22 CD connection:

303 circuit:

33 CD input conversion:

33 circuit:

405 circuit:

405 mods:

Allpass Network shifts Signals 90�: 4/27/95 EDN-Design Ideas 

AM2 circuit:

Control 22 circuit:

Digital Delay Unit for Surround Sound:

Equivalent transistors:

Equivalent valves:

FM3 Mods:

Jones plug pin-out:

Quad 50E adaptors:

Quad 50E circuit:

Quad II circuit:

Quad spares suppliers:

Quadraphonic Amplifier: This is a four-channel amplifier ideally suited for use with quadraphonic equipment such as a Sound Blaster Live card. 

Surround Sound Decoder: This surround-sound decoder is based on the "Hafler" principle, first discovered by David Hafler sometime in the early 1970s. The original idea was to connect a pair of speakers  

Surround Sound Mk1:

Surround Sound Mk2:

Valve codes: