QUAD '303' Balanced!

[Rare Bird]

Does anyone know if Quad offered a modification to balanced the standard '303' Power amp input?

[Dr Bunsen Honeydew]

Does anyone know if Quad offered a modification to balance the standard '303' Power amp input?

Why would you want to?

[Rare Bird]

It doesnt matter why!

[BTH K10A]

I don't know if the BBC versions had a true balanced input but they certainly had XLR connectors.

http://www.ebay.co.uk/itm/Pair-BBC-Monitoring-Speakers-LS3-7-power-amps-/110716676514?pt=UK_ConElec_SpeakersPASystems_RL&hash=item19c73a69a2#ht_500wt_1156

[Barry]

Hi André,

In a word - no. Although many Quad 303s were used in professional situations, Quad always regarded the 303 design as intended for the domestic market. The professional amplifers, the Quad 50D and 50E, had provision to fit internally a transformer permitting 600Ohm balanced line operation.

There were some versions of the 303 modified and fitted with XLR connectors. These are the 303J and the mono bridged version supplied by Quad to Kelsey electronics: the 303K. Neither of these had balanced inputs.

The Quad 303/A2 mentioned by Alan is a specially modified version made by Quad for the BBC to power the LS3/7 loudspeaker. The amplifier used each channel to separately power the low-frequency and high-frequency drivers of the speaker. The active crossover network is housed in the unit underneath the main amplifier. There were two input sockets; an unbalanced 1/4" jack and an XLR socket. I'm not sure if the latter was balanced, but I suspect not.

Fitting a balanced input to the 303 is something that I have thought about, as I believe it is beneficial to position power amplifiers as close as possible to the speakers. In my case that would necessitate long leads from the preamplifier; hence the desirability of a balanced input (my preamp has balance outputs).

To provide a balanced input, one would need to use a 1:1 transformer with a centre tapped primary winding. A suitable device might be the Sowter model 3575.

Regards

[BTH K10A]

The later AM8/16 amp used a Beyer dynamic transformer. These have the advantage of being quite small and frequently crop up on German ebay.

In light of above, I see no reason why the earlier AM8/15 would not have a true balanced input

http://i46.photobucket.com/albums/f120/emttsd15/am816clone_thumb.jpg


This site might provide further info

http://www.mhennessy3.f9.co.uk/rogers/ls58.htm

Andy

[Rare Bird]

Found some line level DI boxes they'll do the trick.