Current Dumping. The way forward !

405man · 28th May 2005, 11:24 AM

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.

405man · 28th May 2005, 11:34 AM

Further information can be found here

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

Stuart

Zombie · 28th May 2005, 11:48 AM

Linn's description of its Chakra design sounds like it would be current dumping...

tlf9999 · 28th May 2005, 01:27 PM

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.

405man · 28th May 2005, 02:28 PM

A more detailed description of the operation can be found here

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

Stuart

andy_c · 28th May 2005, 03:24 PM

Excellent article. Thanks!

Nelson Pass · 28th May 2005, 04:57 PM

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.

Netlist · 28th May 2005, 09:03 PM

This is probably the mentioned article. Unfortunately the .PDF is half broken (over here).

/Hugo

Steven · 29th May 2005, 03:21 PM

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

405man · 31st May 2005, 07:39 AM

Has any one tried any of these mods

Quad 405 mod

The current sink would certainly be suitable for the 606 etc

Stuart

28th May 2005, 11:24 AM	#1
405man diyAudio Member Join Date: Dec 2003 Location: Near Glasgow Scotland	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.

29th May 2005, 03:21 PM	#9
Steven diyAudio Member Join Date: Oct 2003 Location: The Netherlands	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 __________________ The Analog Art shows no sign of yielding to the Dodo's fate. The emergence and maturation of monolithic processing finesse has perhaps lagged a bit behind the growth of the Binary Business. But whereas digital precision is forever bounded by bits, there is no limit excepting Universal Hiss to the ultimate accuracy and functional variety of simple analog circuits. - Barry Gilbert, 1973

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28th May 2005, 11:34 AM	#2
405man diyAudio Member Join Date: Dec 2003 Location: Near Glasgow Scotland	Further information can be found here http://home.jps.net/~shiloh/ Stuart

28th May 2005, 11:48 AM	#3
Zombie diyAudio Member Join Date: Feb 2003 Location: At home	Linn's description of its Chakra design sounds like it would be current dumping...

28th May 2005, 01:27 PM	#4
tlf9999 Account Disabled Join Date: May 2005 Location: none	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.

28th May 2005, 02:28 PM	#5
405man diyAudio Member Join Date: Dec 2003 Location: Near Glasgow Scotland	A more detailed description of the operation can be found here http://www.quadesl.org/Family_Album/...elessW1975.doc Stuart

28th May 2005, 03:24 PM	#6
andy_c Banned Join Date: Apr 2003	Excellent article. Thanks!

28th May 2005, 04:57 PM	#7
Nelson Pass The one and only Join Date: Mar 2001	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.

28th May 2005, 09:03 PM	#8
Netlist diyAudio Moderator Join Date: Jan 2003	This is probably the mentioned article. Unfortunately the .PDF is half broken (over here). /Hugo

31st May 2005, 07:39 AM	#10
405man diyAudio Member Join Date: Dec 2003 Location: Near Glasgow Scotland	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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