Gain reduction ideas?

[dobbhill]

I finally finished my Express!! (3rd attempt) The tone is incredible, but I wish to have a bit more use of the volume control. If 12 o'clock is halfway, then I can only get to 8:30 (barely on) with the guitar volume on 2-4 before it starts getting very distorted. I considered the Komet Fast/Gradual switch, but before I heat up the iron, I though that some of you may have other ideas to try. The only other idea I came up with was to replace the 1meg volume pot with a 750k resistor in series with a 250k pot for volume. I measured the usable range of my volume pot to come up with those values.
Any ideas?
Also, the bass response is a wee bit thin. I thought the best place to tune the low end would be the 0.002 cap between the 2nd and 3rd stages. Please share your experiences.
Thanks, D

[UR12]

Is your vol pot a log or linear? If it's Linear then replacing it with a Log pot might help.

[dobbhill]

It's a alpha log pot. I've been reading some old posts about this and came up with some things to try (after I sleep some!!).
Thanks, D

[Legin]

Have a look at Paul Rubys suggestion for a split load in the following post, I did it and it works a charm.
Nigel

https://tubeamparchive.com/viewtopic.ph ... c&start=30

[Richie]

some might use a 12AY7 in place of the 12AX7 in the preamp or gain stage.. You could also change the feedback resistor from 100k to 27k or there abouts,this will give more clean on the volume control before breakup. There are alot of other ways do do this.. but these would be the easiest to try,that would bot change the circuit much.

Richie

[tubedogsmith]

The split load and lower gain tubes will work to a certain extent but they change the amp. To retain the amp but make it usable you need to really slow the taper of the volume pot. Try a 500k audio pot with a 470k resistor in series with the wiper. Also, if you have a bright cap on the volume pot disconnect it and try it that way. Make sure your 1meg treble pot is audio as well.

[Allynmey]

It's a alpha log pot. I've been reading some old posts about this and came up with some things to try (after I sleep some!!).
Thanks, D

Dob, why don't you just use a PEC 10% taper pot? It will allow you to get to 12:00 before doom sets in!

Allynmey

[dobbhill]

I'll have to try the PEC. Thanks, Allyn. I did get the Komet 82k/22k split load hooked up tonite, but it's too late to crank it. I'll report this weekend, but it sounds promising from the "Power Soaked Trial."
Thanks for all the tips!!!
D

[Legin]

I did get the Komet 82k/22k split load hooked up tonite

That is the values I am using on the Express at the moment which gives me quite a lot more control before ear bleed time.

[Jeph]

Legin, did you notice a dramatic difference in volume with the split load? I tried this a while back when Paul first suggested it but think I might have done it incorrectly (yeah, I can screw up something simple like that ) since I didn't really notice much difference if any with the output level of the amp. I even went down to something crazy like 97k/3k.

[Elcabong]

I have the split load in my amp plus a 100k pot/56k replacing the 156k to ground before the 3rd stage. This allow more flexibility while allowing to return to Trainwreck spec.

I was unable to see half a 12AX7 unsused so I wired the inputs for single/parallel. I later changed the bypass capacitor to 1uf on the single input to improve bass response. The other half remains at 22uf keeping the parrallel input fat.