Quad 303 - Interesting mod :scratch:
I made a silly heart purchase last month and bought a Quad 303 from a house-clearance lot which I thought would need doing up.. In the event, someone (the previous owner?) has beaten me to it.
I'm hoping barry or someone knowledgeable about tweaking these can shed some light on what and why these things were done - it sounds great by the way...
Firstly, the supply and speaker caps..
http://i132.photobucket.com/albums/q.../DSCF1448a.jpg
The caps are Rifa 4700uF at 100V and are now screw type, which should make replacing them easier. The trio of bypass caps on each Rifa is the interesting bit, with 100uF + 1uF + something smaller being an interesting take on things...
The driver boards have had new resistors fitted (1% or better), the caps have been replaced with Ansar, Black gates and also a large electrolytic across the back which doesn't feature in the Quad design as far as I can see.
All the presets have also been replaced by multi-turn ones too.
http://i132.photobucket.com/albums/q...s/DSCF1445.jpg
Have any engineers out there got any opinions? All I feel I can do to put my stamp on it is to consider getting the Net-Audio rectifier board. I'm not sure I'd go as far as to change the output trannies and re-configure for fully-complimentary operation, let alone remove the limiting (I'm not going to drive Apogee, Maggies or 'Briks any time soon with "anything," and the Spendors are a doddle of a load for the Quad in any case.. They certainly sound very charming together, even though the bridged Crowns are the "better" choice, due to better damping and ultimately lower distortion and noise on paper.
P.S. These old amps may well be museum pieces and more than a bit archaic, but the effort that went into designing and making them (no robots in the 33/303 construction) gives them a sort of organic or "human" quality as does the gear Glenn makes by hand.
I dunno, I'd just like to be a careful custodian for these amps as I reckon they'll easily outlive me ;)