WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I have an Audiomat Arpege and I want to add a sub SVS on this. This amp have 2 out TAPE REC (!) and I want to modify one to provide a PRE OUT instead to be able to connect the sub on low level input. Have you some ideas to do this.
Just take your signal from the wiper of the volume control. Since it is a sub out you don't need to worry about HF roll off.
FYI, Audiomat does not give out schematics, and it would copyright anyway.
That's a motorized volume control mounted on a PCB. Connecting to the control's wipers is the only remotely rational method and that idea might be mechanically unsafe.
IMO, a better way to add a S/W is at the power amp, using speaker level I/Ps.