Joe's Nuggets

laatsch55

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#1
For those random posts of Joe's that don't need to be buried in the middle of a thread.. If you find any perusing the old threads here, PM me and I'll gt em moved..
 

laatsch55

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#2
uesday at 9:07 AM
#147




George S. said:


Question: With the dual primary transformer in the PL2000 preamp, I found lowest noise on the unit using the PC based spectrum analyzer with Line connected to the striped transformer wires and Neutral connected to the solid color wires. Has anyone looked at this on the 700 dual primary transformer. I know I wired my 400 S2 like this when I installed the IEC socket.

I have done a bunch of work in this area George. Much depends on the consistency of the winding formula that the transformer manufacturer uses. I am quite sure that PL left those details to the transformer manufacturer and did not provide them a winding sheet which would have made it a specification.

What I have found is that, generally speaking (and this all is conditioned by generally speaking because there are always exceptions):

  1. Transformer makers wind the primary first, closest to the core. Then layer secondaries on the outer winding layers, on top of the primary windings.
  2. With dual primaries, they will lay down a pair of wires at the same time to keep the primary wire lengths the same. Sometimes they use bifilar wire to do this, but not always.
  3. The end of both winding that starts at the core is where your hot wire should go to because these windings are farthest away from the secondaries that get layered on top of the primary windings. This will produce the lowest secondary coupling noise in a North American single phase application where the neutral wire in our homes is effectively earth ground.
  4. In European and other international high voltage applications. it matters much less because both primary input wires are hot. You don't get the US advantage.
  5. The noise is lower if you do this because you effectively have the ground end of the windings in close proximity to the secondary windings and therefore you get less capacitive and stray flux coupling noise between primary and secondary. That old trick of flipping the AC plug (before polarized plugs emerged on the scene) actually had some science behind it.
  6. I have done custom transformer work and provided a winding sheet to the manufacturer of the custom in order to control the winding sequence. Then I confirmed with measurements that the benefit of following the above guidelines actually does occur.
Hopefully this is helpful, and now it is documented here...




Always working on making it better...
 

laatsch55

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#3
Joe, so how does one determine which end of the primary is closest to the core. I'm thinking it's the striped wires, but how to verify?
That's your new WOAD 400 chassis eh?
 

laatsch55

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#4
Hi George
Since the transformers you are using are built to some spec you don't know about, measurement is the only way to determine unless there are physical clues in where the wires exit the winding stack.

  1. Put your DMM on the VAC scale
  2. DMM lead 1 to secondary center tap, other secondary wires left floating
  3. DMM lead 2 to safety ground of your mains plug
  4. Shunt across your DMM with 100K ohm resistor to provide a light load to the transformer coupling effect
  5. Connect L and N to the primaries in one direction. Take measurement
  6. Flip the L and N to the primaries to get the other direction. Take measurement
  7. The lowest measurement is the orientation that you want to use.
Make sense?

No that is the White Oak Audio PL700 chassis pictured.
 

NeverSatisfied

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#7
Moved or copied? Probably best to leave he originals in their proper time and space. If I am understanding your intention, place golden nuggets in a central location?
 
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