I Believe in Power Cords

[NorthStar]

-- TIP: If you have a TV, or a r.a.d.i.o. tuner near by or included in your sound system, be extra careful with all your wiring, including power cords. ...If you must be close to other wires like from a coaxial TV or cable box or satellite box or r.a.d.i.o. tuner transmitter, cross them at 90 degree angles (I'm sure you already know that). ...Power cords and all (Tuner interconnects, TV/Satellite or Cable Box coaxial cables, HDMI cables, ...).

AND! When doing some serious music listening, tune your TV and r.a.d.i.o. tuner to a 'dead' r.a.d.i.o. station, or/and TV channel. ...A place where there is no signal transmission.
Even when your r.a.d.i.o. and TV are off.

Last, unplug your fridge. :b

__________________

Then you can seriously start listening to power AC cords. ...Can you really?

 

[microstrip]

No.

Thanks. Considering your case I must say that it is not typical, and unhappily extrapolating any conclusion from it is very risky.

When you are operating the inverter from the mains it being used only as re-generator. In this case there is a clear relation between the mains and the output - the DC being supplied to the inverter is created by the mains, the batteries only "filter" it. There is coupling between the primary and secondary of any transformer - it will attenuate any interference, but never suppresses it completely. Since you say there is no difference between the two modes of operation I could be tempted to consider that the batteries are not an important element and the function of your unit is DC insulating with some filtering and re-generation.

However you source of mains seems to be a small local diesel generator. I am not prepared to debate the difference of this situation from a typical urban polluted mains.

 

[Phelonious Ponk]

Are you guys still talking about power cables?

Tim

 

[mep]

Are you guys still talking about power cables?

Tim

Nope.

 

[microstrip]

Are you guys still talking about power cables?

Tim

Yes.

 

[NorthStar]

-- Of course we are Tim.

 

[DonH50]

How much relationship is there between THD on the AC input and noise on the output of the power supply, or the amp?

 

[Orb]

Are you guys still talking about power cables?

Tim

I think it was my post that derailed this lol.
But my point was relating to how even just 2.3% THD has a large effect on the swing of both the presented current charge to gear (this is seen when an electronic product is in use and so varies dependant upon item's current demand) and voltage swing.
The most dramatic aspect being though the pulse current charge IMO, although there is still a moderate voltage swing difference of 340V vs 310V.
Can a cable influence this, it should not be able to but it shows one easily quantifiable challenge with "normal" mains to audio equipment.

What a cable may influence though is both the technical-reference ground that audio equipment critically needs and also the noise already carried on the mains due to both the antenna-transmission effect of the house cabling (does not matter if separate spur as that protects from other consumer home products), in theory it is possible for certain noise to be reduced passively by a cable and the shield.
On the subject of separate audio mains ring, how many install a clean earth-ground/zero reference otherwise the audio equipment still shares the earth/ground of everything in the house.
However if you read the 6moons article I provided it shows in reality the antenna effect of the house's cable makes the antenna effect of any other mains cable pretty insignificant.

That said they did notice some very strange interraction between products, such case was the PWT CD Transport (powered off) lowering noise and removing all radio transmissions but introducing a crackling, but the PWT DAC when that was plugged in (and PWT CD removed) introduced another radio stations and increased the noise measured.
Plugging the PWT CD Transport back in while PWT DAC was connected reduced noise to what it was exactly the 1st time the PWT CD was connected and removed 1 radio station - probably the one remaining was the one picked up by the PWT DAC.
The caveat as they mention in the article is that it is unclear what the analyser measures and whether the measured (and heard RFI from its internal speakers) has a detrimental effect on our hifi sound.
Also their house mains suffered from DC offset as well, and they also visited a studio with the noise analyser.

But the challenge is that discussing-measuring cables without the context of interraction with the various active audio gear makes the subjective case difficult to present when cables are considered as an individual component and similar or negligible electronic spec-traits.
Why it is interesting that Keith Howard looked at a more active measurement-analysis with the pulse current charge waveform that must involve powered audio gear and a specific interraction-variable to said mains.
Also their house mains suffered from DC offset as well, and they also visited a studio with the noise analyser.

Cheers
Orb

 

[Orb]

How much relationship is there between THD on the AC input and noise on the output of the power supply, or the amp?

How would you analyse this as it would require measurement within the amp (or even electronic source equipment) and its power supply stage and probably at multiple stages?
But I agree more is needed, so hopefully your itch is large enough that you can have a look into this

From what I have seen so far all we can do at moment is go by subjective reviews of benefits brought by regenerative mains products to audio equipment and analyse the differences between the "normal" mains and that presented by the mains regenerator.
Normally the focus so far has been just the voltage swing (does not require any audio gear), however I think Keith Howard is the only one so far to consider measuring an important aspect of the power supply transformer-rectifier-capacitors context by measuring the current charging pulse (which does require audio product connected and powered-active).

