Maker Pro
Maker Pro

Audio Transformers are like Monster Cables

H

Harry Dellamano

Jan 1, 1970
0
Ok, I need a 10mW audio transformer with a 1:1 turns ratio for my 90R load.
So I look at many vendors and here is a typical spec:
http://www.picoelectronics.com/plugin/pe28_29.htm
Let's forget cost, because we all know that PICO is like Monster Cables.
The first unit I look at is the F-28003 with a pri:sec Z of 10R:10R. There
are many other 1:1 transformers listed but from the data shown, this is the
most efficient, best bandwidth and lowest distortion of all the 1:1
transformers listed. So why list any other 1:1 transformer?
I must be missing something, so spank me with your keyboards.
Harry
 
B

BobG

Jan 1, 1970
0
Harry said:
Ok, I need a 10mW audio transformer with a 1:1 turns ratio for my 90R load.
=================================
I though audio went down to 20Hz. This thing starts at 450Hz. What kind
of audio is that? CB radio audio?
 
P

Phil Allison

Jan 1, 1970
0
"Harry Dellamano"
Ok, I need a 10mW audio transformer with a 1:1 turns ratio for my 90R
load. So I look at many vendors and here is a typical spec:
http://www.picoelectronics.com/plugin/pe28_29.htm
Let's forget cost, because we all know that PICO is like Monster Cables.
The first unit I look at is the F-28003 with a pri:sec Z of 10R:10R. There
are many other 1:1 transformers listed but from the data shown, this is
the most efficient, best bandwidth and lowest distortion of all the 1:1
transformers listed.


** How did YOU make that conclusion ?

The transformers on that page are speced with the same response - ie "
+/- 3db 400 Hz to 250 kHz at 1 mW"

So not an "audio transformer" in the world of pro audio.

So why list any other 1:1 transformer?


** Funny how folk want to use other load impedances than 10 ohms.

Pico seem to be well aware of this.

I must be missing something, so spank me with your keyboards.


** Bandwidth, efficiency and distortion characteristics all depend on using
a transformer at or near its rated impedance values.

The title " 1:1" simply means transformer does not change the impedance
levels in a circuit.



........ Phil
 
E

Eeyore

Jan 1, 1970
0
Harry said:
Ok, I need a 10mW audio transformer with a 1:1 turns ratio for my 90R load.
So I look at many vendors and here is a typical spec:
http://www.picoelectronics.com/plugin/pe28_29.htm
Let's forget cost, because we all know that PICO is like Monster Cables.
The first unit I look at is the F-28003 with a pri:sec Z of 10R:10R. There
are many other 1:1 transformers listed but from the data shown, this is the
most efficient, best bandwidth and lowest distortion of all the 1:1
transformers listed. So why list any other 1:1 transformer?
I must be missing something, so spank me with your keyboards.

All transformers in the signal path introduce various types of distortions.

For decent audio transformers check out Jensen, Sowter and Luhndahl for
starters.

Graham
 
D

Don Foreman

Jan 1, 1970
0
Ok, I need a 10mW audio transformer with a 1:1 turns ratio for my 90R load.
So I look at many vendors and here is a typical spec:
http://www.picoelectronics.com/plugin/pe28_29.htm
Let's forget cost, because we all know that PICO is like Monster Cables.
The first unit I look at is the F-28003 with a pri:sec Z of 10R:10R. There
are many other 1:1 transformers listed but from the data shown, this is the
most efficient, best bandwidth and lowest distortion of all the 1:1
transformers listed. So why list any other 1:1 transformer?
I must be missing something, so spank me with your keyboards.
Harry

10 mW into 90 ohms is 948 mV RMS. 10 mW into 10 ohms is 316mV RMS
-- so a 10 mW 10 ohm xfmr is designed for voltage not exceeding 316 mV
RMS -- which is about 1.11 mW at 90 ohms.
 
Eeyore said:
All transformers in the signal path introduce various types of distortions.

For decent audio transformers check out Jensen, Sowter and Luhndahl for
starters.

Graham

Those are good iron, but does anyone know of a source of audio
transformers a notch lower than say a Jensen. I'd like to break the
ground between communications gear and my notebook, which I use for
recording. Connecting the notebook always effects the performance of
the radio, even if you use ferrite chokes. A $70 Jensen transformer is
overkill in such an application.
 
P

Phil Allison

Jan 1, 1970
0
<[email protected]
Those are good iron, but does anyone know of a source of audio
transformers a notch lower than say a Jensen. I'd like to break the
ground between communications gear and my notebook, which I use for
recording. Connecting the notebook always effects the performance of
the radio, even if you use ferrite chokes. A $70 Jensen transformer is
overkill in such an application.


