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Old 4th November 2006, 11:40 PM   #1
Jessjh is offline Jessjh  United States
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Default British Quad amplifiers

Anybody own, or is thinking about or working on a Quad amp?

The unique aspect of this amplifier is that its output stages run
pure class B. That is, they're not forward biased at all.

This is a British made amp. first one probably made in the 60's.
It's specs are about as good as the best audio power amps.

Another amp, the Mattes, was I think probably made also in the sixties. Iit too
ran its output stages class B.

I'd love to get any info on this amp too.

Thanks Jessjh
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Old 5th November 2006, 09:06 AM   #2
EC8010 is offline EC8010  United Kingdom
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Quad 405 was pure Class B and introduced in the mid 70s. Quad 303 was a (fairly) standard Class AB design introduced in about 1968. Diagrams for either are undoubtedly available if you do a search...
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Old 5th November 2006, 09:27 AM   #3
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You can find the QUAD 405 schematic here;
http://www.audio-circuit.dk/Schemati...0Schematic.pdf
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Old 5th November 2006, 09:43 AM   #4
poynton is offline poynton  United Kingdom
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Quote:
Originally posted by EC8010
Quad 405 was pure Class B and introduced in the mid 70s. Quad 303 was a (fairly) standard Class AB design introduced in about 1968. Diagrams for either are undoubtedly available if you do a search...
I did not think the 405 was class B.

It has a small class A amp with a 'current dumper' (class B) and error circuit.

Andy
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Old 5th November 2006, 09:45 AM   #5
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The 405 is "current dumping" amp
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Old 5th November 2006, 09:45 AM   #6
poynton is offline poynton  United Kingdom
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Quote:
Originally posted by ACD
You can find the QUAD 405 schematic here;
http://www.audio-circuit.dk/Schemati...0Schematic.pdf


That is only 1 schematic.

There are many variations depending on year of manufacture etc.

Andy
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Old 5th November 2006, 09:56 AM   #7
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poynton;

Yep
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Old 5th November 2006, 10:22 AM   #8
poynton is offline poynton  United Kingdom
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Quote:
Originally posted by poynton




That is only 1 schematic.

There are many variations depending on year of manufacture etc.

Andy
I should have added that I have a complete QUAD service manual for the 405

Andy
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Old 5th November 2006, 10:29 AM   #9
AKN is offline AKN  Sweden
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Hi,

http://quad405.com/
http://www.dc-daylight.ltd.uk/Valve-...-405-Mods.html

Samples from the wealth of Quad info on the web.
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Old 5th November 2006, 10:34 AM   #10
forr is offline forr  France
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The Quad output stage is class C, not B.
Class B : at least one branch of push-pull is conducting.
Class C : only one branch can be conducting at a time.

I remember the name of Mattes, has anybody the schematics ?
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