Paia tube head with guitar

[j.frad]

Hey! I've been checking out the paia tube head, which is a starved plate tube dual preamp designed mostly line levels.
The guys at paia tell me the input impedance is medium range and wont load the pickup, but i'm wondering if a slight modification could make it more apropriate.
Do I just set it by changing r25 and r54? schem: http://www.paia.com/tubehsch.pdf
I'm thinking of maybe putting a switch for different input impedances and maybe implement a simple ssm2019 mic preamp into it, it's really just ideas at the moment, and since I'm not really experienced at designing stuff I'd like to get some help adjusting that impedance.
Thanks a lot!
Jules

[RaceDriver205]

I would recommend having a high-input impedance buffer between your guitar and the input. Much easier than modifying the circuit, which may cause it to work incorrectly.

Interestingly with that circuit, it boosts the plate voltage by 4 times, perhaps to make it 'less starved'?

[j.frad]

The buffer is a good idea, if I ever build it, I'll put a switchable one.

[Arn C.]

I built this a long time ago and used it as a guitar preamp.   I actually built a complete tube amp.  I used an old dukane 35watt pa power amp for the power side into a 12" speaker.  The volume was way too low, so it is still sitting in my storage room for 8 years now.  I may have to resurrect it.

Any suggestions for the high-input impedance buffer?   Do you mean like the ones on GGG?   I believe there is a jfet one and an IC one.


Thanks!
Arn C.

[RaceDriver205]

Here's the place to go:
http://www.muzique.com/lab/buffers.htm
Opamp buffers have very very high input impedance

[Arn C.]

Thanks RaceDriver205!

Peace!
Arn C.