Aleph 2 transformer advice

[cowanrg]

hey, im building some aleph 2's and need a little help with the transformer selection.

i am looking at the plitron standard power transformer, 1.5KVA. i have 4 32,000uf caps per channel. i know the rail voltage for the aleph 2 is +-45V, but i have read of people use many different values. in this particular model, plitron carries a 38, 40, and 45V output type. which should i use? i pretty much know how the rest of the amp will work, but i am still a little unsure about the power supply part of the project. any help would be appreciated.

 

[kristijan-k]

Hello cowanrg,


If you can choose amoung the transformer values that you mentioned, then use the transformer with 38 V at seccondaries.
The 1500 VA transformer would be more than enough for the Aleph 2 amplifier.
Also, try to use inductors of 1 - 4 mH between two 32000 uF capacitors.


Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip

 

[skaara]

38V that will become 53V... isnt that a bit too much or the voltage falls so much?

 

[fcel]

1.2 to 1.25 multiplier

38vX1.2=45.6v. It has been mentioned a lot of times on this forum to use 1.2 to 1.25 multiplier for real life sitauation. Square root of 2 is for ideal situation which nothing is.

 

[marjan]

Well, I do use 33 0 33 1,5kW, and my reading on DC rails is 44,3V+-
rgds
Marijan

 

[Peter Daniel]

Maybe because you are using 1.5kW, with 1kW the drop might be bigger.

 

[cowanrg]

hum, plitron only sells them in 38V outputs? how hard is it to undo a couple windings?

would i be ok with 38V?

 

[yldouright]

cowanrg

I believe that the production Aleph 2 used a 750VA toroids in their monoblocks with 31-0-31 secondaries. BTW, that is the size cap I am looking for too. Where did you get them and how much were they.

 

[fcel]

Add inductors ... unwinding wires is just too much work and I don't think it's fun!

 

[cowanrg]

yldouright:

i got them from someone in this forum, for like $80 US shipped for a total of 9 of them. maybe a little expensive, but it sure beats looking around for some...

hum, so i if the production aleph2's used 750VA, why is everyone using like TWICE that? shouldnt i be more than fine with 1KVA?

and how do inductors work? i know you add them in the cap bank, but do they reduce voltage? and if so, whats the formula to figure out what values i will need?

sorry for all the questions, but im no EE, and i searched for all of this, but its just not here, or really hidden somewhere.

 

[fcel]

Inductors applications ... go here http://web.vip.hr/pcb-design.vip/power-2.html

Phillip 26,000uf/75V cap ... go here http://www.apexjr.com/new.htm

 

[Peter Daniel]

Even when you have more voltage than original design it's perfectly OK as long as your caps and heat sinks can deal with it. Alephs are very flexible when it comes to parts and voltage changes.

The original amps used smaller transformers and less caps and no coils and sounded great. I don't know where this fascination with overdoing comes from? 1kW transformer per channel is more than enough.

 

[cowanrg]

fcel:

ive seen those sites before, and they dont tell me much. my cap values are different from the ones they use, so wouldnt my inductors be different too?

and also, thanks again for the phillips caps, i will most likely be using those in my aleph theatre amps.

 

[yldouright]

cowanrg

Really, $80 shipped for 9 30kuF caps that's like $7 a piece! Can you provide me his name and do you know if has any more? Why do you think they're expensive? Are these tantalums or real metal caps? Are they good quality or like automotive grade. The Aleph 4 (stereo amp) used a 1.5kVA but it fed two channels. If I find the parts list, for the Aleph 2 I'll mail it to you.

 

[cowanrg]

nah, they arent tantalums, i dont know much, but i know those are bad. they are real aluminum electrolytics... mepco's i believe... they are brand new too. he is all out of them, he just had a few left over from another project, sorry.

i guess my thing is, if the original used 750VA, i could get away with using a 1KVA, because with plitron they offer a ton more options. for instance, i could go with 25, 30, 31, 33, or 35... so would that be better to do? this is for 6 channels of alephs, so each one wont need that kinda overkill power....

cowanrg

Really, $80 shipped for 9 30kuF caps that's like $7 a piece! Can you provide me his name and do you know if has any more? Why do you think they're expensive? Are these tantalums or real metal caps? Are they good quality or like automotive grade. The Aleph 4 (stereo amp) used a 1.5kVA but it fed two channels. If I find the parts list, for the Aleph 2 I'll mail it to you.

 

[skaara]

So I could use 40-0-40 1.5kW tansformer for aleph2? That would mean (40 x 1.2 = )48V rails..

 

[fcel]

As Marijan as stated, he was able to get 44.3V from 33-0-33. That works out to be 1.34 multiplier. It seems that there is less loss as the transformer gets bigger ... or it also depends on the manufacturer ... or even the type of diodes being used?

 

[jgwinner]

Are you going to use any kind of 'soft start' for that large of a capacitor bank?

 

[marijan]

I used standard quality 4$, 35A/800V bridge.
When I started the project I tryed to get informations from guy`s on passdiy galery (didn`t know about this forum than) who actualy build those aleph amps. If I can remember corectly, Wayn Shorter, the only one at the time on that webside with aleph 2`s, said that Nelson stated that "1,5kW woul`d be even beter" over 1kW which Wayne used, when he asked him for opinion!? So, overkilled or not, in my case they do a job properly. I supouse that anything 800 to 1500W would be fine. Power rating - afect on DC voltage drop??? It should not. Should it?

 

[Peter Daniel]

Regarding transformers: I used 300VA per channel in my Aleph5 which seems OK. But recently I noticed that AC voltage from wall is around 130V AC. One transformer is quite noisy at that increased voltage. When voltage drops to more normal levels, transformer is quiet.

I have to complain to my energy provider.