I have a Perreaux 3400B power amp (the 'B' stands for Balanced).

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

I am not an electrical engineer, but I do have a digital multimeter at
my disposal and I'm pretty good with a soldering iron.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Help much appreciated,

Clytemnestra
rec.audio.pro
rec.audio.tech

Probably the same. You could put a resistor (ex. 47k) in series with the
input, and apply a sine-wave input. Measure voltage across the resistor, and
across the amp input. The ratio of the two (AC) voltages will tell you the
impedance relative to your resistor. Could vary at different frequencies,
though.

I'm not sure how you'd measure input impedance for the balanced input. Maybe
one of the engineer types around here could help......and, I suppose,
correct me if my little measurement scenario has holes in it. :-)

I suspect it would be a multiple, like 1/2 or twice the value, etc.


Mark Z.
(repair tech, not engineer)

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Clytemnestra" wrote in message
...
I have a Perreaux 3400B power amp (the 'B' stands for Balanced).

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

I am not an electrical engineer, but I do have a digital multimeter at
my disposal and I'm pretty good with a soldering iron.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Help much appreciated,

Clytemnestra
rec.audio.pro
rec.audio.tech

Probably the same. You could put a resistor (ex. 47k) in series with the
input, and apply a sine-wave input. Measure voltage across the resistor, and
across the amp input. The ratio of the two (AC) voltages will tell you the
impedance relative to your resistor. Could vary at different frequencies,
though.

I'm not sure how you'd measure input impedance for the balanced input. Maybe
one of the engineer types around here could help......and, I suppose,
correct me if my little measurement scenario has holes in it. :-)

I suspect it would be a multiple, like 1/2 or twice the value, etc.


Mark Z.
(repair tech, not engineer)

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Clytemnestra" wrote in message
...
I have a Perreaux 3400B power amp (the 'B' stands for Balanced).

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

I am not an electrical engineer, but I do have a digital multimeter at
my disposal and I'm pretty good with a soldering iron.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Help much appreciated,

Clytemnestra
rec.audio.pro
rec.audio.tech

Probably the same. You could put a resistor (ex. 47k) in series with the
input, and apply a sine-wave input. Measure voltage across the resistor, and
across the amp input. The ratio of the two (AC) voltages will tell you the
impedance relative to your resistor. Could vary at different frequencies,
though.

I'm not sure how you'd measure input impedance for the balanced input. Maybe
one of the engineer types around here could help......and, I suppose,
correct me if my little measurement scenario has holes in it. :-)

I suspect it would be a multiple, like 1/2 or twice the value, etc.


Mark Z.
(repair tech, not engineer)

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Clytemnestra" wrote in message
...
I have a Perreaux 3400B power amp (the 'B' stands for Balanced).

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

I am not an electrical engineer, but I do have a digital multimeter at
my disposal and I'm pretty good with a soldering iron.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Help much appreciated,

Clytemnestra
rec.audio.pro
rec.audio.tech

Probably the same. You could put a resistor (ex. 47k) in series with the
input, and apply a sine-wave input. Measure voltage across the resistor, and
across the amp input. The ratio of the two (AC) voltages will tell you the
impedance relative to your resistor. Could vary at different frequencies,
though.

I'm not sure how you'd measure input impedance for the balanced input. Maybe
one of the engineer types around here could help......and, I suppose,
correct me if my little measurement scenario has holes in it. :-)

I suspect it would be a multiple, like 1/2 or twice the value, etc.


Mark Z.
(repair tech, not engineer)

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Clytemnestra" wrote in message
...
I have a Perreaux 3400B power amp (the 'B' stands for Balanced).

