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Old 22nd November 2002, 07:09 PM   #11
jam is offline jam  United States
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Carlos,

True but by a different amount. They wired a large value resistor across the fuse so that if the fuse blew you would have some amount of feedback to manintain dc stability. The end result is the same, to take the feedback close to speaker as possible on the assumption that feedback would reduce all non-linearities caused by wire, fuses etc.

Jam
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Old 22nd November 2002, 07:20 PM   #12
alvaius is offline alvaius  Canada
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Unlike a 4 wire resistor measurement though, my feedback connection in this case must have a bandwidth that extends beyond the audio bandwidth. Any noise picked up on the return path essentially gets reflected to the input and becomes noise at the speakers.

If you were bi\tri amping with electronic cross-overs it may offer an improvement, however, the impedance of the inductors and capacitors in the speakers is likely far higher than the cables connecting to them.

Just some thoughts...

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Old 22nd November 2002, 07:58 PM   #13
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Default Re: Speaker feedback

Quote:
Originally posted by carlmart
This arrangement was suggested by Richard Marsh, in The Audio Amateur 3/85.
The speaker feedback was implemented through a 0.15ohm resistor.
This approach has been around a long time for turning an
amp into a constant current source or otherwise raising it's
output impedance.

But it is not the same thing as discussed above. I believe the
thread is addressing the means of enclosing the cables in a
feedback loop so as to lower their impedance.

This is not difficult to do as long as the circuit is very stable
otherwise and the amount of feedback around the cable
is kept at modest levels.
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Old 23rd November 2002, 12:25 AM   #14
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Why not eliminate the speaker cable?
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Old 23rd November 2002, 07:36 AM   #15
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Are nonlinearities in cables a real-world-problem?
The distortion magnitude is probably in the -170dB-range.

Best regards\Morello
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Old 23rd November 2002, 09:17 PM   #16
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Default Hi alvaius,

Sorry that this has nothing to do with this thread. But I haven't heard from you about your G4 x-overs for 3 weeks. How's it going with the x-overs? Somebody e-mailed me a little while ago about building some G4's and he says that Graham says that the 10 db spike at 3,750 Hz goes down to 2 db after 200 hours break in although I have noticed this I think. Just wanted to tell you maybe this will and you and later also myself.
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Old 23rd November 2002, 09:47 PM   #17
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Default Other British outfit

Don't think that DNM have ever used a feedback loop containing the speaker cable. The other British outfit that Werner is referring to is Deltec - unfortunately no longer in existence. They specified their own speaker cable - Black Slink. This was a well regarded Goretex dielectric cable.

James
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