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Quad 303 any good?

Tony L said:
Which did you prefer, 303 or 405?

Tony.
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Well it's too early to judge, because the they both need a service, but....... at the moment, even though the 405.2 has more power, I prefer the 303. It just sounds more natural.

It's worth a mention that the Altec Lancing 501s are 4 Ohm. I believe the 405 doesn't like that, not sure about the 303???
 
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Just be aware that the tracks on many 303 circuit boards are pretty crap quality and lift with minimal heat, i.e. what is in theory a simple job can involve much swearing. Given you are already 40 quid plus postage in on the eBay stuff I'd be tempted to pay about another £60 or so and let Quad do it!

Alternately if you really like the 303 apparently Net Audio can take it to a whole new level.

Tony.

PS I've got a 303 knocking around myself, plus a Net Audio PSU board to fling in it, but it will probably be a fair time until I do anything - as much as anything because I don't quite know what I need a 303 for these days - I just like the idea of having one as it was my first ever hi-fi amp! I've just got too much hi-fi kit to be honest.
 
This is where I picked up on suggestions of phase inverting (can't remember which was first)...

Gradient ESL subwoofer instructions:
http://www.gradient.fi/file_download/4 and http://www.onethingaudio.net/FOR/QUA/57/PDF/9512-QUA-GEN-MAN-SW57.pdf

Notes on modding the 405 for non-inverting input:
http://www.dc-daylight.ltd.uk/Valve-Audio-Interest/QUAD/QUAD-405-Modification/QUAD-405-Mods.html

Also, somewhere on the intarweb I found a table listing inverting vs non-inverting design of the Quad preamps - but haven't been able to trace it for your delectation. It seemed to make sense, as the early transistor pre-power combinations traditionally sold together are listed as inverting - i.e. as Richard said they put you are back to where you started.

In my setup where there is no Quad preamp, connecting the speaker phase "the wrong way round" definitely sounded a lot more lively. But I could easily be wrong... will experiment a bit. Do any 303 owners here have a scope and signal generator?

Mark
 
Tony L said:
Just be aware that the tracks on many 303 circuit boards are pretty crap quality and lift with minimal heat, i.e. what is in theory a simple job can involve much swearing. Given you are already 40 quid plus postage in on the eBay stuff I'd be tempted to pay about another £60 or so and let Quad do it!

Alternately if you really like the 303 apparently Net Audio can take it to a whole new level.

Tony.

PS I've got a 303 knocking around myself, plus a Net Audio PSU board to fling in it, but it will probably be a fair time until I do anything - as much as anything because I don't quite know what I need a 303 for these days - I just like the idea of having one as it was my first ever hi-fi amp! I've just got too much hi-fi kit to be honest.
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I was going to take it to Vintage Quad Clinic in Wakefield (& still may do), but he's out of bits. I just fancied a go myself.

Hmm, what to do??
 
Wasn't there a time when QUAD was considered unlistenable? I had a 33/303 and loved them. Sold after I found a pair of Cambridge Audio TL200's that needed 'different' Watts. They worked fine on the end of a Luxman SQ-507-X BTW.
 
strummer, those bits off ebay are exactly what you need. The same guy also sells WIMA caps for bypassing the 10000uF output caps. Did my own amp with much fear and trembling, and it still works! The new caps are 35mm rather than 38mm diameter, a couple of times round with insulation tape did the trick.

As noted earlier, one thing that makes a huge difference is setting the bias correctly. Sounds scary, but replacement output transistors are cheap (i.e. don't worry about the risk of cooking them) - and getting the bias right makes a big difference.

The "Quad unlistenable" thing was probably when they had become old and nobody had yet thought of having them serviced. IMHO after servicing the 303 sound is good but dated (unsurprisingly) - good for listening to music but doesn't tick any audiopile or flat-earth boxes.

The 33/303 was my first "real" amp and a vehicle for discovery of classical music and jazz. That led to the purchase of speakers which suited this kind of music - but at 4 ohms had the 303 on its knees.
 
honmanm said:
The "Quad unlistenable" thing was probably when they had become old and nobody had yet thought of having them serviced.
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I think it also dates from the period when hi-fi mags / dealers tended to assess whether an amp was any good or not by whether it could drive Linn Saras. The Quads couldn't. It doesn't seem that important these days!

Tony.
 
honmanm said:
strummer, those bits off ebay are exactly what you need. The same guy also sells WIMA caps for bypassing the 10000uF output caps. Did my own amp with much fear and trembling, and it still works! The new caps are 35mm rather than 38mm diameter, a couple of times round with insulation tape did the trick.

As noted earlier, one thing that makes a huge difference is setting the bias correctly. Sounds scary, but replacement output transistors are cheap (i.e. don't worry about the risk of cooking them) - and getting the bias right makes a big difference.
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Thanks very much!!! I'm going to give this a go. As I said, replacing caps like for like is easy. I'll be asking questions when it comes to bypassing & setting bias :eek::eek::eek:
 
Tony L said:
Just be aware that the tracks on many 303 circuit boards are pretty crap quality and lift with minimal heat, i.e. what is in theory a simple job can involve much swearing. Given you are already 40 quid plus postage in on the eBay stuff I'd be tempted to pay about another £60 or so and let Quad do it!