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

I am not an electrical engineer, but I do have a digital multimeter at
my disposal and I'm pretty good with a soldering iron.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Help much appreciated,

Clytemnestra
rec.audio.pro
rec.audio.tech

Clytemnestra wrote:

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

Do you have a schematic for it? The dominant issue is probably the
input shunt resistor. It's probably reasonably high.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

No, it's probably easier to work it out from the circuit. You can find
the input resistance with the tools you have, but that may or may not
be useful depending on the way the input is designed.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Probably not. Why do you care anyway? This isn't 1950 any longer,
when everyone was doing constant-impedance lines for maximum power
transfer. Today as long as the output Z is lower than the input Z,
everything is fine. Unless you're mating to something with a transformer
coupled output, of course.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Clytemnestra wrote:

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

Do you have a schematic for it? The dominant issue is probably the
input shunt resistor. It's probably reasonably high.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

No, it's probably easier to work it out from the circuit. You can find
the input resistance with the tools you have, but that may or may not
be useful depending on the way the input is designed.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Probably not. Why do you care anyway? This isn't 1950 any longer,
when everyone was doing constant-impedance lines for maximum power
transfer. Today as long as the output Z is lower than the input Z,
everything is fine. Unless you're mating to something with a transformer
coupled output, of course.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Clytemnestra wrote:

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

Do you have a schematic for it? The dominant issue is probably the
input shunt resistor. It's probably reasonably high.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

No, it's probably easier to work it out from the circuit. You can find
the input resistance with the tools you have, but that may or may not
be useful depending on the way the input is designed.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Probably not. Why do you care anyway? This isn't 1950 any longer,
when everyone was doing constant-impedance lines for maximum power
transfer. Today as long as the output Z is lower than the input Z,
everything is fine. Unless you're mating to something with a transformer
coupled output, of course.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Clytemnestra wrote:

It's a modified version of the 3400
(http://www.perreaux.com/files/080-3400.pdf), which was specially
configured with XLR inputs, so it could be used in a recording studio
environment. (I was told this sub-line was specifically made for Hit
Factory) - It has both XLR and RCA inputs on the back and you must
chose with a little toggle-switch.

Problem is, the amp has been out of production since 1995, there was
no manual published for it and the Perreaux engineers I contacted
simply don't remember what the input impedance was.

Do you have a schematic for it? The dominant issue is probably the
input shunt resistor. It's probably reasonably high.

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

No, it's probably easier to work it out from the circuit. You can find
the input resistance with the tools you have, but that may or may not
be useful depending on the way the input is designed.

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Probably not. Why do you care anyway? This isn't 1950 any longer,
when everyone was doing constant-impedance lines for maximum power
transfer. Today as long as the output Z is lower than the input Z,
everything is fine. Unless you're mating to something with a transformer
coupled output, of course.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Clyt,

My first question is why you even want to know the input impedance. It's
surely high enough to not be an issue when driving it from any resonable
preamp.

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after. Even easier is to use a potentiometer instead of a fixed
resistor. I'd start with a 100K variable resistor and adjust the sine wave
oscillator to put out one volt. Then move the voltmeter to the amp's side of
the resistor and adjust the resistor until you read 0.5 volts. The amp's
input impedance is whatever the resistor's value is set to. If you can't get
it down to 0.5 volts try a 500K variable resistor instead, then repeat.

--Ethan

Clyt,

My first question is why you even want to know the input impedance. It's
surely high enough to not be an issue when driving it from any resonable
preamp.

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after. Even easier is to use a potentiometer instead of a fixed
resistor. I'd start with a 100K variable resistor and adjust the sine wave
oscillator to put out one volt. Then move the voltmeter to the amp's side of
the resistor and adjust the resistor until you read 0.5 volts. The amp's
input impedance is whatever the resistor's value is set to. If you can't get
it down to 0.5 volts try a 500K variable resistor instead, then repeat.

--Ethan

Clyt,

My first question is why you even want to know the input impedance. It's
surely high enough to not be an issue when driving it from any resonable
preamp.

