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Re: octal tube preamp ideas wanted...

4/21/2004 5:44 PM
Trace - Voodoo Amps
Re: octal tube preamp ideas wanted...
"Have you had any expereince with the GE 6SL7's?"
The black based GE 6SL7's are my favorites, they also usually have the silver tops as you mentioned.  
Hope it helps Craig;  
4/13/2004 5:50 PM
Jim Jones

Hi Ian,  
(Wow it's been a long time since I posted here!)  
I built an amp that was basically a 6V6 Marshall using 6SL7's for the preamp and I will NEVER use them again.  
The tone is great - the noise - intolerable. Maybe I just happened to have three bad tubes, but I went absolutely apeshit trying to figure out where my noise was coming from. I was getting an AC-sounding hum, so I elevated heaters, re-did every ground in the amp and basically resoldered every connection on the board. After all that - it was the frickin' 6SL7's!!! All US made NOS, by the way...  
Granted I should have diagnosed the problem earlier but hey, it's a good thing I don't work in a service shop. :)  
I found I didn't get enough gain out them compared to 12AX7's, too. 12AX7's were adopted en mass for a reason I figger. :)  
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4/13/2004 6:05 PM
Ian Anderson

Cheers for the help guys, the main reason I want to use some octal preamp tubes is because I played an amp at the Matamp factory that used them and it sounded great - anyway, there are millions of amps that use boring old 12AX7s ;) :D  
... Ian :)
4/13/2004 6:36 PM
Jim Jones

...anyway, there are millions of amps that use boring old 12AX7s..  
That's exactly why I tried the 6SL7's, too. :)  
Even if the tubes I had weren't noisy (as in the hum), I probably wouldn't use them again due to the high microphonics.  
4/14/2004 12:41 AM

All of what you describe is true. But you can find some good ones,its just hard to find them. Working on quite a few B15s this is one problem you see alot. I found from even same brand of NOS,they can be quite different,noisey or microphonic.  
4/14/2004 4:13 PM
Jim Jones

Hi Richie,  
How are you doing? You're right, I'm sure there are good ones out there, but debugging that amp pissed me off so badly I won't be hunting any down anytime soon. :)  
Take care!  
4/17/2004 11:58 AM
Maybe use both?
Hi Ian  
You could build a two channel amp with an octal in one and a 12AX7 in the other. And you can put the two channels in parallel to easily select one or the other. I like the 6SL7 and 6SC7 tubes a lot and haven't had the major microphonic problems that others mentioned. You could also try a 12AX7 to 6SL7 adaptor plug.  
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