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Low voltage DIY tube amp designs

post #1 of 8
Thread Starter 

By low voltage, I mean "can be powered off a 24V/1A AC wall wart" :) . Most of the well-known tube designs need fairly high voltages, and require doing your own mains wiring with a toroidal transformer. For people who want to avoid that, what options are there? I've been reading through http://www.head-fi.org/t/402067/a-super-simple-6dj8-headphone-amp , which does sound promising. There also is http://www.head-fi.org/t/663739/hcc86-low-voltage-hybrid-headphone-amp-for-diy-beginners - it's a fairly expensive project though. Do you guys know of other designs that will happily run off a 24V/1A supply?


Edited by yawg3d - 7/18/13 at 6:16pm
post #2 of 8

The bravo/sunrise/indeed are all 24V/1A designs. anything based on those would work. 

post #3 of 8

Look into the starving student amp.  There's a 12AU7 variant, it uses a 48V supply.  24V is not really enough to drive the tube for high impedance headphones.

post #4 of 8

The Cavalli CTH is a great example of a 24v wallwart based tube hybrid amp. It uses a voltage multiplier to get a 80v B+. I have a few of 'em -- one for work one for home. The CTH uses the 12AU7 or 6DJ8 families of tubes. Others work fine like 6CG7 or 12BH7. It's got many pluses and only a few minuses.

post #5 of 8
Quote:
Originally Posted by Mullet View Post

The Cavalli CTH is a great example of a 24v wallwart based tube hybrid amp. It uses a voltage multiplier to get a 80v B+. I have a few of 'em -- one for work one for home. The CTH uses the 12AU7 or 6DJ8 families of tubes. Others work fine like 6CG7 or 12BH7. It's got many pluses and only a few minuses.

 

Yes!  I had figured the OP was talking about DC.  I just re-read and he said AC and not a DC wallwart, so yep, that'll fit in that class too.

post #6 of 8
Quote:
Originally Posted by yawg3d View Post

By low voltage, I mean "can be powered off a 24V/1A AC wall wart" :) . Most of the well-known tube designs (i.e. Cavalli, Millet, ... ) need fairly high voltages, and require doing your own mains wiring with a toroidal transformer. For people who want to avoid that, what options are there? I've been reading through http://www.head-fi.org/t/402067/a-super-simple-6dj8-headphone-amp , which does sound promising. There also is http://www.head-fi.org/t/663739/hcc86-low-voltage-hybrid-headphone-amp-for-diy-beginners - it's a fairly expensive project though. Do you guys know of other designs that will happily run off a 24V/1A supply?

Millett need fairly high voltages?  What well-known "Millett" amp runs on anything other than 24V (except the Starving Student)?  No offense, but there's only one family of low-voltage headphone amp designs that runs the tubes in their manufactured voltage range - that's the "Millett Hybrid" family of amps (Starving Student not included).  Only space-charge tubes are designed for 12-24V on the plates as recommended in their data sheets.

 

The 6GM8 is a low-voltage space charge tube exception to the Millett Hybrid family, but that tube is few and far between and purchasing them is about like purchasing a collector's item.  You can build an EHHA with a couple of them, or play around with modding a Melos amp that uses them, but that's about it.

 

You might want to check Jeff Duntemann's web page on space-charge tubes:

http://www.junkbox.com/electronics/lowvoltagetubes.shtml

 

Those are all pretty much the truly-low-voltage tubes in existence.  The Millett Hybrid family of amps use the 12AE6, 12FM6, and 12FK6 tubes.wink.gif

 

P.S. I should add that the guys above have mentioned some very good amps, but I got a little amped upwink.gif when you were asking about low-voltage tube amps and mentioned that Millett was not one.  The original Millett Hybrid by Pete Millett that was published in Audio Express magazine was a trailblazer for DIY headphone amps because it was all based on 24V:

http://www.pmillett.com/file_downloads/ax_hybrid.pdf

 

It's since been modified some (like in someone's avatar wink.gif).


Edited by tomb - 7/18/13 at 5:33pm
post #7 of 8
Thread Starter 

Oops. I will immediately edit the opening post, seems I was misremembering. Shouldn't have quoted names before double-checking.

(edit: Oh dear... the only HV design on diyforums/Bezaar is the Torpedo, and that one isn't even labelled Millet. Man did I get that one wrong... bigsmile_face.gif)

 

Then again, getting you "amped" up got me a very interesting reply with great information and useful links ;) !

 

Seriously, thanks to everyone who replied so far :)


Edited by yawg3d - 7/18/13 at 6:24pm
post #8 of 8

Ha!  No problem - hope I contributed. biggrin.gif

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