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after. Even easier is to use a potentiometer instead of a fixed
resistor. I'd start with a 100K variable resistor and adjust the sine wave
oscillator to put out one volt. Then move the voltmeter to the amp's side of
the resistor and adjust the resistor until you read 0.5 volts. The amp's
input impedance is whatever the resistor's value is set to. If you can't get
it down to 0.5 volts try a 500K variable resistor instead, then repeat.

--Ethan

Clyt,

My first question is why you even want to know the input impedance. It's
surely high enough to not be an issue when driving it from any resonable
preamp.

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after. Even easier is to use a potentiometer instead of a fixed
resistor. I'd start with a 100K variable resistor and adjust the sine wave
oscillator to put out one volt. Then move the voltmeter to the amp's side of
the resistor and adjust the resistor until you read 0.5 volts. The amp's
input impedance is whatever the resistor's value is set to. If you can't get
it down to 0.5 volts try a 500K variable resistor instead, then repeat.

--Ethan

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

Clytemnestra

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

Clytemnestra

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

Clytemnestra

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

Clytemnestra

Clytemnestra wrote:

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

Frankly, this exceprt makes the gear seem to be expensive junk.

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

You have the right idea, but it gets even worse. Many multimeters measure
AC voltage accurately only at line frequencies, ie, 50 to 60 Hz. You'll
probably need an oscilloscope to perform the test Ethan suggests.

Clytemnestra

--
================================================== ======================
Michael Kesti | "And like, one and one don't make
| two, one and one make one."
| - The Who, Bargain

Clytemnestra wrote:

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

Frankly, this exceprt makes the gear seem to be expensive junk.

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

You have the right idea, but it gets even worse. Many multimeters measure
AC voltage accurately only at line frequencies, ie, 50 to 60 Hz. You'll
probably need an oscilloscope to perform the test Ethan suggests.

Clytemnestra

--
================================================== ======================
Michael Kesti | "And like, one and one don't make
| two, one and one make one."
| - The Who, Bargain

Clytemnestra wrote:

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

Frankly, this exceprt makes the gear seem to be expensive junk.

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

You have the right idea, but it gets even worse. Many multimeters measure
AC voltage accurately only at line frequencies, ie, 50 to 60 Hz. You'll
probably need an oscilloscope to perform the test Ethan suggests.

Clytemnestra

--
================================================== ======================
Michael Kesti | "And like, one and one don't make
| two, one and one make one."
| - The Who, Bargain

Clytemnestra wrote:

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

Frankly, this exceprt makes the gear seem to be expensive junk.

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

You have the right idea, but it gets even worse. Many multimeters measure
AC voltage accurately only at line frequencies, ie, 50 to 60 Hz. You'll
probably need an oscilloscope to perform the test Ethan suggests.

Clytemnestra

--
================================================== ======================
Michael Kesti | "And like, one and one don't make
| two, one and one make one."
| - The Who, Bargain

Here are three "definitive" answers...


One

Since the 3400 is rated at 47k, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Yup, absolutely. The 3400B version almost certainly "piggybacks" the balanced
input on top of the 3400's design. It's highly unlikely they would have changed
the unbalanced input.


Two

Regardless of the amp's input impedance, you're still going to have to LISTEN to
the system and decide whether it SOUNDS right -- as Infinity's instructions
point out.

Set the DIP (not dip) switches to the 47k position, and spend time listening to
a wide range of program material. Then try the 70-80k position and the 26-40k
positions to see what, if any, differences you hear.

Basically, you're listening for a proper blend between the woofer and the
satellites, and the "right" amount of energy in the 140Hz region. These
characteristics are affected by both the crossover frequency (as set by the DIP
switches) and the woofer level.


Three

Borrow a third-octave analyzer.

If you live in the Seattle area, I'd be happy to stop by and set it up for you,
for the cost of mileage and a free lunch. Just don't start prophesying, okay?

Here are three "definitive" answers...


