I note that the audio transformers used in these things have amazing
frequency response - for transformers - while all the small audio
transformers I can find in the catalogs are apparently quite limited. Is
this some peculiarity of transformers in this application, or are they
indeed special?
--
______________________________________________
Insanity is the inability to either tolerate or create ambiguity.

On Sat, 03 Jun 2006 14:49:53 GMT, Palinurus
wrote:

I note that the audio transformers used in these things have amazing
frequency response - for transformers - while all the small audio
transformers I can find in the catalogs are apparently quite limited. Is
this some peculiarity of transformers in this application, or are they
indeed special?

It is because they have a 1:1 turns ratio - both windings can be
optimized for the entire audio band. With different turns ratios, the
larger tends to handle the lows better, while the smaller is good for
the highs. Their best bits don't overlap so well.

d

--
Pearce Consulting
http://www.pearce.uk.com

Palinurus wrote:

I note that the audio transformers used in these things have amazing
frequency response - for transformers

I have no idea since you provided no link and I've never come across one.

Graham

Pooh Bear wrote:

Palinurus wrote:


I note that the audio transformers used in these things have amazing
frequency response - for transformers


I have no idea since you provided no link and I've never come across one.

Graham

-
http://cgi.ebay.com/PAC-SNI-1-3-5-Gr... cmdZViewItem
http://www.bestbuy.com/site/olspage....&ref=06&loc=01
http://www.gadgetgears.com/ground_lo...ator_gl15.html
http://cgi.ebay.com/ws/eBayISAPI.dll...tegory=50 552
http://minidiscaccessories.stores.ya...ounloopis.html
http://www.jr.com/JRProductPage.proc...ed.XIT+GLI1-X1

And so on. Many "purists" turn up their noses at the idea of having
something like this in their signal chains, blissfully ignorant of the
fact that their wonderful music has probably been through several such
before it is pressed into a CD. LPs were the same, but worse. In my
case, it seems to be the only practical way to break a hum loop from an
external USB sound card into the stereo.

--
______________________________________________
Insanity is the inability to either tolerate or create ambiguity.

Palinurus wrote:

Pooh Bear wrote:

Palinurus wrote:

I note that the audio transformers used in these things have amazing
frequency response - for transformers

I have no idea since you provided no link and I've never come across one.

Graham

http://cgi.ebay.com/PAC-SNI-1-3-5-Gr... cmdZViewItem
http://www.bestbuy.com/site/olspage....&ref=06&loc=01
http://www.gadgetgears.com/ground_lo...ator_gl15.html
http://cgi.ebay.com/ws/eBayISAPI.dll...tegory=50 552
http://minidiscaccessories.stores.ya...ounloopis.html
http://www.jr.com/JRProductPage.proc...ed.XIT+GLI1-X1


I don't remotely believe the +-0.03dB 20Hz-20kHz in the first ebay links for starters.


And so on. Many "purists" turn up their noses at the idea of having
something like this in their signal chains, blissfully ignorant of the
fact that their wonderful music has probably been through several such
before it is pressed into a CD.

If it's been through any transformers at all, they won't be cheap Asian ones.

LPs were the same, but worse. In my case, it seems to be the only practical way to break a hum loop from an
external USB sound card into the stereo.

The problem is the PC's power supply.

Graham

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?


--
Any system of knowledge that is capable of listing films in order
of use of the word "****" is incapable of writing a good summary
and analysis of the Philippine-American War. And vice-versa.
This is an inviolable rule.

- Matthew White, referring to Wikipedia on his WikiWatch site
(http://users.erols.com/mwhite28/wikiwoo.htm)

David Nebenzahl wrote:

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

What would these acheive ?

Graham

Blimey! An earth hum, which I am assuming is what you are trying to
remove, is caused by the differing potentials between the two
"grounds". Quite simply, you assume that the ground on your stereo is
0V compared to the ground on your computer. It is quite possible to
have a 20VDC difference, thus causing the noise. To solve the problem,
you are quite right to assume the use of an audio 1:1 transformer,
though I would suggest buying an opto-isolation box which will be
taylored, though I would guess you are using a "cheap" sound card, as
more expesive ones will have the earthing problem sorted out.

kt wrote:

Blimey! An earth hum, which I am assuming is what you are trying to
remove, is caused by the differing potentials between the two
"grounds". Quite simply, you assume that the ground on your stereo is
0V compared to the ground on your computer. It is quite possible to
have a 20VDC difference,

You reckon grounds may be 20V apart ! ?

thus causing the noise. To solve the problem,
you are quite right to assume the use of an audio 1:1 transformer,
though I would suggest buying an opto-isolation box which will be
taylored, though I would guess you are using a "cheap" sound card, as
more expesive ones will have the earthing problem sorted out.

