[mcp6453[_2_]]

It's a long story, but I have several computers that are connected to mixers and
to each other. The ground loops are getting out of hand. Some of them are to be
expected. For some of the computers, the cheapo Radio Shack in-line isolation
transformers work fine because the audio is telephone. However, I'd like to find
a mid-grade 1:1 audio transformer and buy 10 or so, primarily to interconnect
computer sound cards (M-Audio 2496, CardDeluxe) to mixers (Behringer, Mackie).

The SESCOM inline transformers are $45. That's not a bad price, but I'd curious
as to whether there are some less expensive ones. The Lundahl distributor is in
my backyard almost, but those wonderful transformers are overkill for these
applications.

Scott usually has some secret sources up his sleeve. Maybe I'll get lucky here.
I wish I could find my box of UTC A-22s that I've collected over the years.

[Scott Dorsey]

mcp6453 wrote:

The SESCOM inline transformers are $45. That's not a bad price, but I'd curious
as to whether there are some less expensive ones. The Lundahl distributor is in
my backyard almost, but those wonderful transformers are overkill for these
applications.

Scott usually has some secret sources up his sleeve. Maybe I'll get lucky here.
I wish I could find my box of UTC A-22s that I've collected over the years.

How about the Edcor ones? They have little PC boards with 600:600
transformers for something like $20, and the transformers aren't half
bad although they really want to see a low source impedance to be happy.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[mcp6453[_2_]]

On 3/17/2011 1:50 PM, Scott Dorsey wrote:
mcp6453 wrote:

The SESCOM inline transformers are $45. That's not a bad price, but I'd curious
as to whether there are some less expensive ones. The Lundahl distributor is in
my backyard almost, but those wonderful transformers are overkill for these
applications.

Scott usually has some secret sources up his sleeve. Maybe I'll get lucky here.
I wish I could find my box of UTC A-22s that I've collected over the years.

How about the Edcor ones? They have little PC boards with 600:600
transformers for something like $20, and the transformers aren't half
bad although they really want to see a low source impedance to be happy.
--scott

I'm not familiar with them, but I'm off to Google. What happens if they don't
have a low source impedance?

[Scott Dorsey]

mcp6453 wrote:

How about the Edcor ones? They have little PC boards with 600:600
transformers for something like $20, and the transformers aren't half
bad although they really want to see a low source impedance to be happy.

I'm not familiar with them, but I'm off to Google. What happens if they don't
have a low source impedance?

They'll ring, and the output will sound artificially bright.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"mcp6453" wrote in message

It's a long story, but I have several computers that are
connected to mixers and to each other. The ground loops
are getting out of hand. Some of them are to be expected.
For some of the computers, the cheapo Radio Shack in-line
isolation transformers work fine because the audio is
telephone. However, I'd like to find a mid-grade 1:1
audio transformer and buy 10 or so, primarily to
interconnect computer sound cards (M-Audio 2496,
CardDeluxe) to mixers (Behringer, Mackie).

The Radio Shack transformers must be a lot better than you think they are,
because their performance is orders of magnitude better than telephone
grade.

Back in 2006 did some bench tests of Radio Shack's "Ground Isolator"
270-054 using
test signals that maxed out around 2.5 v RMS. ZSource = 150 ohms, ZLoad =
5Kohms.

The measured performance was truely amazing for a pair of transformers case
and cables selling for only $16.65.

All IM, THD, and noise artifacts were at least 80 dB down with most in
the -100 dB range or better. Frequency response showed a 2 dB peak at 20 Hz
and then 10 dB down at 10 Hz. There was a 3 dB peak at about 51 KHz falling
to about 10 dB down around 100 KHz. +0.5 dB at 20 KHz.

I repeated the tests with the secondary loaded with 1.5K, and the peak at 51
Khz became well-damped with only about 0.6 dB rise

[mcp6453[_2_]]

On 3/17/2011 6:47 PM, Arny Krueger wrote:

The Radio Shack transformers must be a lot better than you think they are,
because their performance is orders of magnitude better than telephone
grade.

Back in 2006 did some bench tests of Radio Shack's "Ground Isolator"
270-054 using
test signals that maxed out around 2.5 v RMS. ZSource = 150 ohms, ZLoad =
5Kohms.

The measured performance was truely amazing for a pair of transformers case
and cables selling for only $16.65.

All IM, THD, and noise artifacts were at least 80 dB down with most in
the -100 dB range or better. Frequency response showed a 2 dB peak at 20 Hz
and then 10 dB down at 10 Hz. There was a 3 dB peak at about 51 KHz falling
to about 10 dB down around 100 KHz. +0.5 dB at 20 KHz.

I repeated the tests with the secondary loaded with 1.5K, and the peak at 51
Khz became well-damped with only about 0.6 dB rise

They very well could be. All I was saying was that the quality where they are
used is not that critical. They could be Jensens or Lundahls, and I would not be
able to tell a difference.

Have you tested the Edcors that Scott suggests? They are really priced right.
They're worth checking out.

