In Reply to: Curious posted by rnhood on December 27, 2002 at 17:08:53:
Actually the amount of negative feedback in the JC-1 is fairly high. I don't know the exact number, but we have to meet THX spec as well as make an audiophile product. This means that I do my best to make a linear circuit, then the feedback added to get the distortion acceptable for THX at full output. I don't like negative feedback, but I have to use it in this case.
For the record, negative feedback can cause a significant increase in higher order harmonics and a dynamic FM distortion of the signal, much like jitter in digital products. Therefore, I try to make the actual circuit as linear as possible, without kinks in the transfer function, and then add feedback. If I could increase the open loop bandwidth to above 25kHz, then negative feedback might not be much of a problem, but this requires other tradeoffs, such as stability with difficult loads, and exotic circuit layout. It is also important to have a high slew rate, which is related to negative feedback, but advanced circuit techniques allow for very high slew rates, without changing the feedback factor. We have no measurement equipment that actually measures the bad effects of negative feedback in the commercial marketplace at this time.
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