Researching the service manuals and inspecting the DIN socket on the 303 reveal the following pin configuration.
|Front view with DIN pin numbering|
|From the manual|
There are two popular bi-amping configurations - standard bi-amping (or horizontal bi-amping) and vertical bi-amping. Borrowed the handy illustrations below from the internet.
I decided to proceed with vertical bi-amping. Vertical bi-amping requires two amplifier of similar configuration (as close as possible). I cable the interconnect with output from the Quad 33 LEFT channel to the LEFT&RIGHT for one of my Quad 303. Likewise for the RIGHT channel using my other Quad 303.
|Overview of bi-amp setup|
|View from top of the cabling|
Cost of the experiment was about $20 with the Deltron plugs accounted for most of the cost.
There's definately improvement in the presentation - the soundstage presence, vocals and instruments are much much better defined and realistic; so much so took some getting used to??? At low volumes, the sweet spot sounded like using a single 303 in stereo mode. When the volume was turned up, the sweet spot "grew". At the usual listening position, it was as if I was seated much closer to the speakers. Guess the 303's were having an easy time driving my Meridian A500 speakers (89dB)?
Actually sounds quite divine!!!
Highly recommended for Quad 303 enthusists who want more from their old faithful.
I used my 1st Quad 33 to drive the 303's.
FYI: One of my recent visitors actually inspected the 303's to make sure there were no valves in them!!!