Tube head phone amp

[johnheath]

Hi everybody

I just came up with an idea to build a one tube head phone amp to my friend who have his birthday coming up soon.

I have seen some schematics before where they use 12vdc source for such a project but I can't find it right now.

Please correct me if I am wrong about the 12 vdc… for heaters I get it but for the plate voltage???

Sincerely

John

 

[ruffrecords]

Often these designs use a 12V mains transformer for the heater supply and another 12V transformer wired backwards across the heater supply to get 120VAC for the HT supply. I have also seen some designs that use a SMPSU to generate the HT volts from 12VDC.

Cheers

ian

Cheers

Ian

 

[CJ]

if you don't make the deadline you can stall him out with the CMoy for under $20 and 9v batt>

http://tangentsoft.net/audio/cmoy/

what happened to the Headwize site, that used to be a good source for headphone stuff?

 

[johnheath]

Thanks Ian ... I guess that would be a bit out of my league. I was hoping to build a small gizmo that don't need to much power of any sort.

CJ - I have been looking at the C-moy and the Grado RA1 and actually built one of the latter... but.... eeeeh? No =) Maybe I just

Thera are some schematics on the internet where they use a single tube... using a external 12V "power" supply... if it works or not I don't really know. I'll try to post a link to such a schematic.

http://electronics-diy.com/class-a-12au7-tube-headphone-amplifier.php

Sincerely

John

 

[gyraf]

In that circuit, it's the FET transistor that does the headphone driving - the tube is there mostly for the looks (ECC82 dosn't work all that well on 12V)

Look at e.g. http://groupdiy.com/index.php?topic=1840.0 for real tube headphone driving..

Jakob E.

 

[ruffrecords]

Thanks Ian ... I guess that would be a bit out of my league. I was hoping to build a small gizmo that don't need to much power of any sort.

John

There are several problems using tubes to achieve that goal. First, tubes need considerable heater power; a couple of watts each is typical - and this is far greater than the power needed to drive the headphones. Second tubes are high inpedance devices so you need to do something smart to get them to drive relatively low impedance headphones - a transformer is the obvious answer but I have seen many ingenious alternatives. And third, tubes work best from high voltage supplies so you need some means of converting your 12V  up to a higher voltage.

There are lots of solutions to all of these problems but none of them really results in 'a small gizmo that don't need to much power of any sort.'

Cheers

Ian

 

[johnheath]

Thanks Ian - What you say is roughly what I suspected

Jakob - When I looked at that schematic I was also suspecting that the tube more or less is just a "funny" thing to watch. I'll have a look at the link later on today.

I have a rather small toroid power transformer laying around and maybe I could mess up something to call it a head phone amp… the basics is clear to me but I guess the main concern would be to get hold on a "small" in size output transformer that is suitable for headphones

Regards

John

 

[johnheath]

Jakob - I have been scouting the link but since it is rather old and most of the links doesn't work I must ask you if you could recommend any output transformer for the job?

Regards

/John

 

[johnheath]

CJ - (if you are looking at this) Do you still have the photos and schematics of the content in this thread from 2004?

http://groupdiy.com/index.php?topic=1840.0

If so… Is this something I can have a look at?

Sincerely

/John

 

[CJ]

checked the wayback machine and those pics did not get archived,

you might consider those Raytheon mini tubes, the ones with the floating leads,