could a fast/gradual switch be added to a plexi?

[Roe]

if so, would it result in a faster attack or a slower attack?

[UR12]

You can add the switch to any amp. I think it is more about where you add the switch or what stage you put it in that makes a difference.

[Fischerman]

And it will just reduce gain...might be more of a more-gradual/less-gradual switch since the Komet in Fast mode has way more gain than a plexi-type Marshall (which is already in 'Fast' mode).

What does the Fast/Gradual refer to anyway? I always thought it was how fast/gradual the gain came on as you turned up the volume...not the 'attack' of the note. But that's just a guess...I really have no idea.

[leaveitalone84]

I beleive you are correct.

Fast = Fast ramp up into gain.

Gradual = Gradual ramp up into gain.

But there is some touch sensitivity which is lost in the gradual mode over fast.

[Roe]

so there is no way of doing this so that a plexi will get a quicker attack?
could one replace the 100k plate resistors after v1, or the 100k resistor on v2 pin3, with a switchable 22k/104k resistor?

[leaveitalone84]

so there is no way of doing this so that a plexi will get a quicker attack?
could one replace the 100k plate resistors after v1, or the 100k resistor on v2 pin3, with a switchable 22k/104k resistor?

You would probably want a 22k/82k setup with 2 taps coming out. You don't want to take the preamp tubes too far out of bias with a 22k/104k. I could be wrong but I'm not sure that would be helpful/good for tone. Someone else can chime in that is more experienced.

You will probably be stuck with the response you have now and then a slower version. This mod works with Komets, and 'wrecks because they have such fast response initially. I would recommend looking to increasing the response with other mods, then implementing the fast/grad switch to go back to a stock feel.

[islandamp]

I incorporated a gradual/fast switch and a Plexi/jtm45 switch (shared/seperate v1-v2 cathode) on my new amp. I will have it finished (hopefully ) this weekend and let you know how the response idea works. [/img][/url]

[UR12]

You can experiment with different combinations. 100k = 82k/22k 150k= 120k/33k 220k= 180k /47k. This might add a little more gain but like Leaveitalone84 stated if you stay with the 82k/22k it won't have any more response than the normal 100k in fast mode

[Roe]

I incorporated a gradual/fast switch and a Plexi/jtm45 switch (shared/seperate v1-v2 cathode) on my new amp. I will have it finished (hopefully ) this weekend and let you know how the response idea works. [/img][/url]

please tell us how this turns out!

[Fischerman]

FWIW Roe,
I recently rebuilt a homebrew 50W smallbox (because I had modded it so much and wanted to change the PT) and used a leftover Heyboer Trainwreck PT and it sounded pretty bad using stock values. Like a bad fuzz...thuddy attack, harsh harmonics, buzzy, no sustain, etc. I increased all 3 preamp plates to 180K and increased all 3 preamp cathodes to between 1.8K and 2.7K and left the cathode follower stock. Then I increased the PI plates to 100K/120K, increased the PI cathode resistor to 680, and increased the PI tail resistor to 15K. Then I lowered that first 20K power supply dropping resistor to 4.7K and added a 330K bleeder resistor to the B+1 node. That sounds much, much better...like I 'expect' it to sound. Just food for thought but keep in mind that my amp with the Trainwreck PT is only @ ~400v on the power tube plates.

[islandamp]

After reading some of the opinions here, I may change from the 82k-22k I was going to use and have a switchable 100k and 220k. Seems to be the more usable range.