If you had two "high gain" tubes, what position....?

[xyrium]

I want to spice up channel three, without impacting channel 1 for cleans. I run the gain on channel 3 at 2-3 o' clock. I'm not sure what gain stage I'm at, but I figured almost any socket I put them in will impact another channel one way or another. How does one determine what gain stage they're at based on their settings?

I have the EQ engaged, in Mark IV mode, Bright, Pentode, 10W. Treble is at 2oclock, Mids are at 9oclock, Bass is at 9-10oclock. The EQ is set sort of like a V shape, but 240Hz is at about 10% along with 750Hz. The rest are above 50% (or above what I believe would be considered 0dB). Output is at about 10oclock on average when practicing at home, which is what this head is for.

I was thinking V3 and V6 since I assumed I was in at least stage 3, but any input would be greatly appreciated.

Thanks folks!
Paul

 

[SteveO]

The owners manual has a tube layout that explains which gain stage for which channel each tube handles, I can't remember any of the specifics off hand.

 

[xyrium]

Indeed it does, that's what I used to make the post. However, I'm trying to determine the *most beneficial to Channel 3 and least detrimental to channel 1* spots to put a high gain preamp tube in. Unfortunately, I'm not sure how one is to determine what gain stage they've reached given their settings, so I can aim for a specific socket or two.

 

[Mungo Zen]

! want to clarify your comment "put a high gain preamp tube in"

The 12AX7 is the highest gain pre-amp tube there is. There are a few charts around (linked below) that show the relationship of different pre-amp tubes. Realistically, you can go with a tube like a 12AU7 (or any compatable tube) for a different gain profile (with significantly less gain) or a different brand of 12AX7 for a change to the tone, while maintaining the same relative gain. The Tube Store (first link below) actually reviews different tube types if you wanted to try and get a subjective opinion on what a different 12AX7 might do for you.

http://thetubestore.com/gainfactor.html

http://www.300guitars.com/articles/preamp-tube-gain-factors-and-substitution-chart/

 

[xyrium]

Thanks Mungo. Sellers can hand select tubes that have a higher-than-average gain setting on them and sell them as high gain tubes. If you go to eurotubes.com or dougstubes.com, they both do this.

This said, I did retube the preamp section as noted, and haven't noticed a tremendous difference in tone. I used a mix of JJs, Tung Sols, and one EH in the PI spot.