[andyr]

Here's an interesting quote I picked up on PFM.  It appears to be an amp mfr talking (my emphases):

"In the AP35 we use a 150 V/A toroid. We have listened to numerous different toroids and they all sound different. We now use an Avel Lindberg., which we consider to give us the sound we want. Mark Levinson also uses their transformers.

They are also very compact for their V/A rating because they have found a way of winding the primary outside the secondary, which is actually more difficult. The majority of toroid's secondaries are wound outside the primary, for safety's sake, because when the primary is outside the secondary, if you damage the transformer, you've got mains there, if the insulation goes, so that is why most people wind the secondary to the outside. But this design of transformer is better, you'll lower impedance if you wind the primary outside the secondary."

Never heard of this concept before ... but it sounds like a good thing!!      Anyone know if Harbuch toroids are wound like this?

Regards,

Andy

[AKSA]

I have not heard this either.

The important parameters of a toroid are efficiency (divided into iron and copper losses), interwinding capacitance and leakage inductance.

I have found the power transformer makes less sonic difference than the rectifiers, the power supply topology, and the filter caps.

An outside primary would mean more and/or thicker wire, and I suspect this would reduce copper losses, but it may also increase external fields which is a bad thing.

Cheers,

Hugh

[andyr]

I have not heard this either.

The important parameters of a toroid are efficiency (divided into iron and copper losses), interwinding capacitance and leakage inductance.

I have found the power transformer makes less sonic difference than the rectifiers, the power supply topology, and the filter caps.

An outside primary would mean more and/or thicker wire, and I suspect this would reduce copper losses, but it may also increase external fields which is a bad thing.

Cheers,

Hugh

You may well be right, Hugh, but I will do some investigations by contacting Harbuch and Avel Lindburg.

Thinking purely logically (as I have zero EE education):

*  Possibly, if having the primary on the outside produces lower impedance, this helps increase efficiency?

*  The power trannie may well make less sonic difference than the rectifiers, the power supply topology, and the filter caps but, as we strive to wring the maximum sonics out of our AKSA/LF amps, more and more things become important (and BTW, you forgot coupling caps in your list of important items!  ) .

*  I don't see why winding primary on the inside and secondary on the outside (the "normal" approach") would result in less wire than winding the primary on the outside?

*  And I would suggest that, as copper is non-magnetic, having a covering of (secondary) copper wires around the primary winding will not result in any less magnetic field?  After all, surely a toroid has less magnetic field (or leakage) than a "conventional" transformer because of the "donut shaped" core ... not because of the way it is wound?

Regards,

Andy

[AKSA]

Hi Andy,

I won't argue as I know little about magnetics and in a former life as a consultant I found that categoric statements all too often attracted negative responses, which can be mighty embarrassing.  So much of high end is opinion, and until you've wound a few hundred trafos and tried 'em all you really don't know much.

I agree about coupling caps.  I NEVER forget their importance, but in this case confined myself to the topic - the power supply.  Today such has been my commitment to coupling caps that I fitted two Sonicaps as C1 in one of premium amps.

Cheers,

Hugh

[Seano]

One could always unwind the toroid a ways and then rewind accordingly......but as someone who has unwound a couple of toroids in his time...........I'm certainly not going to volunteer.  Mongrel of a job.

I suspect that it is a job that is on par with vacuuming the roofspace of your house.....you might feel better that it's cleaner.....but it makes bugger all difference to the performance of the house.

[bluesky]

Hi

I have tried reading up on transformers to find some "magic" formula to raise sonic performance.

The Audio Note website claims to have found this (of course) with trafos that cost several times my annual income (not that hard to do on my annual income!).  On the otherhand Sowter, will provde customers with an expensive option to use CCC copper wire, but then provides a caveat by saying they are not convinced that this provides any audible improvement.  All of which leads me to suspect that Hugh's analysis on power supplies is quite correct, ie the transformers are not the main player in this game.  I seem to read quite often how EE type people role their eyes at us audiophools at times and state it is what we do with a certain amount of electrons coming out of the transformer that is important, as long as there's enough of them to do the job, the electrons don't really care either way.

From what I have read to date toroids (usually) provide the best sonics due to better efficiencies, low magnetic leakage and fields due to its circular shape, although EI trafos are quite acceptale as the frequency range of 20Hz to 20kHz is easily handled by both types and this only becomes an issue when you move up the frequency range which then goes into Mhz and Ghz which are many magnitudes higher.  As usual, the more I read the more confused I get.  I don't have very good mathematical skills.  Something neceassry to work through a range of formulas required for every part from wire to core and everything in between.  Well, it seemed like a good idea at the time and it reminded me of the words spoken by Charles Darwin to describe mathematicians as.......

"A blind man, searching a darkened room, for a black cat, that isn't there"!

Which at least makes feel a bit better about my confused state.

Bluesky   

[andyr]

Well, it seemed like a good idea at the time and it reminded me of the words spoken by Charles Darwin to describe mathematicians as.......

"A blind man, searching a darkened room, for a black cat, that isn't there"!

Bluesky   

A "mathematician" is a thing that converts coffee to formulae! 

Regards,

Andy