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In Reply to: RE: In theory balanced power output is an option for this Xformer posted by Tweekeng on April 17, 2010 at 12:27:21
Here are some quick observations;
When I connect one primary (1 & 3) to power, I get an initial saturation noise, followed by silence, then 120V at all three pairs. The two secondary pairs have the 120V, and the unconnected primary has 120V. Does this give me 3 possible outputs?.
When I connect the tranny as Tweekeng says, I get no saturation noise, but I also lose 0.5V.
Tweekeng, quick question;
Do I still need the 0.22uF cap across the output?. I have heard some engineers say that the capacitive nature of the tranny gets rid of HF grunge?.
Follow Ups:
When I connect one primary (1 & 3) to power,
Not correct... You have to use both primary windings. Configure as Tweekeng described in his post. Using only one of the windings cuts the VA rating in half. Instead of 2000VA you have 1000VA
Series the two primary windings. You must follow the diagram for proper polarity of the windings or they will buck one another.....The two secondary pairs have the 120V.
Yes but each is half VA of the halved primary. Each 120V winding would only be good for 500VA.
, and the unconnected primary has 120V. Does this give me 3 possible outputs?.
No... The unconnected primary winding may be reading 120Vac but it is not usable power....One other note; If you do wire the xfmr in a balanced configuration, (primary windings in series connected to 120Vac mains), and the secondary windings in series 120Vac out (60V-0-60V) the VA rating of the xfmr is halved. Good for only 1000VA.
Also the center tap of the two windings must connect to the main electrical service earth ground.
Edits: 04/17/10 04/17/10
Jea, I did wire the tranny as Tweekeng recommended, only now with the center taps wired to ground, same 120V output, so all is good.
I also received an email from a gentleman who recommended this;
Run the primary's in parallel
Run the secondary's in parallel
He thought this would give me twice the max. V output of a series connection
The only problem I have with this configuration is that the saturation noise is back.
Since these will be driving 140W tubed amplifiers, is peak output more important then core saturation noise?.
I hope I am asking the proper questions.
JMHO, I would forget configuring the xfmr for balanced power. Single ended will yield the full potential of the xfmr as it was designed and intended.Best isolation is to series the two primary windings and connect them to 240Vac. Secondary windings paralleled 120Vac out single ended.
I also received an email from a gentleman who recommended this;Run the primary's in parallel
Run the secondary's in parallel
Better than balanced, jmho....The only problem I have with this configuration is that the saturation noise is back.
Transformers do hum. When you had the two primary windings in series and only connected to 120V it would be quieter. You were only running the primary at 1/2 its rated voltage.Make sure you got the polarity correct...
Primary parallel for 120V in (1&4) (3&6)Secondary paralleled for 120V out (7&9) (8&10)
Also you know you have to connect one output Line,leg, of the separately derived power source to earth. This becomes the neutral, the grounded conductor. By code it has to connect to the main grounding system of the main electrical service.
The connection of the xfmr Line and earth also becomes the safety equipment grounding conductor connection. A star ground.If you decide to fed the xfmr from 240V you will need to install secondary overcurrent protection on the ungrounded Line, leg, of the xfmr.
If you decide just to fed the xfmr from 120V (parallel primary windings)
you could probably forgo secondary overcurrent protection....I am surprised no one has commented on whether they think the xfmr is big enough for a 140 watt power amp. Does it have enough head room for the amp?
Edits: 04/17/10 04/17/10
My way of thinking is that if the secondary's are wired in parallel, then I will be grounding one hole side. Is this true?.
My way of thinking is that if the secondary's are wired in parallel, then I will be grounding one hole side. Is this true?.
Yes, but the next question is which side. I am not familiar with the number markings on the xfmr. I am used to seeing X1, X2, X3, and X4.
In this case (X2&X4) would become the neutral, the grounded conductor.
I can only assume (8&10) would connect to ground becoming the neutral conductor.
If that is the case then you should connect (3&6)of the primary to the neutral side of the 120V male plug that will plug into the wall receptacle.
Maybe Tweekeng, and or, djk could chime in with their thoughts....
As for the neutral connection to earth ground I assume the xfmr will have a cord and plug that plugs into a wall 120V receptacle. In that case I assume you will use the safety equipment ground from the receptacle for the earth ground connection. I also assume you will be putting each xfmr in a metal enclosure of some type.
The secondary neutral ground connection, the metal case connection, the xfmr shield connection, and the secondary output safety equipment ground connection should all connect at one common junction point. Star grounding...
There is one more test you may want to preform. If you will be using the two xfmr as well as 120V power from your home's electrical to power audio equipment connected together by ICs you might want to check the output AC polarity of the two xfmrs as well as any wall receptacle outlets you will be using from your main electrical panel. You want all three power sources to be in phase with one another.
Just measure for AC voltage from each Hot contact of each receptacle to the other. If the polarity is correct and the power sources are in phase with one another the voltage reading will measure zero or close to zero. Out of phase will measure closer to 230Vac or 240Vac.
If it's true that the transformer already gets rid of HF grunge, then the cap is not necessary. Since I already have them, any added filtering can't hurt.
Comments?.
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