John Curl's Blowtorch preamplifier part II - Page 2299 - diyAudio
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Old 10th May 2012, 01:19 AM   #22981
bcarso is offline bcarso  United States
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Originally Posted by scott wurcer View Post
One might say boring sophistry. A $25,000 phono whose specs could be equalled by a JFET/IC op-amp composite.
I was impressed by the one preamp's slew rate spec of 330V/ns. That's triggered spark gap territory.
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Old 10th May 2012, 01:27 AM   #22982
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Isn't that 330mA per pF? Or have I lost a few decimal places?

Yikes. Thanks,
Chris
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Old 10th May 2012, 02:32 AM   #22983
bcarso is offline bcarso  United States
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Originally Posted by Chris Hornbeck View Post
Isn't that 330mA per pF? Or have I lost a few decimal places?

Yikes. Thanks,
Chris
It really does read "330V/ns" unless I am totally losing it. But I presume that it was a typo.

The claim is that the designers decided a lot (?) of negative feedback was o.k. as long as the delay time was very short.
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Old 10th May 2012, 03:05 AM   #22984
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Originally Posted by Chris Hornbeck View Post
Isn't that 330mA per pF? Or have I lost a few decimal places?
Chris
Yep, how about 50GHz per volt (simplified single pole but gives you the idea that we are supposed to be able to recognize a three order magnitude typo).

Thanks
-Antonio
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Old 10th May 2012, 03:23 AM   #22985
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Yes, that is were I hang out. TAS! Beats IC rolling. '-)
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Old 10th May 2012, 06:15 AM   #22986
Bonsai is offline Bonsai  Taiwan
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Am I alone in thinking that many of the exciting developments in audio power amplifier design over the last few decades have emerged out of the amateur 'DIY' community?
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Old 10th May 2012, 09:20 AM   #22987
DF96 is offline DF96  England
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Quote:
Originally Posted by bcarso
That issue is not online, but this is (and gives a flavor of what TAS is like these days)
Damping factor above 10000 - wow! (Valin's review) Useful if you have superconducting loudspeaker cables? A sign of crass ignorance in the reviewer for everyone else?
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Old 10th May 2012, 10:01 AM   #22988
SY is offline SY  United States
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Am I alone in thinking that many of the exciting developments in audio power amplifier design over the last few decades have emerged out of the amateur 'DIY' community?
Class D? Chip amps?
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Old 10th May 2012, 11:08 AM   #22989
Bonsai is offline Bonsai  Taiwan
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I am thinking discrete power amplifiers, and particular some of the advances made in compensation design in amongst others. Beyond that, a lot of the stuff done by JLH and Baxandall for example was done 'after hours'

I just don't buy this professional/amateur thing when some of the amateurs happen to be leading lights in the field in their own right.
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Old 10th May 2012, 01:43 PM   #22990
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Originally Posted by scott wurcer View Post
One might say boring sophistry. A $25,000 phono whose specs could be equalled by a JFET/IC op-amp composite.
Scott,

We really got to disagree on this one. There is no way a JFET/IC op-amp composite could meet all the same specs. Although it may match or even better all the presumed common measurements, there is one spec it would never match... the price.

ES
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