Extend freq audio xfmr

[John Popelish]

"John Popelish"




** Can you spell the word " F A N A T I C " for me - John ?

Now that you have given me a hint, sure.


It just seems to me that if you are going to go to all the
trouble of building custom magnetics, you also don't
encircle the mounting bolt with winding currents, and for
impedances as low as 8 ohms at 20 kHz (64 uHy, max) you
don't add extra microhenries in series with it by laying
open loops of wire in the chassis. Anyways, I wouldn't, so
I'm a fanatic.

I'll bet they twisted the pair when they measured the
leakage inductance.

 

[Phil Allison]

"John Popelish"

Now that you have given me a hint, sure.


It just seems to me that if you are going to go to all the trouble of
building custom magnetics, you also don't encircle the mounting bolt with
winding currents,

** Can you spell the word " L U N A T I C '' for me too ?

Know what ASD stands for ?



........ Phil

 

[Don Bowey]

"John Popelish"




** Can you spell the word " L U N A T I C '' for me too ?

Know what ASD stands for ?

I'll take a stab at it..... Allison's Simply Dippy?

Don

 

[Paul Mathews]

I suspect a measurable fraction of that 20 uHy might be just
in the loop area of the lead wires to the connector,
especially if the wires happen to be spread out a bit more
than in the pictures. I think that pair should be twisted.

I usually figure I've done a good job with a transformer design if the
leakage inductance is under 1% of the magnetizing inductance. It's
been a couple of years, but it seems like that one had a much higher
ratio, with the magnetizing inductance well up into the 10s of
milliHenry;. All turns are effectively multi-filar, with no insulation
other than the 'varnish' between the primary and secondary. The main
point I was trying to make is that audio distribution transformers,
when not designed as if they were 50/60 Hz power transformers rated
for high average power and requiring lots of insulation, can have much
better performance. According to my investigations, most of the
popular distribution transformer designs do not take advantage of this
fact.
Paul Mathews.

 

[Phil Allison]

"Paul Mathews"

I usually figure I've done a good job with a transformer design if the
leakage inductance is under 1% of the magnetizing inductance.

** You gotta be joking ???????????

L mag is in the Henries, for a toroidal design.

So that absurd 20mH figure was OK by you after all ?



........ Phil

 

[John Popelish]

I usually figure I've done a good job with a transformer design if the
leakage inductance is under 1% of the magnetizing inductance. It's
been a couple of years, but it seems like that one had a much higher
ratio, with the magnetizing inductance well up into the 10s of
milliHenry;. All turns are effectively multi-filar, with no insulation
other than the 'varnish' between the primary and secondary. The main
point I was trying to make is that audio distribution transformers,
when not designed as if they were 50/60 Hz power transformers rated
for high average power and requiring lots of insulation, can have much
better performance. According to my investigations, most of the
popular distribution transformer designs do not take advantage of this
fact.

That makes good sense. Somewhere in this thread, I thought
you were holding these transformers up as something state of
the art, close to the ultimate, not just very functional and
better than most. Fair enough.

The O.P. seemed interested in finding transformers that
perform well at frequencies (possibly much) higher than 25
kHz, not just in the audio spectrum. Are you proposing he
use these? I was just thinking about where the first
limitations for say, (pulling a number out of my ass) 100
kHz use would occur with your design.

 

[Paul Mathews]

That makes good sense. Somewhere in this thread, I thought
you were holding these transformers up as something state of
the art, close to the ultimate, not just very functional and
better than most. Fair enough.

The O.P. seemed interested in finding transformers that
perform well at frequencies (possibly much) higher than 25
kHz, not just in the audio spectrum. Are you proposing he
use these? I was just thinking about where the first
limitations for say, (pulling a number out of my ass) 100
kHz use would occur with your design.- Hide quoted text -

- Show quoted text -

Those transformers are designed to be much better than those commonly
used for PA distribution without being priced radically higher, and
they are. For crazy Phil's benefit, I dragged one out and measured its
magnatizing inductance: 7.8 Henry at 1 kHz. Leakage inductance, as
measured on the secondary side for the 70.7V (100 watt) tap, was 13
microHenry. That's really pretty good, if I do say so myself. These
are also not autotransformers, which makes the job of reducing leakage
inductance more difficult. However, any transformer designed to
transfer power is a compromise, so choose the best compromise for your
app. Returning to the OP's quest for extended HF response, there have
been several good suggestions. If he sticks with a single transformer,
crazy Phil is absolutely right to say that leakage inductance is the
main limiting factor, but it results in a simple rolloff for at least
an octave or 2, and core saturation is not a problem at high
frequencies, so some sort of pre-emphasis can be used to compensate.
Paul Mathews

 

[whit3rd]

"whit3rd"


** You are an witless ass

No, none of that! Rather, "pedantic ass".

Get it right next time.

 

[Phil Allison]

"whitless ASS"

In fact, it's six of one, half dozen of the other.

** You are an witless ass

- **** off .



........ Phil