One

Since the 3400 is rated at 47k, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Yup, absolutely. The 3400B version almost certainly "piggybacks" the balanced
input on top of the 3400's design. It's highly unlikely they would have changed
the unbalanced input.


Two

Regardless of the amp's input impedance, you're still going to have to LISTEN to
the system and decide whether it SOUNDS right -- as Infinity's instructions
point out.

Set the DIP (not dip) switches to the 47k position, and spend time listening to
a wide range of program material. Then try the 70-80k position and the 26-40k
positions to see what, if any, differences you hear.

Basically, you're listening for a proper blend between the woofer and the
satellites, and the "right" amount of energy in the 140Hz region. These
characteristics are affected by both the crossover frequency (as set by the DIP
switches) and the woofer level.


Three

Borrow a third-octave analyzer.

If you live in the Seattle area, I'd be happy to stop by and set it up for you,
for the cost of mileage and a free lunch. Just don't start prophesying, okay?

Here are three "definitive" answers...


One

Since the 3400 is rated at 47k, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Yup, absolutely. The 3400B version almost certainly "piggybacks" the balanced
input on top of the 3400's design. It's highly unlikely they would have changed
the unbalanced input.


Two

Regardless of the amp's input impedance, you're still going to have to LISTEN to
the system and decide whether it SOUNDS right -- as Infinity's instructions
point out.

Set the DIP (not dip) switches to the 47k position, and spend time listening to
a wide range of program material. Then try the 70-80k position and the 26-40k
positions to see what, if any, differences you hear.

Basically, you're listening for a proper blend between the woofer and the
satellites, and the "right" amount of energy in the 140Hz region. These
characteristics are affected by both the crossover frequency (as set by the DIP
switches) and the woofer level.


Three

Borrow a third-octave analyzer.

If you live in the Seattle area, I'd be happy to stop by and set it up for you,
for the cost of mileage and a free lunch. Just don't start prophesying, okay?

Here are three "definitive" answers...


One

Since the 3400 is rated at 47k, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

Yup, absolutely. The 3400B version almost certainly "piggybacks" the balanced
input on top of the 3400's design. It's highly unlikely they would have changed
the unbalanced input.


Two

Regardless of the amp's input impedance, you're still going to have to LISTEN to
the system and decide whether it SOUNDS right -- as Infinity's instructions
point out.

Set the DIP (not dip) switches to the 47k position, and spend time listening to
a wide range of program material. Then try the 70-80k position and the 26-40k
positions to see what, if any, differences you hear.

Basically, you're listening for a proper blend between the woofer and the
satellites, and the "right" amount of energy in the 140Hz region. These
characteristics are affected by both the crossover frequency (as set by the DIP
switches) and the woofer level.


Three

Borrow a third-octave analyzer.

If you live in the Seattle area, I'd be happy to stop by and set it up for you,
for the cost of mileage and a free lunch. Just don't start prophesying, okay?

On Sun, 11 Jan 2004 07:34:09 -0800, "Michael R. Kesti"
wrote:

Clytemnestra wrote:

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

Frankly, this exceprt makes the gear seem to be expensive junk.

Here's a clue - it is......................

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

You have the right idea, but it gets even worse. Many multimeters measure
AC voltage accurately only at line frequencies, ie, 50 to 60 Hz. You'll
probably need an oscilloscope to perform the test Ethan suggests.

Very true. And of course, he doesn't need to know the input impedance,
so long as it's more than say 10k ohms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Sun, 11 Jan 2004 07:34:09 -0800, "Michael R. Kesti"
wrote:

Clytemnestra wrote:

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

Frankly, this exceprt makes the gear seem to be expensive junk.

Here's a clue - it is......................

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

You have the right idea, but it gets even worse. Many multimeters measure
AC voltage accurately only at line frequencies, ie, 50 to 60 Hz. You'll
probably need an oscilloscope to perform the test Ethan suggests.

