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Old 28th May 2005, 12:24 PM   #1
405man is offline 405man  Scotland
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Default Current Dumping. The way forward !

I have had an interest in current dumping amplifiers for many years having built a Quad 450 clone more than 20 years ago. The current dumping principal seems to offer many advantages with no bias adjustment excellent stability etc and there has been much discussion in the past over how and whether it works as Quad claimed. The later Quad amplifiers such as the 606 aka 707 and 909 are often well reviewed and I think would make the basis for a very good amplifier. Many of the Quad designs are compromised by commercial necessity yet still offer excellent performance. All of these amplifiers were designed before modelling was possible. Would anyone be interested in modelling the Quad 606 to try to further understand how it works and to better realise its potential. I have a few spare 707 clone PCBs but I have not yet had the chance to build one.
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Old 28th May 2005, 12:34 PM   #2
405man is offline 405man  Scotland
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Further information can be found here

http://home.jps.net/~shiloh/

Stuart
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Old 28th May 2005, 12:48 PM   #3
Zombie is offline Zombie  Sweden
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Linn's description of its Chakra design sounds like it would be current dumping...
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Old 28th May 2005, 02:27 PM   #4
tlf9999 is offline tlf9999  United States
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It looks like two amplifiers in one chassis: the upper PNP devices function as a class A amp. When it runs out of juice, the lower PNP-NPN quasi complementory pair (Class B or C as it is underbiased) kicks in.

If the op-amp has sufficient output current capabilities, I am sure you can even eliminate the Class A amp as well.

The key seems to have very fast op-amp so that it can swing extremely fast through the cross-over regions of the Class B amp.

In theory it should work.
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Old 28th May 2005, 03:28 PM   #5
405man is offline 405man  Scotland
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A more detailed description of the operation can be found here

http://www.quadesl.org/Family_Album/...elessW1975.doc

Stuart
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Old 28th May 2005, 04:24 PM   #6
andy_c is offline andy_c  United States
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Excellent article. Thanks!
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Old 28th May 2005, 05:57 PM   #7
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Lipschitz and Vanderkoy (spelling?) wrote an excellent
AES paper on the Quad design around 1980. A very
elegant design with an unfortunate name. It does,
however, presume that ordinary distortion measurements
are the key to good sound.
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Old 28th May 2005, 10:03 PM   #8
Netlist is offline Netlist  Belgium
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This is probably the mentioned article. Unfortunately the .PDF is half broken (over here).

/Hugo
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Old 29th May 2005, 04:21 PM   #9
Steven is offline Steven  Netherlands
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Right, it is the article "Current dumping, does it really work" published in Wireless World, June 1978, by Vanderkooy and Lipshitz.

Interesting also is:
http://audiohi-fi.narod.ru/workshop/quad405.html
It shows several versions of the 405, including PCB layout and how to make the coils.
This site also shows a version with a complementary output (!), from Solntsev (published in 1984, reference 5 in the article).

Steven
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Old 31st May 2005, 08:39 AM   #10
405man is offline 405man  Scotland
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Has any one tried any of these mods

Quad 405 mod

The current sink would certainly be suitable for the 606 etc

Stuart
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