Looking for a good valve preamp

[AndreaVTS]

Hello all,

I have just some parts in my bin (three 6922 tubes, power transformer, etc...), I need only need a line stage preamp. Any idea for a good schematic?

I found interesting the Vacuum State FVP5 / FVP5A projetc. Anyone know/built it?

Thanks in advance!

Andrea

[Glowbug]

Three 6922s...maybe a grounded grid? I'm not sure if the 6922s would work for that though, I've just seen it done with 6SN7s and 12AU7s, of course.

[AndreaVTS]

Hi Jim,
I can by another one...or use only 2 :-)

[DougL]

Question one. How much gain do you need?

[AndreaVTS]

Hi DougL,

I think not too much, I use only cd player and digital sources like pc...
The amps are diytube.com :: View topic - diytube Ike docs & mods *UPDATE 10/11/06*
(el34 push pull)

thank you
Andrea

[booangler]

Originally Posted by DougL

Question one. How much gain do you need?

Doug,

Still new to all this. So how do you determine how much gain you need?

Alan

[DougL]

Originally Posted by booangler

Doug,

Still new to all this. So how do you determine how much gain you need?

Alan

This is much harder if you still have a phonograph.

If you only have CD, The CD player usually has a maximum output specification. This is usually about 2 Vrms
The amp also has an input sensitivity spec, usually under 2 Vrms. for full power. In this case, you do not need gain.

The Heretical is a good example of a tube Preamp without gain. The B1 from Firstwatt is a solid state example.

Does this help?

Doug

[Shoog]

Three 6922's will make you a nice version of the FVP5. I had a thread describing the evolution of my design version of the FVP5 some time ago using three ECC88's. The secret is to substitute MOSFETS for the top triode in the original. This worked very well and I still have it now. I rebuilt it using ECF80's which sounds marginally better. Short of going balanced I cannot see me building another preamp.

Do a search on FVP5 and shoog and you might get a bit of inspiration.

Shoog

[45]

Originally Posted by DougL

This is much harder if you still have a phonograph.

If you only have CD, The CD player usually has a maximum output specification. This is usually about 2 Vrms
The amp also has an input sensitivity spec, usually under 2 Vrms. for full power. In this case, you do not need gain.

The Heretical is a good example of a tube Preamp without gain. The B1 from Firstwatt is a solid state example.

Does this help?

Doug

Actually, the average output from a CD player is much lower than the maximum output.
I think it is not a good idea to determine the gain from that number.
In my experience a 0.2-0.3 Vrms sensitivity for a integrated amp (i.e. 1W output) or 0.1-0.2 Vrms for a preamp (i.e. 1Vrms output) work better.

Cheers,
45