Very true. And of course, he doesn't need to know the input impedance,
so long as it's more than say 10k ohms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Sun, 11 Jan 2004 07:34:09 -0800, "Michael R. Kesti"
wrote:

Clytemnestra wrote:

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

Frankly, this exceprt makes the gear seem to be expensive junk.

Here's a clue - it is......................

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

You have the right idea, but it gets even worse. Many multimeters measure
AC voltage accurately only at line frequencies, ie, 50 to 60 Hz. You'll
probably need an oscilloscope to perform the test Ethan suggests.

Very true. And of course, he doesn't need to know the input impedance,
so long as it's more than say 10k ohms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Sun, 11 Jan 2004 07:34:09 -0800, "Michael R. Kesti"
wrote:

Clytemnestra wrote:

On Sun, 11 Jan 2004 09:16:15 -0500, "Ethan Winer" ethanw at
ethanwiner dot com wrote:

My first question is why you even want to know the input impedance.

It's necessary to know in order to correctly adjust some dip switches
on the crossover control unit for an Infinity Modulus sub/sat system.
Here is the relevant passage from the owners manual:

http://home.nyc.rr.com/acidrock212/infinity-ecu.jpg

Frankly, this exceprt makes the gear seem to be expensive junk.

Here's a clue - it is......................

That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

You have the right idea, but it gets even worse. Many multimeters measure
AC voltage accurately only at line frequencies, ie, 50 to 60 Hz. You'll
probably need an oscilloscope to perform the test Ethan suggests.

Very true. And of course, he doesn't need to know the input impedance,
so long as it's more than say 10k ohms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article writes:

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

The way I measure input impedance for the purpose of a review (not a
lab certified method, just to get an idea of what it's good for) is
pretty simple.

I use a low impedance (a couple of ohms) signal generator as a source,
and connect a variable resistor between the source and the unit's
input connector. I measure the voltage at the unit's input (past the
resistor). Starting with the variable resistor at zero (short
circuit), I adjust the resistor until the voltage drops in half. This
means that the source voltage (out of the generator) is dropped
equally across the variable resistor and the unit's input impedance.

Then I just measure the resistor. That's the input impedance, give or
take a bit.

For a balanced input, I unbalance it, connecting the low side to the
low side of the generator and putting a resistor in series with the
high side of the input. Make the measurement as above, and double it
for the impedance between the high and low terminals (since according
to the definition of "balanced" they'll both have the same input
impedance with reference to a common point).

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

No assumption is safe. I don't know what this unit it. Howver, 47K is
a fairly common input impedance for a magnetic phono cartridge input
since many of them like to see that load for proper damping. Since I
don't know what it is that you're testing, I don't know if this is a
good guess or not. If it's a serious audiophile phono preamp, the
balanced input might be for a moving coil cartridge which wants to see
a much lower input impedance.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

The way I measure input impedance for the purpose of a review (not a
lab certified method, just to get an idea of what it's good for) is
pretty simple.

I use a low impedance (a couple of ohms) signal generator as a source,
and connect a variable resistor between the source and the unit's
input connector. I measure the voltage at the unit's input (past the
resistor). Starting with the variable resistor at zero (short
circuit), I adjust the resistor until the voltage drops in half. This
means that the source voltage (out of the generator) is dropped
equally across the variable resistor and the unit's input impedance.

Then I just measure the resistor. That's the input impedance, give or
take a bit.

For a balanced input, I unbalance it, connecting the low side to the
low side of the generator and putting a resistor in series with the
high side of the input. Make the measurement as above, and double it
for the impedance between the high and low terminals (since according
to the definition of "balanced" they'll both have the same input
impedance with reference to a common point).

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

No assumption is safe. I don't know what this unit it. Howver, 47K is
a fairly common input impedance for a magnetic phono cartridge input
since many of them like to see that load for proper damping. Since I
don't know what it is that you're testing, I don't know if this is a
good guess or not. If it's a serious audiophile phono preamp, the
balanced input might be for a moving coil cartridge which wants to see
a much lower input impedance.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

The way I measure input impedance for the purpose of a review (not a
lab certified method, just to get an idea of what it's good for) is
pretty simple.

