audio-talk

Hi All
No one here a big empty room scary
OK my Headphone amp a Mapletree Audio Design
Ear+ Purist HD
See here
http://hollowstate.netfirms.com/ear+purist.htm
It has gone through many upgrades external choke PSU A.N Tant resistors shunt Alps pot 'SONIQS' SAX capacitors Marconi B339 drive valve output GE 12B4As cans are HD650
Great sounding amp works we’ll with jazz/blues Still not finished 18 month on

Hello Colin.

I have one and a half headphone amps at the moment.

The first is the TubeCAD featured here: http://www.glass-ware.com/tubecircuits/ ... ifier.html



Some of my ramblings are here: http://www.atrj13.dsl.pipex.com/na-tube ... ne_amp.htm

The second "half" is a "proper" build of an Aikido headphone amp using 6CG7 and 6DJ8. Still very much under construction. Circuit located here: http://tubecad.com/2006/09/blog0081.htm with a few minor mods.



Simon.

I should pay attention here. I use headphones at work, and I keep thinking about building an amplifer to use there. So I shall watch with interest to those that have gone before .

Hi All
I have been thinking of building an other headphone amp with the 6as7 valves for some time now and came across this one the head hunter see also the Martian A headphone amp using a rare 832a double Tetrode tube just a couple of ides if your looking for some thing a bit different http://www.platenspeler.com/diy/uk_inde ... headphones

I have a Little Dot 2.



A (cheap) Chinese jobbie that seems to the trick OK for me. It was a present from my better half last Christmas. After a few teething problems it's settled down quite nicely.
2 resistors were cooking after a 41PS tube started drawing excessive current for no reason (dodgy batch I'm told via the US importer replaced FOC).

I'll eventually build summink better (I hope) but it's got me through a few Period Dramas on TV that Julie insists on watching

DTB

Perhaps this should go under Projects, but here's the "finished" 6CG7/6DJ8 headphone amp, although I've got some modern 6922s in place of the 6DJ8s at the moment.



It's pretty much exactly as I had it on the breadboard at the beginning of the year except I've got rid of the cathode bypass cap on the bottom 6DJ8 and star earthed rather than earth buss.

The PSU is a little different as most of my chokes are in the phono at the moment. So using what I had left I've got 600V ct -> humble 1N4007s -> 10H 74R DCR -> 40uF -> 390R -> 94uF Cerafine. B+ is a little high but no problem. Might put another 390R in series with the one already in.

It sounds really rather nice, better than the proto. This could be the absence of the cathode bypass caps, or the PSU, or a bit of both I guess. The response time in PSUD is really rather quick and it definitely sounds very quick to me. Dynamic too. And there's more detail.

Interestingly PSUD predicted 98mV of ripple. I wondered if this might be quite noticeable but the hum is barely audible. The heaters are AC and trying a DC pi filter didn't change the hum so maybe I can just hear the HT ripple? I could try some more L when I have some chokes free, but frankly it's not a problem and it sounds so good anyway I don't feel the need to tinker.

This is the first time I've used 6CG7s and I rather like them. They're 6SN7 equivalents but 9 pin with an internal screen and they're about £5 each nos The internal screen is supposed to make them sound better than 6SN7s but I haven't compared them so can't comment.

One day I'll get around to a nice wooden case to mount on the mdf and some nice shiny knobs - then everyone who visits will think I have a really expensive amp from a shop.

You've taught me something, I wasn't aware of the 6cg7. That would be well worth incorporating into any design.

Hmm, maybe we should buy some before anyone else notices.

Old valve Oscilloscopes are often full of these in special Mullard gold pin versions.

From what I gather Mullard picked the best from runs and plated the pins.

6FQ7s are equivalent to 6CG7 but don't have the internal screen.

Here's a 6CG7, hopefully you can just about see the screen:

Simon I assumed from your post the 6CG7 and 6DG8 were the same valve

I don't think they are?

6DG8 is an ECC88 which is not an equivalent to a 6CG7??

Can you clarify what you are using cos I seem to have lost track here.
Thanks
Darren

I think these are the valves in question

http://www.pentalaboratories.com/pdfs/6CG7.pdf

looks like the screen just separates the two halves.

Ah, sorry Darren, probably wasn't very clear if you didn't realise it was an Aikido...

First valve in the Aikido is 6CG7 or 6FQ7. The 6CG7 has the screen separating the two triodes and apparently the physical stiffening this adds also helps the sound (according to John Broskie...)

The second valve in the Aikido is a 6DJ8 (or ECC88 or 6922).

The circuit is a tweak of the first one you come to on this page: http://www.tubecad.com/2006/09/blog0081.htm

Ah, I see now, this is what got me

here's the "finished" 6CG7/6DJ8 headphone amp

best wishes
Darren