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Jim G
 
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Default Stereo Mini Plugs to RCA Plugs to Receiver Aux In-- Signal Degradation?

Hello. I'm in the process of putting together a PC-Stereo System setup
for my daughter. Budget limitations confine me to using a mini stereo
system (Panasonic SCM PM39D,
http://www.jr.com/JRProductPage.process?Product=3985852), which rules
out using a digital link from her PC soundcard to the receiver (as no
mini systems, to my knowledge, offer digital input).

Ideally I would like to use a stereo mini plug adapter at the soundcard
which includes an input for computer speakers as well as branching off
into left and right RCA plugs for the stereo (see picture here, listed
as "Option 2": http://www.pcstereolink.com/stereocomputer.html).

Can any of you tell me whether this sort of adapter involves any signal
degradation compared to a normal Y-adapter? Also, I'm thinking it might
be more flexible to use an adapter that terminates in female RCAs and
then use an extended Male-to-Male RCA cable to go the rest of the way.
Since this uses an additional coupling, does it entail signal loss or
weakening?

Thx,
JG
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Richard Crowley
 
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"Jim G" wrote...
... mini stereo system (Panasonic SCM PM39D,
http://www.jr.com/JRProductPage.process?Product=3985852),

...stereo mini plug adapter...(... "Option 2":
http://www.pcstereolink.com/stereocomputer.html).

Can any of you tell me whether this sort of adapter involves
any signal degradation


Unlikely any that you would hear on your mini system.

compared to a normal Y-adapter?


It *is* a Y-adapter. Dunno why it would be any different
than a "normal" one (whatever that is?)

Also, I'm thinking it might be more flexible to use an
adapter that terminates in female RCAs and then use an
extended Male-to-Male RCA cable to go the rest of the
way. Since this uses an additional coupling, does it entail
signal loss or weakening?


Not unless the connectors are falling apart. 95% of the quality
of the sound is those speakers. You are worrying about 1/10
of one percent. I wouldn't even give it a second thought.

There is a small possibility that the computer sound card
won't like driving both the computer speakers AND the
input to your mini system, but even that is a 2% chance,
very unlikely in my opinion.
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Laurence Payne
 
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On Thu, 07 Apr 2005 19:47:57 -0400, Jim G
wrote:

Ideally I would like to use a stereo mini plug adapter at the soundcard
which includes an input for computer speakers as well as branching off
into left and right RCA plugs for the stereo (see picture here, listed
as "Option 2": http://www.pcstereolink.com/stereocomputer.html).

Can any of you tell me whether this sort of adapter involves any signal
degradation compared to a normal Y-adapter? Also, I'm thinking it might
be more flexible to use an adapter that terminates in female RCAs and
then use an extended Male-to-Male RCA cable to go the rest of the way.
Since this uses an additional coupling, does it entail signal loss or
weakening?



Electrically, this IS a "normal Y-adaptor".
We're not talking hi-fi here. As long as you keep the connectors
clean I doubt quality will be an issue.

Two thoughts:

If she's connecting computer sound to a stereo system, does she really
need an additional pair of crappy computer speakers? Why?

The 3.5mm stereo minijack is possibly the least robust audio
connection in general use. (Well OK - maybe the old DIN speaker plug
was even crappier :-) When the socket on your soundcard collapses
internally, a repair will probably not be practical. I would avoid
attaching anything heavier than the standard plug.


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I would beg to differ. Maybe it's a question of "how hi" is hi-fi, but
I think you should try listening to the system with one of the output
cables disconnected from the "Y", and then connect the second output
cable to see if you can tell the difference. I can tell quite a
difference when I do this. The impedance mismatch resulting from
connecting the two output cables in parallel really drags down the
signal's amplitude and causes noticeable distortion. If you want to do
it right insert, for example, a $30.00 Behringer mixer at this point
just to isolate the amp output from the two devices that you want to
drive. Another possibility is to construct a proper terminator to
eliminate the impedance mismatch, but that will involve some signal
loss, so the little mixer seems like the way to go.

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Richard Crowley
 
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bcrowell wrote ...
I would beg to differ. Maybe it's a question of "how hi" is hi-fi, but
I think you should try listening to the system with one of the output
cables disconnected from the "Y", and then connect the second output
cable to see if you can tell the difference. I can tell quite a
difference when I do this. The impedance mismatch resulting from
connecting the two output cables in parallel really drags down the
signal's amplitude and causes noticeable distortion. If you want to do
it right insert, for example, a $30.00 Behringer mixer at this point
just to isolate the amp output from the two devices that you want to
drive. Another possibility is to construct a proper terminator to
eliminate the impedance mismatch, but that will involve some signal
loss, so the little mixer seems like the way to go.


I got the impression the OP wanted to feed the line-level sound output
from his computer into two amplifiers, his little plastic computer speakers,
and the mini-stereo system. Since most modern audio circuits have pretty
low impedance (~1K) and most input circuits are rather high impedance
(~10K), it seems pretty unlikely that the computer output would have a
problem with these two pretty high impedance loads. This is traditionally
called "bridging".

If he is trying to combine two different outputs into a single input, then
I'd agree that a passive "Y-adapter" is likely a poor choice.




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Hi, Richard. Well, once recently I tried "Y"'ing up the tape output of
my phono preamp so as to make it feed two supposedly high-impedance
devices, and when I "A-B"'d the arrangement I could hear noticeable
signal degradation.

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Richard Crowley
 
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bcrowell wrote ...
Hi, Richard. Well, once recently I tried "Y"'ing up the
tape output of my phono preamp so as to make it feed
two supposedly high-impedance devices, and when I
"A-B"'d the arrangement I could hear noticeable signal
degradation.


There are single-case examples all over the map because
there are no hard standards for consumer equipment. OTOH,
I believe you have a better than even chance that a modern,
low-impedance source can drive several high-impedance
loads without significant side-effects.

For your "once" I can cite scores of times I have done the
same thing without any problems. But you make a good
point that you can't rely on it.
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Jim G
 
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Laurence Payne wrote:
[snip]



Electrically, this IS a "normal Y-adaptor".
We're not talking hi-fi here. As long as you keep the connectors
clean I doubt quality will be an issue.

Two thoughts:

If she's connecting computer sound to a stereo system, does she really
need an additional pair of crappy computer speakers? Why?

The 3.5mm stereo minijack is possibly the least robust audio
connection in general use. (Well OK - maybe the old DIN speaker plug
was even crappier :-) When the socket on your soundcard collapses
internally, a repair will probably not be practical. I would avoid
attaching anything heavier than the standard plug.


Thx for your answers guys. Richard and Laurence asked why I thought the
pictured piece is not a "normal" Y-adapter. It just seemed that this
extra hole sitting there on the head of this thing could affect the
flow. Glad to hear no one has noticed such.

Does she really need an additional pair of crappy computer

speakers? My reasoning here is it may not be a bad idea to keep the
ministereo powered down if she's gonna be doing serious stuff for an
extended time, yet might still want system sounds at these times, or
even audio for things like super-compressed Real audio, etc., where
source quality is so woeful it doesn't matter if the speakers are made
of Reynolds Wrap. Seems better to give the Panasonic a rest once in a
while, although I understand the thing stil draws power when power
button is off, dang it.

Yeah 3.5mm jacks seem lamentable. I guess for another $10 or so I could
go for an M-Audio card with RCA outputs. Would you do that?

Thx again all, JG
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