Power transformers versus amplifier output power..what is your option?

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Carlos,

I like this thread - since I'm a novice it is meant for me!

This transformer of yours has received some love and labour from you. It's now a special transformer and deserves to be used.

My vote - go unregulated. A big beast like this seems a strange bed-fellow for a regulator. The amplifier is not a separate entity from the power supply. This transformer is part of the whole system and can to be allowed to contribute to the sound.

You have to use high voltage caps, that's just how it is. Then you don't worry about them. You saved money on the Trafo, so you pay it back to the caps. Since you have good ripple rejection on the amp you don't need too much capacitance, so your wallet is not so sore.

Thanks to your thread, I'm going to find a big black inefficient EI transformer for my TGM project.
 
By Megajocke -Transformers take a long time to heat up...

Yes :hot: :hot: I had same trafo as carlos , used it for 2 -100w
amps. It got hot as pistol after an hour !

I think trafo is TAMURA "tamradio" , very common in japanese audio.



the japanese trafo's are designed to "load down" with high currents , that is how the home theater receivers can "get away"
with only 2 output devices in the amplifiers. trafo is the current limiter keeping OP trannies within their SOA.
They get hot :hot: because they are "non-ideal" with inductive leakage and capacitance.
An externally hosted image should be here but it was not working when we last tested it.

(above diagram is how you would simulate a real trafo :D )

So the EI's are safer for a highly abused amp (consumer) as toriods are better for sustained high current use (industrial/audiophile).

http://www.butlerwinding.com/elelectronic-transformer/power_transformer/
OS
 
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Re: Third text part

destroyer X said:



Also you electrolitic condensers will be very expensive, as price
increases not only because the capacitance, but also because
insulation voltage..you gonna need high voltage electrolitc
condensers to use into your pcboard…enormous monsters there
wasting a lot of physical space.


Hi Carlos,
A way to use lower voltage caps for a high voltage supply. resistors are ~4.7k, 2 watt.
 

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Bigun, Ostry and MJL21193

Thank you by your cooperation...i have already decided to use the 45 volts transformer i have made by myself.

The amplifier is almost ready..playing rigth now...wonderfull sound!!!

I will have only to put needles and some stuff..it is all working..volume control, switches and all stuff.

regards,

An externally hosted image should be here but it was not working when we last tested it.
 
Re: Bigun, Ostry and MJL21193

destroyer X said:

Thank you by your cooperation...i have already decided to use the 45 volts transformer i have made by myself.

...I have found a black heavy EI transformer (not for free though). It's not so powerful as yours, but then my amplifier is designed for low power. It's a SS that thinks it's a tube amplifier
:D
 
You see... decision was not good enougth

Supply transformer is producing noises..i have assembled and made a bad work there... when you drain current it starts to buzz.

Also it is producing noises when i reach the limits of clipping..filters are not filling the gaps and ripple is high..i am listening the mains frequency (rectifier output, almost without filter effect)

Sound is fine..but you see what gonna happens if i reach clipping levels.

Better, for a while, till i find substitution to this transformer, to keep volume small than maximum.

regards,

Carlos

......................................................................................................


Here is the youtube movie showing you... this is great to beginners... some of them have never imagined that!

Those are the noises generated by bad designs, bad supplies and bad decisions taken...i made my ship in this case.

http://www.youtube.com/watch?v=VN8hM0CHtBA
 
I have left some E plate loosen..for sure was that

There's an assembling sequence..one plate each time..cannot put one plate up and two plates down..... this can be fixed dismounting...i am searching for courage to do that..because hurtrs our hands a lot.

People, down here,use to cut the transformer and dismount it splitting the iron core in two parts..alike bread into a sandwich.... and them they solder once again after complete the winding works with electrical solder....aaagh!.. results ugly and smelling...looks awfull!

I use to dismount using plier...one blade each time... i use hammer to loosen blades..to unglue them..to separate them.... awfull work... normally i use to cut fingers doing it.

But i will increase the input stages capacitance value...the noise can reduce doing that...maybe the supply noises are entering the first stage (differential) because of the low capacitance used there (only 220uf)

regards,

Carlos
 

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Referring back to your original problem:
How about a capacitance multiplier with a zener diode? You could set it up such that with a light load, the zener would kick in and limit the multiplier's output to a value safe enough for the amplifier's transistors. With a heavy load, the zener drops out and the multiplier's transistor saturates, giving very little voltage drop.
So if you have 80VDC with no load, and 47VDC with the maximum load, you could use 60V zeners (or 2 30V in series). You'd have to do some calculations or experiments to see what size heatsink to use for the cap multiplier.
You'd still need the high voltage rated capacitors before the multiplier, but they could be smaller capacitance...
I used exactly this solution when retrofitting an old Sony VFET amp for a friend, driving a chipamp that couldn't stand the high rail voltage that the Sony power supply provided.
 
