What is wrong with negative feedback?


I am not talking about the kind you get as a flaky seller, but as used in amplifier design. It just seems to me that a lot of amp designs advertise "zero negative feedback" as a selling point.

As I understand, NFB is a loop taken from the amplifier output and fed back into the input to keep the amp stable. This sounds like it should be a good thing. So what are the negative trade-offs involved, if any?
solman989

Showing 1 response by philmagnotta

06-25-10: Jamesgarvin
... "Seems to me the only way to make that determination is to take two identical amps, one with negative feedback and one without, and play them with the same source through the same speakers. I've not heard of anyone who has done that exercise, much less anyone who has heard it."

Hi Jamesgarvin;
Interesting. However, they could not be identical amps, even supposing that they only differed regarding feedback, but I assume you meant it ideally.
Practically speaking, we can, of course, choose one of each type from a number of respected designers and begin there.
When you referred to playing them with the same source, I'd like to reference "source" as recorded source.
Using acoustic instruments as an example:
If we are present in the recording space during the performance and we agree that the sonics are excellent, we'll have to verify that all components: mics, mic pre-amps, console or summing equipment, power-amps,
are non-feedback - as well, the same devices with feedback, We'd have to start there.
If this could be accomplished, we'd still have to consider
Class A, A/B, D, discrete/chips, SS/tube, etc.
We still haven't discussed what reference speaker system.
Considering all of the above, its amazing the amount of effort that drives the talented designers and enthusiastic lovers of audio and music.
For those concerned, having a very satisfying audio system is natural treasure.
I'm glad to see those efforts displayed here.