I use a low impedance (a couple of ohms) signal generator as a source,
and connect a variable resistor between the source and the unit's
input connector. I measure the voltage at the unit's input (past the
resistor). Starting with the variable resistor at zero (short
circuit), I adjust the resistor until the voltage drops in half. This
means that the source voltage (out of the generator) is dropped
equally across the variable resistor and the unit's input impedance.

Then I just measure the resistor. That's the input impedance, give or
take a bit.

For a balanced input, I unbalance it, connecting the low side to the
low side of the generator and putting a resistor in series with the
high side of the input. Make the measurement as above, and double it
for the impedance between the high and low terminals (since according
to the definition of "balanced" they'll both have the same input
impedance with reference to a common point).

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

No assumption is safe. I don't know what this unit it. Howver, 47K is
a fairly common input impedance for a magnetic phono cartridge input
since many of them like to see that load for proper damping. Since I
don't know what it is that you're testing, I don't know if this is a
good guess or not. If it's a serious audiophile phono preamp, the
balanced input might be for a moving coil cartridge which wants to see
a much lower input impedance.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

In article writes:

Q1: Is it possible to take a measurement with the tools I have, that
will answer my question? If so, please give as detailed instructions
as you can.

The way I measure input impedance for the purpose of a review (not a
lab certified method, just to get an idea of what it's good for) is
pretty simple.

I use a low impedance (a couple of ohms) signal generator as a source,
and connect a variable resistor between the source and the unit's
input connector. I measure the voltage at the unit's input (past the
resistor). Starting with the variable resistor at zero (short
circuit), I adjust the resistor until the voltage drops in half. This
means that the source voltage (out of the generator) is dropped
equally across the variable resistor and the unit's input impedance.

Then I just measure the resistor. That's the input impedance, give or
take a bit.

For a balanced input, I unbalance it, connecting the low side to the
low side of the generator and putting a resistor in series with the
high side of the input. Make the measurement as above, and double it
for the impedance between the high and low terminals (since according
to the definition of "balanced" they'll both have the same input
impedance with reference to a common point).

Q2: Since the 3400 is rated at 47kO, is it a safe assumption that the
3400(B) is similarly rated, when used through the RCA inputs?

No assumption is safe. I don't know what this unit it. Howver, 47K is
a fairly common input impedance for a magnetic phono cartridge input
since many of them like to see that load for proper damping. Since I
don't know what it is that you're testing, I don't know if this is a
good guess or not. If it's a serious audiophile phono preamp, the
balanced input might be for a moving coil cartridge which wants to see
a much lower input impedance.



--
I'm really Mike Rivers - )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

On Sun, 11 Jan 2004 08:01:38 -0800, "William Sommerwerck"
wrote:

Yup, absolutely. The 3400B version almost certainly "piggybacks" the balanced
input on top of the 3400's design. It's highly unlikely they would have changed
the unbalanced input.

Thanks, your response was the most helpful so far.

Regardless of the amp's input impedance, you're still going to have to LISTEN to
the system and decide whether it SOUNDS right -- as Infinity's instructions
point out.

That's precisely what I've been doing. It sounds quite good, but I
hear a little cancellation at about 100 Hz. I'm trying to determine if
it characteristic of this type of speakers system, or if something may
be out of adjustment.

Clytemnestra

On Sun, 11 Jan 2004 08:01:38 -0800, "William Sommerwerck"
wrote:

Yup, absolutely. The 3400B version almost certainly "piggybacks" the balanced
input on top of the 3400's design. It's highly unlikely they would have changed
the unbalanced input.

Thanks, your response was the most helpful so far.

