Conrad Hoffman said:
600 ohms is a legacy standard from early telephony days and I'm not sure has anything particularly optimum about it for home use compared to, say, 50 or 75 ohm. 'Zero' impedance current busses, now that makes sense and is a technique common of many analogue recording console backpanes.
No need for sophisticated measurements; tapping the cable, then rubbing them on the surface of the table caused clear microphonics. The stuff was a great transducer. I still have a couple feet of it laying around if you want to try it for yourself.
BTW, the tube amp I mentioned earlier was not anything with the initials AN.
BudP said:
That table needs very carefull interpretation. On the face of it, a delta-impedance of 5% with frequency sounds, well, significant.
Let's plug in some numbers. Assuming a DC resistance of an interlink of 1 ohms, feeding a 10k load from a 100 ohms source. What would be the change in freq response between 20Hz and 20kHz from an interlink change in impedance from 1 ohms to 1.05 ohms?
At 20Hz, attenuation due to cable Z is 10k/(10k+1). That's about -0.00086 dB. Now at 20kHz it's 10k/(10k+1.05). That's about -0.00092 dB. So, the freq response deviation because of a 5% delta in Zcable due to skin effect amounts to about 0.00006 dB. 20Hz sounds 0.00006dB louder than 20kHz. Are you sure you can hear that?
Jan Didden
janneman said:
A more extreme condition would be a low resistance moving coil cartridge (3 Ohms) feeding a transformer that has had its HF response optimised for that 3 Ohms. In which case, the 1 Ohm cable (not unreasonable) would cause the total source resistance seen by the transformer to change from 4 Ohms to 4.05 Ohms; a 1% change that wouldn't cause a noticeable change in HF response of even the most highly optimised transformer/cartridge combination. I really don't think skin-effect is significant at audio, but microphony, oh, I'll believe that.
Correction: I do consider amps that cannot cope with high capacitance speaker cable defect or poorly designed, which really is the same thing. But I wouldn't consider my gear defect because an interconnect makes a difference. I would assume that something has changed and would try to find out what.
Sy,
"edit: I believe that the table is derived using an incorrect formula, the one for skin depth for a planar conductor with no other conductors nearby."
That would be a very interesting point to pursue. The table, as presented, is the de-facto standard used in the transformer industry, for designing high frequency switch mode power transformers. I would be very interested in any additional input.
I posted the chart in an attempt to take "skin effect" completely off of the table, in conductor discussions.
Bud
"edit: I believe that the table is derived using an incorrect formula, the one for skin depth for a planar conductor with no other conductors nearby."
That would be a very interesting point to pursue. The table, as presented, is the de-facto standard used in the transformer industry, for designing high frequency switch mode power transformers. I would be very interested in any additional input.
I posted the chart in an attempt to take "skin effect" completely off of the table, in conductor discussions.
Bud
SY said:
The teflon one, right? I heard the same thing with cheap guitar cables when I was a roadie.
Triboelectricity is a solved problem, anyway. Google up 'triboelectric medical cable' to find all kinds of suppliers who'd be glad to sell you low noise wire. Maybe there's a group buy opportunity here.
I would defy anyone to say, hand on heart, that they COULDN"T hear the difference between a 1m interconnect made from a copper conductor, and an otherwhise identical cable made with a silver conductor.
BTW, I am not alluding to the superiority of one material over another: their relative merit is contextual.
pm
Hand on heart, when I've done controlled comparison with line-level interconnect wires (preamp to power amp, both units being properly engineered), I don't hear a difference, except with pathological cables.
Going to silver on a tonearm is a different kettle of fish and chips, as EC has pointed out- I'd be surprised not to hear a difference, at the very least a perceptible level change.
Going to silver on a tonearm is a different kettle of fish and chips, as EC has pointed out- I'd be surprised not to hear a difference, at the very least a perceptible level change.
I'm just fooling with the conductor issue right now, using tubular conductors of pure silver and brass in free air to eliminate any contribution by the (IMO non-issue) skin effect and the (IMO potential-issue) of dielectric insulation. At first I thought I could hear a difference. Eventually I could force myself to believe the silver was brass and vice versa. After enough swapping and very critical listening, I concluded there was no difference, but the psychological wall on this one is so high I doubt most people could overcome it. There's also the problem of comparing apples with apples, probably not possible with real world cables that have different construction and/or insulation. I also did high gain diff-amp measurements between a channel with brass and a channel with silver. Any differences were hidden in the low level noise and phase shifts. BTW, with enough gain, you'd be amazed at how much difference there is between supposedly identical channels, even after the levels have been matched exactly. I still believe there are audible cable effects, but they arise from well understood causes. The only difference between brass and silver is resistance, and if you have a situation where a difference in resistance can be heard, you'll hear it. If not, they'll sound alike.
Conrad Hoffman said:
I've had a similar experience in two somewhat different cases: comparing a raw feed vs. one compressed ~10 dB by an Aphex Compellor, and the second comparing tracks on a CD sampler I had a producer at work compile of his voice captured simultaneously by different microphones ranging from a ElectroVoice RE20 to a Neumann U87. In both cases switching back and forth I soon lost the ability to differentiate between them. Everything sounded the same. In the case of a delta as subtle, at least for me, as an interconnect I believe it's easy to fool yourself positive or negative in this kind of test without exceptional care, and probably dis-interested 3rd assistance.
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