Tube factor mods? (attached schem link)

[Xavier]

http://www.free-service-manuals.com/Audio___Hi_Fi/Hughes___Kettner/Hughes_&_Kettner_Tube_Factor_Schematic_Diagrams_L66999/

I would like to mod my H&K Tube Factor for more gain . This tube OD has 2 modes, mode 1 sounds pretty goos with plenty of attack but i would like it to have more gain. Mode 2 has more gain but sounds way too dark and compressed for my tastes.

I could obviously mimic the Okko mods by adding a boost circuit , nevertheless maybe changing a couple of resistors / caps would do the trick.

Any suggestion?

[anchovie]

The gain mode switch is what's labelled on the schematic as 'slc3', and is part of the circuitry surrounding IC1A. In high-gain mode, it switches a 220 ohm resistor (R8) in parallel with a 6.8k resistor (R6) that changes the gain of the op-amp stage from x2.2 to about x70. To increase the gain of mode 1, lower the value of R6. Might be worth replacing it with a 5k pot wired as variable resistance so you can experiment, then when you find the level that you like you can measure the pot and replace with a fixed value. There'll be a point somewhere in the sweep of the 5k pot where mode 1 starts to sound like mode 2 and you can then back off from there to find where the signal stays bright.

[Xavier]

Wow anchovie, thanks for the reply    !!!

I will try as suggested, again thank you for taking the time !!!

[kupervaser]

Has anyone tried this already?

A friend of mine has this pedal and asked me to add a second volume control to make it possible to adjust both channels separatly. What should be done?
THanx

[gtudoran]

Or you could use paralel capacitors with R30 and R31: a value of 10uF for a aprox. full range response could be a solution.this will increse the gain a little bit and have a little more tube tone in your sound (more tube drive then op-amp drive).
This is just my ideea.

Best regards,
Gabriel Tudoran
Analog Sound

[gtudoran]

SOrry for double post: or you could change the anode rezistors (form first, second ore both triodes for a maximum of 220k). Or you could sacale down the rezistive divider formed out from R19/R20 witch goes in to the first triode grid.

Regards

[diversionist]

Is there an easy way to extend its bass range, so you can use it with bass guitar?

Cheers,
div