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

[Bigun]

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.

[ostripper]

By Megajocke -Transformers take a long time to heat up...

Yes 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 because they are "non-ideal" with inductive leakage and capacitance.

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

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/elelect...r_transformer/
OS

[MJL21193]

Originally posted by destroyer X



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.

[MJL21193]

A recent stop at Goodwill had me walking out with a late 80's early 90's Realistic SA-1000 with this 45-0-45, 400VA unit inside (plus a few more goodies ). Price? $10.00

TO-264's on top for scale:

[destroyer X]

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,

[Bigun]

Originally posted by destroyer X

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

[destroyer X]

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

[Bigun]

I guess you were not able to seal the new windings - without the proper seal (like a vacuum seal) it will surely buzz like an alien invasion.

[destroyer X]

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

[paulb]

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.