Effectrode Tube Drive Mods

[JoshBernstein]

Hi everyone,

I have an Effectrode tube drive that is too bassy, and I thought you all may be able to help, as it's basically a Soldano SP-77 lead channel in a box. From what I can tell from the manual, the tone control is an active tone control, using one of the 12ax7's to cut/boost the mid-high frequencies, but it does nothing to the lows.

I am considering reducing a coupling cap or two, but am unsure of which I should start with. Its a 4 stage preamp, is there any particular stage I should start with to cut some bass?

Or would reducing/ removing the cathode bypass cap on v1 be more effective?

Thanks!
-Josh

[thejaf]

Do you have a schematic?

[JoshBernstein]

Do you have a schematic?

Unfortunately not of the tube drive itself. The closest I have is the SP-77 schematic, which it is based off of. The tone stack is not the same, but it still uses the same 4 triode gain stages. It is the lead channel of the sp-77

[roberto]

If it's bassy you have to cut lows at the end of the soundchain, if it's flabby you need to cut lows at the beginning.

[tubeswell]

This SP77 schematic is a bit more legible

[tubeswell]

Here's a black-box* preamp schematic

* adapted from a soldano preamp - from this page: http://diy-fever.com/amps/black-box/