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Originally Posted by seancostello  I had thought the same thing (that the loop feedback had random amplitude modulation), when looking at the Blesser patent, as well as a 1978 book chapter that he wrote. In the book chapter, Blesser shows a chorus, with several delay taps that are randomly modulated both in delay length and in amplitude. In his 1980 patent (I think that's the date), it seems as though the feedback taps are modulated in amplitude. However, I think that was Blesser's way of describing linear interpolation, or at least some random cross fading between two taps which may or may not be contiguous to each other, as opposed to a single tap that is randomly amplitude modulated. That part of the patent is confusing to me.
The patent does describe random amplitude mixing of the tap outputs, but this is different than random amplitude in the feedback loops. Plus, I am not confident that the EMT-250 is really that close to the patent, although I would think that at least a few of the claimed ideas were used in the EMT-250.
I have tried random amplitude modulation in the feedback loops, and the result is a very uneven decay. It doesn't sound good, IMO. Delay length modulation sounds good in feedback loops. Other types of modulation can sound good, but you want to maintain as flat a magnitude response as you can with the modulation, and also avoid building up enough energy to make the system unstable. You want to preserve the total energy of the system, and be specific with your losses - i.e. have the losses controlled as a factor of RT60.
Sean |
Sean, Both from papers that Dr Blesser has sent to me and the reading of the original patents I have seen references to amplitude modulations. I have had good results with small random amplitude fluxuations in the feedback loop (very small, less than a dB).
Casey, care to elaborate with something more insightful than "no"? (please...? )
