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Vintage threads from the first ten years

Re: 6K11 tube?

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2/9/1998 3:03 PM

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).

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
Paradiddle7	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. Thanks, Jeff

2/10/1998 1:55 PM

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
Paradiddle7	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. Thanks, Jeff

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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