[Mike Rivers]

On 3/17/2011 6:47 PM, Arny Krueger wrote:

Back in 2006 did some bench tests of Radio Shack's "Ground Isolator"
270-054 using
test signals that maxed out around 2.5 v RMS. ZSource = 150 ohms, ZLoad =
5Kohms.

The measured performance was truely amazing for a pair of transformers case
and cables selling for only $16.65.

I checked this transformer out for an article I wrote about
ground isolators and was also pleasantly surprised. The
problem, though, was that it wouldn't take very much level
before it saturated and distortion, particularly at low
frequencies, went way up. That's sometimes a good thing, but
you don't want it to be there all the time. With so much
gear having a maximum output level of +18 dBu or greater,
you really take a hit in headroom if the output has to go
through those transformers.

To be fair, they give you nearly 20 dB of headroom over the
"consumer" nominal operating level of -10 dBV, so when used
with what they're designed to connect to, they'll work fine.
Put them on the output of a Mackie mixer, though, and when
the meters get more than a couple of LEDs above 0 (mid scale
- and show me the 21st Century engineer who only lets the
meters go half way up scale) and they start to get dirty.

You can practically plug an old Western Electric "repeat
coil" into a 115 V AC outlet and have the 60 Hz come out
clean (hey, it's only about +42 dBu) but don't try it at
home, kids.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Scott Dorsey]

Mike Rivers wrote:

You can practically plug an old Western Electric "repeat
coil" into a 115 V AC outlet and have the 60 Hz come out
clean (hey, it's only about +42 dBu) but don't try it at
home, kids.

The good news is that McCurdy Radio still makes 111C coils to the original
WE specs.

The bad news is that they are $250 now.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[mcp6453[_2_]]

On 3/17/2011 9:48 PM, Scott Dorsey wrote:
Mike Rivers wrote:

You can practically plug an old Western Electric "repeat
coil" into a 115 V AC outlet and have the 60 Hz come out
clean (hey, it's only about +42 dBu) but don't try it at
home, kids.

The good news is that McCurdy Radio still makes 111C coils to the original
WE specs.

The bad news is that they are $250 now.
--scott


I've owned a grand total of ONE of them. I wonder if it is still hanging on the
wall in the telephone room of the radio station we used to own. Hmmm.

[Arny Krueger]

"mcp6453" wrote in message

On 3/17/2011 6:47 PM, Arny Krueger wrote:

The Radio Shack transformers must be a lot better than
you think they are, because their performance is orders
of magnitude better than telephone grade.

Back in 2006 did some bench tests of Radio Shack's
"Ground Isolator" 270-054 using
test signals that maxed out around 2.5 v RMS. ZSource =
150 ohms, ZLoad = 5Kohms.

The measured performance was truely amazing for a pair
of transformers case and cables selling for only $16.65.

All IM, THD, and noise artifacts were at least 80 dB
down with most in the -100 dB range or better. Frequency response showed
a
2 dB peak at 20 Hz and then 10 dB down at 10 Hz. There
was a 3 dB peak at about 51 KHz falling to about 10 dB
down around 100 KHz. +0.5 dB at 20 KHz.

I repeated the tests with the secondary loaded with
1.5K, and the peak at 51 Khz became well-damped with
only about 0.6 dB rise

They very well could be. All I was saying was that the
quality where they are used is not that critical.

It appears to me that you've committed yourself to an expensive search for a
Holy Grail, when you have already been using several of them as drinking
glasses.

They could be Jensens or Lundahls, and I would not be able to
tell a difference.

Then why worry?

Have you tested the Edcors that Scott suggests?

Of course not. That would cost me time and money, and what for?

They are really priced right.

In what alternative universe? Anybody selling them for less than $10 each?

They're worth checking out.

Your time, your money - be my guest.

I guess what I'm saying is you've got a option, check your pride at the door
and get some more RS's a use them for a critical application, this time.

[mcp6453[_2_]]

On 3/18/2011 9:04 AM, Arny Krueger wrote:
"mcp6453" wrote in message

On 3/17/2011 6:47 PM, Arny Krueger wrote:

The Radio Shack transformers must be a lot better than
you think they are, because their performance is orders
of magnitude better than telephone grade.

Back in 2006 did some bench tests of Radio Shack's
"Ground Isolator" 270-054 using
test signals that maxed out around 2.5 v RMS. ZSource =
150 ohms, ZLoad = 5Kohms.

The measured performance was truely amazing for a pair
of transformers case and cables selling for only $16.65.

All IM, THD, and noise artifacts were at least 80 dB
down with most in the -100 dB range or better. Frequency response showed
a
2 dB peak at 20 Hz and then 10 dB down at 10 Hz. There
was a 3 dB peak at about 51 KHz falling to about 10 dB
down around 100 KHz. +0.5 dB at 20 KHz.

I repeated the tests with the secondary loaded with
1.5K, and the peak at 51 Khz became well-damped with
only about 0.6 dB rise

They very well could be. All I was saying was that the
quality where they are used is not that critical.

It appears to me that you've committed yourself to an expensive search for a
Holy Grail, when you have already been using several of them as drinking
glasses.

They could be Jensens or Lundahls, and I would not be able to
tell a difference.

