Where can I learn about "current dumping" amps? Are they linear? The term dumping doesn't sound linear.
The real link:
Link removed by moderation. Please see post #6
Greez
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The Master-Link:
Link removed by moderation. Please see post #6
Link removed by moderation. Please see post #6
Greez
S.K.
The Master-Link:
Link removed by moderation. Please see post #6
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It's a feedforward technique, but it needs negative feedback for it's implementation as used by Quad. It was best explained in a publication authored by J. Vanderkooy and S.P. Lipshitz's JAES article about "Feedforward correction in power amplifiers" - funny thing is that these guys live around the corner from me !
I've read the paper several times - it is very well written. My copy (pdf) exceeds the forum file size limit or I'd post it here.
The problem links have been removed. There was no malicious intent on the part of anyone posting these. Please see post #7 here and the replies:
http://www.diyaudio.com/forums/solid-state/294575-quad-34-405-dilemma.html#post4781727
Thanks to the mods for creating this thread on my behalf. I just asked this question in the Apex Current Dumping amp thread.
I got the paper on Feedforward techniques from Bigun - thanks. It's heavy on math. Going to take some time to understand.
It would be good if someone could summarize it in plain English in 1 sentence. Most amps can be explained in one sentence.
I got the paper on Feedforward techniques from Bigun - thanks. It's heavy on math. Going to take some time to understand.
It would be good if someone could summarize it in plain English in 1 sentence. Most amps can be explained in one sentence.
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Maths is not my strong point either 😉
Here are a couple of amps in simulation, the original Quad 405 Mk1 and Elektors so called current dumping amplifier (in three versions) The Elektor one was from way back in the 70's.
Here are a couple of amps in simulation, the original Quad 405 Mk1 and Elektors so called current dumping amplifier (in three versions) The Elektor one was from way back in the 70's.
The Quad 405 current dumping principle relies on a balanced bridge.
Refering to the atttached image, with the suitable values of Z1, Z2, Z3 and Z3 (in simulation, use resistors first), the voltage at the output is not influenced by the voltage or current delivered by the high power class B amp.
Clear explanations can be found here :
FEEDFORWARD ERROR CORRECTION.
and in
"Sound Engineer's Pocket Book" 2nd Edition by Michael Talbot-Smith (editor)
page 2-133
.
Refering to the atttached image, with the suitable values of Z1, Z2, Z3 and Z3 (in simulation, use resistors first), the voltage at the output is not influenced by the voltage or current delivered by the high power class B amp.
Clear explanations can be found here :
FEEDFORWARD ERROR CORRECTION.
and in
"Sound Engineer's Pocket Book" 2nd Edition by Michael Talbot-Smith (editor)
page 2-133
.
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Interesting link, thanks. I was always fascinated by the Quad as a youngster, and also by Aubrey Sandmans class S.
Clever isn't it. The Elektor one is probably the easiest to get to grips with and the version using HEXFET's greatly exaggerates the crossover region. Look at the current in the inductor and the 22 ohm and how they all come together to give an undistorted output signal. Reduce the signal and all the output is supplied via the class A driver stage.
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It looks a bit scary at first but if you follow along with a pencil and scrap piece of paper you will find much of it drops into place. Once you have been through it and can understand what they're doing you will find you have a very nice understanding of the whole thing to the extent that you can answer most of the questions you'd come up with if you had only a simple explanation.
To be honest, I remain unconvinced that this approach brings a substantial sonic benefit but I appreciate the technical elegance.
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Armed with Doug Self's (excellent) WW index:-
Audio Articles in Electronics World
You should find everything you need here:-
American Radio History: Documenting the History of Radio TV and FM broadcasting
And don't forget Sandman's article from 1974.
Audio Articles in Electronics World
You should find everything you need here:-
American Radio History: Documenting the History of Radio TV and FM broadcasting
And don't forget Sandman's article from 1974.
This link contains some details of the operation of the bridge and measurements that show what its capable of
Quad 405-2 upgrades
Stuart
Quad 405-2 upgrades
Stuart
post12
If the ClassC amplifier were replaced with a low bias ClassAB, would the "fill in" task of the ClassA amplifier be easier to accomplish accurately?
i.e. is the bridge addition philosophy a good way to get exemplary crossover reduction for any ClassAB power amplifier?
This simple portrayal clearly shows that the ClassA amplifier has to respond quickly (and accurately) to sudden changes in output. That is quite an onerous task for any audio amplifier.
If the ClassC amplifier were replaced with a low bias ClassAB, would the "fill in" task of the ClassA amplifier be easier to accomplish accurately?
i.e. is the bridge addition philosophy a good way to get exemplary crossover reduction for any ClassAB power amplifier?
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