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  #1  
Old 21st July 2007, 11:13 PM
novalves novalves is offline
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Default Pre3 - balanced operation

Just re-read the Feb 2007 article on the WD pre3. It mentions balanced operation (connection to a power amplifier) in 2 contexts.

1. The simpler one, pseudo-balanced, presumably means phono-to-phono with an earth screen for the cable connected at one end only to earth on the pre-amp (or amp ?).
2. Fully-balanced link (see start of next-to-last column) to a balanced-input on a power amplifier.

How is (2) done and is it worth doing ?

I'm thinking: phono (pre) to XLR (amp). But what is exactly connected to what ?

a. signal -----------> XLR?
b. earth-return -----> XLR?
c. screen ----------> XLR?

Any thoughts people ?!
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  #2  
Old 26th July 2007, 03:30 PM
John Caswell John Caswell is offline
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Default Re: Pre3 - balanced operation

Hi novalves,
The transformer secondary of the PreIII preamp has a centre tapped winding so you can use it in several ways. I we call the wires A B and C with B being the centre tap and V being the output voltage, then A-B or B-C = V/2, A-C = V and A-B-C = V centre tapped, normally to earth.
A-B, B-C or A-C can be used single ended or pseudo balanced via a phono connector, and A-B-C can be used fully balanced via an XLR connector with pin1 being centre tap and earth, pin2 being +ve phase and pin3 being -ve phase. You will then need to use twin screened cable between the pre and main amp and obviously arrange for the amp to have a truly balanced input as well.

John - Dr John
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  #3  
Old 29th July 2007, 08:00 AM
novalves novalves is offline
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Default Re: Pre3 - balanced operation

- thanks for that Dr John. Just read the latest NL and news of the new balanced version of the pre3. Is there going to be a little upgrade kit for the pre3 or is it just simpler to order the bits ?!
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Old 29th July 2007, 08:27 AM
Dik Dolan Dik Dolan is offline
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Default Re: Pre3 - balanced operation

I'd be interested in upgraded parts kits for the pre3 and phono3. Don't need or want balanced outs, but the cap upgrades would be nice if available as a complete upgrade pack- WD dont list the BHC Aerovox or Stargets, and it would be nice to be able to just order them as upgrades from WD=)
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  #5  
Old 30th July 2007, 12:13 AM
novalves novalves is offline
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Default Re: Pre3 - balanced operation

I have studied Dr John's reply. Does this mean that output to phono can be halved just by taking the output from some other transformer pin ?

The answer re XLR connections is clear - but only if the pin-out of the transformer is known. (HT and CT are obvious ....)

The circuit diagram shows no pin information for the transformers - and there are 12 just on one side!

Last edited by novalves; 30th July 2007 at 12:38 AM.
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  #6  
Old 30th July 2007, 12:26 AM
novalves novalves is offline
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Default Re: Pre3 - balanced operation

I've studied the pictures and come up with:

1. On one side of the transformer the pins are numbered from 7 to 18.
2. Phono output is either x6 or x12 using the + or - pins
3. For balanced operation the pins to use are: CT, + and .............. maybe - ?
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  #7  
Old 30th July 2007, 12:37 PM
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petercom petercom is offline
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Default Re: Pre3 - balanced operation

+ and - are the output pins for full output capabilities. The Centre Tap CT goes to the ground pin of the XLR in the balanced version.

If you are using it unbalanced then connecting + and CT gives you half the output level.
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  #8  
Old 31st July 2007, 10:27 PM
novalves novalves is offline
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Default Re: Pre3 - balanced operation

I found this a clear, coherent, and expert explanation of what balanced operation is all about.

http://www.audionote.co.uk/articles/art_balanced.shtml
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