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Re: 6K11 tube?

2/9/1998 3:03 PM
Jonathan Krogh
Re: 6K11 tube?
Hey you know i was going to bring this up,  
i had mentioned to someone with a vt22 that my amp(v4b) had this feature.  
all you have to do is wire in two 9 pin pc mount sockets and you can kiss 6k11's goodbye  
its so cool, i was amazed that ampeg would be so accomodating as to put this tube conversion choice.  
its such a far cry from the crappily designed amps these days,  
where installing a cathode bias resistor is damn near impossible(pv 5150)  
its for that kinda stuff i give ampeg full points for design(at least in those days).
And now, a word from our sponsors:

2/10/1998 7:45 AM

The V-4B (bass amp) differs from the V-4/VT-22 (guitar amp) only by deletion of the reverb circuit components.  
The two places for 9-pin sockets you found on your V-4B's circuit board was for the 6CG7 reverb driver and the 12AX7 reverb recovery tubes.  
Are you saying that your amp has these two spare locations wired for a pair of 12AX7's, in lieu of a 3-section compactron tube? This would take a bit of pcb trace cutting & jumper wires.
2/10/1998 9:07 AM

Doc and Jon,  
I'd just like to say thanks for your help. It has helped me out tremendously!  
I am interested in this mod for switching to two 12AX7's from the 6K11.  
2/10/1998 1:55 PM
Jonathan Krogh

Doc, i guarantee you, its for a 6K11 replacement,  
i checked every trace cause i was so doubtful that they would do this.  
someone mentioned a 6K11 was like 2 12ax7 and 1 12au7 sections,its just how the board was wired.  
the 2 12ax7 sides of the 6k11 is run to one socket, where a 12ax7 would go,  
and the one 12au7 side of the 6k11 goes to a half of the other socket, where a half of a 12au7 would be used.  
its quite simple really,  
all the 6k11 pin connections are trace routed to the corresponding terminal one the other 2 sockets.  
and the holes are there in the board for the 9 pin sockets, all tinned and everything.  
all you gotta do is wire in 2 9 pin sockets and pop them in.  
therefore all that is needed is
2/11/1998 8:28 AM
Jeff Lacio
this is interesting, but pretty ridiculous -- there are plenty of 6K11/6Q11 tubes out there, in excellent condition, at reasonable prices. buy three or four and you'll have more than you'll ever need for the rest of your life.
2/8/1998 1:38 PM
Ampeg: 12AU7 to 12AX7 Possible?
I found out that the tech has replaced a 12AU7 with a 12AX7 when i pull this tube it doesn't pop and hiss anymore. I don't have a 12AU7 to test to see if that is the problem. I am in the process of getting all new preamp tubes to see if they are at fault.  
2/8/1998 2:36 PM
Jeff Lacio
possible, but probably not a good idea. the amplification factor of a 12AX7 is much higher than the 12AU7 (100 vs. 19). what's the application(s) you're talking about with all these tubes you're asking about?

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