In his subjective experience even using an amp with a regulated power supply benefitted from the P10, and this was when his domestic house mains was working pretty well at 2.3% THD (reduced to around 0.3% THD with the P10 I think), in the past the domestic house mains has been as bad as 7%.
However there is probably more involved than just the current charging pulse as he found the P10 had no side effects with any equipment while another regenerator improved some audio equipment but some would be affected negatively - and this regenerator had better current charging pulse and had better THD measurements than the P10.
So further interraction-variable also needs to be considered as well, which may cause sideways change to audio quality when considering interraction between electrical component and mains.

Cheers
Orb

 

[microstrip]

How much relationship is there between THD on the AC input and noise on the output of the power supply, or the amp?

Don,

You have just asked a difficult question. I have owned a PSAudio P300 multiwave power regenerator - basically a signal generator followed by a bridged amplifier generating 110-120 mains. The european version added a step-up transformer to raise the voltage to 220-240V. The multiwave could generate several waveforms - 50 Hz, 60Hz, but also some fancy distorted waveforms - including asymmetrical waveforms. I used it mainly on the source components and preamplifier. Although a few of them affected significantly the sound of the system, most of them had no effect, irrespectively of the distortion they added. Unhappily I did not keep records of the listening tests. The PSAudio is long gone - a friend owning a turntable needing a 60Hz 110V source requested it and I lost track of it.

My first power re-generator was built for a pair of electrostatic SoundLab A2 long ago - just to power the HV supplies that needed 115V. Courtesy of "The Art of Electronics", my electronics bible for a long time! I just added a Wien oscillator, as it had very low noise and was very stable. The first version was powered by two lead batteries.

 

[DonH50]

How would you analyse this as it would require measurement within the amp (or even electronic source equipment) and its power supply stage and probably at multiple stages?

I would measure the input noise and the output noise and run a correlation. Ideally I would inject noise on the AC line and measure the resulting output as it would be much easier to isolate noise components from everything else.

Without taking anything apart, I would focus on what matters, starting with just a test load on the amp. Does the output of the amp (or whatever component) change if I inject noise (or remove it) on the AC line? By how much?

Certainly different components will exhibit greater or lesser isolation. I do not know but do wonder just how sensitive the output is to line noise. This should be easy to mesaure, given the components and equipment, but setting up the noise injection could be tricky if you want a controlled source. I do not have a 120 Vrms generator handy, most of the RF stuff I play with does not need that kind of drive and would blow up if I used it. Maybe if I was in a power transmitter group...

 

[DonH50]

Don,

You have just asked a difficult question. I have owned a PSAudio P300 multiwave power regenerator - basically a signal generator followed by a bridged amplifier generating 110-120 mains. The european version added a step-up transformer to raise the voltage to 220-240V. The multiwave could generate several waveforms - 50 Hz, 60Hz, but also some fancy distorted waveforms - including asymmetrical waveforms. I used it mainly on the source components and preamplifier. Although a few of them affected significantly the sound of the system, most of them had no effect, irrespectively of the distortion they added. Unhappily I did not keep records of the listening tests. The PSAudio is long gone - a friend owning a turntable needing a 60Hz 110V source requested it and I lost track of it.

My first power re-generator was built for a pair of electrostatic SoundLab A2 long ago - just to power the HV supplies that needed 115V. Courtesy of "The Art of Electronics", my electronics bible for a long time! I just added a Wien oscillator, as it had very low noise and was very stable. The first version was powered by two lead batteries.

Very interesting, thanks microstrip. A lot of inexpensive UPS units use a pretty coarse stepped-sine approximation that generates very high distortion and I could see that impacting the sound if the power supply was not robust and input noise filters limited. Transformers in power supplies tend to suppress some of the LF noise but HF noise (and RFI) can blow by through shunt capacitance.

I realize this is taking us away from the power cord discussion, though I would argue is related and relevant, but I shall desist from chasing too far down the rabbit hole. My main question/concern is how much AC input quality really matters given a real-world power supply. Seems like the answer, as usual, is "it depends".

Onwards - Don

 

[Orb]

Very interesting, thanks microstrip. A lot of inexpensive UPS units use a pretty coarse stepped-sine approximation that generates very high distortion and I could see that impacting the sound if the power supply was not robust and input noise filters limited. Transformers in power supplies tend to suppress some of the LF noise but HF noise (and RFI) can blow by through shunt capacitance.

I realize this is taking us away from the power cord discussion, though I would argue is related and relevant, but I shall desist from chasing too far down the rabbit hole. My main question/concern is how much AC input quality really matters given a real-world power supply. Seems like the answer, as usual, is "it depends".

Onwards - Don

Well I would say it is more than "it depends" Don because 2.3% THD is usually reasonably good for domestic home, and while it relies upon subjective review Keith Howard identifies the magnitude of affect 2.3% has on the current pulse load from an amp attempting to draw 5A and also other electronic equipment.
I like the test because it is analysing exactly the environment required in the context of transformer-rectifier-capacitor, although this is a mix of subjective and not measuring a signal output such as at the amp's speaker terminals (still not sure though what would be test-measured as the debate all good amps measure the same vs sound different has never really been resolved).
Yeah agree with ideally at the output and measuring signal would be interesting, but looking for what when considering the argument about "all good amps measure the same" that exist on every forums.
Maybe need to be something along the idea of a BERT tester concept?
Although again this would not translate into audible trait.

