An slightly unusual DIY balanced power supply project.

[86Ivar]

Hi!
Recently at school, i got 10 free 200VA double bobbin trafos that I want to try to use for the main powersupply for my amp the one that powers the speakers, know this might be overkill, but i dont mind trying because i got those for free anyway.
Anyway, the trafos dont have dual primaries nor secondaries, but I think in almost all countries but Albania and Norway, where im from, we do not have neutral in the wall plug, so the power is balanced from the wall plug anyway, if I havent misunderstod the "balancing" thing.

To make it easy i put up these questions.
-Do i really need to have dual prim sec? is it the balancing that makes the cleaning or the narrow hz range (50-60hz)?
-Is it better to make a bal power supply out of many small trafos like this, or with two big ones? once read many trafos in paralell get lower impedance.

Thank you for your time:)

[assendor]

Hello Ivar,

you are so right about the mains here in Norway, and Albania..
Crazy people that designed these systems here.

You do not want to use small sized transformers for power amps, because this will kill the dynamics, they say.
This is very possible.

When using mains isolation transformers for smaller consumers, it is better to have small transformer ratings, theoretically.

If anything is better or worse when the earthing is done "correctly", that is another question.

You may also try it out, since you have all these transformers anyway.

You can make your own Isolated Network on the Secondary, with your own grounds and stuff....
Primary is of course like it is, 230VAC input, and then you have 230VAC output in Secondary, potentially with a center tap, that you then take to GROUND.
THEN YOU HAVE THE SAME SYSTEM WE HAVE HERE IN NORWAY, and IN ALBANIA; YES.
But you are out of the noisy Mains network, theoretically.
OR not.. there are two main systems in Norway, one has the center/Star of Grid trans to ground, and the
other system does not. Even if, or not, it is most likely no matter what connected to ground because of
various faults in the system. Then the floating Center of the trans are automatically connected to ground.
It is a strange system.
BTW, in new areas we have the 400Volt system here in Norway too now. Even worse when this is implemented in the old areas.?? Crazy people.

If no center tap, you may as well Ground one of the Secondary Leads, and put a good capacitor between
secondaries for killing potential noise.
This will be much the same as the above too, but you will have a setup with then a Neutral, and a Phase.
SO THIS CANNOT BE DONE TO ALL Consumers, if you don't have control of what is inside them consumers of earthing philosophies.
To get rid of this Neutral/phase Philosophy in this case, you again has to use one more Isolation trans
to get a Floating 230VAC, with NO ground... =?=  this will work well.

What a Mezz..
Please make some drawings of what you are planning, then you will most likely get answers to those, instead of a lot of crazy stuff like you get from me now.. HAHAHA!!

-Jonas

[86Ivar]

Thank you
Nice to meet someone from norway in here. So where are you from then?

But i meant many small, so th VA was the same as with two big ones, if that is better or not.
My amp has 1000VA toraid, i made the amp myself, truepath 2x300w .
Im not shur i understand everything, remember those TNS TN and IT nets was a bit hard to understand at school.
But it is the balanced output that makes the "cleaning"? thought it was the windings, like an low pass filter.

Anyway here i have an idea:


This is a neat java simulation app you can try here: http://www.falstad.com/circuit/

This circuit is not really complete, (i gotta go to school now)
I tried with several secoundaries combinations, like seies and paralell, but did not make much difference in noise reduction, even implemented the earth, but no difference. Think it is because the program is theoretically with no resistance in the windings etc.
Implementing capacitors (like 100uf) made the circuit swing alot in an odd way, got much higher output like 1,5kV, but output was cleaner

If this post seem very odd, thats because I wrote it in a hurry, gotta go to school..

you can also import this project to yout computer (file and import at the java window)
here is the code:
$ 1 5.0E-6 10.20027730826997 35 5.0 43
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T 336 256 368 272 0 4.0 1.0 -0.19145301598262615 -0.2946672113696741 0.999
T 256 304 288 320 0 4.0 1.0 -0.677956532656266 0.1914530159827117 0.999
T 336 304 368 320 0 4.0 1.0 -0.1914530159827116 -0.2946672113696862 0.999
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T 336 160 368 176 0 4.0 1.0 -0.19145301598268377 -0.29466721136968616 0.999
T 256 160 288 176 0 4.0 1.0 -0.6779565326563342 0.19145301598268377 0.999
T 256 112 288 128 0 4.0 1.0 -0.6779565326562713 0.1914530159826364 0.999
T 336 112 368 128 0 4.0 1.0 -0.19145301598263625 -0.29466721136959595 0.999
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o 58 64 0 34 640.0 9.765625E-5 0 -1
o 67 64 0 34 640.0 9.765625E-5 1 -1

[assendor]

Hello Ivar,

West Coast, Karmøy.

Truepath, .. I've got some of those...

You should pay rather good attention to the 5volt supply, at least this is my guessing to be the most
important thing on that amp.
Long time since I played on it.

You do like it well then I guess...+?

I have some more testing to do when it comes to mains filtering, and especially Common Mode filters and
Isolation transformers.
Last test we did here, didn't show any difference in sound at all, using common mode filter and NONE..?
It was strange.

OH yes, the DAC had Common mode filter, and all grounding was done the way it's described, or almost..
As Kent English is explaining in the link/PDF file posted by wong I think it was..?= Not sure.

-Jonas

[86Ivar]

To be honest it has been on the work bench for 1-2 years for a rebuild from something that was not a very complete amp. But i remember it sounded very good.
Im from Begen but Now study in trondheim ntnu, and the amp is in Bergen so the progress is a bit slow

I have two power inputs for the amp, isolated, one for 5v and the two supplies for the monica. All with seperate balanced supplys, 3 total! 
I made a second power input for the 1000VA trafo wich is for the speaker power, because i wanted to try bal power supply there too.
I have nothing to loose trying with these trafos but I want to know more of the theory behind how the filter works.
Do you have som kind of blog or pictures i can see of your projects? i will make some when i come home.

Ivar

[yeo]

hi ivar

hmm... i don't really understand what you have in your hands now. you said you have some huge iron. are there windings on your bobbin? is it wound? what's the ratio?

the concept of balanced refers to equal impedance between live and earth, and neutral and earth. thus common mode noise will see this path to earth, away from corrupting the downstream. that's the idea anyway.

it's much faster to build and listen rather than rely on simulation. 

yeo

[86Ivar]

Nice to see you again yeo!

Thank you for the explanation:)
I know, But the only problem is that Im not at home where my amp is no i have to wait for the summer when im going home, but this is also why I ask if these trafos will be usable, because if not I do not want do stress abaout getting those trafos home (like 40kg+ total and have to pay for heavy baggage on the plane)

Maybe i explained with the wrong words, the trafos is wound, 220v primary (blue wires), and 30,7v secoundary (red wires), also got 4 v secoundary (white wires). I found them in some thrown away old UPS's. I have 10 of them.
You can see the pic, fork is for size comparison.
http://www.home.no/fetus/IMG_2918.JPG
I used sim only to draw schematic to assendor to view how i intended to wire those trafos. is faster than mspaint

Ivar

[yeo]

hi ivar

200va is a lot. you could still make an effective isolation transformer by wiring it back to back.

220/30 wired to 30/220.

so all you have is 220v in and 220v out. well, there'll be slight loss when you have current flowing through.

from this 220v, then you connect to your existing power trans. i'll try this with cdp, dac or preamp as they consume lower current. if you are really macho, have one for each gear! one for cdp, one for dac...

i'm sure it'll sound good!

yeo