Class G - newbie opinion

[bentoronto]

My 2-cents on class-G; hope it is of interest to the slightly different class-D crowd:

Entirely by chance, I ended up driving most of my system with 2 stereo amps of the Kenwood Basic family which I understand are Class G. Aside from the advantage of running cool in the summer, I would never given even the briefest consideration to having an ungainly output design of that sort in my high-quality music system. Never.

After about 8 months of listening and system renewal testing, I find no reason to think they sound any way different than other hifi amps. (I believe there are no mysterious and ear-only differences between amps unless there also are measurable differences that distinguish them.)

You can see from my signature below that I use ESL speakers. My Kenwood M2A is driving the mid-range seven octave speakers is frequently running full blast, something quite rare this side of PA applications with cone speakers. In other words, the high-power transistors are coming into play substantially and the transition line is crossed lots.

BTW, for 40 years I have been interested in motional feedback from the voice coil of drivers. The Sigma Drive circuit of the Kenwood Basic M1 and M2 are cousins to that feedback concept... a concept sorely needed to make its way into sound reproduction.

[tomi]

Out of interest - and off topic I know - I've taken some passing interest in using feedback to "servo" drivers (played around with some ideas, but never got anywhere).
Have you had any success doing this, and if so what kind of sensing techniques have you used?

[bentoronto]

Originally Posted by tomi

Out of interest - and off topic I know - I've taken some passing interest in using feedback to "servo" drivers (played around with some ideas, but never got anywhere).
Have you had any success doing this, and if so what kind of sensing techniques have you used?

At last, somebody has shown an interest in the final frontier of open loop.

To make a long story short, I think there is no defensible method of feedback except using a dual voice coil or putting the voice coil in a Wheatstone Bridge that balances away the static coil values leaving the motional impedance.

It can only be applied to sealed boxes correctly but the result is fabulous. Ever have a driver push back at you when you shove the cone? Its ALIVE!

i have a theory that it eats room resonances.

Try not to destroy any drivers while experimenting.