Alembic F2b & Ampeg PF800

[afinitemind]

Just built up a single channel Alembic F2b & I'm curious about using it with the power amp in on my Ampeg PF800.

I've got them connected up and I dig the sound of this little preamp at lower volumes. I've pretty much got to keep the F2b volume below 10:30-11o'clock cause it's already unbelievably loud at that volume & seems to start overloading past that.

I'm guessing this is not the most ideal pairing at the moment, so I'm hoping for some input on how to run this setup safely - I've read about people putting a tube buffer stage after the F2b...unfortunately my power transformer is tiny and doesn't have the juice to run another preamp tube. Volume control at the output like the attached schematic?

Also - anyone know the PF800's power amp input impedance? Online searches haven't yielded anything solid yet. I'll try to get some info from Ampeg on the subject but thought I'd ask here first.

Thanks, y'all!

 

[Steve Dallman]

The power amp input is 100k. The effects return is 1meg. If I remember right the output impedance of an Fb2 is 90k.

I built a tube preamp in the 90's with the same output impedance. Later I added an IRF940 follower to lower the impedance.

I tried my old preamp with my PF-500 last year, both with the follower or right off the tube and could not hear a difference. I don't remember if I used the effects return, the power amp in or tried both.