I Believe in Power Cords

[DaveyF]

Tbone, I agree with you. In another thread, I happened to mention that the connector's can make or break a power cord.

 

[TBone]

Tbone, I agree with you. In another thread, I happened to mention that the connector's can make or break a power cord.

Yes, and even what they're connected too.

Connection quality is a critical consideration, even with interconnects.

tb1

 

[Speedskater]

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

Jim Brown at Audio Systems Group is both the AES committee chair on EMI/RFI and a Ham radio operator. He has about 50 very good papers and PowerPoints most on cables and interference.

http://www.audiosystemsgroup.com/publish.htm

 

[Speedskater]

Getting back to DC blocker's before it drifts away, some threads on the subject.

DC Blocking

Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?
http://www.diyaudio.com/forums/powe...t-buzzing-toroid-transformers-what-right.html
100 posts

dc filter
http://www.diyaudio.com/forums/solid-state/2080-dc-filter.html
298 posts

Noisy transformer
http://www.diyaudio.com/forums/power-supplies/149330-noisy-transformer.html
43 posts

Powerline DC blocking and conditioning circuit
http://www.diyaudio.com/forums/power-supplies/83784-powerline-dc-blocking-conditioning-circuit.html
83 posts

DC Filter against humming Toroidal's - Summary of the most interesting Comments
http://www.diyaudio.com/forums/soli...oidals-summary-most-interesting-comments.html

also see:
Blocking Mains DC Offset
http://sound.westhost.com/articles/xfmr-dc.htm

**********************
and a very technical paper about transformers.

AES 109th CONVENTION, LOS ANGELES, 2000 SEPTEMBER 22-25 1
MEASURING ACOUSTIC NOISE EMITTED BY POWER TRANSFORMERS
Menno van der Veen

http://www.idc-online.com/technical...MEASURING_ACOUSTIC_NOISE_EMITTED_BY_POWER.pdf

 

[microstrip]

Getting back to DC blocker's before it drifts away, some threads on the subject.
(...)
AES 109th CONVENTION, LOS ANGELES, 2000 SEPTEMBER 22-25 1
MEASURING ACOUSTIC NOISE EMITTED BY POWER TRANSFORMERS
Menno van der Veen

http://www.idc-online.com/technical...MEASURING_ACOUSTIC_NOISE_EMITTED_BY_POWER.pdf

Speedskater,

Glad you bring the paper from Menno van der Veen. He is a great transformer designer and the author of many papers about transformers. I have bough great audio and power transformers designed by him from Plitron and Amplimo in the past.

He answers our question about DC clearly in the paper you supplied the link at point 1. :

We researched which mains conditions generate noise inside power transformers and found three major
causes:

1: The mains 'sinusoid' is not symmetrical. This is identical to a DC-voltage on the mains. A very nice example is:
the single phase rectifier used in hair dryers at lower power by means of one series diode. The combination of this
rectifier with the actual load resistance and the resistance of the mains wires create an effective DC-voltage on the
mains. See Figure 13 for an explanation of this effect of hair dryers.
(It is very easy to test a particular transformer for noise under this "DC on mains" condition. Connect a 100 or 200
W light bulb in series with a proper diode to the same mains socket of the transformer under test and check for
transformer noise by listening).
Our measurements indicate that only a few mV-DC can be large enough to bring a transformer into its noisy region.
We did many tests to determine the amount of DC-voltage on the mains by means of the light bulb and other loads
in series with a diode and by observing the DC content on the mains due to asymmetrical loading elsewhere in our
or other buildings connected to the same distribution transformer. We found a DC-component smaller than 100 mV
for 120 V at 60 Hz mains. However, by experience we know that bad conditions today surely will be worse
tomorrow. We therefore propose to take an extra margin and to use 250 mV-DC as our standard condition for
"adverse" mains. (For 230 V at 50 Hz mains, the standard adverse mains condition equals the same 250 mV-DC).

2: Over voltage brings the transformer into its saturation region as well. Example: in Europe the transfer from
220 V to 230 V @ 50 Hz mains voltage takes place in a period of several years, combined with a certain plus/minus
deviation. Now suppose, an older 220 V transformer design, having to operate at 230 V (and sometimes in practice
up to 240 V). When such a design is constructed with no safety margin of magnetic headroom, saturation will occur
at larger input voltages. Our research showed us that 10 % over voltage is a good margin for testing a transformer
under conditions of over voltage.

3: Transformers designed for 60 Hz mains frequency can be used in a 50 Hz mains frequency environment. When
no magnetic headroom is available, a 60 Hz transformer will saturate at 50 Hz and become noisy. However, it is our
opinion that manufacturers clearly should identify on their transformers the mains frequency of safe and silent
operation. In this research we assume that all transformers are operating at the right mains frequency of design.


Many manufacturers exporting their products from the US to Europe had great problems with 2. and 3. 2. was critical in the UK that had 240V.

 

[DonH50]

Some of the advice in Internet forums is just scary...

I liked the next-to-last article, seemed to provide a good description of cause and effect as well as a viable solution that covers all the major bases (clamping, in-rush control, impedance requirements, etc.) Haven't gotten to the last one yet.

The threads and articles seem to indicate a much larger (or more common) problem than I had thought, although many causes are transitory in nature.

 

[Speedskater]

I think that Menno van der Veen's point #2 (line voltage) is a big part of the problem.

In the US, a very long time ago, the standard line voltage was 110V then some time after WW2 it was 115V than 117V and more recently 120V. But now it's approaching 125V. The NEC code book has listed 125V for several years. My house often has over 123V.

So power transformers designed for 110 or 115V very well could have problems with 125V.

 

[dave03hd]

I have switched all of my power cords over to Pangea (AC-9SE, AC-9, AC-14SE) I tell you, people who don't think power cords make a difference are missing the boat. Now I realize there are more expensive cords out there but, for the money, these Pangea's have made a huge difference to my system. The bottom end is bigger, and tighter. imaging much wider, noise floor...nice. Now it takes a little time for these to break in, when I first switched I'm like, these sound like sh*#, But as they broke in, it was...wow. I do have to mention that I do have the PS Audio P-10 Power Plant which takes the power out of the wall and turns it into DC (which cleans it up) and then turns it back into AC, which made a huge difference. But for those on a budget, I suggest going Pangea. Audio Advisor has them on sale, very reasonable.

 

[MrAcoustat]

Cables cables cables yes i'm a believer but to a certain point, what i look for is a good cable well made with good plugs and at a decent price ( this company as them all ) http://audiosensibility.com/blog/products-2/power-cables-2/i have a friend using his speaker cables in a system with Tenor Audio amp & preamp and Kingsound speakers, also a salesman in an audio store using his Statement power cords in another very expensive rig, the store he works for sells Sunyata.

PS: Steven is one good guy to deal with honest and knowledgeable.