Tube Headphone Amps

CJ · Aug 24, 2004

I forgot if I ever posted this project.
No biggy, just a couple of all tube headphone amps side by side in a rack.
One is (gulp!) an amp I saw at (gulp) Pat's site and the other is a design I saw at Headwize, an Eric Barbour design. Both are transformerless.
I used 5687's for Pats design and 6SN7 and 6BQ5's for Erics design.
Guts:

http://vacuumbrain.com/The_Lab/TA/Headphone_Amp/hp_1.jpg

I soldered leads directly to the tubes and heatsinked them to the chassis as they run quite hot.
I do not know if soldering direct improved the amp, but it does have incredible detail but low headroom. If you want to hear everything in a mix at low volume, this is the amp. You have to scrape the leads on the tubes to remove the plating for a better solder joint. Hey, who wants to send away for sockets and wait two weeks! Those tubes are for

http://vacuumbrain.com/The_Lab/TA/Headphone_Amp/hp_2.jpg

I scored some silver foil caps for half price at the surplus for output. Buck and a quarter a piece!

http://vacuumbrain.com/The_Lab/TA/Headphone_Amp/hp_4.jpg
here are the links to the schematics and article.

http://www3.telus.net/public/vintage1/phones.jpg

http://headwize.com/projects/showfile.php?file=barbour_prj.htm

Erics amp has a lot more headroom and is the choice for ear damage and enjoyment, whereas Pat's is used when critical listening is done.

PRR · Aug 25, 2004

> a design I saw at Headwize

http://headwize.com

I'm sure Cmoy would be very happy to see this posted over there.

Why are there TO3 transistor insulators under the tubes? And glop??? All those sand-state artifacts will rub-off right into the tube.

Get a block of aluminum (silver if you find a good deal on THAT). Mike the OD of the tube and bore the block a few thousandths bigger. Slide the tube in, then wedge some asbestos paper in one side to keep it tight to the other side. (If you have not yet had your fatal dose of asbestos, use oak hardwood split down to a toothpick.) Or bore a hair oversize, then bandsaw the block in two, bolt it together with springs under the boltheads.

Your approach is correct. In all small tubes, heat radiation through the glass is almost zero. Glass is opaque at the temperatures and IR range that small tubes run at. All heat has to conduct through the glass. We normally convect the outside, but good conduction is better.

I have frankly had much more trouble with dirty sockets than sick or dead tubes. Solder-in sounds like a good idea.

Guest · Aug 25, 2004

http://vacuumbrain.com/The_Lab/TA/Headphone_Amp/hp_1.jpg
.[/quote]

If you solder wires directly to the (normal) tube, its warranty voids.
...and it is hard to solve without gold plating...

xvlk

gyraf · Aug 26, 2004

Nice project!

I've also tried an adaptation of one of the headwize projects -
http://headwize.com/projects/showfile.php?file=ciuff2_prj.htm

http://img.photobucket.com/albums/v172/gyraf/Headphoneamp.jpg

Schematic:

http://img.photobucket.com/albums/v172/gyraf/Phone_Amp.gif

..VERY simple, but it's our favorite singer-headphones driver in the studios..

Jakob E.

Gustav · Aug 26, 2004

Now where did I see that badass before ?

Gustav

gyraf · Aug 26, 2004

Maybe we have a new DIY-project here?

PCB Layout (rough drawing - may be cleaned up if there's any interest):

http://img.photobucket.com/albums/v172/gyraf/Phoneamp_layout.gif

..this headphone amplifier will, however, only work well with headphone impedances of 150 Ohms or higher!

The shown 10x16cm "eurocard" holds two stereo headphoneamps..

Jakob E.

zebra50 · Aug 26, 2004

Thanks for this - I've been looking for a headphone amp project for a while.

Is there an easy way around the 150ohms trick? I'm rather fond of my 80ohm DT250s. Maybe a transformer at the out? Or more tubes?

:thumb:

gyraf · Aug 26, 2004

[quote author="zebra50"]Is there an easy way around the 150ohms trick?[/quote]

Yes, simply double the number of tubes (or use both halves of the layout in parallel) - but remember to use a larger value output capacitor as well.

