I recently came into a Groove Tube adapter that is suppose to allow you to use a 12AX7 in a 6SC7 socket. Thought I would try this in one of my GE and Fisher tube phono preamps that use 6SC7. Long story short, with the adapter it passes signal, but has a pop a regular intervals. Is there anything unique about these 6SC7 phono pres that would require re-wiring the socket even with the adapter?
Have you tried more than 1 12AX7 specimen?
There's not much to the adapter's internal wiring: "strap" the heaters for 6.3 VAC and tie the 2 cathodes together.
FWIW, a 5751 is electrically closer to a 6SC7 than a 12AX7. Grid and plate connections are simple pass through.
Those GE style preamps rely on the inductance of GE variable reluctance cartridges to get the RIAA curve correct. Tweaks, including a 47 Kohm I/P impedance, are needed to use a modern MM level cartridge with a GE style phono preamp.
There's not much to the adapter's internal wiring: "strap" the heaters for 6.3 VAC and tie the 2 cathodes together.
FWIW, a 5751 is electrically closer to a 6SC7 than a 12AX7. Grid and plate connections are simple pass through.
Those GE style preamps rely on the inductance of GE variable reluctance cartridges to get the RIAA curve correct. Tweaks, including a 47 Kohm I/P impedance, are needed to use a modern MM level cartridge with a GE style phono preamp.
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6SC7 to 12AX7 adapter
Thanks for the reply. yes I have tried a couple of 12AX7s and a 12AT7 same thing sort of a motor boat pop with signal under it
Thanks for the reply. yes I have tried a couple of 12AX7s and a 12AT7 same thing sort of a motor boat pop with signal under it
6SC7 has a single cathode for both triodes,,, the 12Axx tubes have two separate K (pins 3 and 8)... If your adapter doesn't connect the 12Axx cathodes together, you may have to do it...
Thank you Knockbill. the pin out on the 6SC7 shows pin 6 to be the cathode, so which do I connect? pin 6 to what other pin on the 6CS7?
appreciate the help,
jack
appreciate the help,
jack
I think Groove Tubes did 2 versions of the ''SUB'' to 12AX7. One for 6SL7 (SUB-1) and another for the 6SC7 (SUB-2) I'm guessing? Which one do you have? If you have a multimeter it should be easy to work out which pin is connected to which on your SUB...
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Pins 3 and 8 are cathodes of 12AX7,,, so if you want them tied together jump the AX7 socket 3 and 8 pins and connect to pin 6 on the 6SC7 plug...
6SC7 to 12AX7 adapter
Have an adapter made by Groove Tube, the Substi Tube #2 made to adapt from a 6SC7 to a 12AX7......The necessary rewire is taken case of inside the adapter base FOR A NORMAL 6SC7 circuit...........the adapter however does not work in my application, a GE Phono Preamp.. .....My question is, do I need to change wiring on the 6SC7 socket to get the adapter to work?? Anyone familiar with these?? thanks jack
Have an adapter made by Groove Tube, the Substi Tube #2 made to adapt from a 6SC7 to a 12AX7......The necessary rewire is taken case of inside the adapter base FOR A NORMAL 6SC7 circuit...........the adapter however does not work in my application, a GE Phono Preamp.. .....My question is, do I need to change wiring on the 6SC7 socket to get the adapter to work?? Anyone familiar with these?? thanks jack
Just meter it. If 3 and 8 are connected on the top of the adapter socket, you'll see zero ohms 🙂