It is much better in controlling the idle current. The VBE temperatur drift of the output transistors is now in a DC feedback loop.
About distortion is it hard to say. This output stage goes very well with a current feedback amplifier so i see no difference there.
The questions are just how much lower distortion will we get. And how much do we want to pay for that and the stable idle current.
Before anyone has build it we dont know how it will be in practice.
About distortion is it hard to say. This output stage goes very well with a current feedback amplifier so i see no difference there.
The questions are just how much lower distortion will we get. And how much do we want to pay for that and the stable idle current.
Before anyone has build it we dont know how it will be in practice.
That's almost a call to swap partners at will, isn't it?
Technically and economically, an elaborate design of the last stage makes no sense whatsoever if it does not provide significantly better data in direct comparison with a known simple output stage and this is what is needed.
0.03% THD is my personal benchmark.
If, for example, a KRILL spin-off does not clearly crack this mark, the question of the additional effort is justified. But as we all know, a THD number alone is not worth much in terms of “sound”.
That's a damn good question for the Kendall Castor-Perry proposal to ask itself. Various practical tests can provide an answer, as can extensive metrological investigations.
With Morten's PCB, nothing now stands in the way.
By the way - I do not believe that there will be any significant improvements for daily practice, because where are they supposed to be?
For a large company, however, integration, i.e. an IC that regulates the bias, can be worth a lot - and make a lot of sense. And this is exactly what the design by Kendall C-P shows.
HBt.
Agreed, the feedback keeps the bias current very constant.
The feedback does not reduce distortion by much because the emitter resistors are outside of the feedback loops. Mismatch between the two resistors will generate even-order distortion.
The feedback around the output stage introduces a low-frequency pole. That is not good because the pole takes away from the possible global feedback. Having two identical feedback loops that can see each other is also not good.
The approach is interesting, though.
Ed
True, but the same holds for the boring old output stages almost everyone else uses.
Complementary emitter follower (or source follower):
An emitter follower (or source follower) is nothing but a common-emitter stage (or common-source stage) with local voltage follower feedback. The emitter resistors are outside the feedback loops and the NPN and PNP emitter followers see each other.
Complementary Sziklai pairs:
A Sziklai pair is a two-stage negative-feedback voltage follower or two-stage negative-feedback amplifier with a voltage gain somewhat higher than 1. The collector resistors are outside the feedback loops and the push and pull Sziklai pairs see each other.
The differences between class-i and the conventional solutions are the more complex circuit, the much better control of the quiescent current, the non-switching behaviour and the better controlled transition from one side to the other. The question is how wideband you can make the local voltage followers.
Complementary emitter follower (or source follower):
An emitter follower (or source follower) is nothing but a common-emitter stage (or common-source stage) with local voltage follower feedback. The emitter resistors are outside the feedback loops and the NPN and PNP emitter followers see each other.
Complementary Sziklai pairs:
A Sziklai pair is a two-stage negative-feedback voltage follower or two-stage negative-feedback amplifier with a voltage gain somewhat higher than 1. The collector resistors are outside the feedback loops and the push and pull Sziklai pairs see each other.
The differences between class-i and the conventional solutions are the more complex circuit, the much better control of the quiescent current, the non-switching behaviour and the better controlled transition from one side to the other. The question is how wideband you can make the local voltage followers.