Johny B Good wrote:


Mention of "high quality screened cable" reminds me of another
possible reason for the predominence of HF harmonics and other noise
in your test signal. Some, so called screened cable can have very poor
screening, in some cases just 3 or 4 strands spiral wrapped around the
signal wire, which makes them very prone to pick up electric fields
radiated by nearby (and sometimes, not so nearby) mains wiring around
the room.


** Gotta back you up on that one.

Typical light gauge RCA leads from China have no screening at all - the insulated inner core simply runs parallel with bare copper strands up one side of the core.

The only thing they are good for is low impedance, line level signals with the proviso you never run them alongside speaker wires.

Plus, some of the heavy gauge RCA leads are little better, having only a thick outer cover and much the same inside as the light gauge ones.

I expect you will have to pay a fair old price to get decent quality, woven shield, low capacitance RCA leads that are suitable for connection of a MM or MC phono cartridge to an RIAA stage.

When repairing guitar amps, the leads to and from the Reverb Tank can need replacing and the cheap Chines ones are a disaster - producing loud buzzing hum and even high frequency oscillation if installed in the back of a combo amp.



..... Phil