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Old 24th September 2009, 01:39 PM   #4961
udailey is offline udailey  United States
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No, nothing special. Maybe you have dropped voltage over the resistors in your power supply.
Uriah
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Old 24th September 2009, 01:48 PM   #4962
sekess is offline sekess  United States
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Default Low Voltage

Hi Samoloko,

I don't know your circumstances. But, I too had slightly low rails on one of my builds -- about 22V or so. It's probably from one of the following:

1. low mains voltage

2. tramsformer's specs and regulation are such that you get lowish secondary voltage

or

3. you're dropping too much voltage across the dropping resistors

Steve
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Old 24th September 2009, 01:51 PM   #4963
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by samoloko View Post
has anyone compared bridge block vs MUR30x0
I use bridge block (KBPC3510) at now but got low rails - 21.8Vdc
I wonder how on semi ultrafast and softrecovery devices would perform
Is there something special about bridge mr Pass use In his F amps
with shottky diodes you'll have somewhat higher voltage , but not much .

just compare voltage sag across plain vs. shottky diodes , and you'll know .

Papa uses plain bridges in his F amps ,at least to my knowledge
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Old 24th September 2009, 03:24 PM   #4964
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thx for your reply
after transformer I got 18.2 Vac
after block bridge 22.1 Vdc
after resistor 21.8 Vdc
could It be old smoothing caps
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Old 24th September 2009, 03:57 PM   #4965
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a smoothing cap with high ESR will run "hot" -- the energy has to go somewhere.
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Old 24th September 2009, 05:54 PM   #4966
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Industrial Strength F5:

Click the image to open in full size.
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Old 24th September 2009, 08:54 PM   #4967
Lucas_G is offline Lucas_G  Netherlands
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I live in the Netherlands and there are not so many options for transformers to use in the F5.

RS Components sells some excellent 18 V AC trannies that are shielded and dead quiet. However the maximum they offer for 18 V AC is 225 VA.

http://nl.rs-online.com/web/search/s...duct&R=2238825


I guess that is not really enough for two channels F5.

My intention is to build a stereo amp that uses 2 F5 in parallel per channel, so 4 F5 amps for a stereo amp. I also use the CViller PSU boards.

My question to the more experienced:

Can I use two of these 225 VA trannies to feed one PSU board that will feed 2 F5 amp boards, without running into trouble with hum or sound degradation? (Of course I would be forced to use the outputs of the trannies in parallel and use one for the positive rail and one for the negative rail).

Or is it neccesary to use two PSU boards for one channel? That would make 4 PSU boards for the stereo amp, and since I want to use chokes (CLC instead of CRC) that would require 8 chokes, which calls for a lot of space and money!
Or is this the preferred route?

Please can some expert give me advice?

Thanks!


Lucas
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Old 24th September 2009, 09:59 PM   #4968
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Quote:
Originally Posted by jackinnj View Post
Industrial Strength F5:
Nice chassis. Did you make it yourself?

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Old 24th September 2009, 10:02 PM   #4969
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RS components are usually quite expensive when it comes to transformers. I would try seaching for a local manufacturer, who will make the transformers to your exact requirements. In Australia we have Harbuch http://www.harbuch.com.au/toroids1.htm , he builds an absolute quality product to whatever requirements you would like. I am not neccessarily suggesting you should buy from him, but maybe have a look around locally for someone like him.
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Old 24th September 2009, 10:06 PM   #4970
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Originally Posted by thanh1973 View Post
RS components are usually quite expensive when it comes to transformers. I would try seaching for a local manufacturer, who will make the transformers to your exact requirements. In Australia we have Harbuch http://www.harbuch.com.au/toroids1.htm , he builds an absolute quality product to whatever requirements you would like. I am not neccessarily suggesting you should buy from him, but maybe have a look around locally for someone like him.
Try www.farnell.co.uk
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