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Old 26th March 2012, 11:51 AM   #3991
gk7 is offline gk7
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"J12 Distortion reduction MC current drive" I have, which is the second one ?
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Old 26th March 2012, 11:54 AM   #3992
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Found it, itīs J14
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Old 26th March 2012, 01:30 PM   #3993
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Originally Posted by bcarso View Post
This wiki is o.k., although I dissent that Nelson really invented the concept, as such feedback goes way back (a tube amp with feedback to the input device cathode for example) --- and I believe that Comlinear lost some battles after that patent issued.

Current-feedback operational amplifier - Wikipedia, the free encyclopedia

Good for high slew rate, usually not so good for d.c. properties and distortion. Would represent a huge sea change in the context of the Hafler at this point.

Does anyone know of a high-end power amp that uses this approach? I vaguely recall some such but forget who it was, maybe dating back to the '80's when fast slewing was all the rage. On a bog-standard level the NAD3020 power amp section uses current feedback, and an ancient IC from STMicro, the TDA2007A, tried to have a current-feedback front end and additional voltage gain following, and was the devil to stabilize.
There are many, one fine example is accuphase, they use it on all there amps and preamps. I could probably mention another dozen if given a day or two to recall them all.
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Old 26th March 2012, 06:13 PM   #3994
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Thank you, gk7.
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Old 26th March 2012, 06:19 PM   #3995
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Rather than consider products whose prices are from the la-la land, I investigated the current and past series of mid priced Marantz integrated amps, regarding which Marantz boasts of using current feedback.

I didn't see any of their schematics.

Frankly, I was somewhat underwhelmed. I was probably expecting more, based on the hype, but what I got was a rather typical sound of most serious contenders in that price bracket. If anything, the sound was a little loose, as if it was not under complete control - subjectively.

In short, not unpleasant, no obvious failings, but also nothing to particularly recommend them either. About what you'd expect for the money.
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Old 26th March 2012, 07:53 PM   #3996
tvrgeek is offline tvrgeek  United States
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Originally Posted by janneman View Post
Close, but no cigar . POOGE was coined by Walt Jung and Richard Marsh in Audio Amateur many years ago.
But I agree that NP has done more for the audio diy scene than anybody else I know.

Absolutely right. My bad. These two gentlemen also have contributed highly. I guess I read so much from N.P. that was significant, I forget.
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Old 26th March 2012, 08:13 PM   #3997
bcarso is offline bcarso  United States
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Since it took me some time to discover what that acronym meant in the days before search engines, here for those who may wonder: POOGE: Progressive Optimization Of Generic Equipment.
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Old 26th March 2012, 08:56 PM   #3998
KSTR is offline KSTR  Germany
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Let's not confuse speakers and drivers. With 99.9% of speakers in use being passive multiway there is not many choices other than more or less perfect voltage drive, given the crossover designs. Fullrangers and active systems are more open to be used with an "optimum damping impedance profile" (as I call it) as seen by the VC (or any other motor principle) with its Rdc factored out. These profiles tends to be complex and offer more than just Rdc (voltage drive, simplified -- medium feedback) or infinity (current drive -- no feedback) or zero (full velocity feedback right in the driver itself, idealized).
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Old 26th March 2012, 09:20 PM   #3999
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Old 26th March 2012, 10:12 PM   #4000
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Any luck with the wife/amp thing?


I must have a shirt with that on it. I've got some old IATSE shirts around here that would be perfect.


Last edited by revboden; 26th March 2012 at 10:16 PM.
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