Post by Owen Y on Feb 14, 2020 15:19:15 GMT 12
HEGEL MUSIC SYSTEMS (Norway) founder and lead designer Bent Holter discusses: - Amplifier distortion - Negative Feedback & time delay problems in audio amplifiers. - The HEGEL SoundEngine2 circuit topology uses feed-forward distortion cancellation.
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Post by cartridgeguyonline on Feb 14, 2020 15:31:20 GMT 12
I look forward to reading Colinf or GaryM comments on this !
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Pundit
Post by garym on Feb 14, 2020 17:12:14 GMT 12
Everyone has their own ideas. I wouldn't want to critique anyone, the proof of the pudding is in the listening...
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Post by Owen Y on Feb 14, 2020 20:26:40 GMT 12
Oops I'd forgotten that we'd previously discussed on an earlier thread the DARKO video above of HEGEL's Bent Holter. Also DARKO's brief comments about the sound quality of the HEGEL H190 & HEGEL H590 integrated streaming DAC-Amplifiers.
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Post by colinf on Feb 14, 2020 23:34:47 GMT 12
Feed-forward error correction can be implemented many ways, it’s been used before in a few amplifiers over the years. Sansui had a simple form that reduced crossover distortion in the output stage. Hawksford feed-forward error correction was designed in 1980. The idea of testing an amplifier by subtracting the output signal from the input and listening to the error was talked about by David Hafler in the manual for the XL-280. What’s interesting in the Hegel design is the use of a threshold circuit in the error correction circuitry to pass undistorted signals unchanged but correct the error above a certain level, determined empirically. I wonder why...does the Hegel error correction add distortion below the threshold level and thus needs to be used only when necessary, hence the need for a threshold circuit? Or is it something to do with patents? I use a form of Hawksford error correction in my own mosfet amp. Mosfets are very fast devices and although they add more distortion than bipolars, that can be corrected to within an inch of their lives at frequencies far above human hearing, and into the radio transmitter range. The error introduced at MHz frequencies can then be removed with a specific RF filter, that also defines the total output impedance of the amp.
AMR-iFi R&D
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Post by colinf on Feb 20, 2020 4:20:38 GMT 12
An interesting brochure on Sansui’s 1980 Super-Feedforward system.     .
AMR-iFi R&D
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Post by cartridgeguyonline on Feb 23, 2020 8:07:28 GMT 12
Which one did you listen to at the Bristol show Colin ?
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Post by colinf on Feb 24, 2020 0:11:38 GMT 12
There were quite few rooms using Hegel amplification. But went quickly through the rooms, so many things to see in such a short time! The Kef LS50s driven by a Hegel pre-power combo stick in my mind as being wonderfully dynamic and woke them up a bit. The mids and treble shimmered like I hadn’t heard before from an LS50. Other good sounds were the Magneplanar LRS with Simon’s Wand turntable. It’s a brilliantly dimensioned turntable and I suspect it will do well here. The LRS had that engaging and satisfying cohesiveness in a small package for typical UK rooms. And the Klipsch RP600Ms driven by Musical Fidelity sounded far better than a lot of the more costly systems, supple, uncoloured and dynamic with communicative harmonics. I think the Tractrix horn allows you to couple more intimately to the speaker which lets you hear right into recordings in a way that’s hard to do with a conventional setup. Other fine sounds were from Spendor, Harbeth, Fyne Audio and Proac. Falcon Acoustics were showing a new, small, stand-mounted transmission line with classic LS3-5A drivers which had blissful toe-tapping rhythm and involvement. They just sounded ‘right’! The Harbeth room featured open reel as a source and it once again shows that tape might be superior as a format, it’s distinctive openness easy to notice. The show was so busy though that it was reasonably difficult to listen to things with the interfering noises coming from other rooms, and to get decent photos as the crowds were in the way! Good that it was busy though, people are still very much passionate about audio here.    
AMR-iFi R&D
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Post by Owen Y on Feb 24, 2020 9:42:57 GMT 12
Well I never... stacked LS3/5As!
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Pundit
Post by simonb on Feb 24, 2020 10:14:58 GMT 12
Thanks Colin! Think it is the Klipsch RP600Ms that Herb Reinhardt of Stereophile is very fond of.
Simon Brown
Design Build Listen Ltd,
Makers of The Wand Analogue Products
Distributor of Hana Cartridges
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Post by michaelw on Feb 24, 2020 11:23:02 GMT 12
Well I never... stacked LS3/5As! folks have been doing that for ages.
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Post by colinf on Feb 25, 2020 3:15:45 GMT 12
The stacked LS3/5As weren’t playing when I went in but they looked great! The cost would be excessive though. Magneplanar LRSs would be a good alternative for far less dosh. Also, I had a great chat to Max Townshend of Townshend Audio. He was showing his new passive autotransformer line stage Allegri Reference with 120 taps of 0.5db steps, wound and hooked up with what he calls ‘fractal’ wiring. The wire has been treated using his special process. Very costly though at £8000. Max is an Aussie but has been in the UK since 1973. I ended up buying some seismic isolation pods for my Graham-Simon-Garrard 401 turntable.
AMR-iFi R&D
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