The earthing problem has zero do with either cheap or expensive sound cards at
all and everything to do with the PC's power supply.

Graham

Pooh Bear wrote:

kt wrote:


Blimey! An earth hum, which I am assuming is what you are trying to
remove, is caused by the differing potentials between the two
"grounds". Quite simply, you assume that the ground on your stereo is
0V compared to the ground on your computer. It is quite possible to
have a 20VDC difference,


You reckon grounds may be 20V apart ! ?


thus causing the noise. To solve the problem,
you are quite right to assume the use of an audio 1:1 transformer,
though I would suggest buying an opto-isolation box which will be
taylored, though I would guess you are using a "cheap" sound card, as
more expesive ones will have the earthing problem sorted out.


The earthing problem has zero do with either cheap or expensive sound cards at
all and everything to do with the PC's power supply.

Graham


-
We're getting rather far afield here. I'm not going to replace my PC
power supply, and I'm not going to fake up something with opto-isolators
(which, BTW, have much worse linearity problems than transformers) and
I'm not going to invest in a new, expensive sound card. I'm just looking
for the best sort of transformers for this application, and I'm not
interested in something with oxygen free pure silver wire smelted from
Thai holy relics wound on an unobtainium core and frozen in liquid xenon
by the light of the harvest moon. The only other thing I might try is
faking up a junkbox special linear +5 supply for the sound card separate
from the USB supply from the computer. Since it would be grounded at
only one point, there'd be little chance of a hum loop.

--
______________________________________________
Insanity is the inability to either tolerate or create ambiguity.

On Sat, 03 Jun 2006 12:19:33 -0700, David Nebenzahl wrote:


Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.

"Pooh Bear" wrote
in message
Palinurus wrote:

I note that the audio transformers used in these
things have amazing frequency response - for transformers

I have no idea since you provided no link and I've never
come across one.

Maybe he's referencing what I posted 4/24:

I just 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 =
10K ohms.

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.


Presuming that mutual inductance is high across the audio band, the load on
the transformer is equal to the sum of the source and load impedances. IOW
in the case of my test, the total load was 10,150 ohms, which is the
stronger effect. How that is broken up between the input and output would be
the weaker effect.


I did a test where I added an additional 10K in parallel with the output of
the transformer. This reduced the bass peak to about 2 dB, and reduced the
treble peak to 0.6 dB. Both referenced the midband response which was flat
within 0.1 dB from 50 Hz to 10 Khz.

Since this part may vary, I should point out that the
UUT differed at least cosmetically from the picture at:


http://www.radioshack.com/sm-see-all...i-2062214.html


The cylindrical case on the sample tested is more truely
cylindrical, with sharper corners far less nomeclature.
The markings are on a black sticker and lack the
pictorals of signal connections and text related to
them. A RCA (female) to 3.5 mm TRS adaptor was
provided.

AZ Nomad wrote:
On Sat, 03 Jun 2006 12:19:33 -0700, David Nebenzahl wrote:



Palinurus spake thus:


... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.


How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?


Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.


-
Great idea! Just send me about $400, and I'll do it!


--
______________________________________________
Insanity is the inability to either tolerate or create ambiguity.

Arny Krueger wrote:
"Pooh Bear" wrote
in message

Palinurus wrote:


I note that the audio transformers used in these
things have amazing frequency response - for transformers

I have no idea since you provided no link and I've never
come across one.


Maybe he's referencing what I posted 4/24:

-
I wasn't, but those are some pretty impressive specs. Thanks for the info.

--
______________________________________________
Insanity is the inability to either tolerate or create ambiguity.

