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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 17th July 2019, 07:14 PM   #25321
john curl is offline john curl  United States
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Halcro made a 'virtually distortionless' power amp. It sounded OK, but not great, and is not made anymore.

Unless stereo imaging is your thing, then room placement and even quality is not that important to hear differences in amp-speaker combinations.
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Old 17th July 2019, 07:18 PM   #25322
scott wurcer is online now scott wurcer  United States
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Quote:
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Halcro made a 'virtually distortionless' power amp. It sounded OK, but not great, and is not made anymore.
Benchmark makes one now, people rave about it. Boulder, Bryston, Halcro all the same story boring and clinical sound no PRAT, yawn. John do your Parasound amps fail if the load has 30 degrees of phase?
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Old 17th July 2019, 07:28 PM   #25323
vacuphile is offline vacuphile  Netherlands
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Where back-EMF is highest, impedance is highest too and phase shift=0 degrees. In other words, this is the operating point where a loudspeaker driver presents the easiest load to an amplifier.
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Old 17th July 2019, 07:28 PM   #25324
john curl is offline john curl  United States
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Probably.
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Old 17th July 2019, 07:30 PM   #25325
john curl is offline john curl  United States
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Back EMF is scary. It goes right to the input of the amp through the primary feedback resistor. IIM distortion, if you are not careful.
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Old 17th July 2019, 07:42 PM   #25326
vacuphile is offline vacuphile  Netherlands
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What is scary about back EMF?

People believed certain trees housed evil spirits. The trees were real, the spirits not as progressing insights have revealed.

Back EMF increases impedance -clearly visible at resonance in plots - and any competently designed amplifier can handle the associated phase shifts as Scott mentioned.

Back EMF makes it easier on an amplifier. At resonance, you need the least amount of power to accelerate the cone.
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Old 17th July 2019, 08:05 PM   #25327
Evenharmonics is offline Evenharmonics  United States
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Unless stereo imaging is your thing, then room placement and even quality is not that important to hear differences in amp-speaker combinations.
Anything else besides (speaker) placement? Because there are many more in the "to do list" of room acoustics.
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Old 17th July 2019, 09:22 PM   #25328
john curl is offline john curl  United States
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Back EMF is both from the resonant frequencies AND any external room noise that goes backward into the speaker. Unless you have a NATURALLY LOW IMPEDANCE, without feedback, the feedback has to generate one in order to absorb the back voltage. It does this by changing the input to create an opposite voltage. Input stages distort and can overload on such signals. IIM folks, look it up! Triodes rule!
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Old 17th July 2019, 09:27 PM   #25329
scott wurcer is online now scott wurcer  United States
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Input stages distort and can overload on such signals.
Right, clamp two speakers face to face and do the experiment you won't see much.
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Old 17th July 2019, 10:03 PM   #25330
john curl is offline john curl  United States
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I measured it between two K-horns without any trouble.
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