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Transformer secondary voltage reduction
Transformer secondary voltage reduction
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Old 25th May 2012, 04:00 PM   #1
Jeffrey Davison is offline Jeffrey Davison  United States
diyAudio Member
Join Date: Sep 2006
Default Transformer secondary voltage reduction

Planning to put together a power supply for a 26 pre.
I'll be using a RGN 1064 mesh anode rectifier. It requires 4 volts on it's heater, but I can only find transformers at 5 volt.
Calculations on a dropping resistor on the 5v secondary are pretty easy as the filament draw is a tick over 1 amp (1.1A). 1 volt drop @ 1 amp = 1 ohm @ 1 watt.

My concern, since the rectifier is directly heated, is the potential sonic degradation that might be incurred using this method, if in fact it does degreade the sound. There will be a voltage regulator of some sort downstream after the LCLC filter ( still undecided and playing around / looking at S.S. or tube based regs), so if the dropping resistor effects the over all sonics it might just be extremely minimal if at all ?... But I have no experience in this area.

I would be using a separate transformer for the heater so it would be possible to do something on it's primary to not have to worry, but I have little if no knowledge on how this would be done....

Probably the "best" way would be to deconstruct the beast and unwind, but that is beyond my current skill set and I would mostlikely destroy the part and create a pile of scrap from what had been a good part.

Soooooo...... this post.

Thanks fella'a

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Old 25th May 2012, 04:09 PM   #2
pdul is offline pdul  Denmark
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Join Date: Jan 2009
Location: Copenhagen
Why not use dc for the heater and a 1,5-2amp regulator with heatsink. There is probably already some useable setups here, if you search the forums.
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Old 25th May 2012, 07:00 PM   #3
DF96 is online now DF96  England
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Join Date: May 2007
A dropping resistor will not affect 'sonics'. Just make sure you take output from the rectifier filament and not the heater winding. Using DC to heat a directly heated rectifier means a floating supply, and is unnecessary.
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Old 26th May 2012, 12:18 PM   #4
pdul is offline pdul  Denmark
diyAudio Member
Join Date: Jan 2009
Location: Copenhagen
If everything here , were strictly based on necessity, there wouldn`t be much debate left It was just a suggestion on how to solve the voltage problem in a stable manner. Not a must. There are a lot left in the toolbox yet to go for I guess.
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