** Try Radio Shack.

http://www.radioshack.com/product/index.jsp?productId=2062214&cp

Two channels for $17 is OK



......... Phil
 
E

Eeyore

Jan 1, 1970
0
Those are good iron, but does anyone know of a source of audio
transformers a notch lower than say a Jensen. I'd like to break the
ground between communications gear and my notebook, which I use for
recording. Connecting the notebook always effects the performance of
the radio, even if you use ferrite chokes. A $70 Jensen transformer is
overkill in such an application.

OEP ! Not quite so 'esoteric' but very adequate.
http://www.oep.co.uk/

RS components and Farnell certainly used to stock them

Graham
 
T

Tony Williams

Jan 1, 1970
0
Ok, I need a 10mW audio transformer with a 1:1 turns ratio for
my 90R load. So I look at many vendors and here is a typical
spec: http://www.picoelectronics.com/plugin/pe28_29.htm Let's
forget cost, because we all know that PICO is like Monster
Cables. The first unit I look at is the F-28003 with a pri:sec Z
of 10R:10R. There are many other 1:1 transformers listed but from
the data shown, this is the most efficient, best bandwidth and
lowest distortion of all the 1:1 transformers listed. So why list
any other 1:1 transformer? I must be missing something, so spank
me with your keyboards. Harry

10mW in a 90R load is about 1Vrms Harry.

All these transformer do a maximum 20mW at 400Hz.
For the 10R+10R that is only about 0.45Vrms.

To run with 1Vrms at 400Hz you need to choose one that
does 20mW into between 50R and 90R. Say F-28030/28045.

If you are driving from a low source impedance, (say an
opamp), you can get an improvement in the low frequency
response by pushing the choice even further.
 
J

John Woodgate

Jan 1, 1970
0
Those are good iron, but does anyone know of a source of audio
transformers a notch lower than say a Jensen. I'd like to break the
ground between communications gear and my notebook, which I use for
recording. Connecting the notebook always effects the performance of
the radio, even if you use ferrite chokes. A $70 Jensen transformer is
overkill in such an application.

The type of transformer used in modems will do that. In a phone circuit,
the primary inductance limits the low-frequency range to some 300 Hz,
but you notebook will drive it from a source much lower than 600 ohms,
at a voltage much less than the maximum phone line voltage, so it will
work OK.

No doubt a dozen people will give you reasons why it won't, so I suggest
you just try it.
 
F

Fred Bartoli

Jan 1, 1970
0
John said:
The type of transformer used in modems will do that. In a phone circuit,
the primary inductance limits the low-frequency range to some 300 Hz,
but you notebook will drive it from a source much lower than 600 ohms,
at a voltage much less than the maximum phone line voltage, so it will
work OK.

Hmmm, the ones I've just tested have 65R primary and secondary resistance.
Suitable for 600R impedance, but at 90R?

No doubt a dozen people will give you reasons why it won't, so I suggest
you just try it.

Either than that, no pb. So I'm half of those people.
Still 11.5 other people to find.
 
J

John Woodgate

Jan 1, 1970
0
In message <[email protected]>, dated Sat, 16 Sep
2006, Fred Bartoli
Hmmm, the ones I've just tested have 65R primary and secondary resistance.
Suitable for 600R impedance, but at 90R?

Two things:

1. I've never seen a notebook or anything else in audio with a 90 ohm
input impedance, so I'm doubtful about that. It certainly wouldn't suit
an electret mic or any line-level source.

2. There is plenty of spare gain in such a set-up, so the transformer
losses are very likely quite negligible.
 
F

Fred Bartoli

Jan 1, 1970
0
John said:
In message <[email protected]>, dated Sat, 16 Sep
2006, Fred Bartoli


Two things:

1. I've never seen a notebook or anything else in audio with a 90 ohm
input impedance, so I'm doubtful about that. It certainly wouldn't suit
an electret mic or any line-level source.

2. There is plenty of spare gain in such a set-up, so the transformer
losses are very likely quite negligible.

Oh, OK I just read the 90R load and missed the notebook blahh...
 