Then why worry?

Have you tested the Edcors that Scott suggests?

Of course not. That would cost me time and money, and what for?

They are really priced right.

In what alternative universe? Anybody selling them for less than $10 each?

They're worth checking out.

Your time, your money - be my guest.

I guess what I'm saying is you've got a option, check your pride at the door
and get some more RS's a use them for a critical application, this time.

All I was saying was that I have used the Radio Shack transformers only in
non-critical applications. They could be wonderful or they could be garbage. It
would be impossible to tell from the non-critical (except for isolation)
applications. I don't have a clue what pride has to do with anything. I was
simply reporting my experiences.

You're a really complex person, Arny.

[Arny Krueger]

"mcp6453" wrote in message


All I was saying was that I have used the Radio Shack
transformers only in non-critical applications.

No, you were also saying that you needed something better, even though you
hadn't actually tried the S parts in that role.

They could be wonderful or they could be garbage.

So why not try them?

It would be impossible to tell from the non-critical (except for
isolation) applications.

So why not try them for your new critical application?

How many plugs would you have to plug/unplug?

I don't have a clue what pride has to do with anything.

Looks to me like you prejudged them pretty harshly.

I was simply reporting my experiences.

Not true, if I can believe your earlier posts. You said had no experience
with the RS transformers in the new more critical application even though
you apparently have them at your disposal.

You're a really complex person, Arny.

What's complex about this situation? You've got the RS transformers at your
disposal, but you continue to refuse to test them in your new, more-critcial
application.

Yet, you've asked me to somehow obtain some other more expensive
transformers and test them?

[mcp6453[_2_]]

On 3/18/2011 12:10 PM, Arny Krueger wrote:
"mcp6453" wrote in message


All I was saying was that I have used the Radio Shack
transformers only in non-critical applications.

No, you were also saying that you needed something better, even though you
hadn't actually tried the S parts in that role.

They could be wonderful or they could be garbage.

So why not try them?

I will

It would be impossible to tell from the non-critical (except for
isolation) applications.

So why not try them for your new critical application?

How many plugs would you have to plug/unplug?

I have and I will.

I don't have a clue what pride has to do with anything.

Looks to me like you prejudged them pretty harshly.

That may be a reading comprehension issue. That's not what I said.

You're a really complex person, Arny.

What's complex about this situation? You've got the RS transformers at your
disposal, but you continue to refuse to test them in your new, more-critical
application.

Yet, you've asked me to somehow obtain some other more expensive
transformers and test them?

No, I said YOU were complex. You're taking a simple question and twisting into a
controversy. I've always appreciated your posts. Now I feel like you're picking
a fight for absolutely no reason.

I have found the answers to my questions, including your answer. Thank you for
that. No further responses are necessary.

[villem teder]

When these transformers became available back then, I measured similar
results to Arny's. When fed from a low impedance source into a high
load, at reasonably "semi" levels, the results didn't seem all that
bad. The biggest issue I saw was that in all the RS units I tested, as
well as several "copies" was that they were all POL ARITY INVERTING!
Is that really that important? (ducking for cover!)

Regards,

Villem Teder

Toronto



On Thu, 17 Mar 2011 18:47:11 -0400, "Arny Krueger"
wrote:

"mcp6453" wrote in message
m
It's a long story, but I have several computers that are
connected to mixers and to each other. The ground loops
are getting out of hand. Some of them are to be expected.
For some of the computers, the cheapo Radio Shack in-line
isolation transformers work fine because the audio is
telephone. However, I'd like to find a mid-grade 1:1
audio transformer and buy 10 or so, primarily to
interconnect computer sound cards (M-Audio 2496,
CardDeluxe) to mixers (Behringer, Mackie).

The Radio Shack transformers must be a lot better than you think they are,
because their performance is orders of magnitude better than telephone
grade.

Back in 2006 did some bench tests of Radio Shack's "Ground Isolator"
270-054 using
test signals that maxed out around 2.5 v RMS. ZSource = 150 ohms, ZLoad =
5Kohms.

The measured performance was truely amazing for a pair of transformers case
and cables selling for only $16.65.

All IM, THD, and noise artifacts were at least 80 dB down with most in
the -100 dB range or better. Frequency response showed a 2 dB peak at 20 Hz
and then 10 dB down at 10 Hz. There was a 3 dB peak at about 51 KHz falling
to about 10 dB down around 100 KHz. +0.5 dB at 20 KHz.

I repeated the tests with the secondary loaded with 1.5K, and the peak at 51
Khz became well-damped with only about 0.6 dB rise

[Peter Larsen[_3_]]

villem teder wrote:

When these transformers became available back then, I measured similar
results to Arny's. When fed from a low impedance source into a high
load, at reasonably "semi" levels, the results didn't seem all that
bad. The biggest issue I saw was that in all the RS units I tested, as
well as several "copies" was that they were all POL ARITY INVERTING!
Is that really that important? (ducking for cover!)

Yes, for all kinds of reasons, audibility included, but the simple
showstopper is "combineability".

Villem Teder

Kind regards

Peter Larsen