Questions for the student No. 141
 

A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.

Is this report what we would expect? What is the key mechanism at work
here? Suggest some ballpark values.

Newbies especially welcome.

Andre Jute
Invigilator

Questions for the student No. 141
 

"Andre Jute" wrote in message
ups.com...
A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.

Is this report what we would expect?

**Possibly. When connecting the two sources together, the results can be
expected to be unpredictable.

What is the key mechanism at work
here?

**A stupid operator.

Suggest some ballpark values.

**I would expect that the output impedances of the two sources would be
between 100 Ohms and 1,000 Ohms. You haven't listed any brand/model numbers,
nor the specs, so speculation is the order of the day.


Newbies especially welcome.

**Only a rank newbie would connect two sources together and expect anything
but disaster.

Trevor Wilson

Questions for the student No. 141
 

On Wed, 07 Nov 2007 13:54:31 -0800, Andre Jute
wrote:

A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.


It sounds as if it doesn't have parallal input ports at all (which
would be most unusual). It has an input port and a through port,
designed to link to a secong amplifier.

Questions for the student No. 141
 

Andre Jute wrote:

A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports".

You must have just discovered the word "PORT" it seems.

The word 'port' is only used by people who haven't a clue what it really is and
what to really call it.

Graham

Questions for the student No. 141
 

Laurence Payne wrote:

Andre Jute wrote:

A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.

It sounds as if it doesn't have parallal input ports at all (which
would be most unusual). It has an input port and a through port,
designed to link to a secong amplifier.

"input port" = *input*

The 'port word' is an obfuscational verbal device used by the clueless to try
and hide their incompetence and inadequacy. Widely used by Google Groupers.

Graham

Questions for the student No. 141
 

In article . com,
Andre Jute wrote:
A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.

Is this report what we would expect? What is the key mechanism at work
here? Suggest some ballpark values.

I assume they're not, of course, both inputs even although they are
parallel connected. One will be an input, one an output. I can't conceive
of any reason you'd want to parallel two different sources.

--
*The problem with the gene pool is that there is no lifeguard *

Dave Plowman London SW
To e-mail, change noise into sound.

Questions for the student No. 141
 

On Nov 7, 10:26 pm, Laurence Payne NOSPAMlpayne1ATdsl.pipex.com
wrote:
On Wed, 07 Nov 2007 13:54:31 -0800, Andre Jute
wrote:

A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.

It sounds as if it doesn't have parallal input ports at all (which
would be most unusual). It has an input port and a through port,
designed to link to a secong amplifier.

Bril. That's what the student is supposed to work out for himself.
It's a trick question. It's an amp to drive highvoltage electrostatic
headphones, and supply HV bias for the the diaphraghms. As such it has
to be inserted in existing chains. Therefore, through-ports.

I'm listening to Rachel Masters play Gliere's Harp Concerto on the
Stax SR-202 Headphones right now. It is a stunningly beautiful sound.
I recommend Stax headphones to anyone, especially those with small
listening spaces, or who listen late at night, as a cheap way to get
95 per cent of what Quad floorstanding electrostatics deliver.

Those of you in Europe needn't pay the exorbitant prices of the
official importers; you can import directly from Japan at a huge
saving. I wrote an article about my experiences with direct import of
Stax headphones which you can read he
http://www.head-fi.org/forums/showthread.php?t=215182

Andre Jute
"I was at a board meeting for the LA Chapter of the Audio Engineering
Society last night on XM Satellite radio audio and data transmission.
Sadly, we missed you there, and at the SMPTE and Acoustical Society
recent meetings as well. Everyone was asking, 'Where is that wonderful
Andre Jute? The world just doesn't rotate without him...'" -- John
Mayberry, Emmaco

Questions for the student No. 141
 

On Nov 8, 12:24 am, "Dave Plowman (News)"
wrote:
In article . com,
Andre Jute wrote:

A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.
Is this report what we would expect? What is the key mechanism at work
here? Suggest some ballpark values.

I assume they're not, of course, both inputs even although they are
parallel connected. One will be an input, one an output. I can't conceive
of any reason you'd want to parallel two different sources.

They're input and throughput sockets; it is a trick question. However,
I must say I'd rather have some switching capability than a
throughput, though I understand why it is designed as it is; see my
post to Laurence Payne. Sometimes i used the Stax headphones for
movies on my computer screen, sometimes for music from a Quad 66
player. Putting plugs in and pulling them again is a nuisance I can do
without.

--
*The problem with the gene pool is that there is no lifeguard *

Dave Plowman London SW
To e-mail, change noise into sound.

Andre Jute
"I was at a board meeting for the LA Chapter of the Audio Engineering
Society last night on XM Satellite radio audio and data transmission.
Sadly, we missed you there, and at the SMPTE and Acoustical Society
recent meetings as well. Everyone was asking, 'Where is that wonderful
Andre Jute? The world just doesn't rotate without him...'" -- John
Mayberry, Emmaco

Questions for the student No. 141
 

On Nov 7, 4:54 pm, Andre Jute wrote:
A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.

