Sorry, bad translate.
Spurious feedback, stray feedback, parasitic feedback.
In above mention paper
1. Mills P. G. L., Hawksford M. 0. J. Distortion Reduction in Moving-Coil
Loudspeaker Systems Using Current-Drive Technology. — JAES, vol. 37, ¹3,1989, March,
p. 129—148.
2. Mills P. G. L„ Hawksford M. 0. J. Transconductance Power Amplifier Systems for
Current-Driven Loudspeakers. — JAES, vol. 37,¹ 10, 1989, Oct. p. 809—822.
authors writes about decrease distortions in output stage with common base.
Output stage with common emitter or collector has this parasitic feedback from load to input because of low own impedance if we used their in current-source.
Spurious feedback, stray feedback, parasitic feedback.
In above mention paper
1. Mills P. G. L., Hawksford M. 0. J. Distortion Reduction in Moving-Coil
Loudspeaker Systems Using Current-Drive Technology. — JAES, vol. 37, ¹3,1989, March,
p. 129—148.
2. Mills P. G. L„ Hawksford M. 0. J. Transconductance Power Amplifier Systems for
Current-Driven Loudspeakers. — JAES, vol. 37,¹ 10, 1989, Oct. p. 809—822.
authors writes about decrease distortions in output stage with common base.
Output stage with common emitter or collector has this parasitic feedback from load to input because of low own impedance if we used their in current-source.
Why on earth do all electronics terms have two or three different meanings?
Phase_accurate,
when you use the phrase "transconductance amplifier" in the sense that Cherry and Hooper and Nordholt define it, it simply means an amplifier with a high input and high output impedance having an accurate voltage to current transfer (in other words, a voltage to current converter), regardless of how you implement it. In this sense, an amplifier with a floating load and with feedback from a sense resistor in series with the load is a transconductance amplifier.
Millwood, I'm not sure if I understand what you mean, but I think compensating for the level dependence of the loudspeaker impedance in the equaliser in my proposed self-equalising amplifier system is the last thing you'd want. This would bring back all the compression effects you got rid off by using current drive. The equaliser should simply be adjusted according to the small-signal impedance, which can for example be measured with a simple tone sweep just after switch-on.
Phase_accurate,
when you use the phrase "transconductance amplifier" in the sense that Cherry and Hooper and Nordholt define it, it simply means an amplifier with a high input and high output impedance having an accurate voltage to current transfer (in other words, a voltage to current converter), regardless of how you implement it. In this sense, an amplifier with a floating load and with feedback from a sense resistor in series with the load is a transconductance amplifier.
Millwood, I'm not sure if I understand what you mean, but I think compensating for the level dependence of the loudspeaker impedance in the equaliser in my proposed self-equalising amplifier system is the last thing you'd want. This would bring back all the compression effects you got rid off by using current drive. The equaliser should simply be adjusted according to the small-signal impedance, which can for example be measured with a simple tone sweep just after switch-on.
Mills and Hawksford use a rather exotic amplifier having a class-AB complementary current follower with floating power supplies driving the loudspeaker. The only advantage I see is that since the open-loop output impedance is high and since they don't need a Zobel network (Boucherotnetwerk), the high output impedance is better maintained at high frequencies, assuming that the transformer capacitance of the floating supplies doesn't spoil it. I also wonder if this is really worth the trouble.
I would have thought an 8 year old abandoned thread would be a good indicator of there being no plans.
I briefly tried high impedance drive on a 3-way once - it sounded awful.
My experimental current-driven loudspeaker with motional feedback from a second voice coil worked rather nicely. Pity I didn't have a practical application for it.
Another way to get rid of the response peak around fundamental resonance is to just equalise it out with a filter (Linkwitz transform circuit or other type of filter with two zeroes and two poles). The problem with this is that the filter zeroes will never be exactly on the loudspeaker poles. As a result, you will get some small ringing that damps out slowly.
Another way to get rid of the response peak around fundamental resonance is to just equalise it out with a filter (Linkwitz transform circuit or other type of filter with two zeroes and two poles). The problem with this is that the filter zeroes will never be exactly on the loudspeaker poles. As a result, you will get some small ringing that damps out slowly.
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