Regardless of the amp's input impedance, you're still going to have to LISTEN to
the system and decide whether it SOUNDS right -- as Infinity's instructions
point out.

That's precisely what I've been doing. It sounds quite good, but I
hear a little cancellation at about 100 Hz. I'm trying to determine if
it characteristic of this type of speakers system, or if something may
be out of adjustment.

Clytemnestra

On Sun, 11 Jan 2004 08:01:38 -0800, "William Sommerwerck"
wrote:

Yup, absolutely. The 3400B version almost certainly "piggybacks" the balanced
input on top of the 3400's design. It's highly unlikely they would have changed
the unbalanced input.

Thanks, your response was the most helpful so far.

Regardless of the amp's input impedance, you're still going to have to LISTEN to
the system and decide whether it SOUNDS right -- as Infinity's instructions
point out.

That's precisely what I've been doing. It sounds quite good, but I
hear a little cancellation at about 100 Hz. I'm trying to determine if
it characteristic of this type of speakers system, or if something may
be out of adjustment.

Clytemnestra

On Sun, 11 Jan 2004 08:01:38 -0800, "William Sommerwerck"
wrote:

Yup, absolutely. The 3400B version almost certainly "piggybacks" the balanced
input on top of the 3400's design. It's highly unlikely they would have changed
the unbalanced input.

Thanks, your response was the most helpful so far.

Regardless of the amp's input impedance, you're still going to have to LISTEN to
the system and decide whether it SOUNDS right -- as Infinity's instructions
point out.

That's precisely what I've been doing. It sounds quite good, but I
hear a little cancellation at about 100 Hz. I'm trying to determine if
it characteristic of this type of speakers system, or if something may
be out of adjustment.

Clytemnestra

On Sun, 11 Jan 2004 09:40:22 -0500, Clytemnestra
wrote:


That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

Sure - there are way to get test tones using either a CD player or a computer
sound card output.

http://www.esser.u-net.com/ttg.htm

http://www.globalshareware.com/Mp3-Audio/Utilities-Plug-Ins/SigJenny-download.htm

http://www.dogstar.dantimax.dk/testwavs/



The fact that your digital meter may not be well suited to measurements other
than line frequency really don't matter much, as any error will be the same for
the measurement of source voltage, dropping resistor voltage and voltage across
the amp's input as long as you make these measurements at the same frequency.

On Sun, 11 Jan 2004 09:40:22 -0500, Clytemnestra
wrote:


That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

Sure - there are way to get test tones using either a CD player or a computer
sound card output.

http://www.esser.u-net.com/ttg.htm

http://www.globalshareware.com/Mp3-Audio/Utilities-Plug-Ins/SigJenny-download.htm

http://www.dogstar.dantimax.dk/testwavs/



The fact that your digital meter may not be well suited to measurements other
than line frequency really don't matter much, as any error will be the same for
the measurement of source voltage, dropping resistor voltage and voltage across
the amp's input as long as you make these measurements at the same frequency.

On Sun, 11 Jan 2004 09:40:22 -0500, Clytemnestra
wrote:


That said, you can determine the input impedance fairly easily by feeding a
1 KHz tone through a resistor, and measuring the voltage before the resistor
and after.

I appreciate the advice, but as I said before I only have a digital
multimeter at my disposal. It sounds like I'd have to bench the amp
and connect it up to a tone or sine wave generator to do what you
suggest. Am I interpreting you correctly?

Sure - there are way to get test tones using either a CD player or a computer
sound card output.

http://www.esser.u-net.com/ttg.htm

http://www.globalshareware.com/Mp3-Audio/Utilities-Plug-Ins/SigJenny-download.htm

http://www.dogstar.dantimax.dk/testwavs/



The fact that your digital meter may not be well suited to measurements other
than line frequency really don't matter much, as any error will be the same for
the measurement of source voltage, dropping resistor voltage and voltage across
the amp's input as long as you make these measurements at the same frequency.