[AliG]

DISCLAIMER: This is not a thread for people who do not believe that cables can make a difference, please stay away

I just had a conversation with a well-known cable design guru (won't mentioned his name), his cable is known to have very good bass control, I as him how in the world can speaker cables affect the bass, he said it improve the damping factor of the amplifier. I then asked him, if a power cord will do a better job in controling the bass, he said no, speaker cable does a better job.

I recalled reading somewhere that a well-known amplifier designer once claimed that his amplifier do not need exotic cables because it works well under ALL conditions.

My question is then, what materials can you put in the cable to enhance the damping of the amplifier? And do you think the claim of the amplifier designer has any validity at all, that the quality of an amplifier design can be judged by how it is NOT being affected by swapping cables?

Any thought and comment?

[Ethan Winer]

DISCLAIMER: This is not a thread for people who do not believe that cables can make a difference, please stay away

Since you asked what seems like a serious technical question I'll give you a serious technical answer, even though I don't generally buy into cable claims.

what materials can you put in the cable to enhance the damping of the amplifier?

Low resistance. And low inductance and low capacitance. Those are the only three parameters that affect cable. If a connection is poorly soldered that can cause distortion, but I'll assume good connections.

And do you think the claim of the amplifier designer has any validity at all, that the quality of an amplifier design can be judged by how it is NOT being affected by swapping cables?

I agree with the amp designer. If a cable has a high resistance it will harm the amplifier's damping factor. But as long as the cable's resistance is substantially lower than the speaker's inherent resistance, lowering the wire's resistance further should have no benefit.

--Ethan

[BrianM]

This for me is one of the more interesting questions in audio these days.  People tend to assume that any and all gear is subject to changes in cable, though often with the qualifier that every combination is potentially different.  But as for the possibility of ZERO impact, due to a component's design, it doesn't get much consideration.   As for designing an amp to be indifferent to speaker cables, I would think any amp is dependent on the basic parameters laid out by Ethan Winer.  As for designing an amp to be indifferent to power cords (and outlets, and AC lines, etc etc), I would think that a competent engineer would have MUCH more control over this aspect, though I could be wrong.  If I'm right then it would seem self-evident that the best gear would be judged according to its indifference to, and not its dependence on, certain cables.

And yes, I have heard SMALL differences in different signal carrying cables.

[Steve Eddy]

I just had a conversation with a well-known cable design guru (won't mentioned his name), his cable is known to have very good bass control, I as him how in the world can speaker cables affect the bass, he said it improve the damping factor of the amplifier. I then asked him, if a power cord will do a better job in controling the bass, he said no, speaker cable does a better job.

Since damping factor is calculated by dividing 8 ohms by the amplifier's output impedance, no speaker cable can possibly improve damping factor. It can only make it worse to a greater or lesser degree.

And since a power cord hasn't any effect on the amplifier's output impedance (the power cord's not even in the power supply circuit the majority of the time anyway) a power cord won't have any effect on damping factor one way or the other.

se

[jneutron]

I just had a conversation with a well-known cable design guru (won't mentioned his name),

Why do you not mention his name??

Low resistance. And low inductance and low capacitance. Those are the only three parameters that affect cable. --Ethan

With the added correlary...lowest LC product, and lowest cable Z.

As for designing an amp to be indifferent to power cords (and outlets, and AC lines, etc etc), I would think that a competent engineer would have MUCH more control over this aspect, though I could be wrong.  If I'm right then it would seem self-evident that the best gear would be judged according to its indifference to, and not its dependence on, certain cables.

And if the (otherwise) competent engineer does not understand the issue of ground loop pickup, they may not be able to control it at all.

Since damping factor is calculated by dividing 8 ohms by the amplifier's output impedance, no speaker cable can possibly improve damping factor. It can only make it worse to a greater or lesser degree.

Uh oh, gettin picky again, eh??

Ok, the wires won't affect the amplifier's damping factor...they will affect the system's damping factor.  (8 ohms plus wire resistance)/amp impedance.

