[Thomas M. Alldread]

Greetings:

I wonder if anyone in this group knows the industry standard
for subwoofer low level input interfaces? I would like to know the rms
(or ptp - please specify) input voltage level and input impedance.

Better still I would like to know who sets the standards for
consumer HiFi gear and where to obtain them. Are these standards
archived on the web? Any pointers to web site address(es) for
obtaining these standards would be appreciated.

Please reply to both my email address and to this forum to
help me ensure I don't miss any associated posts.

Many thanks in advance!
Tom Alldread

[Richard Crowley]

"Thomas M. Alldread" wrote ...
I wonder if anyone in this group knows the industry standard
for subwoofer low level input interfaces? I would like to know the rms
(or ptp - please specify) input voltage level and input impedance.

Does "low level" mean "line level" (vs. "speaker level")?
Just guessing because otherwise "low level" and "line level"
(which you seem to be asking about) seem incongrouous.

Better still I would like to know who sets the standards for
consumer HiFi gear and where to obtain them. Are these standards
archived on the web? Any pointers to web site address(es) for
obtaining these standards would be appreciated.

http://en.wikipedia.org/wiki/Line_level
The world may not be as "standardized" as you would like.

The whole issue is somewhat academic as practice varies widely.
Perhaps if you mentioned a particular piece of gear and/or the
reason for your question?

[Thomas M. Alldread]

Greetings:

As a labor of love I am trying to repair/rebuild a 100W
amplifier built into a subwoofer speaker. Unfortunately I cannot find
a schematic for this "Paradigm Cinema Sub 0.2" subwoofer.

The subwoofer low level input is intended to be fed from a
surround sound, JVC receiver equipped with a sub woofer output. This
subwoofer output is internally fed from both left and right channels
which are mixed together and then low pass filtered to pass only low
frequency audio to the sub woofer output phono jack which resembles a
line output.

The output appears to have a high source impedance and a level
less than 100mV.

In my search to find specication standards for low level
subwoofer interfaces I ran across a sub woofer amplified speaker with
a specified low level input level of 75 mV rms and input impedance of
50KOhm. I think this one is probably similar.

In comparison to normal line outputs the level here appears to
be much less and the interface impedance seems relatively high.

The sub woofer was manufactured by Paradigm and is a model
"Cinima Sub 0.2". I wish for a schematic for the amplifier which is
built from discrete components.

The receiver/amplifier is a JVC MODEL RX-6042
AUDIO VIDEO CONTROL RECIEVER.

Thanks in advance to anyone who can enlighten me on typical
subwoofer low level interface operating levels and impedance.

Tom Alldread



On Sun, 2 Nov 2008 15:36:08 -0800, "Richard Crowley"
wrote:

"Thomas M. Alldread" wrote ...
I wonder if anyone in this group knows the industry standard
for subwoofer low level input interfaces? I would like to know the rms
(or ptp - please specify) input voltage level and input impedance.

Does "low level" mean "line level" (vs. "speaker level")?
Just guessing because otherwise "low level" and "line level"
(which you seem to be asking about) seem incongrouous.

Better still I would like to know who sets the standards for
consumer HiFi gear and where to obtain them. Are these standards
archived on the web? Any pointers to web site address(es) for
obtaining these standards would be appreciated.

http://en.wikipedia.org/wiki/Line_level
The world may not be as "standardized" as you would like.

The whole issue is somewhat academic as practice varies widely.
Perhaps if you mentioned a particular piece of gear and/or the
reason for your question?

[Kalman Rubinson[_3_]]

Buy an amp. Easier.
http://www.parts-express.com/webpage... 505&sm=1&so=1

http://www.mcmelectronics.com/search...er%20amplifier

Kal



On Tue, 04 Nov 2008 03:21:33 GMT, Thomas M. Alldread
wrote:

Greetings:

As a labor of love I am trying to repair/rebuild a 100W
amplifier built into a subwoofer speaker. Unfortunately I cannot find
a schematic for this "Paradigm Cinema Sub 0.2" subwoofer.

The subwoofer low level input is intended to be fed from a
surround sound, JVC receiver equipped with a sub woofer output. This
subwoofer output is internally fed from both left and right channels
which are mixed together and then low pass filtered to pass only low
frequency audio to the sub woofer output phono jack which resembles a
line output.

The output appears to have a high source impedance and a level
less than 100mV.

