Simple Aleph 2 transformer question

BrianGT

diyAudio Moderator Emeritus
2002-01-21 2:42 pm
near Atlanta, GA
www.chipamp.com
I am ordering some custom toroid transformers for my Aleph 2 monoblocks that I am building. For the transformer, I have the choice of two difference sizes.

Should I get a pair of 1kVA transformers or a pair of 2kVA transformers? I saw that Mr. Pass stated that 1kVA is the minimum. Is there any drawbacks if I go with 2kVA, besides the weight difference?

--
Brian
[email protected]
 

rtirion

Member
2000-11-24 12:02 am
2kva is fine.

Drawbacks are price, size and weight(check if you can put them reliable in your enclosure) and larger inrush current when you turn them on (this can be taken care off).

pros are:
Lesser voltage drop and they will probably run cooler.

If the drawbacks are not to much of a problem for you, I would say, get the 2kva's

Regards
 

BrianGT

diyAudio Moderator Emeritus
2002-01-21 2:42 pm
near Atlanta, GA
www.chipamp.com
You could always put some big inductors/choke on your power supply to lower the voltage enough for the amplifier to work.

I am planning on going for the 2kVA transformers. It probably is overkill... 4kVA total for a pair of monoblocks, but that is the life of an engineer.

What is the ideal capacitance per Aleph 2? If I can recall, the production had 4x22,000 uF capacitors. Would it sound better with twice the capacitance? (I will take care of the inrush current for this amplifier, most likely with a relay circuit).

--
Brian
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WayneS

Member
2002-03-24 11:44 pm
Dallas
gents,

The 35V 1500VA from plitron is the reaosn I didn't go with that transformer as it took the supply voltage higher.

Yes the amp will handle it, IF you increase the heastsinking to reject the extra heat. You may have to hack with some other component values but I'd wager its going to fire right up.
 

WayneS

Member
2002-03-24 11:44 pm
Dallas
Brian,

Why not just use 2x 650VA Plitorn transformers at 33+33V ???? If you really look at "the one and only"'s advice, he says that you want to have 4x the idle POWER rating of the amp. For an Aleph 2, that means that you want about 1200VA, which is over 1000VA, but less than 1500VA. If 1200VA was commonly available, I'd wager Nelson would say that that's enough. I'm going by memory here, being too lazy to check the Plitron site myself this minute, but I think they have 650VA and 750VA sizes, meaning that if you're going to double up, you don't have to double up on 1000VA loops - you can go with smaller ones quite comfortably.

Jest an idea.....
 
Simple Transfrormer question

Hi Gabster,

I would image the 1000va will be fine.

You may find the DC rails under load will be slightly higher for a given no load voltage (ie 35 volts) rating in the transformer with the higher VA models, but yiour choice of rectifier will have a bigger impact on the final DC voltage.

At any rate the Aleph is not critical of supply rail voltage and imaging +-5% is more than within margin.

The other thing is a bigger transformer is run cooler which may be imprtant if the box is closed.

best regards

macka
 

BrianGT

diyAudio Moderator Emeritus
2002-01-21 2:42 pm
near Atlanta, GA
www.chipamp.com
I just figured that with the cost increase not being too much. The main price of the toroid is the cost of the core. With the place I am going through, once you step up to the bigger core, it can take anywhere between 1.2kVA and 2kVA. Then, you are just paying for the wire by the pound, which is not that much. The maximum that he can get on the smaller core that he stocks is 1kVA.

That leaves me with $100 for the 1kVA (with shielding around the outside) and $130 for the 1.5kVA and $150 for the 2kVA (with shielding added).

With shipping, the 1kVA from plitron won't cost much less then the 1kVA from this local place ( Victoria Magnetics ), since I don't have to pay shipping.

I figured that if I am going for overkill, 2kVA is the way to go, which is almost 7 times the idle power rating. If I decide to make the Aleph 2 stereo in a single chassis later, I will be able to do this with the 2kVA.

--
Brian
[email protected]
 
I have used two different 1kVA transformers running my Aleph 2s. The Plitron was cool to the touch. The other (whatever Apex JR was selling with the four secondaries--Toroid Corp?) runs just barely warm to the touch.
You can easily use a 625 or 750VA if you want. I just happen to believe in overkill. A personality fault, according to some, but it leads to better sounding gear...

Grey