adding a fourth pre amp tube

[fixer2]

I would like to know more on how the fourth pre amp tube gets into the mix on a amp like a laney aor or a more of a lee jackson modded Marshall from back in the day can I switch on and off a fourth tube using for the one have of a tube like is being done in that great one wire mod of casscading pre amp tubes in a plxi making it sound like a mega plexi yes kind of making my own vintage modern marshall out of my very own made by me 50 watt pelxi 1987 style amp from valve storm parts any layouts or pointers would be great if it is not able to be done o well

[RockinRocket]

Was there a question or even a sentence in that mess of words??

All kidding aside. A laney AOR has 4 gain stages. Its more or less a JCM 2204 circuit with a extra gain stage in front of a 2204. It also has what appares to use a triode in a local negative feedback circuit after the tone stack. Would be interested in what exactly the tone it produces?

[neikeel]

You need space inside teh amp and patience and really good lead dress

[fixer2]

ok so you is able to be done to a 1987 style lay out and kind of have a switchable in and out one wire mod style of using this extra tube like how you use the normal channel of the tube in to the bright channel side but this way I dont change anything from the three tube lay out to be able to have the best of both world kinda

[neikeel]

In your 1987 you will be tight for space (the US id full of hacked 50w where people squeezed an extra preamp tube in. You have to use stand offs and PTP wiring so it can be messy,

You are much better off implementing the SDM 2 in 1 layout to switch from 1987 to 2204. My layout (with single 1M push pull pot is a neat way of doing this to be able to set the volume of normal channel and gain of cascade fro quick switch over.

The real benefit would be to footswitch it with a relay - when I find time that is my next task on a project which has its own PT tap for the relay.

[fixer2]

I can't wait to see it.Do you have any layouts of this I would like to do some type of switchable one wire mod or kind of a one wire mod using part of a fourth tube.