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
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
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...
Just meter it. If 3 and 8 are connected on the top of the adapter socket, you'll see zero ohms
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