D

Don Bowey

Jan 1, 1970
0
Ok, I need a 10mW audio transformer with a 1:1 turns ratio for my 90R load.
So I look at many vendors and here is a typical spec:
http://www.picoelectronics.com/plugin/pe28_29.htm
Let's forget cost, because we all know that PICO is like Monster Cables.
The first unit I look at is the F-28003 with a pri:sec Z of 10R:10R. There
are many other 1:1 transformers listed but from the data shown, this is the
most efficient, best bandwidth and lowest distortion of all the 1:1
transformers listed. So why list any other 1:1 transformer?
I must be missing something, so spank me with your keyboards.
Harry

Right off the top, you want one rated for 10 mW and the absolutely greatest
one you provided a link to, is rated at 1 mW.

Don
 
H

Harry Dellamano

Jan 1, 1970
0
Tony Williams said:
10mW in a 90R load is about 1Vrms Harry.

All these transformer do a maximum 20mW at 400Hz.
For the 10R+10R that is only about 0.45Vrms.

To run with 1Vrms at 400Hz you need to choose one that
does 20mW into between 50R and 90R. Say F-28030/28045.

If you are driving from a low source impedance, (say an
opamp), you can get an improvement in the low frequency
response by pushing the choice even further.
Hi Tony,
Now that makes sense. So I should NOT try to match my load to their Z for
best efficiency but choose the lowest Z that will support my voltage levels.
So, I need 1.0V and they will transform to a max of 20mW so the lowest Z=
E^2/P = 1/20m = 50R. They do have a 50R, the F-28030 so that is my
selection.
We had this discussion before and you had a good rule of thumb to
determine primary inductance and better model these units, please refresh my
mind. Why don't they list the max Vac, at maybe 5% distortion that each unit
can operate? The data given is for users with little knowledge of
electronics, maybe the "golden ears" crowd.
Harry
 
J

John Woodgate

Jan 1, 1970
0
dated Sat said:
Now that makes sense. So I should NOT try to match my load to their Z
for best efficiency but choose the lowest Z that will support my
voltage levels. So, I need 1.0V and they will transform to a max of
20mW so the lowest Z= E^2/P = 1/20m = 50R. They do have a 50R, the
F-28030 so that is my selection.

I think you are very confused. First of all, where did you get '90 ohms'
from? It's a very strange value, not associated with audio (or anything
else that's analogue) at all.

Second, do you know the signal voltage that will be applied to your
transformer? If it's feeding a normal notebook audio input, it is likely
to be between 10 mV )from a microphone) and 0.5 V (from a line-level
output).

You simply don't choose transformers by the methods you are using.
 
P

Phil Allison

Jan 1, 1970
0
"Don Bowey"
Right off the top, you want one rated for 10 mW and the absolutely
greatest
one you provided a link to, is rated at 1 mW.


** This dopey ham radio asshole must be completely pissed.

LOL !!



....... Phil
 
H

Harry Dellamano

Jan 1, 1970
0
John Woodgate said:
I think you are very confused. First of all, where did you get '90 ohms'
from? It's a very strange value, not associated with audio (or anything
else that's analogue) at all.

Second, do you know the signal voltage that will be applied to your
transformer? If it's feeding a normal notebook audio input, it is likely
to be between 10 mV )from a microphone) and 0.5 V (from a line-level
output).

You simply don't choose transformers by the methods you are using.
--
John, I am doing circuit design, not hooking up audio boxes. Believe me,
the load is 90R at 10mW so that is 0.95Vrms. To be most efficient I want the
lowest loss in the transformer. Matching loads to sources is overrated. It
will give you max power transferred at 50% efficiency but who can live with
all those losses. It is much better to use the lowest Z transformer that can
support your volt seconds. This is just between circuit designers but don't
try to convince your audio crowd that.
Harry
 
J

John Woodgate

Jan 1, 1970
0
In message <[email protected]>, dated Sat, 16 Sep
2006, Fred Bartoli
Oh, OK I just read the 90R load and missed the notebook blahh...

No, there is confusion between two posts. The OP. Harry, has a 90 ohm
load. It's 'miso' who wants a transformer for his notebook.
 
J

John Woodgate

Jan 1, 1970
0
dated Sat said:
John, I am doing circuit design, not hooking up audio boxes.

It would have been helpful, then, to give more details.
Believe me, the load is 90R at 10mW so that is 0.95Vrms. To be most
efficient I want the lowest loss in the transformer. Matching loads to
sources is overrated. It will give you max power transferred at 50%
efficiency but who can live with all those losses.
Indeed.

It is much better to use the lowest Z transformer that can support your
volt seconds.

That just doesn't make sense. A transformer doesn't have an 'impedance'.
This is just between circuit designers but don't
try to convince your audio crowd that.

Matched loads haven't been used in audio for around 50 years.
 
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