|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
69.248.17.62
In Reply to: Re: Triode mode = zero negative feedback? posted by onemug on March 29, 2007 at 18:08:16:
It is in my experience that whenever we lower the amount of feedback, or when we remove the feedback, the soundstage ALWAYS gets larger, as in more depth, width and height.
However, feedback can cause some great benefits. Tighter bass, flattened and extended frequency response, more dynamic range/headroom, are just easy examples of feedback compensation network benefits. Chosen correctly, feeback is a good thing.
Of course, I prefer the triodes, or triode connected pentodes, in push-pull, with no feedback, using interstage transformers to split the phase.
I usually find that R-C coupling(reistor-capacitor)sounds too bright. That must be why so many engineers choose feedback, in their triode mode amps. Good interstage trannies are not easy to find or pay for...
Interestingly, feedback phono EQ, is still the way to go, IMHO...
Follow Ups:
I agree. I have been listening to the Art Audio Quartet monoblocks. They are PP Class A 845 amps. They have a switch on the back for 0 or 6 db NFB. Joni Mitchell was holographic in the 0 position. When I gravitated toward more complex material, the 6 position helped. I think Joe Fratus is a genius for incorporating that switch. Saves me from buying 2 types of amps.
" agree. I have been listening to the Art Audio Quartet monoblocks. They are PP Class A 845 amps. They have a switch on the back for 0 or 6 db NFB. Joni Mitchell was holographic in the 0 position."Because, with varying feedback, the output impedance changes and as the output impedance changes the frequency response change with it the soundstage. As Frank Waller has mentioned, if you are really this keen about it, get an equalizer, then you can play with the soundstage and more besides all day long.
" When I gravitated toward more complex material, the 6 position helped."
In otherwords, distortion became audibly unpleasant.
Music making the painting, recording it the photograph
You are ASSumming that the speaker has highly variable impedance and/or that the output impedance of the amp is very high. If these conditions are not true then the variation in FR will be negligible, far less than the room interaction is likely to be (unless of course you are equalizing and then it is irrelevant anyway).
This post is made possible by the generous support of people like you and our sponsors: