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The screw holding the ground lugs had actually broken off.

The plug was a strange (to me) version where one of the flat blades is at right angles to the other.



After replacing it with a new plug, I turned the unit on. Immediately there was a bit of mechanical hum which went away after a few seconds. Since then the unit has stayed plugged in and has remained quiet.

It became obvious that the sound is different using the transformer and so far I think it is better. There is more background detail, less glare and a deeper sound-stage. I read the Stereophile review and remembered that I had a CD of the Rolling Stones album that Art Dudley mentioned. I have it digitized on my server so started it up. I remembered it as a crappy sounding CD at best, but now it sounded relatively impressive. Electric guitars sounded more real.

Other familiar pieces sounded different and improved as well.

I still haven't done the experiment where I remove the unit so just think of this as a preliminary comment but so far I think it was $40 well spent.

ray

That is a standard NEMA 5-20P connector. It was used instead of the usual NEMA 5-15P because is needs to be used on a 20amp circuit if full capability is to be realized. Here is a link to a NEMA chart:

http://www.trci.net/media/4682/nemaplug ... ations.pdf

Actually, the Bryston is basically an empty box. It has a huge transformer and a small circuit board (series protection), a circuit breaker and outlets. No heat sinks (other than the box). It run cold, and is DEAD quiet.

That really is a great deal!

Presuming that the isolation transformer makes a difference, should we automatically add a smaller version to all of our amplifiers? Take an existing amp with power transformer and add an additional transformer connected between the power transformer and the fuse.

Here is an example of the additional transformer.

http://www.antekinc.com/as-2t230-200va-230v-transformer/

ray

It depends. If the power supply in the equipment was properly designed an isolation transformer is not needed. In that case it can actually be a detriment as it will add additional impedance between the mains and the power supply. In my case of the laptop/DAC noise problem I only used the isolation transformer as an additional safety measure as I lifted the ground connection to the laptop. That is an unusual case because the laptop itself, not the power supply was feeding noise onto the ground circuit. Lifting that ground connection prevented the ground noise from sneaking back along the ground circuit into the signal circuit of other equipment on the line.

Also remember that the main purpose of an isolation transformer is to help prevent electrical shocks. It is a safety isolator, not a noise isolator.

_________________
Walt

If you want a real isolation transformer -

http://www.surplussales.com/item/_tp/12-11t35sr.html

https://www.head-fi.org/threads/topaz-l ... er.857448/

I used this brand for experiments at the Nevada Test Site in the late 60's and early 70's.

_________________
Walt

Isolation transformers will not prevent a shock if you get your fingers across the secondary. Remember, they have to provide significant power to the isolated load. Get stupid and put your fingers in the wrong place and you will get a significant shock. They will prevent the most common shock hazard, that of getting between a hot lead and anything that is grounded either electrical or otherwise because of the neutral to ground connection in all mains lines.

It is interesting to note that the mains system can be refered to as an unbalanced supply similar to an unbalanced audio circuit. In the early days, the mains lines were balanced the same as a balanced audio circuit. There was no connection to earth ground for the "signal" and the two or more "hot" lines were floating. That worked OK in the beginning until someone figured out that lightning was hitting the power lines and with no utility supplied connection to ground, the lightening usually traveled down the line until it found something like a washing machine where it jumped to ground. After a significant number of houses were burned down this way they changed to an unbalalced design where a "neutral" wire was added and connect to ground for safety. Then lightning strikes had a path to ground through the utility equipment instead of your house. As mentioned before, neutrals also act as a balancing element in split phase configurations.

As far as using a balanced transformer for noise reduction, some of them will reduce noise to a minor degree, but a good noise filter will reduce the high frequency noise far more with less power reduction and for far less money. If you are worried about hot line to ground safety, an isolation transformer is the solution. If line noise is the primary concern, a noise filter Here ae a cpouple of links you might find interesting:

http://www.te.com/usa-en/products/emi-f ... lters.html

https://product.tdk.com/en/products/emc ... uct_08.pdf

https://www.onfilter.com/ac-power-line-emi-filters

I have sucessfully used the Corcom filters in power supplies that I have built. Here is a photo of a 20 amp version. Note that it hase two common mode chokes, four capacitors and a resistor inside the shielded case that is like a small brick. It will blow away any isolation transformer I have ever seen as far as noise but provides no additional safety for line to ground shocks.