From: ornitz@kodak.kodak.com (Barry Ornitz)
Newsgroups: rec.audio.high-end
Subject: Re: Power Conditioners
Followup-To: rec.audio.high-end
Date: Wed, 14 Oct 92 22:00:08 GMT
Organization: Eastman Chemical Company
Distribution: net
Reply-To: ornitz@kodak.com
NNTP-Posting-Host: 129.89.7.4
Summary: Constant Voltage Transformers
Originator: tjk@csd4.csd.uwm.edu

In article <1beqtoINNncu@uwm.edu> <MPA15C!ARTHUR@TRENGA.tredydev.unisys.com> 
writes:
>I noticed some rather unusual power conditioners in the latest Audiomart.
>They are made by a firm called SOLA, and the list prices are a whopping $7500
>for a 10KVA model, and $6500 for a 7.5 KVA job.  The owner is selling them for
>a few hundred bucks each.  Although I am intrigued with constructing my own
>conditioners based on the discussion herein a few weeks back, these guys are
>alleged to be expensive enough to raise an eyebrow.  Can anyone shed some light
>on them?  I've never heard of the firm.  Yeah- I know- I could call the guy,
>but it's always fun to get a discussion going here.

What was discussed here a few weeks ago was simple power line filtering and
radio frequency suppression thrown in with simple transient suppression if I
remember correctly.

Sola transformers are in an entirely different league.  They use a specially
wound resonant transformer arrangement to provide both voltage regulation
and input/output isolation.  Sola's virtually always include the internal
resonating capacitor.

The output of most Sola transformers actually looks like a square wave. Special
harmonic neutralized versions are available at higher cost; these produce sine
wave outputs.  The harmonics of the power line frequency present in the square
wave units makes the standard Sola units less suitable for audio applications.

Typical Sola units can regulate their output voltage to 0.5 to 1% changes for 
input voltage changes of up to +/- 15%.  Thus they can be quite useful if your 
subdivision is plagued with voltage dips or "brownouts".  

The real advantage in hi-fi systems, though, is their isolation between input
and output.  Common-mode noise typically does not pass through them, and
differential mode noise is greatly attenuated.  They can do a far better job
than simple power-line filters and transient suppressors.  While not offering
perfect protection (which is really impossible), they do a very good job of
protecting equipment from lightning damage from the power mains.  Other
companies besides Sola make similar "constant voltage transformers" but Sola
is the best known.  Topaz and a few other companies make high-isolation
transformers without the voltage regulating feature.

Proper sizing of these transformers is important.  They are rated for a maximum
volt-ampere capability, and their performance tends to suffer greatly if this
is exceeded.  They are also big, ugly, and heavy!
						Barry
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|  ___  ________  |       Dr. Barry L. Ornitz          WA4VZQ
| |  / /        | |       Eastman Kodak Company
| | / /         | |       Eastman Chemical Company Research Laboratories
| |< < K O D A K| |       Process Instrumentation Research Laboratory
| | \ \         | |       P. O. Box 1972, Building 167B
| |__\ \________| |       Kingsport, TN  37662       615/229-4904
|                 |       INTERNET:   ornitz@kodak.com
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