Dear @atmasphere - I’ve read many of your comments with great interest, even though the technical info usually goes way over my head! I’ve read you say that you’ve built zero feedback amps for decades. Are your latest Class D amp zero feedback also? I am a Vandersteen owner, looking at new possible zero feedback amps (eg, Ayre, SMc (Steve McCormack) custom, Aesthetic Mimas, SimAudio (?), etc). THANKS!
http://www.atma-sphere.com/en/classD.html
Damping Factor and Overall Negative Feedback.
These specifications are assigned to some amplifiers but what is the difference between them? I had thought they were the same thing. I read the specs on a Karan Acoustics KSA 450 amp today with a high damping factor (?dumping factor?) and no overall negative feedback.
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I’ve read you say that you’ve built zero feedback amps for decades. Are your latest Class D amp zero feedback also? I am a Vandersteen owner, looking at new possible zero feedback amps @patrickdowns No, our class D amps run a lot of feedback. We tried zero feedback but they proved to be less musical. BTW, you can run amps with feedback on Vandersteens no worries despite what Richard says. When you are talking about solid state amps, even without feedback the output impedance is so low that the amp can still behave as a Voltage source. So this isn't about the output impedance of the amp as far as Richard's speakers are concerned- its about how the amps 'sound'. Feedback is a bit trickier to implement than it might look. Designing a feedback loop that doesn't cause the amp problems is the tricky bit. There is a 'problem area' between about 12dB and 30dB where you can get into trouble. A lot of solid state amps made over the last 50 years fall into this area. Another problem is if the amp amp does not have enough gain and bandwidth. If its lacking in that department it may not support the feedback properly and so at some point in the audio band, the feedback falls off and so distortion rises at that frequency. Its my theory that this rising distortion with frequency is one of the reasons solid state amps with feedback tend to sound bright and harsh. Again, many solid state amps made in the last 50 years have this issue. Its possible to build a class D amp that gets around these problems. Such an amp will be fine on Richard's speakers. |
Thank you, @atmasphere ! I wish I had a better understanding of these very technical design issues and parameters for hi-fi. It's all Greek to me, so a layman's explanation is wonderful. |
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