Question for Atma-sphere, will expensive power cables improve your amplifiers?

Power cables do not change sound. Anyone who says otherwise is lying or willfully ignorant.

@squared80 My surmise is you've not read through this thread. But to keep it short, the statement above is only true in certain circumstances. If we are talking about a high power OTL with a substantial filament circuit and zero feedback, the Voltage drop across the cord can be measured and the effects of that Voltage drop measured at the output of the amp. 

This is true also of higher power solid state amps, especially if they are biased heavily and so have substantial power draw at idle.

Put in a more simple way, its a good idea to take some measurements first before making blanket statements such as this one. Otherwise your assessment is entirely anecdotal.

This being the case, may I assume then, that aside from the measurable quantities of voltage drop and bandwidth of the cable, nothing else will have an effect on sound quality from power delivered by a power cable, everything else unchanged? And, how difficult is it to build a power cable with the greatest possible bandwidth?

@kevn I previously described the two most important aspects that affect an amplifier, insofar as a power cord is concerned. There are other effects but there are so minimal they can be ignored. I don't think the 'greatest possible bandwidth' is all that important, since the charging time we're talking about is milliseconds rather than microseconds (so not particularly high frequencies). So the task is actually pretty easy once you understand that fact. The raw AC Voltage drop across the cord dominates the equation, so to speak.

would it be safe for me to summarise that you are of belief the primary and perhaps even only issue of the effect of a power cable on sound has to do with voltage drop across the cable and little else?

@kevn No. Bandwidth makes a difference too. I mentioned this at the top of the previous page.

these cables are often coaxial speaker cables that may work fine with Tube amplifiers or other bandwidth limited constructions.

We’ve made OTLs with more bandwidth than some solid state amps. All 'constructions' (which might mean 'amplifiers') are bandwidth limited no ifs ands or buts. If you have enough feedback in the amp (+30dB) it can correct for phase issues that for which you otherwise need the bandwidth which is how class D amps do it.

The bandwidth of the equipment used has nothing to do at all with whether or not the power cable will have an audible effect on it.

But I do agree with some of the warnings presented; you don’t want to use a cable that could start a fire or cause electrical problems; that bit is just common sense.

@westcoastaudiophile Yup! What you are describing is beyond most audiophiles. Many of them have a DVM though and it can show that there's something going on...

@westcoastaudiophile Usually the power transformer is one of the most expensive parts in any amp, unless SMPSs are used.

Its very difficult to measure the RLC (especially the R) on a lot of power cords (you need a really good meter), but its fairly easy to measure the Voltage drop across it. You can measure how it behaves with those current spikes we both mentioned too.

claiming as thicker than 100ft house wiring 3ft PC will tangibly affect sound is not justified! 

@westcoastaudiophile As I explained earlier the wiring in the walls is far higher performance than most power cords so Voltage drops in it are less of a problem unless you're really drawing some current. Some audiophiles have 20Amp circuits installed on this account.

Why is solid core wire illegal in a power cord?

@immatthewj They can be a significant fire or shock hazard for the reasons @61falcon and others laid out.

Very few audiophile cables made today use stranded wire.

@jea48 Just so you know, solid core wire for a power cord is illegal and for a good reason! On that account, I'm pretty sure your statement above isn't correct.

@mitch2 Yes! You also want good solid connections at either end so they don’t heat; heat means a Voltage loss.

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If you want an inexpensive means of building a power cord, use the kind of AC power cord used by an electric dryer or stove. Put a set of decent connectors on either end so you don’t get the connections heating up (which represents a Voltage drop) and you’ll have a very competent power cord.

Of course you have to watch things like which side is hot and which side is neutral so an electrician might have to be the one to do the work for you.

Any tube amp has in addition to the high Voltage power supplies, also a filament supply which is usually not regulated. So when there’s a Voltage drop across the power cord, not only is the B+ Voltage on the power tubes a little lower but the tube is less efficient since the cathode (heated by the filaments) is running at a lower temperature since the filaments are running cooler.

Put another way this means that tube amps are generally more sensitive to power cords than solid state amps are. But solid state amps can be affected too. The more regulation that is used (for example, in our MP-1 preamp where all the power supplies are tightly regulated) the less sensitivity you’ll have to the power cord.

One variable I've not mentioned yet: In a power supply there are rectifiers that convert AC from the power transformer to DC and filter capacitors that are charged by that DC. But the rectifiers only conduct when the output of the power transformer is higher than the Voltage on the other side of the rectifier. The filter capacitors retain a charge from one iteration of the AC power waveform to the next, so the only time the rectifiers conduct is at the peak of the AC waveform. At that time, the current has to move swiftly to charge the cap and so there is a current spike when the AC Voltage is at the peak. This might only be for a few milliseconds. If the power cord has troubles with what is essentially a higher frequency (due to the steepness of the current spike itself) it could limit the charging time.

That could result in a lower power supply Voltage with more noise. Some power cords are better at this than others.

That is why you can hear differences between power cords. Anyone that says otherwise clearly has not measured the effect they can have on equipment. IOW what I’ve said here can be backed up with measurements.

One question, do you mean voltage drops from the "wall" or within the amplifier itself due to volume adjustment.

@aberyclark I’m referring to Voltage drops from the wall. In the case of our class D the volume control will affect the Voltage drop.

Usually the house wiring has far less Voltage drop than the power cord. This has a lot to do with the fact that wiring in the wall is solid core. Such wire is not legal for power cords. So if anyone is wondering about the ’last 6 feet’ that’s the answer.

A better question may be "why do the manufacturers of a $7,000 amplifier even bother to include a power cable", given that it will be immediately replaced?

@tony1954 Because the customer has to be able to plug it in right away. Even though they may never use the stock cord, if you were a manufacturer and didn't include it you'd hear about it right away.

"Question for Atma-sphere, will expensive power cables improve your amplifiers?"

@aberyclark Power cords affect the sound of an amp due to Voltage drop across the power cord. Due to the power draw of our tube amp power cords can affect them quite a lot but not so much for our class D where the power draw at idle is insignificant. If you were pushing that amp hard all the time then the power cord would make a difference in theory; so far we've no feedback on that at all.