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Dirty-South Blues Harp forum: wail on! >
tube adapter for 12sl7 to 12ax7
tube adapter for 12sl7 to 12ax7
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K_O_E_N_J
21 posts
Mar 15, 2012
4:47 AM
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Hey there
I just bought a tube adapter
Its a 12ax7 to 6sn7 adapter. (with a 6sn7 pinout in the amp to a 12ax7 pinout tube.
But if i put it in my amp (with a 12sl7 socket) and put a 12ax7 tube on top of the adapter there is no sound coming out of my amp.....
In my amp with a 6sl7 pinout it works.... (masco ma17)
Wy doesnt it work on my geloso with 12sl7 tube socket.
The 12sl7 and 6sl7 have the same pinout....
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5F6H
1105 posts
Mar 15, 2012
5:16 AM
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The tube's pin out might be the same between 6SN/L7 and 12SN/L7 but your "12AX7 to 6SN7" adaptor is expecting to see a 6.3VAC heater circuit (like in the Masco - where a 12A#7 would have pins 4&5 tied together), the Geloso runs 12VAC heater arrangement (a 12A#7 tube's heaters would run on the difference in potential between pins 4 & 5 - heater voltage in on one pin, out on the other - NOT tied together).
So in the Geloso your heaters are probably shorted with this adaptor (there is a reason it says "6SN7" on it & not "12SN7") - DON'T keep putting it in there, when the heaters are shorted you are reducing the negative bias voltage in the Geloso and this will probably kill the 6V6 power tubes!
Like I said before, if you want to sub different tubes in the Geloso, use 12SN7, or get the sockets replaced & rewired for 12A#7 tubes running at 12v heaters.
Just because a tube has the right number of pins doesn't mean that you should stick it in a socket. There are tube amp techs in Holland, give one of them some work before you destroy your amps...as you get to know them they might field some of your questions - BEFORE you go shorting things out ;-)
Enjoy your tube subbing in the Masco...
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www.myspace.com/markburness
Last Edited by on Mar 15, 2012 5:17 AM
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slowblowfuse
52 posts
Mar 15, 2012
6:14 AM
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Hello Koen,
contact Marc Vos at Fox Amps. www.foxamps.com.
he'll sort you out.
Bye,
Ski9nny Dog
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Skinny Dog
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