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In Reply to: RE: Jon Risch Balanced AC Instructions..Anyone? posted by triodesteve on July 06, 2021 at 05:59:15
Attached is the balanced power schematic that was drawn and sent to me by a member many years ago. I built it and the results are amazingly clean sound from what appears to be a black background.
Edits: 07/06/21Follow Ups:
After dragging my SU-2 from the basement...damn I have gotten a lot older, I compared my handiwork to the drawing above. It took a few minutes to realize that I have the SU-2, and it is indeed different.
Does anyone have the original instructions for the SU-2?
Thanks
I'm not sure you can use an SU-2 as when the secondary's are paralleled you get 240 volts whereas the DU gives you 120 volts.
Posted by Jon Risch on February 9, 2000 at 21:46:34
In Reply to: Re: to J. Risch concerning Balanced power posted by Michael Donahue on February 9, 2000 at 10:54:59:
The Signal SU-2 is nominally a step-up OR step-down transformer. It is due to the flexibility afforded by the dual windings on both what are called the Primary and Secondary that it can be used as a balanced isolation unit.
If you read and follow my wiring instructions in the note, you will find that I have what Signal calls the Secondary windings in parallel and they are being used as the input windings, while what Signal calls the Primary windings I have in series, and am using them as the output windings. This is what provides the balanced AC power, with the center tap.
See Batman's post for further explanation. If you can not understand how to wire the transformer given the instructions in the note and these further comments, I strongly recommend you seek aid to wire the unit, or you run the risk of damaging your equipment, or possibly hurting yourself. If the transformer is wired incorrectly, it is theoretically possible to achieve several thousand volts across certain windings.
Jon Risch
Posted by Batman on February 9, 2000 at 19:09:10
In Reply to: Re: to J. Risch concerning Balanced power posted by Michael Donahue on February 9, 2000 at 10:54:59:
You are correct, Jon calls for this transformer to be wired "backwards" ie. with the wall current connected to the secondary of the transformer. BUT note carefully, unlike what he calls out for the DU-2 transformer, in this design the two 240-volt windings are connected in PARALELL. That is, the two "0" taps are connected togther and the two "240" taps are connected together. On the other side of the transformer, the two 120-volt coils are connected in SERIES, that is with the "120" lead of one coil connected to the "0" lead of the other coil.
Looking at it another way, the two 240-volt coils each have twice the number of turns (2N) as each of the two 120 volt coils (1N). Since the voltage across a transformer is a function of the ratio of the number of primary turns to the number of secondary you end up with a transformer with a turns ratio of 1:1. This is because the paralelled 240 volt windings only count as 2N windings while the series secondaries become 2N (1N+1N). Since the ratio of the turns is 1:1 (2N:2N), the output voltage (across the entire secondary) will equal the input voltage.
Thanks. I built my unit years ago but it has been sitting in the basement.When your entire system is run off batteries, ac is an afterthought. I just wanted to check my work before plugging it in again. And then I saw the drawing for the DU-2 which confused the hell out of me....I should have paid more attention!!!!
Thanks for your help.
Where can the transformer used be acquired? What are the transformer specs?
Thanks!
They are Signal Transformer Company step-up/step/down isolation transformers.
Holy Cow Batman!! I'm not sure if I ever thanked you for the schematic so thank you very much! It's the best improvement to my system ever. I also have a smaller DU 1/2 KVA balanced power tranny that just feed my digital DAC & CD transport.
You're welcome, glad you found it useful.
Like you I build a separate unit for my front end componenets. It contains two smaller Signal trafos, one for the CD and one for the DAC. I don't think it made as much difference as the big one for the amp.
And have any number of balanced power units in my various systems. I've had the same results as others here have mentioned: Music seems to come out or a blacker background.
After acoustic treatments (also a la Jon Risch)this is the most significant change I've made in my systems. Much more than any component change I've ever made.
I had the same experience with Balanced AC, much better sound in addition to getting rid of RF interference. I also built a mini balanced AC box with filtering for my digital player. Have a separate power switch for that so the deck is completely disconnected from AC when I am playing playing vinyl.
Mike
If you follow the schematic shown here but use a dropping transformer to take 240VAC input down to 120VAC, it becomes cleaner yet.
The primary price is having a 240VAC outlet installed or converted from 120VAC nearby your installation (by a fully qualified electrician). 10 amps is enough though 15 is nice. The dropping (2:1) transformer may not be more expensive than a simple isolating transformer.
The one change to the schematic that is absolutely necessary is fusing the second hot input to the transformer. In the schematic as shown, that line is the 120VAC neutral, but with 240VAC that is now 120VAC antiphase, and hot.
Thank you!!
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