Palinurus wrote:

snip

-
We're getting rather far afield here. I'm not going to replace my PC
power supply, and I'm not going to fake up something with opto-isolators
(which, BTW, have much worse linearity problems than transformers) and
I'm not going to invest in a new, expensive sound card. I'm just looking
for the best sort of transformers for this application, and I'm not
interested in something with oxygen free pure silver wire smelted from
Thai holy relics wound on an unobtainium core and frozen in liquid xenon
by the light of the harvest moon. The only other thing I might try is
faking up a junkbox special linear +5 supply for the sound card separate
from the USB supply from the computer. Since it would be grounded at
only one point, there'd be little chance of a hum loop.



Good suppliers of quality small signal audio transformers include
Sowter and Jensen. Cinemag and even Sescom have some usable pieces too.
I would avoid MagneQuest which is a fraudulent operation and Radio
Shack for obvious reasons.

"Palinurus"

I note that the audio transformers used in these things have amazing
frequency response - for transformers - while all the small audio
transformers I can find in the catalogs are apparently quite limited.


** Dunno what "catalogues " you are perusing - but small, cheap
transformers with flat, audio band response have been around for many
decades. They are found inside microphones like the SM58, for example, and
many others.

Usually, the core material is laminated Mu-Metal or similar, which takes
care of the low frequency performance. Also, when the impedance ratio is
1:1, it is easy to achieve good high frequency response - much harder with
step up transformers like the common " Lo Z to Hi Z " converter types.

Beware of misleading specs; the response figures quoted were obtained under
OPTIMISED source and load conditions. By carefully adjusting the load
resistance and parallel capacitance on the secondary, a very flat high
frequency response can be obtained. This is just what the makers of those
units have done - then NOT told YOU !

Another reason for the low cost is mass production in China.

Also note, these cheap transformers have no magnetic shielding and so pick
up hum interference from nearby AC power transformers, CRT monitors and AC
power wiring.

Also note, their ability handle large signals at low frequencies without
gross distortion may be very limited.

No spec is given for this - unlike the famous brand name transformers that
spec everything.

This link shows a good quality 1:1 transformer that IS magnetically
shielded hence suitable for installing INSIDE an AC powered amplifier etc.
(prices in Aussie dollars) .

http://www.altronics.com.au/index.as...=item&id=M0706





........ Phil

Phil Allison wrote:
"Palinurus"

I note that the audio transformers used in these things have amazing
frequency response - for transformers - while all the small audio
transformers I can find in the catalogs are apparently quite limited.



** Dunno what "catalogues " you are perusing - but small, cheap
transformers with flat, audio band response have been around for many
decades. They are found inside microphones like the SM58, for example, and
many others.

Usually, the core material is laminated Mu-Metal or similar, which takes
care of the low frequency performance. Also, when the impedance ratio is
1:1, it is easy to achieve good high frequency response - much harder with
step up transformers like the common " Lo Z to Hi Z " converter types.

Beware of misleading specs; the response figures quoted were obtained under
OPTIMISED source and load conditions. By carefully adjusting the load
resistance and parallel capacitance on the secondary, a very flat high
frequency response can be obtained. This is just what the makers of those
units have done - then NOT told YOU !

Another reason for the low cost is mass production in China.

Also note, these cheap transformers have no magnetic shielding and so pick
up hum interference from nearby AC power transformers, CRT monitors and AC
power wiring.

Also note, their ability handle large signals at low frequencies without
gross distortion may be very limited.

No spec is given for this - unlike the famous brand name transformers that
spec everything.

This link shows a good quality 1:1 transformer that IS magnetically
shielded hence suitable for installing INSIDE an AC powered amplifier etc.
(prices in Aussie dollars) .

http://www.altronics.com.au/index.as...=item&id=M0706





....... Phil




-
Not bad, not bad. I wish I had a shop like that around here.


--
______________________________________________
Insanity is the inability to either tolerate or create ambiguity.

Palinurus wrote:

Pooh Bear wrote:

kt wrote:

Blimey! An earth hum, which I am assuming is what you are trying to
remove, is caused by the differing potentials between the two
"grounds". Quite simply, you assume that the ground on your stereo is
0V compared to the ground on your computer. It is quite possible to
have a 20VDC difference,

You reckon grounds may be 20V apart ! ?

thus causing the noise. To solve the problem,
you are quite right to assume the use of an audio 1:1 transformer,
though I would suggest buying an opto-isolation box which will be
taylored, though I would guess you are using a "cheap" sound card, as
more expesive ones will have the earthing problem sorted out.