Cheers
Orb

 

[mep]

In consideration of the power cord Krell sent Mark, I guess one needs to lower their expectations!

In fairness to Krell, I need to say something here. When I bought my KSA-250, it came to me broken and sans power cord. When I sent it back to Krell the first time, I asked them if I could get a new power cord thinking I would pay for it and they would send me a heavy duty power cord befitting a product they want plugged into a 20A outlet. The first time they sent the KSA-250 back to me, they forgot the power cord I had requested. When it went back the second time to fix the hum I was experiencing through my speakers, I reminded Krell again about the power cord. Krell did pay for the round trip shipping of my amp for the second repair and didn't charge me a penny for the repair. Shipping alone was worth around $700. Krell threw in the power cord for free too, but they didn't give me the type of power cord that would have come with the KSA-250 or any of their other amps that demand a 20A circuit. The original power cords that I have for my Krell KPE Reference phono stage and the Krell KRC-HR are all much more heavy duty and well built than the cord they sent me for the KSA-250. Bottom line is that I think it was just a mistake they sent me the cord they did. Take one look at the Pangea power cord, and we can see we are light years away. More importantly, plug in the Pangea and the hum from the transformer goes away (and again, the hum wasn't coming through the speakers like it did before I sent it back the second time, it was audible only if you walked up close to the amp) and now I think it's worth every penny I paid which in the grand scheme of things, it wasn't very much.

In summary, I'm pretty sure that if you bought a KSA-250 brand new that it came with an adequate power cord that was heavy duty.

 

[Orb]

Regarding cables,
the following paper is of reasonable interest, more so in the context of the variables relating to cable structure.
Best to read from page 19 onwards, may had been posted in the past on here as pretty well known paper, but IMO does not answer everything.
Common-Mode to Differential-Mode Conversion in STP Cables (Shield-Current-Induced Noise) [behaviour]
http://audiosystemsgroup.com/AES-SCIN-ASGWeb.pdf

Cheers
Orb

 

[ack]

Regarding cables,
the following paper is of reasonable interest, more so in the context of the variables relating to cable structure.
Best to read from page 19 onwards, may had been posted in the past on here as pretty well known paper, but IMO does not answer everything.
Common-Mode to Differential-Mode Conversion in STP Cables (Shield-Current-Induced Noise) [behaviour]
http://audiosystemsgroup.com/AES-SCIN-ASGWeb.pdf

Cheers
Orb

Eye-opening; thanks for posting!

 

[Orb]

Welcome ack.
Don, sorry re-reading your post it does seem I was thinking along the same lines of you with a BERT test concept but for analogue; where the mains is perfect (controlled environment) and then a tester tool injects a high level of THD% distortion (hopefully replicating behaviour of say the current pulse interraction and voltage waveform) and watch output at exact same time.
I was thinking maybe the signal output could be intermodulation such as what JA does (so 19khz+20khz) at say 10W and then increase after each test to see what effect if any it has on the measured spuriae at time of the injected THD% (also start test with say 10%THD and gradually increase/decrease separately to the amp watts output to build a trend if any).
Downside is it will probably blow the amp lol.
But I think would provide best way of seeing any difference in the output, although ideally it needs to be equivalent to an advanced analyzer in that it can analyse-record a real world behaviour and replay-mimic it to create a true simulated accurate environment, freaking expensive from what I remember.

Cheers
Orb

 

[DonH50]

Close to what I had in mind, yes, just not sure I have the tools to do it... Our SAs are designed for high data rate systems (Gb/s) and do not reach down to the audio band. Note 1% distortion is 1.2 V, not outrageous for a signal generator, but you need some way to couple it in and I don't have any 60 Hz couplers or power dividers that would work in the AC line. I had thought to see if it was possible to couple a signal via a capacitor or transformer. I have a vague memory of using a transformer in the past, with the line simply passing through (in series with) the primary and the secondary used to inject signals. Injecting something close but not harmonically related, like a 59 Hz tone or square wave, would make it easy to look for any traces of the injected noise at the amp's output. The idea being to actually measure the sensitivity of the amp (or whatever) to power supply noise. When I was in college we had a power lab and noise injection and line distortion wsa actually one of the things they did. Unfortunately, I was not a power major... Although I did work on the thing as it used an analog computer; I helped design and implement some new functions for it whilst working in the EE Dept.

 

[RBFC]

Mark,

When I purchased my EV403 amp, the included power cord was quite robust, with one prong rotated 90 degrees so that it would only fit a dedicated 20 amp outlet. You probably got a "freebie" meant for a CD player or similar.

Lee

 

[TBone]

I believe that the connection qualities of ANY power cord is as important as the cord itself.

tb1