How to get more treble out of my Eighteen ROG

[debutvm]

I have added the 220pF cab to the volume pot to get some more treble. It did work however it was a minor adjustment. I need alot more treble. What would be a good value cap to try instead of the 220? Also I read this thread: http://www.diystompboxes.com/smfforum/index.php?topic=24304.0

and saw the part where this was said: :x In the earlier version the 2n2 cap between the 15k resistors was not connected into ground - result: more treble and little more gain in my ears.  :shock:

Does this mean that by  not connecting the 2n2 cap to the ground I can achieve more gain and treble??

Thanks for the help everyone

[Gary]

The two 2n2 caps to ground nearest the Volume control roll off highs to help emulate a speaker response.  If you have a dark sounding amp, you may want to omit one or both of these caps.  You will not have more gain, but you will have much more treble.  Try this simple mod and see if it helps.

Good luck,
Gary

[stm]

Several things you can try and combine:

1) The 220pF treble bleed capacitor can be increased to 330p or even 470p for more mids.

2) The 120R and 47uF pair on the third JFET source can be replaced with 1k and 150nF for extra presence (assuming you are using an "average" J201).  You will need to retrim the drain pot for around 6V at the drain of the third JFET.  These values were obtained using the newly introduced Fetzer Valve Revisited calculator, and with the default J201 parameters included therein.

3) As Gary said, remove one or both of the 2.2n capacitors at the very end. Try one at a time first, as the overall result is different in each case. In an extreme situation you can remove them both, as someone reported a couple of days ago having good results when doing this to a BSIAB II.

Cheers.