yes, i design and build them......
Do you design and build isolation transformers for safety, or for reducing RFI?
Isolation transformer by itself doesn't provide enough RFI filtering.
RFI filter intended for mains supply by itself, usually doesn't provide enough RFI filtering - partly because RF is transmitted from the filter's input to its' output.
The best solution is a combination of both - isolation transformer with RFI filters before the primary and after the secondary. Those RFI filters should be enclosed in Mu-metal cases.
Some of the points you raised I addressed above.
As for RFI, you wouldn't hear RF from your amp and speakers … however, the presence of RF in amps' circuits degrades the sound quality.
Please elaborate.
Do you think Mu-metal enclosures for RFI mains filters are over-doing?
Indeed, the better power conditioning units are the best solution.
Alas, they are beyond my budget.
Please elaborate where you think RFI filters with MU metal cases can be bought.
Then think connections, seals are 75% of the problem (imho).
isolation transformers are not meant for RFI reduction. If such a transformer reduces EMI by its parasitic properties or a dedicated grounded screen winding, this is considered an additional gadget and not its purpose of existence.
What do you want the transformers for?
regards
I don't know of any commercial filter like that, I intend to DIY - to design a filter and a metal case and to order the metal case from a local factory. The filter's metal housing will also cover the input and output mains outlets.
The transformer and filters combination is meant to serve 2 purposes:
1. Ground loops isolation;
2. RFI filtration.
Whatever isolation transformers are meant for initially, I can use it to my intended purpose.
I'll check the costs. It seems that the work will cost much more than the material. However, a steel enclosure may be efficient enough to block any RFI through the enclosure.
for safety.....a 100ohm 5 watt resistor in series with a 0.1 cap attenuates rfi from transformer primary......
another way is to keep all your interconnects as short as possible, use only enough long speaker cables......
Actually I think the whole exercise is overdoing it unless you have found you have a problem.
Have you measured any RF getting into your system? Is it coming from your interconnecting cables or the power main? How do you know you need to take these steps? Have you measured any RF in any of the stages in your audio chain? Measured your power supplies, along the audio path? When you build your transformers and filters how will you know they will be doing their job?
Not that I think any of that maters but you may find these of use.
A quick search gave me these.
http://www.gaia-converter.ca/content/datasheet/FGDS-20A-50V.pdf
http://www.gaia-converter.ca/content/datasheet/EMIfilterMIL461CDEto300W.pdf
These were a couple of my bibles in another life.
http://www.goes-r.gov/procurement/flight_documents/MIL-STD-461E.pdf
http://www.wbdg.org/ccb/FEDMIL/hdbk419a_vol1.pdf
I use 3 isolation transformer at present and have been using some type of isolation transformer in my audio system for 6 years with great results.
I use a 2.5Kv Elgar isolation transformer for my mono block amps (Acoustat D/D Tube amps). I use another 2.5Kv Elgar switched into Balanced power for my preamps and separate power supplies. Then another smaller one for Digital gear.
Years ago when I tried a isolation transformer (Topaz) for the first time, I used it on just my Digital gear, I was amazed at the improvement, lower noise floor, the clarity was very noticeable. That is what started me on knowing that addressing A/C can bring some real positive gains. Quality of the isolation transformer can make quite a difference, some very good Brands are Topaz, Elgar, Xentek.
I also use on the secondary of each isolation transformer, a DIY power strip, with the box made of 1/8 plate Aluminum, the outlets used have a brass backstrap with nylon and brass fasteners used where needed. In the Aluminum box I also use some passive filters to further clean things up.
Here some info on Elgar isolation transformers: http://www.programmablepower.com/pr.../HIT Series - High Isolation Transformers.pdf
As a General rule, (and I don't know who made up the rule) it is said to have 2-3 times the power rated needed. I have noticed in the past that using a bigger vs smaller transformer with give a more open, effortless, and more dynamic presentation.
This is very important if using one on an amp!!
This ofcourse is with my system and my ears, YMMV!
I use a 2.5Kv Elgar isolation transformer for my mono block amps (Acoustat D/D Tube amps). I use another 2.5Kv Elgar switched into Balanced power for my preamps and separate power supplies. Then another smaller one for Digital gear.
Years ago when I tried a isolation transformer (Topaz) for the first time, I used it on just my Digital gear, I was amazed at the improvement, lower noise floor, the clarity was very noticeable. That is what started me on knowing that addressing A/C can bring some real positive gains. Quality of the isolation transformer can make quite a difference, some very good Brands are Topaz, Elgar, Xentek.
I also use on the secondary of each isolation transformer, a DIY power strip, with the box made of 1/8 plate Aluminum, the outlets used have a brass backstrap with nylon and brass fasteners used where needed. In the Aluminum box I also use some passive filters to further clean things up.
Here some info on Elgar isolation transformers: http://www.programmablepower.com/pr.../HIT Series - High Isolation Transformers.pdf
As a General rule, (and I don't know who made up the rule) it is said to have 2-3 times the power rated needed. I have noticed in the past that using a bigger vs smaller transformer with give a more open, effortless, and more dynamic presentation.
This is very important if using one on an amp!!
This ofcourse is with my system and my ears, YMMV!
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