Effects of isolating transformer on sound

[dubai2000]

Hello everybody,

I presume I am overdoing it in search of perfecting my Mc/Klipsch combo, but when I came across a used isolating transformer (I've learnt a new word) formerly used by the army I couldn't resist. The effect strikes me as quite dramatic. Having read about the wall of sound on this forum before I think this is a definite step towards it. Granted, my speakers are too close to each other in this flat (will improve in January, but suddenly the music seems to be even more removed from them than before (and that was the most striking thing I noticed when listening to my friend's La Scala for the first time!). This observation is even true when listening to FM (even via my MR77 - but that's a different topic)-suddenly it makes sense to talk about soundstage even with an indoor antenna. The transformer is a rather huge piece of equipment and certainly ugly, but the cool thing is that it has six AC outputs,so it can be used for almost all of my gear. I don't know how this 'beast' works (perhaps somebody will explain in a way that a non-technician like myself can understand?) but it strikes me as great. The company also sells a device that guarantees constant voltage so I might try this also at some point. Sorry if this post got a bit long, but I felt like sharing this experience with you.

Thanks for reading....Wolfram

PS. Yes, there is a drawback, this particular transformer hums a bit too much, but the shop has a second piece which strikes me as more quiet.

[ckt]

Its probally a ferro-resonant transformer. Several companys in the US make them.

I used one (a Sola 500 watt unit) while overseas, as the power was very unstable. One night the lights went just about all the way out for about 10 seconds and the stereo just kept on going with no change in the sound. But, the transformer sure got hot making up the voltage difference. Our voltage was allways low, around 105 volts. It was not uncommon for it to brown out to 60 and 70 volts.

Most audio power amps does not have a real voltage regulator in the power supply. So at high levels the voltage drops down due to the increased load. The more load you pull, the more voltage drop on the wall outlet wiring back to your electrical service entrance. Basically you are regulating the voltage to a constant level at your amplifier.

If the voltage is low to the amplifier, it will not be able to develop full power. We don't need full power, but we need the peaks to be clean. By regulating the input voltage, you are insuring that the amplifier will have maximum dynamic range.

Let me point out a couple of problems with the voltage regulator transformers. Some have a high THD on their output (Sola low distortion unit is 3 percent - I think their normal unit is around 15 percent). Also, the transformer needs to be located as far away as you can get it. It can induce a very large magnetic field, enough that you can hear it on a turntable pickup or tape head if it too close. I had mine mounted about 18 feet away from the system.

This message has been edited by ckt on 08-13-2001 at 04:37 AM

[dubai2000]

Hi ckt,

I don't know if we are talking about the same kind of transformer as the one I've got does not regulate the voltage output but avoids intrusion of any high frequency 'disturbances' (sorry for the unprofessional wording!). Anyway, for those who want to have a look at what I am talking about look at the following:

http://www.helmut-singer.de/fix/shd.html

the item in question is a Siemens transformer which somewhere on this website is called an 'isolating transformer'. Be that as it may, the unit is certainly worth it's money (around US $80.00) and its weight (47Kg -which is over 100lbs if I am not totally wrong)

Wolfram

[ckt]

We'll, from what you described about it helping, the power line must have a lot of trash on it. The isolation helps by not providing any path thru your system.

The SOLA I described also gave isolation. I noticed it dropped the hum level quite a bit, when I was using it in the Philippines. Since I moved back to USA, the power is very stable and I could not tell a difference using the transformer (I live about 1 mile from a major power substation - so they power is very stable).

I keep the transformer on my electronics bench now, and if I run into an old AC/DC radio, where the power line is directly coupled to the chassis, I use it. I also use it when I am working on microphone and phono preamps as it makes everything a little bit quiet when making performance measurements with test equipment.