tube preamp: adding headphone out

[then_dude]

hello everybody,

i wanne build a tube pream as a preamp for a tripath amp.

i have already found a design, i wanne use it because i can get the parts very easy. and also the design is well documented.

now i still have a problem, i would like to use this amp with a headphone, (something between 32 -600 ohm) but it has not a headphone out and mute switch.

could anybody give me a hand on adding this to the design ?

i have mailed the original builder but i think he receives so much mail that he isn't able to answer it all.

thanx

here is the original scheme.

http://www.triodedick.com/cleo_6/Cleo_6_versterker.GIF

[then_dude]

nobody ?



i'm gonna cry me a river

[danielw]

30-600ohms is quite a range...

I can't tell if this schematic has enough drive capabilities to drive a headphone amp directly. If it does, the least you should do is increase the value of the output cap. The current value is good enough for driving the high input impedance of a power amp. Driving a low impedance with this cap would result in a lack of bass.

This high-valued cap (~100uF or more) is then most likely a electrolytic cap. You can leave the high-quality film cap that is in there now, and put a switch. So you can choose to drive either your power amp through the high-Q cap, or your headphone through the large valued cap. This gives you the required 'mute' function as well.

[then_dude]

indeed that 's what i' wanna do.

a parrarel cap in the output something like this.
(www.dhtrob.com)

[Ryssen]

I made one with 6888 and 6c45 and it sure has capability to drive my 300 ohms HD 650,I have an outputcap of about 10uf.

[then_dude]

10uf, isn't that a bit low,

if you need a 220uf for 32ohm ; then i would suggest that you need 23uf for a 300 ohm headphone

i'm thinking of buying a hd-650 especially for its high impedance,
but then again i lke the akg k 701 more, it has an impedance of 64 ohm,

i have found elna cerafine 220/220uf at 350 volt for 30 dollar,that's not costing an arm or a leg. so i think i'm going for that, and put even 22/22uf parrallel, and maybe even 2/2uf,
does that make sense to anybody ?

thanx a lot

[Ryssen]

Ok,I have 2 10uF paralelld,I have messaured it with RMAA 5,5 and it is okay in the frekvensy..

[pengboon]

I used a white cathode follower with 5687 after the 12B4 on my preamp, with variable feedback, it is supposed to drive 32-300ohms, though I've only used it on my 250ohm DT990.

Let us know how this turns out.

[then_dude]

hello,

i have just contacted the author of the original scheme,
dick: a ducth guy who is a)very friendly b)very good at what he's doing, and also has this wonderfull site,

anyway, he told me that the amp is powerfull enough to drive a headphone; okee, so that's very good news

he told me to start with a 220uf cap and see what it does, and then adjust a bit, probably i end up with 110uf for my 64ohm headphone.
we will see what happens, but first some exams, haha,
and then building like a mad man. I just wanna get setltled on the design allready.

anyway thanx everybody
greetings me myself and I

[then_dude]

oh yeah another thing

i have red somewhere, (on the headwize site on a project) that putting a cap parralel with a greater value in the output cap isn't always good. what could be wrong with it ?

thanx a lot