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Old 30th January 2013, 06:58 AM   #1
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Default make adapter from 6n2p to 12ax7

hello amp take three 12ax7 preamp tubes but i want to put the russian i think to make a adapter converter between 9 pin chassis tube and the 6n2p vacuum tube.....some guys tell me is simple to make it but i don't know the wiring....please anyone help me?
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Old 30th January 2013, 10:47 AM   #2
DF96 is offline DF96  England
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The heater wiring is different. Google for details on each valve pinout and you will see.
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Old 30th January 2013, 12:22 PM   #3
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I've made octal socket converters to allow the use of the 6AR6 in place of a 5881/6L6. It's a matter of printing out the two tube pinouts and then drawing the necessary connections for the adapter.

As DF96 says, the main difference is the way the heater is used. With the 6N2P, it requires ~6.3V (AC or DC) to operate. The 12AX7 is a little different since it can operate on 6.3 or 12.6V, depending how the filament pins are used. Check the valve pinout and it should be obvious - the heater is "center tapped:

eg: In the 12AX7, pin 9 is the center tap of the filament. For 12V operation, only connect pin 4 to pin 5 to the heater supply. For 6V operation, connect pins 4 and 5 together, and pin 9 to the other half of the heater supply.
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Old 30th January 2013, 12:32 PM   #4
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mmmm in pictures maby anderstand .......i found something but i don't know it socket (chassis socket tube) have 9 pins, on 5 and 4 pin have the filament( black) and on 9 pin have the filament( red) to make the converter adapter ( on adapter, i cut the 9 pin and i connect the 4 pin to work th 6n2p on 12ax7 socket????........right?
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Old 30th January 2013, 01:22 PM   #5
DF96 is offline DF96  England
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6n2p pin 4 to 12AX7 pins 4 and 5.
6n2p pin 5 to 12AX7 pin 9.
6n2p pin 9 to something grounded, or one of the cathodes.

That was the result of a very quick Google, so check it yourself - I might have got it wrong.
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Old 30th January 2013, 01:40 PM   #6
TheGimp is offline TheGimp  United States
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DF96, that might work IF the amp in question has a CT heater transformer with CT tied to pin 9 of the 12AX7s. However it is unlikely that the current transformer has enough capacity to drive the 6.3V heaters.

The problem with making an adapter is getting a 9 pin plug to wire to a 9 pin socket. It would be easier to rewire the socket.

The difference between the 6N2P and 12AX7 are:

(1) the 12AX7 has the two 6.3V heaters from pin 4 to pin 5 tied in series with the center tap connected to Pin 9.

(2) The 6N2P has both heaters tied in parallel from pin 4 to 5. Pin 9 is a shield between segments of the 6N2P.

Since 12AX7 has no such shield it is best to connect pin 9 of the 6N2P to the ground side of one of the cathode resistors.

You will need to change from 12.6V for pins 4/5 of the 12AX7 to 6.3V for pins 4/5 of the 6N2P. You will probably need to add a 6.3V 2A (3 X 600mA) transformer to supply the heaters of the 6N2P tubes.

Last edited by TheGimp; 30th January 2013 at 01:44 PM.
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Old 30th January 2013, 05:00 PM   #7
DF96 is offline DF96  England
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The OP's description sounds like he has 6.3V heater wiring so no need for an extra transformer.
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Old 27th May 2014, 02:23 PM   #8
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TheGimp - I respect you - absolutely, but I have to disagree with the need to install a separate 6.3v tranny. Most of the common valve types used in guitar amps are designed to have their heaters run in parallel from a constant voltage source. ... and most of these amps have a 6.3v winding (typically 3.15-0-3.15, i.e. CT) running to pin 9 and to pins 4+5 (shorted together). This covers Fenders, Marshalls, etc.. for certain, and various clones and derivatives (Dumble, e.g.) I will say that running from these, typically AC supplies, at 12.6v *would* cut the current by half and reduce the electromagnetic radiation emitted from them - making it less likely to be picked up by other parts of the amplifier. Some folks choose to go to a separate DC heater supply to deal with this. Still, with proper lead dress and tidy twisting and isolating of the heater supply lines, I have experienced few problems with the typical 6.3 volt (parallel) implementations found in most of these amps. Of course, while typically they all operate at the same voltage (usually 6.3V), the current demands may vary and must be accommodated by the supply.
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