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Amps for Maggies

Low capacitance means high inductance. Not sure that would be good for the frequency response - but it might protect an amp from the speaker load at HF.

It does indeed, but the effect on response can be ignored for typical cable lengths for the slightly spaced conductor cables such as those from Linn and Exposure.
 
Lots of suggestions. Thanks but looks as though they’ll be moving on as they’re not proving popular with the family
and the second system room is tiny.
 
Why does low capacitance equal high inductance?

Basic EM physics (simplified)

c = constant/(L' x C')

Where c is the velocity of the EM propagation, L' is the inductance/metre, C' is the capacitance/metre.

Given that the value of c can't be higher than the speed in vacuo it follows that if you try to reduce the C' value beyond a certain level you find that L' has risen.

Similarly, real materials tend to alter the constant in way that reduces the c value in the medium (cable).
 
Yes. The laws of physics apply regardless. However, as you realise, making the cable shorter will reduce *both* the series L and shunt C values. But for a given length you can't beat the above, so there will be a minimum on one value set by the value of the other.

I suspect the reality in this case is slightly different. That someone says "choose a cable with lower capacitance/metre" as a way of indirectly saying "you need more inductance". Perhaps to avoid admitting a given amp isn't happy with the loading without sufficient inductance in the path. i.e. blame the cable. :)

The snag with that is someone might simply use a much shorter cable, so not get the 'benefit' they expected.
 
Yes. The laws of physics apply regardless. However, as you realise, making the cable shorter will reduce *both* the series L and shunt C values. But for a given length you can't beat the above, so there will be a minimum on one value set by the value of the other.

I suspect the reality in this case is slightly different. That someone says "choose a cable with lower capacitance/metre" as a way of indirectly saying "you need more inductance". Perhaps to avoid admitting a given amp isn't happy with the loading without sufficient inductance in the path. i.e. blame the cable. :)

The snag with that is someone might simply use a much shorter cable, so not get the 'benefit' they expected.
this forum.

I love the new learning on this forum. It’s such a treasure trove of info.
 
I kept wanting to give the equation that ties the factors together. But have no idea how I can type symbols like mu sub-zero or sub-r into this! 8-]

However, for anyone who wants to dig, it's one the points that comes out of the investigations wrt cables on my website. :)
 
Yes. The laws of physics apply regardless. However, as you realise, making the cable shorter will reduce *both* the series L and shunt C values. But for a given length you can't beat the above, so there will be a minimum on one value set by the value of the other.

I suspect the reality in this case is slightly different. That someone says "choose a cable with lower capacitance/metre" as a way of indirectly saying "you need more inductance". Perhaps to avoid admitting a given amp isn't happy with the loading without sufficient inductance in the path. i.e. blame the cable. :)

The snag with that is someone might simply use a much shorter cable, so not get the 'benefit' they expected.

The Naim way, or at least it was for many years.
 
Low capacitance means high inductance. Not sure that would be good for the frequency response - but it might protect an amp from the speaker load at HF.

Ran stats for years & amp/cables make a huge difference into a 1ohm load
2,000wpc monos @ 8ohm 100+ volts & 100a amps output stage normally 4/8 trannies
these used 128 per channel virtually all amps are unstable or a fire risk into 1ohm load

Stats are a capacitor, and amplifiers find capacitors very hard to drive. If the cable adds more capacitance, it only makes things that much worse for the amplifier.
To an amplifier or speaker cable, ESLs appear as a capacitor, while magnetic speakers appear as a combination of a resistor and inductor An ESL is driven by a high-voltage, step-up transformer. T/x takes low voltage of an amplifier to the several thousand volts needed to drive an ESL

transformers have leakage inductance. This inductance interacts with the capacitance of an ESL to form an L/C (inductance/capacitance) resonant circuit. This produces an undesirable, high-frequency, resonant peak in the frequency response of the ESL.
this can destroy class D amps

resonance must be kept in the 20-50 KHz + region so that it doesn't alter the high frequency response of the speaker. to get the resonance high is to build a transformer with very low leakage inductance.

you want buckets of power + buckets of voltage for Stats
 
Ran stats for years & amp/cables make a huge difference into a 1ohm load

To an amplifier or speaker cable, ESLs appear as a capacitor, while magnetic speakers appear as a combination of a resistor and inductor An ESL is driven by a high-voltage, step-up transformer. T/x takes low voltage of an amplifier to the several thousand volts needed to drive an ESL

The above is a good argument for choosing:

1) An amp that is unconditionally stable.

2) And if that means it needs a small output inductor, then its value should be low enough not to impact the audio band.

It isn't an argument for simply choosing a cable with a high series inductance and/or resistance.

Given (1) and (2) a modest length of cable shouldn't be a problem, either. if it is, you need to change something.

BTW not all ESLs are simply 'capacitors'. cf for example the comments here


http://ukhhsoc.torrens.org/makers/Q...eview_reprint_StereoReview_Aug_82/Page04.jpeg

And at HF/ultrasonic an input transformer can become like a capacitor. Just as a mismatched cable length+load can flip as you go to higher frequencies. cf some measured examples here

http://www.audiomisc.co.uk/HFN/Cables3/TakeTheLead.html

more info here

http://www.audiomisc.co.uk/HFN/Cables2/OhmAndAway.html
 
A low reactance means BOTH low capacitance AND low inductance.
Yet, that may be/is most likely also true only in a defined frequency range. Not necc a useful one at that- by which I mean, without measurement (the way the so very many audio add-on sellers do stuff.)

& Jim remains the physicists' physicist ... and not that we get many posting on our weird hobby interest here.
 


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