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6SJ7 versus EF86


 
12/12/2000 3:31 PM
Mike B
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6SJ7 versus EF86
Any thoughts on one or the other?  
 
 
 
I've used the EF86 in a couple of circuits and found that microphonics can be a problem. I'm assuming the same is true of the 6SJ7....  
 
 
 
Are there any noticable tonal differences between the two?  
 
 
 
Thanks,  
 
Mike B
 
12/12/2000 3:56 PM
John Martin
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I like the 6SJ7 a little better for guitar amps. The glass version of the tube is better sounding and less microphonic then the metal one in my experiance. I have built about 8 amps so far with this tube with good results. The plate to screen voltage difference is important for the best sound. I start off with the screen at 2/3 plate voltage and tweak from there. Plate voltage can be any where from 100 to 300v. Most vintage equipment is at the low end 100-125v.  
 
 
 
jm
 
12/14/2000 12:55 PM
MKB
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The great thing about 6SJ7's is that they are CHEAP. I picked up six different NOS 6SJ7's from a tube vendor at a hamfest for $3 each. Several were JAN RCA's, some TungSol, GE, and others. They all sounded slightly different (preamp tube in a Rt66 clone) and some were more microphonic than others. In my experience the glass ones are more microphonic than the metal, and not as quiet (where do you get an octal tube shield?) BTW, a standard metal GE sounded the best, very balanced with good highs. The RCA's were all a little dark but had a lot of gain, may be good with a Strat. The TungSol sounded very good tonally but was too microphonic to use.  
 
 
 
I haven't compared them with an EF86, but 6SJ7's sound very good overall. But some are unusable due to microphonics, both metal and glass. At their price you can buy a bunch and get the good ones.
 
12/14/2000 3:11 PM
Mike B
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Thanks for your responses...I've got a stash of NOS 6SJ7's (among other things) sitting around and I'd like to use this tube in my next design instead of the EF86. I've got both metal and glass versions so I'll have to experiment.  
 
 
 
Mike B
 
12/14/2000 5:02 PM
John Martin
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The glass 6SJ7 has an internal sheild connected to pin 1, just like the case is on the metal versions. I have an old Silvertone amp with sheilds around the 6SL7's. Just a piece of rolled metal with a lead soldered on to it that runs to the chassis. Has ribs in it like an old trash can.  
 
 
 
One time the metal shell of a 6SJ7 in one of my amps got connected to B+ by accident. Got a big suprise when I went to tap on it to see if it was noisy!  
 
 
 
jm
 
12/14/2000 4:58 PM
Ken Gilbert
i say screw pentodes altogether and use cascodes!  
 
 
 
more stuff to screw with = more fun to be had.  
 
 
 
kg
 
12/14/2000 5:34 PM
Mike B
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Yeah, I was also thinking of using a 6n1p in a cascode configuration like the one in your preamp Ken. I'll probably end up fooling around with a bunch of different designs...  
 
 
 
Mike B
 
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