And since a power cord hasn't any effect on the amplifier's output impedance (the power cord's not even in the power supply circuit the majority of the time anyway) a power cord won't have any effect on damping factor one way or the other.

If there exists some feedback mechanism for the low frequencies to alter the ground loop  currents, then the lf damping factor could indeed be altered.  If the lf power draw magfield on the pc is able to couple to the ground loop...voila.

Testing that would be a beech, however.  Lab testing need not apply...
Cheers, John

ps...happy holidays steve..






Cheers, John

[Steve Eddy]

Uh oh, gettin picky again, eh??

Picky? Moi? Naaaaah. You must be thinkin' of some other guy.

Ok, the wires won't affect the amplifier's damping factor...they will affect the system's damping factor.  (8 ohms plus wire resistance)/amp impedance.

Right. And I was simply trying to dispel the notion that cables could possibly improve damping factor.

If there exists some feedback mechanism for the low frequencies to alter the ground loop  currents, then the lf damping factor could indeed be altered.  If the lf power draw magfield on the pc is able to couple to the ground loop...voila.

Sorry, John, I'm not following you here. It sounds a little like "If frogs had wings..." Exactly what "ground loop currents" are you referring to here?

ps...happy holidays steve..

Thanks, John! And the same to you and yours!

se

[jneutron]

Right. And I was simply trying to dispel the notion that cables could possibly improve damping factor.

I was referring to the damping factor at the speaker binding posts, which is where it matters.  That will be affected by the wire resistance.  You're correct in that the actual damping factor of the amp is unchanged.

If there exists some feedback mechanism for the low frequencies to alter the ground loop  currents, then the lf damping factor could indeed be altered.  If the lf power draw magfield on the pc is able to couple to the ground loop...voila.

Sorry, John, I'm not following you here. It sounds a little like "If frogs had wings..." Exactly what "ground loop currents" are you referring to here?

Why, the ones in the ground wires of course...   (what was the question???) .

The haversine current within a line cord will reflect (in some fashion), the power draw of the load being driven.  The magfields caused by that power draw can couple to the ground loop formed by the amp, the source, and the pc's and the ic between...this is exactly the mechanism responsible for ground loop hum, but there the agressor is a single frequency..  Single ended input amps refer to their ground for signal, and that ground can be compromised by the loop currents formed by the wires we are forced to use.

I can certainly understand why you do not realize this...after all, it involves the use of "AC"...people like you who use batteries, nevermind...

Cheers, John

[Steve Eddy]

Why, the ones in the ground wires of course...   (what was the question???) .

The haversine current within a line cord will reflect (in some fashion), the power draw of the load being driven.  The magfields caused by that power draw can couple to the ground loop formed by the amp, the source, and the pc's and the ic between...this is exactly the mechanism responsible for ground loop hum, but there the agressor is a single frequency..  Single ended input amps refer to their ground for signal, and that ground can be compromised by the loop currents formed by the wires we are forced to use.

Ok. And this relates to damping factor... how exactly?

I can certainly understand why you do not realize this...after all, it involves the use of "AC"...people like you who use batteries, nevermind...

I know about AC all too well. Why do you think I use batteries?

se

[jneutron]

Ok. And this relates to damping factor... how exactly?

I described a feedback loop..albeit a messy one.

Cheers, John

[Steve Eddy]

I described a feedback loop..albeit a messy one.

You described a ground loop. I didn't see any loop which would impact damping factor however.

se

[Big Red Machine]

Pictures really tell the story.  Any way to show one?

[jneutron]

You described a ground loop. I didn't see any loop which would impact damping factor however.

A ground loop which involves the IC ground, will couple the loop currents to the input of the amp.  If that loop is intercepting a signal which is comprised of the output signal in any way, damping factor will be altered.

Worst case, the loop is bad enough to force oscillation...been there, "fixed that"

Coulda brought the poles and bait, the motorboating was so bad....