The earthing problem has zero do with either cheap or expensive sound cards at
all and everything to do with the PC's power supply.

Graham
-
We're getting rather far afield here. I'm not going to replace my PC
power supply,

Unlikely to help much anyway. They're all similar.

and I'm not going to fake up something with opto-isolators
(which, BTW, have much worse linearity problems than transformers)

I forgot to mention that. Optos are fine for isoalting digital signals but a no-no
for audio.

and I'm not going to invest in a new, expensive sound card.

One with balanced inputs would fix the problem in a trice. In fact this *is* the
best answer.

I'm just looking
for the best sort of transformers for this application,

I dare say they'll be adequate, just not as good as you imagined.

and I'm not
interested in something with oxygen free pure silver wire smelted from
Thai holy relics wound on an unobtainium core and frozen in liquid xenon
by the light of the harvest moon.

Sensible approach to audiophool nonsense.

The only other thing I might try is
faking up a junkbox special linear +5 supply for the sound card separate
from the USB supply from the computer. Since it would be grounded at
only one point, there'd be little chance of a hum loop.

You're tackling the 'hum loop' in the wrong place there. The USB interface needs to
have its ground at the same potential as the PC.

The problem is the difference between the audio's ground and the PC's ground.

Graham

AZ Nomad wrote:

On Sat, 03 Jun 2006 12:19:33 -0700, David Nebenzahl wrote:

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.

For analogue ?

Graham

On Sun, 04 Jun 2006 00:26:43 GMT, Palinurus wrote:


AZ Nomad wrote:
On Sat, 03 Jun 2006 12:19:33 -0700, David Nebenzahl wrote:



Palinurus spake thus:


... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.


How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?


Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.


-
Great idea! Just send me about $400, and I'll do it!

More like $200. Must suck making minimum wage.

On Sun, 04 Jun 2006 07:52:18 +0100, Pooh Bear wrote:




AZ Nomad wrote:

On Sat, 03 Jun 2006 12:19:33 -0700, David Nebenzahl wrote:

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.

For analogue ?

Do you have a 30's analog computer?

AZ Nomad wrote:

On Sun, 04 Jun 2006 07:52:18 +0100, Pooh Bear wrote:

AZ Nomad wrote:

Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.

For analogue ?

Do you have a 30's analog computer?

That's a silly response. All audio starts off as and ends up as analogue.

Graham

"Pooh Bear" wrote in message
...


AZ Nomad wrote:

On Sun, 04 Jun 2006 07:52:18 +0100, Pooh Bear
wrote:

AZ Nomad wrote:

Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.

For analogue ?

Do you have a 30's analog computer?

That's a silly response. All audio starts off as and ends up as
analogue.

But I'd bet that nobody on this newsgroup has an analog
computer at home (or even at work).

On Sun, 04 Jun 2006 08:49:47 +0100, Pooh Bear wrote:




AZ Nomad wrote:

On Sun, 04 Jun 2006 07:52:18 +0100, Pooh Bear wrote:

AZ Nomad wrote:

Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.

For analogue ?

Do you have a 30's analog computer?

That's a silly response. All audio starts off as and ends up as analogue.

Answer the damn question. Do you have an analog computer?
If not, then the audio is in the digital domain and can stay digital
until it is in the receiver.

AZ Nomad wrote:

On Sun, 04 Jun 2006 08:49:47 +0100, Pooh Bear wrote:

AZ Nomad wrote:

On Sun, 04 Jun 2006 07:52:18 +0100, Pooh Bear wrote:

AZ Nomad wrote:

Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.

For analogue ?

Do you have a 30's analog computer?

That's a silly response. All audio starts off as and ends up as analogue.

Answer the damn question. Do you have an analog computer?
If not, then the audio is in the digital domain and can stay digital
until it is in the receiver.

Since the OP is connecting an analogue signal what I have or do is irrelevant.

Graham

Pooh Bear wrote:

Answer the damn question. Do you have an analog computer?
If not, then the audio is in the digital domain and can stay digital
until it is in the receiver.


Since the OP is connecting an analogue signal what I have or do is irrelevant.

Graham


-
True. My apologies, BTW, for being the proximate cause of his going off
like that.

