

[PhenomXFx]

Hello everyone!

My name is Tony. I'm new to the forum and to amp building. I've got a question regarding headphone amps and regular amps to power a larger speaker. I want to build a small amp, roughly 1w output to power a Weber 6" guitar speaker. I've found lots of headphone amp schematics and I think the 6p1n would be a good tube to base my amp on. I haven't found much for guitar amps without a preamp. I have plenty of preamps and just want something to drive the speaker. My question is what specifically makes the amp a headphone amp? I would assume output transformer...? Is there anything else? can I just take a headphone amp and change the transformer? Thanks for the help!!!

[ampgeek]

Welcome Tony!

Yes. From a very broad and general perspective, you can change the OT to match the amps power output section to a guitar speaker as opposed to a headphone "speaker".

Post up your schematic or link and any information that you can find regarding its transformer and I am sure that a reasonable OT specification can be generated.

Also include the impedance of the speaker that you want to use.

Whether or not the "optimum" OT is readily available will be the next major question to address.

Finally, the volume that is ultimately attained largely depends on the efficiency of the speaker. You might be underwhelmed with a 1W power output driving a 6" speaker. I have never done that so hopefully someone who has will chime in.

Cheers,
Dave O.

[ampgeek]

Hmmmm....it just dawned on me that your headphone amp vision is most likely a stereo affair.

Guitar amps are typically monophonic. Shouldn't be a problem if you are doing a scratch build though.

But....definitely post up the schematic that you are leaning toward.

Dave O.

[PhenomXFx]

Thanks for the fast response! I may have found something to go on.
http://www.diyaudio.com/forums/tubes-va ... tubes.html

Stereo wouldn't be bad as I use some stereo effects units... but mono might be easiest to start. My original idea was to modify something like the Little Dot sold on amazon, but I'm not sure how a headphone amp would distort in comparison to a guitar amp.

I saw this thing http://www.thegearpage.net/board/showth ... p=19175331 but I think it has too much color from the preamp section, I'm just looking for a clean power amp to get that tube power amp distortion sound that a cranked amp has, just at an extremely low volume. And something I can test multiple preamps and speakers with.

The speaker I would likely use is the Ceramic 6" sold here: https://taweber.powweb.com/weber/ Maybe even a smaller speaker (or multiple speakers) if I could find something fitting.

[Leo_Gnardo]

the volume that is ultimately attained largely depends on the efficiency of the speaker. You might be underwhelmed with a 1W power output driving a 6" speaker. I have never done that so hopefully someone who has will chime in.

Cheers,
Dave O.

Just revived a Sears Silvertone 1391, cool old combo with a 6" speaker, powered by a single 6V6 from a 285V power supply. Very Champ-like but half the power, 2.4W measured at 500 Hz. Because of cheap OT's in this (and Champs) you can't expect very much clean power at low frequencies. No matter, it's a great sounding little amp. You mic that up for recording, let 'er blast and nobody will know how small it is. Little amps sound terrific for recording, and small cones are light and move fast. As long as you can get along with low volume, you know you're not likely to bug the neighbors. Building your own, I could recommend 6AQ5 output tube, commonly used in old clock radios & plug&play phonographs back in the 50's and 60's. Plenty of those still around for cheap.

For a stereo headphone amp you're going to have to go more hi fi. If you build a well filtered power supply to keep hum down, run a single 6AQ5 or EL84 or 6V6 per channel, should make a fine can amp. Good reasonably priced hi-fi OT's available from Edcor in New Mexico. One thing that's a bit of a hassle with headphone amps is the wide range of headphone impedances. There's plenty of 8 ohm cans, 32 ohms is less often found but some popular cans do run at that impedance. All the way up to 600 ohms for some other popular models. If you know what phones you're going to use, get OT's with secondaries to match and stick with 'em.

[RWood]

If you want bedroom volume fender/plexi type sound that's built on the cheap without a tube...http://www.runoffgroove.com/ruby.html cost me about $25 to build and will drive 1x12, 2x12, and even my 4x12 speakers with 9v or 12v battery power. I often do a gig at a fire circle in the woods at a rehab facility and we bring 3 of them with 3 small speakers with drummer on Cajon.

No need for preamp but I did play for about 30min with a Valvecaster in front with no problems. I don't know if that would harm it in the long run but it seemed easily 1 watt.