British Quad amplifiers

Jessjh · 4th November 2006, 11:40 PM

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

EC8010 · 5th November 2006, 09:06 AM

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...

Jan Dupont · 5th November 2006, 09:27 AM

You can find the QUAD 405 schematic here;
http://www.audio-circuit.dk/Schemati...0Schematic.pdf

poynton · 5th November 2006, 09:43 AM

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

Jan Dupont · 5th November 2006, 09:45 AM

The 405 is "current dumping" amp

poynton · 5th November 2006, 09:45 AM

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

Jan Dupont · 5th November 2006, 09:56 AM

poynton;

Yep

poynton · 5th November 2006, 10:22 AM

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

AKN · 5th November 2006, 10:29 AM

Hi,

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

Samples from the wealth of Quad info on the web.

forr · 5th November 2006, 10:34 AM

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 ?

4th November 2006, 11:40 PM	#1
Jessjh diyAudio Member Join Date: Nov 2006	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

5th November 2006, 09:06 AM	#2
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	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... __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

5th November 2006, 09:27 AM	#3
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	You can find the QUAD 405 schematic here; http://www.audio-circuit.dk/Schemati...0Schematic.pdf __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com

5th November 2006, 09:45 AM	#5
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	The 405 is "current dumping" amp __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com

5th November 2006, 09:56 AM	#7
Jan Dupont diyAudio Member Join Date: Apr 2003 Location: Copenhagen, Denmark	poynton; Yep __________________ Free Schematic and Service Manual downloads www.audio-circuit.dk, Company: www.dupont-audio.com, Joint venture: www.DupontMantra.com


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5th November 2006, 10:29 AM	#9
AKN Enjoy good sound diyAudio Member Join Date: Aug 2005 Location: In the middle of Sweden	Hi, http://quad405.com/ http://www.dc-daylight.ltd.uk/Valve-...-405-Mods.html Samples from the wealth of Quad info on the web. __________________ / Anders

5th November 2006, 10:34 AM	#10
forr diyAudio Member Join Date: Dec 2004 Location: Next door	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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