Or use a 2:1 output transformer, but it has to be one that will work with high levels.

I also have this solid-state headphone amplifier box - the design dating back to the good old days before computerized layout:

http://www.gyraf.dk/tmp/Gyraf_headphone_box.PDF

It's a basic design - bass, treble and volume controls - bootstrapped transistor output stage to get the most from the +/-21.9V that are allowed for 5534's. Hot? Hell yes, but they still run happily on their 12'th year or so...

Jakob E.

nik-- · Feb 14, 2006

sorry for replying to a so old thread, but.....

I'am very interested in the tube headphone amp from Jakob

cause all of Jakobs Projekts I have build sound great ! (especially the pultec clone)

I search a good headphone amp to controll my mixes via my headphones (after mixing via my Monitor speakers),
because the one of my old digi desk is not sounding good.

but there are a few problems:

I mainely use 2 Headphones to do this : Beyerdynamic DT 770

and one Sennheiser hd 25 Headphone.

the beyerdynamic is rated at 2* 250 Ohm
the hd 25 is rated 70 Ohm

so what could I do to get both headphones working on one AMP ??

two other things : first, does the amp give much Tube colour ??
cause I want the mixes to sound like they are and not toooo polished,
because I wanna make the right decissions by control listening via them

and not think that its the best mix of my life .....

second has anyone from the forum tried Jakobs Headphone Tube Amp Layout PCB ?
are there any things to be changed or updated ??

would love to get some input from the "danish chef" himself

Nik

gyraf · Feb 15, 2006

Hi Nik,

The layout is untested, as far as I know. But it's such a simple construction, that it shouldn't be very wrong (i.e. unfixable) anyway.

For good effiancy in lower impedance headphones, you need either more tubes, or a step-down transformer at the output. See posts above.

This box is still one of our favorite monitorboxes for vocal recording.

Jakob E.

nik-- · Feb 15, 2006

Thanks for the Input,

do you think that straight paralleling of the two amps boards will do the trick ??

whats about the sound ? is it more neutral or more tube coloured ?

Nik

nik-- · Feb 15, 2006

forgot to say that the lowest impedance I will use is 75 OHM

gyraf · Feb 15, 2006

Two boards in parallel will drive 300 Ohms happily. But output transformers are probably the best way.

For 75Ohms drive, you'll need something like a 3:1 stepdown output transformer of sufficient core size (i.e. power). You'll need to experiment with types to find the right one - I can't help you with that.

Jakob E.

nik-- · Feb 15, 2006

and what about my other headphones with 2*250 OHM's --- what do you think will be needed for this ? one card, two cards paralleled or with output transformer ? maybe I will just use this headphones for it.

sorry for asking too much questions. but I really wanna test the board - maybe you could make it a new DIY Projekt afterwards.

Nik

kevinc · Feb 15, 2006

Here's a link to the schematic of a vacuum tube headphone amp I designed and built. Balanced ins, about 15dB of gain and very low output impedance (in the teens without any feedback) to make it pretty universal. It is very useful for monitoring purposes.

http://www.audioasylum.com/forums/KandK/messages/4428.html

CJ · Feb 15, 2006

wow. kind of a push pull Kimmel.
where buy mosfet?

kevinc · Feb 15, 2006

Not quite. The output is taken from the plate rather than the source, so the MOSFETs are only plate loads, in this case as variable loads, also used to balance the output stage. I have the MOSFETs in stock and you can also use the pin compatible IXYS 10M45S, obtainable from Digi-Key.

kiira · Feb 15, 2006

Hey CJ are there some (cheap-ish) 5:1 output xformers you would recommend for someone building that 5687 amp? My best friend wants to build a headphone amp but he wants transformers in it.

Kiira

CJ · Feb 15, 2006

That Haufe you have will work, if fed from a big cap.
I stuck in the MEQ 5 and it sounds lucious.

Mailliw · Feb 28, 2006

Jakob,

Would the Hammond 269BX be a suitable power transformer for your tube headphone amp? The high voltage secondary gives 150-0-150.

Would that 10V difference change much? If so, could I remedy it by reducing the value for that power supply filter resistor, the 5Watter?

Thank you,
William

Tube Headphone Amps

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