In my search to find specication standards for low level
subwoofer interfaces I ran across a sub woofer amplified speaker with
a specified low level input level of 75 mV rms and input impedance of
50KOhm. I think this one is probably similar.

In comparison to normal line outputs the level here appears to
be much less and the interface impedance seems relatively high.

The sub woofer was manufactured by Paradigm and is a model
"Cinima Sub 0.2". I wish for a schematic for the amplifier which is
built from discrete components.

The receiver/amplifier is a JVC MODEL RX-6042
AUDIO VIDEO CONTROL RECIEVER.

Thanks in advance to anyone who can enlighten me on typical
subwoofer low level interface operating levels and impedance.

Tom Alldread



On Sun, 2 Nov 2008 15:36:08 -0800, "Richard Crowley"
wrote:

"Thomas M. Alldread" wrote ...
I wonder if anyone in this group knows the industry standard
for subwoofer low level input interfaces? I would like to know the rms
(or ptp - please specify) input voltage level and input impedance.

Does "low level" mean "line level" (vs. "speaker level")?
Just guessing because otherwise "low level" and "line level"
(which you seem to be asking about) seem incongrouous.

Better still I would like to know who sets the standards for
consumer HiFi gear and where to obtain them. Are these standards
archived on the web? Any pointers to web site address(es) for
obtaining these standards would be appreciated.

http://en.wikipedia.org/wiki/Line_level
The world may not be as "standardized" as you would like.

The whole issue is somewhat academic as practice varies widely.
Perhaps if you mentioned a particular piece of gear and/or the
reason for your question?

[Chris Hornbeck]

On Mon, 03 Nov 2008 22:51:39 -0500, Kalman Rubinson
wrote:

Buy an amp. Easier.

It's especially unclear, even based on the murky standard of
this newsgroup, what, perzactly, the OP is intending to ask,
so your post seems the most appropriate response.

And, FWIW, there is no standard subwoofer input level, no
standard subwoofer crossover frequency or slope (even,
practically, within THX) and if there were it'd be bogus,
because nothing else is standardized...


The current "surround receiver" paradigm is a box that includes
bass management and a microphone. Although a long step below
an actual dedicated (meaning: incorporating the filter functions
and sensitivities of associated speaker drivers) crossover, it's
still a big step up from the crap-shoot that preceded it.

And both are still pretty much a wing and a prayer without
room mode damping. Hence the ongoing confusion - it's like
politicians talking about taxes - nothing actually true and
interesting can be said; it'd be too complicated for the audience's
attention span.


Integrating a "subwoofer" (actually *always* meaning a real
woofer in these discussions - crossover wavelengths comparable
to room dimensions are *not* negligible) to another speaker and their
resulting response simply *doesn't have* a simple answer. Much
as we all desire simple answers...


Much thanks, as always,
Chris Hornbeck

[Richard Crowley]

"Thomas M. Alldread" wrote ...
As a labor of love I am trying to repair/rebuild a 100W
amplifier built into a subwoofer speaker. Unfortunately I cannot find
a schematic for this "Paradigm Cinema Sub 0.2" subwoofer.

The subwoofer low level input is intended to be fed from a
surround sound, JVC receiver equipped with a sub woofer output. This
subwoofer output is internally fed from both left and right channels
which are mixed together and then low pass filtered to pass only low
frequency audio to the sub woofer output phono jack which resembles a
line output.

The output appears to have a high source impedance and a level
less than 100mV.

You are refering to the "subwoofer output" from the JVC
receiver? Agreed that 100mV seems unusually low.
What do you mean by "high source impedance"? As
measured how? I would expect source impedances
for consumer line level to be lower than 10K and more
on the order of 1K

So what happens if you swap the receiver and/or subwoofer
with annother?

Are you sure the low level is not a result of the LF content
of the program material?

Did this combination *ever* work properly in the past?
How do you know they are compatible? There was a
large body of info revealed from a Google search for:
subwoofer sensitivity

In my search to find specication standards for low level
subwoofer interfaces I ran across a sub woofer amplified speaker with
a specified low level input level of 75 mV rms and input impedance of
50KOhm. I think this one is probably similar.

In comparison to normal line outputs the level here appears to
be much less and the interface impedance seems relatively high.

75mV seems like a rather sensitive input.
Dunno why the 50K input impedance would be an issue?

