Do I understand correctly, The Adcom has balanced out and the Marchland has balanced in?
It sounds like that’s your interconnect path if that’s how the devices are configured.
I understand that you are considering building the gain clones and the crossover into single chassis that would be located with each speaker. That also sounds like a good thing.
You could place the crossovers and the preamp at the listening position and run two balanced lines to gain clones located at the speakers. This would allow you to make adjustments to the crossovers while listening to them but you would have to add the expense and complexity of adding balanced outs to the crossovers and balanced in to the gain clones.
I think your idea works better.
-Dave
It sounds like that’s your interconnect path if that’s how the devices are configured.
I understand that you are considering building the gain clones and the crossover into single chassis that would be located with each speaker. That also sounds like a good thing.
You could place the crossovers and the preamp at the listening position and run two balanced lines to gain clones located at the speakers. This would allow you to make adjustments to the crossovers while listening to them but you would have to add the expense and complexity of adding balanced outs to the crossovers and balanced in to the gain clones.
I think your idea works better.
-Dave
Getting back to the original question.........
The main reason for putting the amps near the speakers is to reduce the effect of the impedence and the resistance of the speaker cable on the interaction between the amplifier and the speakers. If you run long lines of speaker cable, the impedence and resistance that builds up in the speaker cable can change the x-over frequency and phase response of your speakers. This is the ONLY reason for doing this.
As far as running long interconnects, you can run an unbalanced interconnect up to about 20 feet before losing significant HF response to to the capacitance of the unbalanced cable. This is one of the reasons why the consumer world has stuck to RCA connections for all these years. At distances of 3 feet or so (the typical distance between source and amplifier) the negative effects of an unbalanced cable are negligible. If you want to run longer runs, definately go balanced. The advantages to running balanced cable are as follows:
1: You get a hotter signal
due to the fact that you are running two signals side by side, and summing them at the input of your amp.
2: Any noise that is picked up in the twisted pair will be eliminated at the terminus. This is done by reversing the polarity of pin 3 at the terminus. Any noise on pin three will now have a reversed polarity to that of the noise on pin 2. These two noise signals are summed and cancel each other out, leaving only the origianal signal that was transmitted along the balanced line in the first place.
3: It's just a lot cooler to run everything balanced. You'll make all your friends green with envy
As far as the signal being 14dB hotter, this is not quite true. I thing you are looking at the -10/+4 consumer/pro levels. These are just two different standards. You can run -10 balanced or unbalanced. When you run balanced, you only gain about 3dB of signal when you sum the two signals.
If you are looking to balance the input of your amps, you can do this a couple of different ways. One, you can get a high quality balancing transformer from Jensen, or you can build a small balancing circuit from a couple of op-amps. either way will work just fine.
I hope this helps.
Cheers,
Zach
The main reason for putting the amps near the speakers is to reduce the effect of the impedence and the resistance of the speaker cable on the interaction between the amplifier and the speakers. If you run long lines of speaker cable, the impedence and resistance that builds up in the speaker cable can change the x-over frequency and phase response of your speakers. This is the ONLY reason for doing this.
As far as running long interconnects, you can run an unbalanced interconnect up to about 20 feet before losing significant HF response to to the capacitance of the unbalanced cable. This is one of the reasons why the consumer world has stuck to RCA connections for all these years. At distances of 3 feet or so (the typical distance between source and amplifier) the negative effects of an unbalanced cable are negligible. If you want to run longer runs, definately go balanced. The advantages to running balanced cable are as follows:
1: You get a hotter signal
due to the fact that you are running two signals side by side, and summing them at the input of your amp.
2: Any noise that is picked up in the twisted pair will be eliminated at the terminus. This is done by reversing the polarity of pin 3 at the terminus. Any noise on pin three will now have a reversed polarity to that of the noise on pin 2. These two noise signals are summed and cancel each other out, leaving only the origianal signal that was transmitted along the balanced line in the first place.
3: It's just a lot cooler to run everything balanced. You'll make all your friends green with envy
As far as the signal being 14dB hotter, this is not quite true. I thing you are looking at the -10/+4 consumer/pro levels. These are just two different standards. You can run -10 balanced or unbalanced. When you run balanced, you only gain about 3dB of signal when you sum the two signals.
If you are looking to balance the input of your amps, you can do this a couple of different ways. One, you can get a high quality balancing transformer from Jensen, or you can build a small balancing circuit from a couple of op-amps. either way will work just fine.
I hope this helps.
Cheers,
Zach
Although what I suspect is suspect is......
"What you would need however, unless you're using a single driver with no intervening crossover network, is a symmetrical crossover. Most crossovers are asymmetrical and will unbalance the line and degrade common-mode rejection. Though I suspect that like a transformer, the voice coil will have a considerably high common-mode input impedance and should still give very good common-mode rejection even if driven from a wholly unbalanced source."
Crossovers unbalance the line?
Common-mode rejection for a speaker?
I think I have figured out what problem
is.........
