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Old 15th April 2013, 11:23 PM   #21
n3szd is offline n3szd  United States
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In-Rush Currents
A consequence of the superior magnetic properties of a toroidal transformer is that the transformer "remembers" what polarity the primary voltage had immediately before the power was last shut off. Whenever the voltage has the same polarity when the transformer next is turned on, the core will saturate for part of a half-cycle, and a high in-rush current will flow in the primary of the transformer. This in-rush current is larger than the in-rush current in a conventional transformer, but it is of very short duration, so it will not affect slow-blow fuses or magnetic overload protectors with thermal delay characteristic. (Some delayed magnetic overload protectors act instantly if the current exceeds a certain value. These cannot be used with large toroidal transformers unless a current limiting resistor is used as described below.) For very large transformers (1,500VA and up),it is common to use a small current-limiting primary resistor to reduce the magnitude of the in-rush current, and a delayed by-pass relay to short out the resistor after 30-200 milli-seconds. This method eliminates external voltage dips caused by the in-rush current, but slow-blow fuses or delayed magnetic overload protectors must still be used, as is the case for all types of transformers.



5,000 va 10.4"x4.7" 56 lbs

Sounds like the solution to inrush is to make it not remember, or turn it on and off at the right time everytime!

Last edited by n3szd; 15th April 2013 at 11:49 PM.
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Old 15th April 2013, 11:27 PM   #22
n3szd is offline n3szd  United States
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Quote:
Originally Posted by AudioSan View Post
i hope you'r not serious about this.
that will demand a X'ed cuircut. with +/-70V rails and 16A bias pr half.
and a dissipation of about 4500W pr ch. with 120V mains, you are looking at almost 40A Draw pr ch. good luck
That number is close to what I was told. Thanks. Getting rid of the heat should not be a big issue, but power might be, love to learn.

Last edited by n3szd; 15th April 2013 at 11:30 PM.
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Old 16th April 2013, 12:15 AM   #23
n3szd is offline n3szd  United States
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Caps are the BIG issue. I rember that it was the single most expensive part of my aleph. 100v prices are not good at all. I know in one of mazda's new cars they have a supercapacitor, it can runn all the accesories for up to a minute, andyone wreck one lately? Must be the prelude to the still impossible to get flux capacitor.
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Old 16th April 2013, 02:36 AM   #24
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If you are building a 1000 watt Aleph, you will need more than 100V caps.

Rails at +/-100 V will give you about 600 rms watts tops (about 1200 watts
peak). You are looking at 150, better yet, 200V

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Old 16th April 2013, 02:45 AM   #25
n3szd is offline n3szd  United States
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Quote:
Originally Posted by Nelson Pass View Post
If you are building a 1000 watt Aleph, you will need more than 100V caps.

Rails at +/-100 V will give you about 600 rms watts tops (about 1200 watts
peak). You are looking at 150, better yet, 200V

It seems the price really skyrockets as that v number goes up. And I would assume you need even more of them to boot. My aleph3 has 4 68,000uf 25v caps. Running at around +/- 24v now. Maybe I should have put a safety margin in?
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Old 16th April 2013, 02:48 AM   #26
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I'm sure you're fine.

But you are getting a quick picture of how much cost is involved with a
1000 watt Aleph.

It could be worse, the SIT-1 has about 6% efficiency or so. Imagine having
to source and dissipate 16 KW.

per channel.

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Old 16th April 2013, 02:53 AM   #27
n3szd is offline n3szd  United States
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Quote:
Originally Posted by Nelson Pass View Post
I'm sure you're fine.

But you are getting a quick picture of how much cost is involved with a
1000 watt Aleph.

It could be worse, the SIT-1 has about 6% efficiency or so. Imagine having
to source and dissipate 16 KW.

per channel.

It wouldn't be a problem to get rid of the heat, it wouldnt be real expensive. The amps and power supplies don't need to be fancy, just work. I think the 5kw transormers will work though (each mono). Need to do more math, im learning and getting my head back into it. I can do good work, and this can be done. I just wish there would be a way to use less outputs, just bigger ones as it would make it easier. Thank you
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Old 16th April 2013, 02:55 AM   #28
n3szd is offline n3szd  United States
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Quote:
Originally Posted by n3szd View Post
It seems the price really skyrockets as that v number goes up. And I would assume you need even more of them to boot. My aleph3 has 4 68,000uf 25v caps. Running at around +/- 24v now. Maybe I should have put a safety margin in?
150 sounds like a good round number, yikes, I need the cap fairy but im not going to give up on this, these really are "simple" construction amplifers, I looked inside a sony, what a mess!

Last edited by n3szd; 16th April 2013 at 03:02 AM.
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Old 16th April 2013, 03:31 AM   #29
n3szd is offline n3szd  United States
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Quote:
Originally Posted by AudioSan View Post
2500VA??? you need 10.000VA pr ch.
and around 1.500.000uF cap bank pr ch. and a softstart AND a slowcharge that can handle this. and you will need some serious mains to handle this. 9000W at idle.
just forget it.
Im only worried about caps now. 1.5 farads? Really? It's the only thing in the way, but there must be one... Seriously, is there some caluculation, Id ask my stepdad but he still won't talk to me, it's a shame. In time maybe, oh can he work a caluculator and make boards! He just thinks his .007% amp is superior, he needs to do some reading too. Maybe he has a box of caps? wifey...
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Old 16th April 2013, 03:46 AM   #30
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Quote:
Originally Posted by n3szd View Post
I just wish there would be a way to use less outputs, just bigger ones as it would make it easier. Thank you
Use mosfet in isotop case.
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