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Old 21st September 2012, 10:41 AM   #1
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Default Quad 303 Upgrade - How far is too far?

Hi, I've owned a 303 for a year or so now, it had the original capacitors so I refurbed it with the Net Audio capacitor kit and replaced the butchered front plate with a home made one which included proper input and output sockets and some decent mains in and out sockets. So it's "sort of" original (at least sound wise). I use it with my 57s. and I like the results. (Incidentaly I use a DAC to feed it, am I the only one? Most people seem to spend time and money upgrading their Quad pre amps and still people knock them).

I just bought (maybe unwisely) another 303 and I'm tempted to go the whole hog and get the two mono Net audio full upgrade kits. Has anyone gone down this road and is brave enough to give a truthful (not coloured by expenditure!) report of the outcome? Will I loose the Quad sound as some people say (do they actually know this to be so or is it just a desire to keep originality?). I suppose that if I do the upgrade and don't like it I can always put my first amp back as it is now and sell the second one with all the upgrades.

So, should I stick with what I have, or am I missing out on the 'wonders' of Mk3 upgrades and the 'essential' benefits of monoblocking to get the best from my 57s?

Some objective help, maybe on the outcome of each part of the upgrade process, required here!
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Old 21st September 2012, 09:42 PM   #2
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Read someone who doesn't have a financial or singular interest in their "upgrade" kits or services. The same is true everywhere of opinions expressed by owners who accept glib high-end audio sales pitches and buckle to the snobbery of the devotees.

You will not get valid opinions within the experience of Quad devotees because money is at the bottom of upgrades and having spent it, we naturally feel it is going to be justified - if not, why do we keep modding and modding our gear into nothing original? Is only the case and transformer worth keeping? It is also worth noting how little most modified audio is worth, compared to that in original condition, whatever opinion holds as better performance or whose ideas were implemented.

My suggestion is to limit enthusiasm to rational ideas and procedures that genuinely improve the usefulness and preserve the sound quality of the original, such as those by Keith Snook, whom I'm sure you're aware of. Otherwise, play about rebuilding with inexpensive clone boards which are every bit as good as the originals.QUAD 303 Amplifier modification to general purpose Lab amp from 303 A2
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Old 21st September 2012, 10:30 PM   #3
wahab is offline wahab  Algeria
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Ian summarized it efficently...

On the technical side it is worth pointing that the only valuable
mod on such an amp is to increase the output capacitance to get
lower distorsion at low frequency as well as better frequency response.

For the rest , the perfs are surprisingly good with the original amp
and wont be improved significantly with any other modification than
the one above..
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Old 21st September 2012, 10:50 PM   #4
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Old 21st September 2012, 11:20 PM   #5
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I've owned at least a dozen Quad 303s. The most dramatic work i did on them is outlines here: Quad 303 monobloks

When i listened to my last one i switched from a 3875 chipamp. Quickly flipped the 303 and said to myself, never again unless it is at a give-away price. I love the chassis.

dave
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Old 21st September 2012, 11:23 PM   #6
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303 forever!

Regards zeoN_Rider
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Old 22nd September 2012, 05:34 AM   #7
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Quote:
Originally Posted by zeonrider View Post
303 forever!

Regards zeoN_Rider
Wow, man, you must LOVE your 303's! That is epic work.
I traded mine in on a 405 back in nineteenmumblymum and was never sure I did the right thing....

Still got a soft spot for the old fella and it's 33 companion.
Those and my Sugden P51/C51/T51 are the only amps I ever regret selling. Oh, and the Astronic 1222s as well. And the Haflers. Maybe the Meridians too. The Krell? Happy to see the back of it. And don't get me started on the bloody Metaxas.........

Rgds,
blakksmokemits (from the Metaxas, mainly)

ps. I agree with Dave. A decent chip amp kills them. But I kind of wish I was listening to one now even so.... Nostalgia - It's free!

pps. Oh, and the Cambridge P40 that blew up every second Tuesday. It sounded great for the thirteen days in between!

Last edited by blakkshepeaudio; 22nd September 2012 at 05:37 AM. Reason: Forgot the Cambridge
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Old 10th October 2012, 11:06 AM   #8
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Love the work you have done.

To answer the original question you need to change all the electrolytic capacitors as these are the parts that fail with age as the electrolyte dries up. Don't worry too much about specs as any current capacitor you buy will be better than its 1970s' counterpart and return the amp to its original sound, if not better. Mains cable should be at least the 40 strand 13 amps mains type.
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Old 28th March 2013, 05:50 AM   #9
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I had a go at upgrading a 303 with serial number 84XXX. I went pretty far, recapped, put MJ15003 output transistors on (kept it NPN-only output), new input stage transistor, silver input cable, better speaker terminals & cable, chunkier Power supply and output filter capacitors, new trimpots, I did the inductor and diode mod to increase the output current, and replaced the bridge with MUR diodes. I then powered her up. She sounded a BIT better, but I was very frustrated that it still had a very limited soundstage (like the sound was "stuck" L & R in each speaker), and horrible horrible brittle highs that rolled-off like a valve amp response, resulting in very little definition & detail. I was actually all ready to relist the amp on the auction site where I found it. THEN I replaced the horrible 38495 & 38496 driver transistors on the amplifier PCBs with 5320 & 5322 transistors, and lordy lordy - she opened right up with a nice spread-out soundstage, massive amounts of nice smooth topend response (nice and sweet topend) and tons more detail. If the "quad sound" is what this amp is meant to sound like before I made this last change, then you can keep it! The 303 is now currently the best amp I've ever heard or owned. I'd thoroughly recommend this mod to anyone with this amp. It truly unlocks the amp's true potential.
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Old 28th March 2013, 11:02 AM   #10
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I wonder if any of you has a scope ....nothing else ...

(twisting power supply cables , with ground , with signal, with input, with output,with base leads ,with emitter leads, with collector leads , and all of these times X 2 since we have 2 channels WILL RESULT that at some point that the mess of cables will MODULATE the base leads with catastrophic results times X2 if load is more capacitive )

This type of modulation will insert various types of harmonics in the signal which easily can be perceived as "" unique sound"' BUL to my understanding , expect crosstalk to hit the sky and a zillion of other problems like oscillation or inter modulation and any form of this type of interaction to be present and pollute your signal ...

The number one thing one should to is to re arrange wiring separate channels but most important keep the base cables free of problems

Kind regards
a ...Japanese Lover
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Last edited by east electronics; 28th March 2013 at 11:16 AM.
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