"What you would need however, unless you're using a single driver with no intervening crossover network, is a symmetrical crossover. Most crossovers are asymmetrical and will unbalance the line and degrade common-mode rejection. Though I suspect that like a transformer, the voice coil will have a considerably high common-mode input impedance and should still give very good common-mode rejection even if driven from a wholly unbalanced source."
Crossovers unbalance the line?
Common-mode rejection for a speaker?
I think I have figured out what problem
is.........
Attachments
Re: Although what I suspect is suspect is......
Asymmetrical crossovers do, yes. Stick an inductor or capcitor on just one line. That line will no longer have the same impedance with respect to ground as the other line. That will unbalance the line and result in mode conversion from common-mode to differential, reducing common-mode rejection.
Yes. A driver responds to the differential signal across its terminals. In other words, it differntiates. Feed it a common-mode signal and you get nothing. 1 - 1 = 0. That's common-mode rejection.
se
Fred Dieckmann said:
Asymmetrical crossovers do, yes. Stick an inductor or capcitor on just one line. That line will no longer have the same impedance with respect to ground as the other line. That will unbalance the line and result in mode conversion from common-mode to differential, reducing common-mode rejection.
Yes. A driver responds to the differential signal across its terminals. In other words, it differntiates. Feed it a common-mode signal and you get nothing. 1 - 1 = 0. That's common-mode rejection.
se
Welcome back
"Asymmetrical crossovers do, yes. Stick an inductor or capcitor on just one line. That line will no longer have the same impedance with respect to ground as the other line. That will unbalance the line and result in mode conversion from common-mode to differential, reducing common-mode rejection."
"That line will no longer have the same impedance with respect to ground as the other line."
WHAT!!!!!????
I would like to know why a speaker is effected by common mode. A crossover on one wire will unbalance the line with respect to what? What is the common mode impedance of a speaker. Do most amps drive speakers differentially to ground. Don't more amps have one speaker lead at ground potential?
"Yes. A driver responds to the differential signal across its terminals. In other words, it differntiates. Feed it a common-mode signal and you get nothing. 1 - 1 = 0. That's common-mode rejection."
"In other words, it differntiates"
IT DOES? What exactly do you mean?
http://www.m-w.com/cgi-bin/dictionary?va=differentiates
Doesn't "1 - 1 = 0" mean that a speaker completely rejects common mode signals. How does that result in mode conversion from common-mode to differential when you said it completely ignores common mode? What would this conversion come from? Are these signals current or voltage or both? What is the common mode impedance that the amp sees looking at the speaker?
Why do you do this to yourself over and over again?
"Asymmetrical crossovers do, yes. Stick an inductor or capcitor on just one line. That line will no longer have the same impedance with respect to ground as the other line. That will unbalance the line and result in mode conversion from common-mode to differential, reducing common-mode rejection."
"That line will no longer have the same impedance with respect to ground as the other line."
WHAT!!!!!????
I would like to know why a speaker is effected by common mode. A crossover on one wire will unbalance the line with respect to what? What is the common mode impedance of a speaker. Do most amps drive speakers differentially to ground. Don't more amps have one speaker lead at ground potential?
"Yes. A driver responds to the differential signal across its terminals. In other words, it differntiates. Feed it a common-mode signal and you get nothing. 1 - 1 = 0. That's common-mode rejection."
"In other words, it differntiates"
IT DOES? What exactly do you mean?
http://www.m-w.com/cgi-bin/dictionary?va=differentiates
Doesn't "1 - 1 = 0" mean that a speaker completely rejects common mode signals. How does that result in mode conversion from common-mode to differential when you said it completely ignores common mode? What would this conversion come from? Are these signals current or voltage or both? What is the common mode impedance that the amp sees looking at the speaker?
Why do you do this to yourself over and over again?
"GEPCO, NEGLETZ, MOGAMI, or GOTHAM!"
Did you say you were interested in putting the GC in the same chassis as the X-Over? Its a good idea weather you place the amps w/ the speakers or not. Me, I still recommend a balanced interconnect between the x-over and the preamp. It might mean spending some bucks to upgrade. So far no one has mentioned anything better than the Belden 9451 for cable. Its good but I find it surprising that no one has jumped up yelling, "GEPCO, CANARE, NEGLETZ, MOGAMI, or GOTHAM!" (who did I leave anyone out?)
I would not however recommend locating the amps and crossovers with the speakers if you are tempted to do it with unbalanced interconnects. If you must interface the pre to the xo unbalanced, make yourself some nice speaker cables.
Did you say you were interested in putting the GC in the same chassis as the X-Over? Its a good idea weather you place the amps w/ the speakers or not. Me, I still recommend a balanced interconnect between the x-over and the preamp. It might mean spending some bucks to upgrade. So far no one has mentioned anything better than the Belden 9451 for cable. Its good but I find it surprising that no one has jumped up yelling, "GEPCO, CANARE, NEGLETZ, MOGAMI, or GOTHAM!" (who did I leave anyone out?)
I would not however recommend locating the amps and crossovers with the speakers if you are tempted to do it with unbalanced interconnects. If you must interface the pre to the xo unbalanced, make yourself some nice speaker cables.
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