Taming EF86 Tube Circuit - Reducing bottom end?

[bw1985]

Hey all,

I recently implemented an EF86 preamp in a single ended build with 1/2 of a 12AX7 following it and it sounds fantastic!
Plenty of gain on hand, and the tone is very beefy! However, I'm hoping to tame some of the bottom end in favor of giving it a bit of a mid boost.

After much tweaking I've used the cathode of the 12AX7 with a 3.9k resistor and 4.7uF which has helped the bottom end a bit. I'm not super familiar with pentodes, so I'm wondering if anyone has any advice for the EF86 section on different values that could help give a bit of a mid/high boost and tame the flubby bottom end.



This is the circuit and values I've used, I did not implement the pentode/triode switch however.
I noticed different manufacturers have used different values for these preamps, so hoping I can get it to where I want it!

R1 - 910K
R2 - 47k
R3 - 22k
R4 - 220k
R5 - 910K
R6 - 2.2k
C1 - 10nf
C2 - 22uf
C3 - 100nf
C4 - 10uf

Thanks!

[Jazz P Bass]

Lowering the value of the cathode capacitor (C2) should help with the 'flubby' bass.

[alexradium]

Lowering the value of the cathode capacitor (C2) should help with the 'flubby' bass.

also you can put a smaller cap in series of C1, could be 1 or 2.2nF with a switch in parallel.

[bw1985]

also you can put a smaller cap in series of C1, could be 1 or 2.2nF with a switch in parallel.

Very cool! Thanks Jazz P Bass and alexradium! I'm going to alligator clip in some different values in both places until I find what I like!