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Old 3rd September 2012, 08:42 AM   #7181
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I am not familiar with this setup with a choke before the bridge... What's its purpose? I would think that a RC / LC filter (after the bridge) would filter out RF/HF anyway no?
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Old 3rd September 2012, 08:44 AM   #7182
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Quote:
Originally Posted by Joachim Gerhard View Post
I have shown it several times but for the new comers here it is again:
I use the Preregulator from my Opus Magnum Phono Stage.
Because Block does not have 2 x 24V transformers i use 2 x 2 x 12V per side where i put the windings in series. The diode bridges are IXIS Silicon Carbide snubbert with REL teflon caps. The 10.000uF caps are slit foils, today i would use Mundorf 4 pole. The common mode chokes are from Lundahl. Loaded, the supply puts out plus-minus 30V, the maximum i recommend for the Paradise R3.
Are the Lundahl coils before the IXIS bridges in this prereg ?
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Old 3rd September 2012, 08:57 AM   #7183
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Sorry, i do not find the time to explain the "choke before the bridges" thing at the moment. Frans did the original circuit and it must be somewhere on the thread.
This is the correct way to use a common mode choke.
To use a choke behind the bridges in a pi filter is fine too. The Telema is high in value enough to be "raped" to do that job. It is better though to use chokes that are optimized for this duty and they are usually bigger in value and size. The Lundahl i use in this sense behind the bridges and between the caps. One glance at the picture makes that obvious. The only "speciality" of my pre regulator is that i have setup the Lundahl as a common mode choke too.
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Old 3rd September 2012, 09:00 AM   #7184
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Here is the spec sheet of the Lundahl that also shows how to connect for common mode :http://www.lundahl.se/pdf/2733.pdf
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Old 3rd September 2012, 09:55 AM   #7185
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So in this case you actually mimic the effect of a four pole cap

CAP + common mode choke + CAP
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Old 3rd September 2012, 10:10 AM   #7186
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http://www.yccc.org/Articles/W1HIS/C...S2006Apr06.pdf
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Old 3rd September 2012, 10:15 AM   #7187
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I think that the 4 pole caps work a bit different.
The common mode coil works in such a way that noise that is common in both phases cancels. The rest of the circuit is a conventional CLC filter. It works like a low pass, suppressing high frequency artifacts. Here 50Hz is a high frequency, so the low pass is set very low.
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Old 3rd September 2012, 10:17 AM   #7188
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Here is some information about the 4 poles :http://www.mundorf.com/deutsch%201.1/kondensatoren2.htm
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Old 3rd September 2012, 10:19 AM   #7189
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Here is the english version :http://www.mundorf.com/english%201.1/kondensatoren2.htm
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Old 3rd September 2012, 11:13 AM   #7190
FdW is offline FdW  Netherlands
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Quote:
Originally Posted by Joachim Gerhard View Post
Sorry, i do not find the time to explain the "choke before the bridges" thing at the moment. Frans did the original circuit and it must be somewhere on the thread.
This is the correct way to use a common mode choke.
To use a choke behind the bridges in a pi filter is fine too. The Telema is high in value enough to be "raped" to do that job. It is better though to use chokes that are optimized for this duty and they are usually bigger in value and size. The Lundahl i use in this sense behind the bridges and between the caps. One glance at the picture makes that obvious. The only "speciality" of my pre regulator is that i have setup the Lundahl as a common mode choke too.
These are the most important/relevant messages regarding PSU and Pre-Reg.

Mpp - Post 4375 PSU-pre-regulator

Mpp - Post 4610 V2 Schemas UPS and Amp

Mpp - Post 6506 CCS fine-tuning

Mpp - Post 6462 PSU with my notes

Mpp - Post 6809 Do not try to feed the CVS of the CCS of the shunt with a regulated power supply

Have a look at these and the following messages (#4375 for the pre-reg where the chokes are used to get rid of net/transformer HF).
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