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power line conditioners...

When I worked in high end audio, our guru placed a 120v-120v transformer (heavy duty -- 1000va) between the wall socket and the power amp in the system being auditioned. This was just before power line conditioners became available as audio system accessories.
I found a Sola 500va 120-120 transformer in the trash and tested it -- it worked. I tried it between the wall socket and my power amp. The sound stage opened up. Also, bass was tighter and more authoritative. I felt like the high end was also clearer. I am using a Dynaco st70 in triode mode driving Kef 102's, a dynaco PAS-3X, a VPI MK-IV turntable with an Alphason HRS-100 arm, various cartidges, and a Micromega Stage3 cd player. As my room is rather small, I don't feel the need for a sub-woofer now.
I wonder if any of you other members have any experience with PLC's, or Sola 120-120 transformers? And if you have any thoughts on why the sound is improved. Could it be simply reduction/elimination of voltage fluctuations coming from the wall, or are there other things happening like availability of stored energy in the transformer for musical peaks or transients?
Another question that I have is how are the audio-specific PLC's different than a 120-120 transformer? Are they different? Are they worth the extra money?
After hearing the differences that the Sola made, I am convinced that there is something to be gained from power line conditioning. I just don't understand it very well now, and would like to!
Cheers!
bicycle_man
bicycle_man OP
100 posts
 
Thanks for the replies! Very interesting information. And, it seems very reasonable about the hf hash being filtered out.

Kennyt, perhaps because the power supply in my st70 is the original the quad filtering cap is so far gone that filtering out garbage and fluctuations helps even with such limited current availability. I am currently modifying the ps with the SDS Labs power supply board.

By the way, I ride a 1981 Eddy Merckx with full Campagnolo Super Record. I sometimes swap the derailleurs out with Nuovo Record. I recently had it restored by Tom Kellogg in the Molteni paint scheme. He did a wonderful job on the bike! I do my own mechanics, and build my own wheels. Brazing in a new headtube was beyond my capabilities, so off it went to Mr. Kellogg.

Thank you, again, Kennyt and Al for your thoughtful replies!
tobias
1,534 posts
 
A transformer also can't do anything to control or eliminate spikes or drops in the power, it will simply reproduce them on the output side.

Quite right that an iso tranny won't do anything for power sags, brownouts, dips or cuts. For that, you need an auxiliary source of juice. However an iso tranny offers excellent protection from spikes.

I've been using isolation transformers from Hammond, Deltec, Magnetek, Xentek and Topaz with digital sources, preamps and amps for five or six years now. The improvement the OP mentions is always there to a greater or lesser degree, depending on the quality of the gear, and even non-audiophiles can easily hear the difference. I even think that an isolator of proportional value should be part of the budget when you buy a digital player or transport. I have not heard a single player that did not benefit, up to my Esoteric P-10.

If you want more comments on the use of isolation transformers, look up posts in the archives by Sean and Lak.
psacanli
535 posts
 
The Equitech site has info on balanced transformers and MITs site has some papers on noise reduction.
ngjockey
1,042 posts
 
An iso tranny also presents an inductive and capacitive load, when shielded, which should sound familiar with passive XO's. They can eliminate DC offset but aren't fond of it and can hum in protest.

The general rule of sizing, in our case, is that an iso tranny should be rated for double the maximum draw of the electronics to prevent saturation. They do not, or should not, provide ground isolation because, by code, the ground should be continuous. However, they do provide common mode (line to ground) filtration. Normal mode (line to neutral) noise is transferred through, to some degree, but most power supplies handle that in the rectifying process.

They are best used independantly as in one for CDP, one for preamp, etc. They are a defacto standard in hospitals and many industrial/laboratory applications where they prevent noise from going back into the line. Step-down transformers are common in all commercial buildings and have dual purpose.

The difference between toroidal and EI-core is mostly packaging. Toroids are less prone to mechanical hum but are not quite as effective as a filter.
magfan
1,583 posts
 
My Panamax PC came with a small iso transformer. Very good results, and even the TV had a better picture, with none of the hash present from the untouched power line.
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