--
______________________________________________
Kindness is not without its rocks ahead. People are apt to put it down
to an easy temper and seldom recognize it as the secret striving of a
generous nature; whilst, on the other hand, the ill-natured get credit
for all the evil they refrain from. -Honore De Balzac

Palinurus wrote:

Pooh Bear wrote:

Answer the damn question. Do you have an analog computer?
If not, then the audio is in the digital domain and can stay digital
until it is in the receiver.

Since the OP is connecting an analogue signal what I have or do is irrelevant.

Graham
-
True. My apologies, BTW, for being the proximate cause of his going off
like that.

No problem. He was just trying to hijack the thread to pursue another agenda.

Graham

On Sun, 04 Jun 2006 17:15:05 +0100, Pooh Bear wrote:




AZ Nomad wrote:

On Sun, 04 Jun 2006 08:49:47 +0100, Pooh Bear wrote:

AZ Nomad wrote:

On Sun, 04 Jun 2006 07:52:18 +0100, Pooh Bear wrote:

AZ Nomad wrote:

Better yet, use a sound card with an optical output and a receiver
with an optical s/pdif input.

For analogue ?

Do you have a 30's analog computer?

That's a silly response. All audio starts off as and ends up as analogue.

Answer the damn question. Do you have an analog computer?
If not, then the audio is in the digital domain and can stay digital
until it is in the receiver.

Since the OP is connecting an analogue signal what I have or do is irrelevant.

I was responding to:


Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

Pooh Bear spake thus:

David Nebenzahl wrote:

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

What would these acheive ?

The same thing as a chassis ground wire on a turntable (remember
those?)--hum elimination.


--
Any system of knowledge that is capable of listing films in order
of use of the word "****" is incapable of writing a good summary
and analysis of the Philippine-American War. And vice-versa.
This is an inviolable rule.

- Matthew White, referring to Wikipedia on his WikiWatch site
(http://users.erols.com/mwhite28/wikiwoo.htm)

In article , David Nebenzahl wrote:
Pooh Bear spake thus:

David Nebenzahl wrote:

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

What would these acheive ?

The same thing as a chassis ground wire on a turntable (remember
those?)--hum elimination.

The computer has signal grounds referenced to "ac ground". A turntable's
output is not referenced to ground, except for some capacitance.
When you ground the turntable, you are making a shield for
the signal. By adding another ground between PC and stereo,
you are just reducing the resistance, reducing noise, but not
elimnating it.

greg

David Nebenzahl wrote:

Pooh Bear spake thus:

David Nebenzahl wrote:

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

What would these acheive ?

The same thing as a chassis ground wire on a turntable (remember
those?)--hum elimination.

Very different. In the case of the turntable it was the only ground wire. Not so
in this case.

Graham

GregS spake thus:

In article , David Nebenzahl wrote:

Pooh Bear spake thus:

David Nebenzahl wrote:

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

What would these acheive ?

The same thing as a chassis ground wire on a turntable (remember
those?)--hum elimination.

The computer has signal grounds referenced to "ac ground". A turntable's
output is not referenced to ground, except for some capacitance.
When you ground the turntable, you are making a shield for
the signal. By adding another ground between PC and stereo,
you are just reducing the resistance, reducing noise, but not
elimnating it.

In any case, it would do no harm, and it might do some good, so why not?


--
Any system of knowledge that is capable of listing films in order
of use of the word "****" is incapable of writing a good summary
and analysis of the Philippine-American War. And vice-versa.
This is an inviolable rule.

- Matthew White, referring to Wikipedia on his WikiWatch site
(http://users.erols.com/mwhite28/wikiwoo.htm)

David Nebenzahl wrote:

GregS spake thus:

In article , David Nebenzahl wrote:

Pooh Bear spake thus:

David Nebenzahl wrote:

Palinurus spake thus:

... In my case, it seems to be the only practical way to break a hum
loop from an external USB sound card into the stereo.

How about running a ground wire between the PC and stereo? Reversing the
power plug on the receiver?

What would these acheive ?

The same thing as a chassis ground wire on a turntable (remember
those?)--hum elimination.

The computer has signal grounds referenced to "ac ground". A turntable's
output is not referenced to ground, except for some capacitance.
When you ground the turntable, you are making a shield for
the signal. By adding another ground between PC and stereo,
you are just reducing the resistance, reducing noise, but not
elimnating it.

In any case, it would do no harm, and it might do some good, so why not?

It's just the wrong 'solution' I'm afraid.

Graham