Is this report what we would expect? What is the key mechanism at work
here? Suggest some ballpark values.

Newbies especially welcome.

Andre Jute
Invigilator

So, you tried this by accident, got results that are utterly
predictable as no competent design would permit this to happen. That
second "port" is to drive a speaker amp as the amp you describe is for
headphones.

What are you, some kind of idiot that would attempt to look "smart" by
posing a stupid question?

Peter Wieck
Wyncote, PA

Questions for the student No. 141
 

On Wed, 07 Nov 2007 16:34:34 -0800, Andre Jute
wrote:

It sounds as if it doesn't have parallal input ports at all (which
would be most unusual). It has an input port and a through port,
designed to link to a secong amplifier.

Bril. That's what the student is supposed to work out for himself.
It's a trick question. It's an amp to drive highvoltage electrostatic
headphones, and supply HV bias for the the diaphraghms. As such it has
to be inserted in existing chains. Therefore, through-ports.

Not a trick question, but a misleadingly incorrect one. There are not
parallal input connections.

Questions for the student No. 141
 

Peter Wieck wrote:
On Nov 7, 4:54 pm, Andre Jute wrote:
A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.

Is this report what we would expect? What is the key mechanism at work
here? Suggest some ballpark values.

Newbies especially welcome.

Andre Jute
Invigilator

So, you tried this by accident, got results that are utterly
predictable as no competent design would permit this to happen. That
second "port" is to drive a speaker amp as the amp you describe is for
headphones.

What are you, some kind of idiot that would attempt to look "smart" by
posing a stupid question?

He usually asks these questions through West so as not to appear stupid
himself.
His next question will be how to put the magic smoke back in after doing
the same with power amps.

The best answer is a switch box.
Another method would be to put a 10k resistor in each cable; then if both
sources are powered up, they would see a 20k load and the amp would see
aproximately a 5k source resistance. With only one source powered,
results are unpredictable.

--
Eiron.

Questions for the student No. 141
 

Andre Jute wrote:
A STAX 252A amp, same as the 2050 sold in anglo markets, has parallel-
connected input ports, called "through ports". With both sets of
inputs connected, one to a CD player, one to a computer output, the
sound is muted, dulled. With the computer leads pulled, the sound is
louder and brighter.

Is this report what we would expect? What is the key mechanism at work
here? Suggest some ballpark values.


"This is left as an exercise for the student" :-)

For more fun, consider when one of the sources isn't even powered up.

The typical op-amp output stage has ESD protection diodes connected to
the power rails. So anything exceeding about 0.7V above or below the
respective positive or negative supplies will get clamped. And from 0.4
to 0.7 it's gonna be rather nonlinear. So it's still gonna sound really
bad...

Questions for the student No. 141
 

E

You must have just discovered the word "PORT" it seems.

The word 'port' is only used by people who haven't a clue what it really is and
what to really call it.


No, it's used by people who prefer port to vermouth... :-)

Questions for the student No. 141
 

Another method would be to put a 10k resistor in each cable; then if both
sources are powered up, they would see a 20k load and the amp would see
aproximately a 5k source resistance. With only one source powered,
results are unpredictable.


I've done that back in my distant past...

Works fine if both sources are powered up, and one outputting silence,
but if one source is not powered up, the ESD diodes in its output op-amp
will start to conduct at above and below 0.7V (as the supplies are at
zero volts), and that will make for horrid non-linear clipping or sorts.

Questions for the student No. 141
 

On 8 nov, 01:48, Andre Jute wrote:
"Where is that wonderful Andre Jute? The world just doesn't rotate without him...'" -- John
Mayberry, Emmaco

"Apprenez que tout flatteur Vit aux dépens de celui qui l'écoute" Jean
de La Fontaine.

Questions for the student No. 141
 

On Nov 8, 8:05 pm, robert casey wrote:
Eeyore wrote:

You must have just discovered the word "PORT" it seems.

The word 'port' is only used by people who haven't a clue what it really is and
what to really call it.

No, it's used by people who prefer port to vermouth... :-)

And by the gin-and-pink drinkers too, as in POSH -- port out,
starboard home...

....out being India, home being England, and the side of the ship being
important because it will be in the shade.

Andre Jute

Questions for the student No. 141
 

Andre Jute wrote:
On Nov 8, 8:05 pm, robert casey wrote:
Eeyore wrote:

You must have just discovered the word "PORT" it seems.
The word 'port' is only used by people who haven't a clue what it really is and
what to really call it.
No, it's used by people who prefer port to vermouth... :-)

And by the gin-and-pink drinkers too, as in POSH -- port out,
starboard home...

...out being India, home being England, and the side of the ship being
important because it will be in the shade.

False etymology.
And before the opening of the Suez Canal it would have been SOPH.

--
Eiron.