I have tested minutes ago.... i had too much voltage drop

now testing the electronic regulator.... will test tomorrow to see how long it wii accept short circuit into the output,,,,will install more power transistors in paralell and will let the system heat up for a couple of minutes,,,, short from positive to ground and from negative to ground simultaneously.

Why that monster behavior?

Safety!.... amplifier can burn,....,shorts can happens into power amplifier board (this happens sometimes when hard used, bad cooled or too much low speaker impedance),.... fuses can fail to open the circuit.... then overload can short the series pass transistors into the electronic supply....this happening will send 80 volts to the amplifier circuit..... well.... i want to avoid this mess beeing sure the regulator will survive, even shorted for a couple of minutes.

The electronic stabilizer circuit (output voltage adjustable) will keep the voltage pre adjusted within 10 percent.... also allow you to adjust perfectly... so you can adjust 50123 milivolts to the positive and 50123 milivolts negative if you decide to to this way... when transformers never has, absolutelly, the same voltage.

Carlos

An externally hosted image should be here but it was not working when we last tested it.
 
I have tested a modified electronic supply...more transistors into the output

And i had positive regulation...ahahahahah!...very good that..when you enter the load the voltage increases in the place to decrease.

Difference of voltage, under load (regulation) from positive rail to negative rail is less than 1 volt when you adjust to 50 volts the output..when 2.27A each rail load enters, then the voltage increases to 52 volts in the place to decrease.

I have also made tests using lower voltage..around 35 volts..and current was 5 amperes each rail.... also i could have positive regulation.

Well... camera battery is charging..soon i will upload to youtube and then will post a link here.... so you will be able to see.

The supply was tested 20 seconds with a short circuit.... to see if it will burn output transistors... was fine.

Also heat is fine because input voltage descends...drops under load..so..power over the series pass transistors are not so high.

The current under short circuit i could not measure.... maybe i can, using low ohm resistance (shuntO. and measuring voltage...but for sure is very high...hummmm...maybe 50 amperes under short...or more than that... voltage zero and very high current because of short.

Well..movie will show you.

regards,

Carlos
 
First video uploaded to youtube about transformer and supply

http://www.youtube.com/watch?v=ocVA90cPUhE


soon you gonna have the link to the other one, where the voltage was adjusted to 50 volts.

The supply works fine till we reach 55 volts..then the voltage starts to drop and regulation goes bad... at 60 volts the voltage drop goes to 15 percent.

regards,

Carlos
 
First video uploaded to youtube about transformer and supply

http://www.youtube.com/watch?v=ocVA90cPUhE


soon you gonna have the link to the other one, where the voltage was adjusted to 50 volts.

The supply works fine till we reach 55 volts..then the voltage starts to drop and regulation goes bad... at 60 volts the loss goes to 15 percent.

regards,

Carlos
 
What i have to tell you folks

I have made testings:

My first assumption was thinking the vbe multiplier capacitance existent into my circuit could could filter without using big condensers (big capacitance values) into the supply...i was wrong...we need that capacitance..no way... when sucking amperes the noises appear..the filtering into the electronic power supply helped a lot...but could not fix.

My second assumption is that i would not need too much speed to correct voltage errors.... the error amplifier could work without problems because was a reasonable transistor... wrong once again!... speed was a problem.. i have perceived into the sound reproduction... the attack was strange...had a delayed decay but had a decay.

This approach, this supply, this idea, will not fit even a class A amplifier where you have not too much current variation..say..starts high and continues beeing high... comparing maximum power current into class A amplifier to the stand by current results in smaller number compared to the division of maximum current by the stand by current into class AB amplifiers.

This one, with electronic regulator, at least this one, cannot be used with class A amplifiers too because of filter size...the idea was to use small filter after rectification..but this do not works...the electronic supply cannot make the miracle i was wishing.

This is what happened folks..i will continue with my buzzer transformer playing good sound till i have better transformer to replace.

regards,

Carlos
 
My transformer solution is an older microwave oven of at least 1 kw. The high voltage transformer gets a new secondary and the primary gets 10 turns added to it. They are fan cooled and intermittent duty in the microwave so you need to add a bit of inductance to the primary.
 
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