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After rewiring my turntable tonearm with Cardas wire I decided to go one step further and upgrade the phono interconnect cable.
The (Technics 1200) original factory phono cable was soldered to the circuit board on one end, and terminated with RCA connections on other end. It is a coax type cable "positive" wire in center with "negative" as the shield (but it's not a braided shield, rather densely wrapped in one direction), for each channel.
1. This is NOT a good solution, for high quality phono interconnect, is it not?
By the way I am using a MM Ortofon cart.
So here is my problematic attempt to make a DIY "improved" version:
I used a french braid of FOUR runs (per channel) of 28ga solid core copper wire with cotton wax insulation, 2 for positive two for negative. Without shielding they sounded fantastic but obviously hummed and therefore I made a second version with shielding.
I took some basic coax cable I had around, pulled the shield off and carefully slipped it over the above DIY cable braid. The shield was connected to ground at the turntable end ONLY. So here is the problem now: I am hearing an echo of EVERY sound coming through this shielded cable. Like it's a microphone feeding back.
2. Is this a capacitance issue or am I missing some big fault?
Would appreciate any advice and recommendation in this matter.
Thanks,
Herman
Follow Ups:
Try connecting the shield at the phono preamplifier end of the cables instead of the turntable end.
Duster,
thanks for the advice. I tried that, and it did not solve the problem. Could it be that the capacitance is too high, causing this "echo"?
Herman
A severe impedance mismatch caused by the cable design is the likely culprit rather than capacitance. The particular DIY cable might present such an improper source to load impedance ratio, that it produces audible cable reflections, which is an unusual thing for analog applications. You might try spacing the shield farther away from the conductors.
You can tap on the wire with your finger to test for feedback. It's possible that it's mechanical, in which case, some physical damping should help or cure the problem. Heat shrink or teflon plumber tape over the whole assembly should take care of it, IF the problem is mechanical -- which it seems. Test for it though.
I tapped the wire, that does not cause any audible effect. The thing is that I made two identical interconnects, except one has a shield, other one doesn't. The one with the shield has this "echo". Is the shield adding capacitance?
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