The sub woofer was manufactured by Paradigm and is a model
"Cinima Sub 0.2". I wish for a schematic for the amplifier which is
built from discrete components.

There are newsgroups and other online forums where repair
of consumer electronics is the primary focus. You would
likely have better luck asking for repair information in one
of those forums. for example: news:sci.electronics.repair

The receiver/amplifier is a JVC MODEL RX-6042
AUDIO VIDEO CONTROL RECIEVER.

Thanks in advance to anyone who can enlighten me on typical
subwoofer low level interface operating levels and impedance.

It seems to me that simply trying the receiver with annother sub
or the sub with annother receiver would be much simpler and
faster than researching consumer line level practices.

[Chuck]

On Tue, 04 Nov 2008 03:21:33 GMT, Thomas M. Alldread
wrote:

Greetings:

As a labor of love I am trying to repair/rebuild a 100W
amplifier built into a subwoofer speaker. Unfortunately I cannot find
a schematic for this "Paradigm Cinema Sub 0.2" subwoofer.

The subwoofer low level input is intended to be fed from a
surround sound, JVC receiver equipped with a sub woofer output. This
subwoofer output is internally fed from both left and right channels
which are mixed together and then low pass filtered to pass only low
frequency audio to the sub woofer output phono jack which resembles a
line output.

The output appears to have a high source impedance and a level
less than 100mV.

In my search to find specication standards for low level
subwoofer interfaces I ran across a sub woofer amplified speaker with
a specified low level input level of 75 mV rms and input impedance of
50KOhm. I think this one is probably similar.

In comparison to normal line outputs the level here appears to
be much less and the interface impedance seems relatively high.

The sub woofer was manufactured by Paradigm and is a model
"Cinima Sub 0.2". I wish for a schematic for the amplifier which is
built from discrete components.

The receiver/amplifier is a JVC MODEL RX-6042
AUDIO VIDEO CONTROL RECIEVER.

Thanks in advance to anyone who can enlighten me on typical
subwoofer low level interface operating levels and impedance.

Tom Alldread



On Sun, 2 Nov 2008 15:36:08 -0800, "Richard Crowley"
wrote:

"Thomas M. Alldread" wrote ...
I wonder if anyone in this group knows the industry standard
for subwoofer low level input interfaces? I would like to know the rms
(or ptp - please specify) input voltage level and input impedance.

Does "low level" mean "line level" (vs. "speaker level")?
Just guessing because otherwise "low level" and "line level"
(which you seem to be asking about) seem incongrouous.

Better still I would like to know who sets the standards for
consumer HiFi gear and where to obtain them. Are these standards
archived on the web? Any pointers to web site address(es) for
obtaining these standards would be appreciated.

http://en.wikipedia.org/wiki/Line_level
The world may not be as "standardized" as you would like.

The whole issue is somewhat academic as practice varies widely.
Perhaps if you mentioned a particular piece of gear and/or the
reason for your question?



I worked for a Paradigm dealer for many years and Paradigm would'nt
supply us with subwoofer schematics. All sub amps went back to them
for repair. So unless their policy has changed recently, the chance
of getting a schematic is nil. Chuck

[jakdedert]

Thomas M. Alldread wrote:
Greetings:

As a labor of love I am trying to repair/rebuild a 100W
amplifier built into a subwoofer speaker. Unfortunately I cannot find
a schematic for this "Paradigm Cinema Sub 0.2" subwoofer.

The subwoofer low level input is intended to be fed from a
surround sound, JVC receiver equipped with a sub woofer output. This
subwoofer output is internally fed from both left and right channels
which are mixed together and then low pass filtered to pass only low
frequency audio to the sub woofer output phono jack which resembles a
line output.

The output appears to have a high source impedance and a level
less than 100mV.

In my search to find specication standards for low level
subwoofer interfaces I ran across a sub woofer amplified speaker with
a specified low level input level of 75 mV rms and input impedance of
50KOhm. I think this one is probably similar.

In comparison to normal line outputs the level here appears to
be much less and the interface impedance seems relatively high.

The sub woofer was manufactured by Paradigm and is a model
"Cinima Sub 0.2". I wish for a schematic for the amplifier which is
built from discrete components.

The receiver/amplifier is a JVC MODEL RX-6042
AUDIO VIDEO CONTROL RECIEVER.

Thanks in advance to anyone who can enlighten me on typical
subwoofer low level interface operating levels and impedance.

