Quad 303 Pics.

[southall-1998]

Does this Quad 303 have any upgrades? Please take a look at the pics below.

I bought this one almost a year ago. Does sound nice I must say.

Cheers.


http://i602.photobucket.com/albums/tt104/TDL-STUDIO/182.jpg

http://i602.photobucket.com/albums/tt104/TDL-STUDIO/181.jpg

http://i602.photobucket.com/albums/tt104/TDL-STUDIO/183.jpg

http://i602.photobucket.com/albums/tt104/TDL-STUDIO/184.jpg

[Reid Malenfant]

The green PCB isn't standard, that looks like a modified regulator ;)

The blue capacitors are also non standard, they look like decent screw terminal Philips computer grade jobbies to me :)

[southall-1998]

Hehehehe..should I send it to Quad and have the parts changed to standard :)

[Reid Malenfant]

Noooooo :eyebrows:

If it sounds good then I say keep it sounding good :)

[southall-1998]

Does the NET Audio PSU remove some of that original Quad 303 characteristics?

Strange question to ask really, but can't help it :)

[DSJR]

Probably not Shane, but for all the peeps here who don't have access to the Quad Yahoo Group, where you've also asked questions about it, I should say that the Net-Audio regulator is a linear type, whereas the original is a shunt type. Mr Malenfant should be able to explain, but apparently Peter Baxendall designed, or assisted in, the design of the regulator, a shunt type being the preferred option for the 303.

Shane, the supply caps look to be good types and if the electrolytics on the amp boards have been replaced with decent ones, they should be left alone as well (mine has Ansar and Black Gate's) I think. With these amps, the main thing I believe, is to make sure the voltages are ok and to use speakers that don't demand too much from it - and you seem to be following that trail with an assortment of different speakers passing through your hands right now. That way, the 303 will sing sweetly and with huge charm - it's still a lovely, if limited, little amp I think and better overall than the valve Quad II's, which shouldn't be used daily these days IMO if the remaining life of the GEC KT66's is important.

Shane, I don't know how the Dada boards compare to the Net-Audio ones, but if you can find a Quad original regulator board (Quad Service Dept may have them still), then my advice is to have one retro fitted and have the amp checked and re-set up, keeping the rest as-is. DON'T flog it on, but keep it as a general reference while you work your way through all the other stuff you buy and sell :)

[rwacka]

"use speakers that don't demand too much from it"

Dave, can I ask what you mean by this please?
Cheers
Richard

[Rare Bird]

"use speakers that don't demand too much from it"

Dave, can I ask what you mean by this please?
Cheers
Richard

Uprate the Output Inductor

[julesd68]

Shane,

Another route to consider is Red Hill Audio -

http://redhillaudio.co.uk/upgrades.html

Lee recently did a service on my 405-2 and replaced a few bits for me -
I did say that I wanted to keep all the character of the amp and he's certainly done that.

cheers.

[DSJR]

The 303 is very modest in its current output, since it's limited to 4 amps max approx. Yep, you can modify or remove this limiting, but then the output trannies could easily fry as they are old now and not up to swinging large current values. This means you have to change these transistors to modern ones and, while you're at it, why not convert the output stage to fully complimentary etc etc etc etc.. You end up with an "on the edge" amp that is anything but the safe and gentle sounding 303 you started off with, so why buy a 303 in the first place?

Modern main-market speakers are not hugely sensitive and often have a lowish impedance curve to pull more power from the amp. I'm not altogether sure a 303 would be truly happy with this. The Capacitor coupling doesn't favour flabby badly tuned speaker ports either, although I hadn't tried "mine" with higher value output caps which apparently improve this somewhat.

My advice for any prospective 303 owner is to get the thing properly serviced and re-capped and use easy-load speakers (many well loved vintage models are 8 ohms minimum, rather than average and Tannoys like Marco's were rated at 11 ohms, ideal IMO). Like the II's which preceeded it, it's a charming little amp with a delightful sound. Sounds good with Croft preamps too, but benefits from the input gain being reduced (two resistors to change, one on each amp board).

[RobHolt]

If driving 4 Ohm loads, the coupling caps can be usefully uprated to 6800uf.
This lowers the point where the LF rolls away and the damping factor drops.
It won't play any louder, but it will play cleaner and with better control at the bottom into such loads.

Leave the PSU caps alone. The old 60s rectifier won't thank you for uprating these substantially.

Rob