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6SL7 highest gain octal triode?

8/22/2000 1:55 AM
Chris B
6SL7 highest gain octal triode?
I was wondering if there was ever a high Mu twin triode built on an octal socket with an amplification factor of 100? I am looking for ideas for a new PP 6V6 amp. Also how does a 6SL7 sound different from a 12AX7? I have a huge chassis for this amp, guess I over figured on the space I needed. I was thinking of filling some of the space by using octal tubes so it dosen't look so empty, also I have plenty of sockets.  
Chris B
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8/22/2000 2:11 AM

I'm pretty sure that there were higher mu octal twin triodes but I'll have to look. Remember that the hypothetical amplifaction factor of a triode isn't actual stage gain and 12AX7s never acutally amplify 100 to 1. The 6SL7 (and it's sisters) have plenty enough gain for any reasonable purpose - you just have to design in the stage gain you want.  
8/22/2000 2:12 AM

as far as I know, the 6sl7 is the highest gain octal dual triode. they are prone to being microphonic. they sound fatter and smoother than a 12ax7. a project on angela's website shows a 9-pin and an 8-pin socket wired in such a way that you can use either a 12ax7 or a 6sl7, if you have a large chassis, this is somthing you may want to do. BTW, I have a pair of NOS, never been used phillips/sylvania JAN 6sl7 tubes for sale for $10. email me if you're interested.  
8/22/2000 4:43 AM
Uncle Ned

A 2C52 is an octal dual triode with a mu of 100,  
but they're kinda hard to find, and they *only*  
run on 12.6V filament.  
Of course, if you have plenty of chassis space, you  
can use 6F5's, 6SQ7's or 6SF5's, which are single octal triodes with a mu of 100. Heck, if have the space you could use a hole for a 6SJ7 pentode,  
which can have a lot more gain than any single  
8/22/2000 6:30 PM

I agree with Graywater about a 6SL7 having more than enough gain for any amp you'll build. I've built several amps with these in there and I've recently built a gain amp (3=6SL7's) and it hs evey bit as much gain as a clone with 12AX7's.  
The 6SL7's do sound fatter and "wider" (for lack of a better word)...there seems to be some cool "girth" that goes along with these tubes. The best sounding 6SL7's I've ever used were black based RCA's. I've used some RCA's that didn't have a base and were just all glass but they didn't sound very good at all. No bottom end when compared to the black based RCA's.  
Hope it helps  
8/22/2000 8:29 PM
Chris B

I have a 360V, 90 mA transformer, so I think that running a 6SJ7 and phase inverter and two 6V6s would be drawing a lot of current. Do you think that two 6SL7s will give me plenty of gain with a master volume? The second tube would be wired as a phase inverter, of course. I looked at Joe Piazza's schematic site and found a schematic of a Reverbrocket, or at least I think that is what I've got. It was the R-12 schematic. Is there a way of wiring two preamp stages so that the stages go, stage 1 + tone stack (bass, middle, treble) + volume + stage 2 + master volume, and then on to the phase inverter?  
Chris B
8/22/2000 8:50 PM
All one has to do is plug a guitar into one of the Ampeg b-15 amps thats been tweaked some.. they do pretty good.. And they use Sylvania and Rayethon..Good sounding tubes,these like all preamp tubes you just have to listen and pick some good ones..  

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