installing a make shift Gain switch

[EETStudent]

i figure a way to switch between low and high gain settings is too install some kind of switch after the first stage, the switch from there directs the signal either through or around the next two middle stages, and the signal either way meets back up just before the fourth gain stage. This is how my amp is set up so thats how I would do it. Is this practical?

[Enzo]

That is done all the time. That is how Peavey did the Classic 30,and the 5150-2, just off the top of my head.

[G-hoppa]

I'm looking to do a similar thing to my Heath A7 project-- does it make more sense, for tone or convenience, to use that switch to bypass the first gain stage, or a middle stage?

[EETStudent]

Well heres what I thought about doing. In one position, the switch would just send the signal through all four stages as usual. In the other position, the switch would bypass the two middle stages, sending the signal from the first stage straight to the fourth for a much cleaner tone. My amp is a marshall, and the tone controls come after the fourth gain stage(cathode follower). As it would be, when I switch to clean mode the chain would first gain stage, fourth gain stage, tone controls. However, Id like to wire mine up as first gain stage, tone controls, fourth gain stage. Something like a Fender setup with Fender tone controls. That way my higher gain mode would be my marshall 800, the clean would be any old fender. Thanks for clarifying that Enzo

[d95err]

Well heres what I thought about doing. In one position, the switch would just send the signal through all four stages as usual. In the other position, the switch would bypass the two middle stages, sending the signal from the first stage straight to the fourth for a much cleaner tone. My amp is a marshall, and the tone controls come after the fourth gain stage(cathode follower). As it would be, when I switch to clean mode the chain would first gain stage, fourth gain stage, tone controls. However, Id like to wire mine up as first gain stage, tone controls, fourth gain stage. Something like a Fender setup with Fender tone controls. That way my higher gain mode would be my marshall 800, the clean would be any old fender. Thanks for clarifying that Enzo

The cathode follower is not a gain stage (at least, gain is slightly less than unity). This is how I'd do it:

Replace the cathode follower with a MOSFET (see the "MOSFET follies" article at www.geofex.com). This frees one triode. Use this triode stage as the second stage of a Fender-style channel. Use the first gain stage in common for both channels. Mix the two channels before the PI using mixing resistors.