Switchable Parallel input gain stage, would it work well?

[Ripthorn]

Hi all, I currently am doing some submini stuff and I really like Dana's submini express. I am wanting to do the preamp of this, but I always feel bad having an unused triode. I have always been interested in a parallel input stage, so I am wanting to try it. My question is whether I can just have a switch to engage/disengage the input signal to the extra triode. I don't see why not, but maybe someone knows something that I don't. I couldn't find anything on this when searching, I only found a lot of talk about the Spitfire. Are there any things I need to take into consideration when implementing this?

[collinsamps]

You could have a switch between the output/input easily enough, or a two input design where one input bypasses he first gain stage(like jcm800's low Z input) and then switch(relay or manual) between one or both inputs to get 1 or both stages. The JCM isn't a parallel wired stage but depending on component values used you would get the desired result.

[Bob-I]

I did that on a JTM45 like amp. Instead 2 channels I used the second triode connected to a push/pull volume pot. I'd say the parallel mode is a tad brighter and fatter at the same time, but I don't really feel that there's more gain on tap. Maybe if you adjust the Rp and Rk values to match the parallel triodes better.

Basically I leave it on parallel mode all the time now. Sounds great.

[collinsamps]

When doing that I usually split the cathode with 1.5K's and use a switch to tie the inputs when you want to. That way you can blend the amount of bright or normal you want while getting the advantage of the extra triode. Do that with a suitable pre or post PIMV and you have an extremely versatile amp. My favorite is with Heyboers HHR OT and JJ 6L6's. It ends up being Bassman meets JTM with a boost/blend option to get good crunch with the MV, but also outstanding headroom with it wide open & out of the circuit. Very SRV in a box.