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AllegedRetroFreek wrote:

Bernardduur wrote:I would use something like the other suggested Cathode follower

Check the schematics of the Vox FX loop, the Valvulator or the Dumbleator.

I used something like this, with a tad more gain, on my newest amp build to overcome the (impedance) problem of 8 powertubes

I'm bringing this post back from the dead. Gilmour uses a modded Alembic F2B Preamp which is then sent to the power amp sections of the hiwatts. The Hiwatt preamps are bypassed completely. I've read that Pete Cornish modified the Alembic to better suit guitar (it's a bass preamp) but the values are pretty well unknown. It could be that the Cornish tube buffer is the input stage of the F2B. I can't add the schematic as I'm on my ipad but it's widely distributed. Any thoughts on what the buffer schem would look like?

I am convinced that the mystical mod to Dave´s Alembic preamp is only a cathode follower, because that is what the Alembic F2-B originally is missing.
The mod to make it more suitable for guitar is probably only a change of the bypass caps values to attenuate bass frequencies.
You can also fiddle about the tone stack, but again, no magic here.

The Cornish tube buffer is probably also no witchery: an input gain stage coupled to a cathode follower.
Bernard is right, the Dumbleator is nothing else ... a great sounding "tube buffer", even with an FX loop.
You could copy it 1:1 without having to agonise over the PC buffer and yield a result that will be on a similar tonal quality level.