A few Cardas cables can be pretty high...
http://www.cardas.com/clear_sp.php
This one is
278 pf / foot x 10 = 2780 pF for a 10 ft cable- that's pretty high This is probably their highest capacitance cable By comparison - The Van den Hul D352 is
32.5 pF / meter. so that's about 100 pF for a 10 ft cable Don't let that put you off Cardas - some of their cables are much lower At least Cardas makes the capacitance of their cables knowm - which makes me think they are aware of the issue - and feel the audiophile should know about it Many companies do not Regards - Steve |
Speaker Cable:
Speaker cable is a bit different from a lot of the interconnect cables we handle, in several respects. Because speakers are driven at low impedance (typically 4 or 8 ohms) and high current, speaker cables are, for all practical purposes, immune from interference from EMI or RFI, so shielding isn't required. The low impedance of the circuit, meanwhile, makes capacitance, which can be an issue in high-impedance line or microphone-level connections practically irrelevant. The biggest issue in speaker cables, from the point of view of sound quality, is simply conductivity; the lower the resistance of the cable, the lower the contribution of the speaker cable's resistance to the damping factor, and the flatter the frequency response will be. While one can spend thousands of dollars on exotic speaker cable, in the end analysis, it's the sheer conductivity of the cable, and (barring a really odd design, which may introduce various undesirable effects) little else that matters. The answer to keeping conductivity high is simple: the larger the wire, the lower the resistance, and the higher the conductivity. Hello Steve - I copied the above from the Blue Jeans site. I wonder if their, "...barring a really odd design, which may introduce various undesirable effects...." is tacit acknowledgement of the oscillation risk you raise (among other things, I suppose). In reply to your original question, knowing an amp was susceptible to high capacitance induced oscillation would not put me off from buying that amp (assuming it was desirable to begin with) BUT I would certainly exercise care with the speaker cables attached to it. Thanks for the Cardas info. By contrast to the high capacitance number for their Clear spkr. cable I note their Parsec cable is 30 pf/ft. If bi-wiring, how would these capacitance numbers work...simply additive? or something else?? Anyone have an idea about capacitance of the Clear Day Double Shotgun speaker cable? Thanks again. |
If bi-wiring, how would these capacitance numbers work...simply additive? or something else?? Parallel doubles capacitance and halves inductance and resistance. Bi-wiring separates the load into two parts. Response for each part differs from a single drive. Don't know a thing about Clear Day and they provide no technical information. From reading their information, it seems their product comes from 'messing about' and may be very specific or just generic. Solid core will be stiff. Price seems too low for pure silver of a reasonable gauge, say 18. That's about 4oz of pure silver ~$65. 18ga solid silver hookup wire is about $9/ft. 32 feet for two 8' runs is ~$288. Add in connectors, heat shrink and labor and the price is too low. |
ieales - Thanks for the bi-wire capacitance info. Don’t want to sidetrack this thread into a defense of Paul Laudati and Clear Day Cable though I will say I’m inclined to take him at his word. Paul has been around a while and it would be a fairly easy task to "autopsy" one of his cables and refute his solid silver claim if it were bogus. To my knowledge, that has not happened. I can report the Double Shotguns were better with my gear than Morrow Audio SP-4 silver plated copper...and not by a little bit. They are also preferred in one amp/speaker combination I have over Cardas Parsec cable. The review at the link below, while largely anecdotal, might be of interest. http://www.highfidelityreview.com/clear-day-audio-cables.html |
@unsound I found a link to the paper from which the excerpt shown at the link you provided was taken: http://sound.whsites.net/cable-z.htmMy conclusion reading all of this is that I wouldn’t worry about his allegation that the resistor value chosen by Goertz is not ideal. As he even said, based on his simulations: (Comments shown in brackets are mine): Even 100nF in series with 10 ohms restores the amplifier phase margin to normal.... 4.7 ohms is preferable, but the phase margin is barely affected. The speaker end response has a small ’lump’ with 10 ohms [between about 5 and 10 MHz!], and phase goes ’wobbly’ at above 20MHz. This is probably not a concern, and you will almost certainly get away with it. I don’t, however, see any reason to doubt his statement that: It is very evident that this particular cable [Goertz MI 1] should never be used without a Zobel at the speaker end.... Best regards, -- Al |
