Saturday, February 11, 2012

Bi-amping with the Quad 303(s)

Finally had the time to bi-amp the Quad 303(s).

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

Side view
Cabling was completed using three Deltron 4-pin DIN plugs, recycled (normal) phone wire and my handy speaker cables. Normal phone wire??? Yes, many of my visitors were very surprised at its excellent quality (not reveal to them initially). They couldn't believe their ears till they listen for a while and wanted to know what cabling was deployed!!!!

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!!!


  1. FYI - My friend (who bought my Philips CD460 and Sansui AU-4400) drop by to hear the bi-amp 303's and was extremely impressed by it's ability to sound musical while delivering details with precision, in a transparent manner - well balance tonally throughout the bass, mid and highs!

  2. I have to agree that bi-amping with a pair of 303's is a very good step up. I use mine in vertical bi-amp mode to drive a pair of B&W P6's and the sound stage is very wide, and the sense of 'air' around the individual notes seems better than the single amp set up.

  3. Not sure if this is still active, but I am bi-amping the same setup youäve done above. The difference is, my speakers are not biwired (meaning, I only have 1 + connection and 1 - connection. Not 2 & 2 as above). Is there any risk or issue in connecting both + wires from amp to + pole in speaker, and the same for the . wires? Thanks in advance! Brad

    1. I would not advise doing anything else which does not adhere to the wiring illustrated by the pix(s) or the link below.

      Please refer to

  4. hi, I've inherited my dads Quad 303 speakers, quad 303 amp, and FM 3 tuner, quad 33 amp (it has all the options buttons like tape, disc, radio on the front.) I have a number of the original cables, wires. I need help because I dont want to blow it up by connecting it all wrong. I have the original mains leads for the speakers, please the leads from 303 amp to speakers. Can you tell me what plugs in where etc? i could send a photo of what I have? I would appreciate any help! Francesca Black

    1. Someone has already done it on youtube -