Pictures really tell the story.  Any way to show one?

Who is that question aimed at?

Cheers, John

[Steve Eddy]

A ground loop which involves the IC ground, will couple the loop currents to the input of the amp.  If that loop is intercepting a signal which is comprised of the output signal in any way, damping factor will be altered.

Ok. But you'll pardon me for asking you to carry that through a bit farther as to altering damping factor.

Coulda brought the poles and bait, the motorboating was so bad....

What? No beer? Remind me never to go fishing with you.

se

[jneutron]

A ground loop which involves the IC ground, will couple the loop currents to the input of the amp.  If that loop is intercepting a signal which is comprised of the output signal in any way, damping factor will be altered.

Ok. But you'll pardon me for asking you to carry that through a bit farther as to altering damping factor.

The damping factor of an amp goes all to "heck" just before it breaks into oscillation.

Coulda brought the poles and bait, the motorboating was so bad....

What? No beer? Remind me never to go fishing with you.
se

sigh...beer.  Man I miss it..

Cheers, John

[Big Red Machine]

[/quote]

Who is that question aimed at?

Cheers, John
[/quote]

Everybody who is posting who has an idea of what this situation is all about.  I'm just here for the beer, er, knowledge.

[BrianM]

And if the (otherwise) competent engineer does not understand the issue of ground loop pickup, they may not be able to control it at all.

Would using a 2-prong power cord be one way around this potential problem?

[Steve Eddy]

The damping factor of an amp goes all to "heck" just before it breaks into oscillation.

Ok, so let's now take this back to where we started:

The haversine current within a line cord will reflect (in some fashion), the power draw of the load being driven.  The magfields caused by that power draw can couple to the ground loop formed by the amp, the source, and the pc's and the ic between...this is exactly the mechanism responsible for ground loop hum, but there the agressor is a single frequency..  Single ended input amps refer to their ground for signal, and that ground can be compromised by the loop currents formed by the wires we are forced to use.

How exactly do we get from haversine current pulses on the line cord to amplifiers on the verge of oscillation?

se

[jneutron]

How exactly do we get from haversine current pulses on the line cord to amplifiers on the verge of oscillation?
se

I had an amplifier pushing 300 watts into 4 ohms.  The input was tied to a source, that source plugged into an outlet along with the amp.

When I turned the system on, it motorboated.  Long story short, it was the line cord of the amp, a very rugged three conductor wire, flat, with the ground wire in the center.  When this cord carried current, it's design made a large dipole magnetic field.

The source cord ground formed a loop with the amp ground cord, and the IC that tied the two.  Hence, the loop.

The amp was of sufficient voltage gain, that the IR drop within the amp chassis on the ground wire of the input, created a signal which the amplifier attempted to um, amplify.

Several things acted in concert to cause this condition.

1.  Input was not differential, so could not reject the inducted voltage.
2.  The amplifier star ground didn't have a sufficiently large guage ground wire to the input terminal...it had an IR drop.
3.  The amp had insufficient storage capacity in the supply.
4.  The amp line cord wasn't twisted, so it's geometry was almost the worst possible one.  The worst would be if the hot of the amp cord ran with the IC to the source chassis, then along the source chassis cord to the outlet.  That would be the ultimate one turn transformer...
5.  The amp had too much internal gain.

With an amp close to instability, it's damping factor is not very good...

Cheers, John

[jneutron]

Would using a 2-prong power cord be one way around this potential problem?

You would think so.  But in USA, neutral ties to ground at the service panel, so it gets rather complex.  As frequency goes up, so does coupling.  So I don't think any hard and fast rule can be used..

Cheers, John

[BrianM]

Would using a 2-prong power cord be one way around this potential problem?

You would think so.  But in USA, neutral ties to ground at the service panel, so it gets rather complex.  As frequency goes up, so does coupling.  So I don't think any hard and fast rule can be used..

Cheers, John

All my gear has 2-prong plugs, and I don't notice anything complex.