Tom Alldread



On Sun, 2 Nov 2008 15:36:08 -0800, "Richard Crowley"
wrote:

"Thomas M. Alldread" wrote ...
I wonder if anyone in this group knows the industry standard
for subwoofer low level input interfaces? I would like to know the rms
(or ptp - please specify) input voltage level and input impedance.
Does "low level" mean "line level" (vs. "speaker level")?
Just guessing because otherwise "low level" and "line level"
(which you seem to be asking about) seem incongrouous.

Better still I would like to know who sets the standards for
consumer HiFi gear and where to obtain them. Are these standards
archived on the web? Any pointers to web site address(es) for
obtaining these standards would be appreciated.
http://en.wikipedia.org/wiki/Line_level
The world may not be as "standardized" as you would like.

The whole issue is somewhat academic as practice varies widely.
Perhaps if you mentioned a particular piece of gear and/or the
reason for your question?


Component level testing until you find out what's not working, then
replacement would seem to be the best bet. If you can't find a
schematic, try to find one for something similar which uses the same (or
similar) components and reverse-engineer it.

Once you've got it making sounds again, inject a measured signal and
monitor the output. Once it starts clipping, whatever level you're
feeding it is your sensitivity spec. If that's too low for your system,
you'll either have to change some component values or add a stage of
amplification in order to drive it fully. If it's too high, pad it.

If none of this makes any sense to you (or you don't have a signal
generator, scope and dummy load), replace it....

jak

[Thomas M. Alldread]

Greetings:

Many thanks to all those that responded to my post on this
subject. I decided it may be of use to let everyone know that the
subwoofer is now repaired and doing its job nicely.

As I mentioned this was a labor of love repair job as the cost
to have it repaired would not have been economical.

Sometime in this woofers previous life a mouse had crawled in
through the base reflex port and got caught between the power switch
terminals and one end of the audio pre-amp board in the area of the
+/-12V regulators. This could be considered a "high end" mouse trap as
the mouse certainly never survived.

At the onset, before taking this task on, the distributer for
Paradigm audio products was contacted. They advised there were no
replacement boards available for this 4 (?) year old product,
schematics were proprietary and there was not any service depot
available for it.

About 3 square inches of the board was charred beyond
component identification. As there was no other option I decided to
try and repair it. To start I cut the charred area of the pcb away
with my Dremel tool which removed what I thought was probably just the
+/- 12V dual polarity power supply regulator. I built a new power
regulator daughter board using a couple of TO220 style variable
regulators. With this effort I managed to get it back to life, but
without sufficient sensitivity to work with the amplifier it was
purchased with.

Finally a few days ago I decided to byte the bullet and do
some reverse engineering. I drew out portions of the schematic by
tracing the components. The amplifier uses legacy, leaded components
which I found surprising but which made my job easier. The pre-amps
are made up from conventional LM324 and LM741 DIP package op amps. A
Cmos logic device is provided for muting.

The primary power supply is +/- 42V. When I built the
regulators off the pre-amp board I decided to leave this disconnected
from the preamp. Since the preamp is powered from the +/- 12V supply
and I thought the charred area I removed contained only the regulator
circuitry I thought the primary DC voltages were probably no longer
needed on the preamp board. My presumption was proven wrong as it
turns out the +/- 42V was also used to mute the amplifier until the
voltages stabilize during power up.

To make a long story short I ended up bypassing some of the
original mute protection and maximum level protection circuitry which
once had some components in the burnt region of the board. The
sensitivity is now around 20 - 50 mV p-t-p into a Z of 10K and it will
put out 80V ptp into the speaker before clipping which is well beyond
what the speaker can handle. One must now be careful to ensure the
power is off when hooking up the input cables else the speaker could
be blown with 60 Hz pickup.

I had never worked on an amplified subwoofer before and had no
idea that the inputs are so Hi Z and so sensitive! I expected, like
most I think, to find the Z around 600 Ohms and the level around 1V
ptp. I should also mentioned that the receiver is rated for 100W and I
don't imagine we were testing it at more than 10W. But scaling that
back it would still be 300 mV reference 1V at 100W. Had I measured the
receiver output at maximum I think I would have found it around 100 mV
ptp about 20dB down from normal line levels.

It seems odd that the industry has adopted such a low
interface level for a subwoofer which is subject to hum pickup.

In any event happiness is nice music now with lots of good
base!


Thanks again!
Tom Alldread