Alternately if you really like the 303 apparently Net Audio can take it to a whole new level.

Tony.

PS I've got a 303 knocking around myself, plus a Net Audio PSU board to fling in it, but it will probably be a fair time until I do anything - as much as anything because I don't quite know what I need a 303 for these days - I just like the idea of having one as it was my first ever hi-fi amp! I've just got too much hi-fi kit to be honest.
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It is worth getting the PSU board in and buying the cap upgrade kit. Really does work wonders, and.... sounds amazing with tannoys!
 
Just put in a Net Audio PSU board... and as dom says, makes a big difference, sounds like a different amp (in other words... gets in the way a lot less than before). I must confess to liking the classic 303 sonic signature, however with the PSU board everything is more neutral and the 303 can cope with orchestral climaxes etc. Nearly effortless but not quite there yet.

Regarding phase, this system is a lot better with the speaker phase inverted (speaker + to amp - and vice-versa). Connecting speakers the "right way round" results in a muffled sound without well-defined notes. Inverting speaker phase, the overall effect is a bit bright, but that is possibly some other part of the system. Note that there is no Quad pre in the system at the moment.
 
strummer said:
Well it's too early to judge, because the they both need a service, but....... at the moment, even though the 405.2 has more power, I prefer the 303. It just sounds more natural.

It's worth a mention that the Altec Lancing 501s are 4 Ohm. I believe the 405 doesn't like that, not sure about the 303???
Click to expand...

Neither are really designed for 4 ohm loads, however the 405 doesn't just stop working, it simply current limits beyond a certain point. I don't have the graph to hand but the 405 manual has all the info you need.
It will drive 4 ohm loads - you just need to ensure that it plays loudly enough for your needs. From memory I think the 4ohm continuous rating is about 70w.
 
strummer said:
How do I unclip the boards without damaging the plastic cable-tie things?
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Make sure you unclip the right side, i.e. not the side with the cable loom - just gently prize the clips apart and the boards will clip out and hinge on the other side for access.

Tony.
 
Robert said:
Neither are really designed for 4 ohm loads, however the 405 doesn't just stop working, it simply current limits beyond a certain point. I don't have the graph to hand but the 405 manual has all the info you need.
It will drive 4 ohm loads - you just need to ensure that it plays loudly enough for your needs. From memory I think the 4ohm continuous rating is about 70w.
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Thanks Robert

Hmm, I can see these being used in another room, because I think the Altec Lansings are keepers!



Tony L said:
Make sure you unclip the right side, i.e. not the side with the cable loom - just gently prize the clips apart and the boards will clip out and hinge on the other side for access.

Tony.
Click to expand...

Thanks Tony

I will give that a try now!
 
Robert said:
Neither are really designed for 4 ohm loads, however the 405 doesn't just stop working, it simply current limits beyond a certain point. I don't have the graph to hand but the 405 manual has all the info you need.
It will drive 4 ohm loads - you just need to ensure that it plays loudly enough for your needs. From memory I think the 4ohm continuous rating is about 70w.
Click to expand...

Something else that came up in an original Gordon King review, when case of the 405 gets hot, the power output drops to around 32W into 8 Ohms IIRC and it's easy to get the 405 in any version rather hot to touch..

if you need more current from the 303, have a look at the net-Audio mods (if you haven't already), as replacing the output devices to MJ1500 types means you can turn the output into fully complementary and reduce or practically remove the current limiting to give 8 Amps each channel, a far more practical current output for your 45W IMO...
 
DSJR said:
Something else that came up in an original Gordon King review, when case of the 405 gets hot, the power output drops to around 32W into 8 Ohms IIRC and it's easy to get the 405 in any version rather hot to touch..

if you need more current from the 303, have a look at the net-Audio mods (if you haven't already), as replacing the output devices to MJ1500 types means you can turn the output into fully complementary and reduce or practically remove the current limiting to give 8 Amps each channel, a far more practical current output for your 45W IMO...
Click to expand...

Indeed Dave, the sinking on the 405 isn't large enough to support full output for long periods and Quad hint at this when they advise against using the amplifier under test conditions playing test tones. However they do state that very hot running is not a concern. I remember my old Mk1 getting nearly too hot to touch when running Celestion SL6s - mind yuo, least said about those the better!
A 405 should be fine under dynamic music conditions though, and a 405/2 should manage moderately difficult loads in the real world. Certainly the mk2 I bought and serviced a couple of weeks back sounds great with the ESL.

I've just bought a nice Quad 33 to add to the growing collection of Quad electronics, with the intention of giving it a thorough clean and recap. Hope to pick up a 303 next month. Then I shall go seeking the valve stuff.
 
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