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Old 14th December 2010, 09:46 AM   #1
Skorpio is offline Skorpio  Denmark
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Default Choke input PSU...

Hi,

I would like to try a choke input supply instead of my current capacitor type.

The output voltage is now around 50V and minimum current is 2.6A (idle current for two class A channels).

The current transformator is 36Vrms, and this must be changed to about 60V for same DC output voltage. Then I need a choke of approx. 25-33mH and able to handle 3A...where can such a part be supplied?

And, if output current exceeds the 3A, output voltage will go up....this might be good for dynamics in short musical passages?
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Old 14th December 2010, 09:52 AM   #2
Skorpio is offline Skorpio  Denmark
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Would this be useable:

Jantzen 33mH 14 AWG C-Coil Toroidal Inductor
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Old 14th December 2010, 11:44 AM   #3
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Originally Posted by Skorpio View Post
Hi,

And, if output current exceeds the 3A, output voltage will go up....this might be good for dynamics in short musical passages?
When I tried simming a choke input in PSU2 for an F5 I got the voltage going so high and so low on different current draw that I feared for both power-caps and transistors in the amp. You need CLC to keep the voltage stable. Only a few amp-circuits with absolute constant current draw is suitable for choke input. (I am no expert, just my findings based on some discussions and sims).
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Old 14th December 2010, 02:05 PM   #4
Magura is offline Magura  Denmark
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Exactly! CLC is the way to go, and a 2.0 mH air core does the trick. Keep in mind that the inductor must be rated for the power you intend, and not just be a x-over piece.


Magura
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Old 15th December 2010, 07:53 AM   #5
Skorpio is offline Skorpio  Denmark
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The whole idea is to remove the current spikes from the rectifier in the first place, not to filter them out after they are produced...as by CLC...
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Old 15th December 2010, 10:00 AM   #6
MRupp is offline MRupp  Germany
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I am using a choke input filter at ca. 55V 2A for a ZENV4 and it works like a charm. My coils are a bit "on the big side" with 300mH and 4A rating (do not ask how I arrived at that value), size is 150b, weight 10+ kilo a piece, and they where custom made by a local manufacturer.

Thye X-over coil you showed "looks" to be a bit small. I found a formula on the WEB on this page Tauscher chokes (also in English). They calculate the energy requirement for a coil as E = 0,5 L IČ and you can then look up the necessary size for a given coil type. With a normal EI type E96 core you would be in the right ballpark. Maybe you find E96 coils for crossover networks that have the right inductance. Otherwise you would be better off having them custom made. Btw., having a higher than necessary inductance does not do any harm.
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Old 15th December 2010, 05:28 PM   #7
DougL is offline DougL  United States
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Martin,

What is the DCR on those beasts?

I solute you, sir.

Doug
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Old 16th December 2010, 08:02 AM   #8
MRupp is offline MRupp  Germany
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Hello Doug,

DC resistance is 0.7 Ohms, low enough that they do not warm up noticeably at 2A load. I started off with some wrong assumptions/plans, hence more inductance than I needed, but it turned out that more inductance does not do any harm (except the higher cost). The only problem is getting the whole (outboard) PS assembled into one box.
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Old 17th December 2010, 10:18 PM   #9
PW is offline PW  Germany
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I'm using Mundorf E-I-Core (former NOS106, 12mH, 0.24Ohm) in my balanced F4 (5A Bias). While working fine from the electrical point of view, they have a quite loud mechanical hum. I recommend custom chokes for this application (I will replace the Mundorfs next year).

Peter
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Old 19th December 2010, 07:35 AM   #10
joda is offline joda  Italy
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look at the filament choke ,
are also used to input inductive power supply
LL1694........LL2733 .........
http://www.jacmusic.com/html/order/j...-pricelist.PDF


best regards
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