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thanks for your help! :)
porl
On 20/06/07, Dominique Michel  wrote:

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>

> Le Tue, 19 Jun 2007 20:51:58 +1000,

> "porl sheean"  a =E9crit :

>

> > thanks for the links!

> > the ax84 one is really good, pretty much exactly what i was after -

> short

> > and to the point (i don't mind a bit of complex math as long as it is

> > explained why i am doing it :)

> > i've looked through a few old valve books (

> > http://www.pmillett.com/technical_books_online.htm is an awesome site)

> but

> > it was hard to find certain info.

> >

> > i should probably have told you that i am making a guitar amp that i

> want to

> > sound dirty (not heavy metal distortion, but old overdriven blues

> sound). i

> > was only talking about a 4k primary because i'm pretty sure that is wha=

t

quoted text
> the

> > OT that i gutted from my fender hotrod (a bit high rated for this

> project

> > but i can't afford to buy much at the moment). i have tried the same

> tactic

> > with PTs of old amps off ebay (the fender one doesn't have a 5V output

> and i

> > want to use a tube rectifier), but even the small one i realised is

> > 375-0-375 for the primary! i think this is a *little* over what i need,

> so i

> > am going to have to buy a new PT. i can't figure out how the old amp

> used

> > this voltage: it was only a p/p el34 amp (2 output tubes). how would it

> have

> > brought the voltage down enough to not kill the valves? maybe el34s can

> > handle a lot but i didn't think the preamp tubes could.

> >

> > anyway, sorry about how off topic this is. i should probably take my

> > questions elsewhere.

> >

> You can try the diyaudio forum. It is a thread with a lot of links on

> vacuum

> tubes theory:

>

> http://www.diyaudio.com/forums/showthread.php?s=3D5fc6a5fdf8f4d9101e3f07...

60bc6c498&threadid=3D38278

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>

> You can find some with amule too. Just search for vacuum, valves or tubes=

.

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>

> About the EL34, 375V for Ua is a very low voltage for such a tube. (You

> can

> find the datasheet from http://www.nj7p.org/Tube.php or with google).

> You can go up to 600 or even 700 V without problem. But you are right whe=

n

quoted text
> you

> said at 375 is too much for the preamp tubes. Only some old japanese

> preamp

> tubes can handle such voltages, and they are very hard to find. The best

> is to

> made a separate and low-noise alimentation for the preamp. A simple R-C

> can be

> enough.

>

> For the tubes, I generally prefer new tubes over old ones. Some new tubes

> are

> even better as the best old ones. The engineers of today know what they

> are

> doing when they manufacture a new tube.

>

> Dominique

>

> > porl

> >

> >

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