For one week only - the Quad 303(K)

[Barry]

For one week only – the Quad 303(K)


Whilst sorting out some surplus equipment, I decided it might be interesting to listen again to the Quad 303 amplifier. Actually the item in question is closer to the Quad 303K; the K suffix denoting items modified by Quad for Kelsey Electronics, which have all the audio connectors replaced by XLR type. In my case the modification was made by Audiocraft, and differs from the Kelsey version by having separate connectors for the two channels and an XLR type mains connector.

http://i780.photobucket.com/albums/yy88/barrydhunt/012-1.jpg

But under the hood it is the same as a standard 303, a 45W/channel solid-state design introduced by Quad in 1968. The power amp replaced my Mark Levinson ML-2, (modified) Quad 405 and Quad 510 monoblocks. It is fed by a Mark Levinson ML-28 preamp and in turn feeds a pair of Quad 57 ESLs (original and unmolested).

http://i780.photobucket.com/albums/yy88/barrydhunt/004_zpstpu3oi2u.jpg

Given the recent discussion of how equipment designed in the ’70s and ‘80s compare with more modern fare, I have to say that after 45 years the Quad 303 design still holds it own and is a joy to listen to.

“Pipe and Slippers”? Well not really – I can’t speak for the behaviour of the 303 into other (moving coil) speakers, as I haven’t used the 303 with my B&W DM2As for some time now, and that was for AV duties in my second system. But when partnered with the Quad 57s the sound is mighty fine.

Despite being capacitor coupled, and having a modest output impedance of ~ 1 Ohm, the 303 works very well into Quad 57s for two reasons:

Being electrostatic, the moving mass of the Quads is very low, so there is very little back emf generated that needs to be damped by the amplifier (‘tail wagging the dog’)

Quad cleverly chose the value of the output capacitor so that it would form a series resonance with the inductance of the audio transformer of the 57, extending the low-frequency response of the combination. (http://www.audiomisc.co.uk/57and303/interact.html)


Compared to the above-mentioned amplifiers, the Quad 303 is a touch warmer, and perhaps a little slower dynamically, but focus and sound-staging are equally as good. As too is the three-dimensionality of the image: performers seem real and solid, not like cardboard cutouts. Regardless of source, nothing I have played so far has caught it out.

So I’ll be hanging on to the 303, and given the enjoyable experience of listening to this vintage piece of kit, I’ve a good mind to dig out a pair of Quad 50E monoblocks – a design even older than the 303 and see how they fare.

[Jimbo]

Nice review Barry. I have had many Quad amplifiers myself from the past including the 303,405 and 606 as I used to sell them back in the late 70's, early 80,s. We used to have a repair shop upstairs where some old guys with vast electronics knowledge would be able to repair virtually anything but that was because they were from a time when PCB,s were a new fangled thing!:) They always said Quad amps were some of the best quality bits of HIFI they ever worked on!

Always a massive fan of Quad gear ever since I visited Pebble Mill BBC and saw loads of them used around the building so I thought if they were good enough for the BBC they must be good enough for me!

[Firebottle]

Looking very nice Barry. Interesting link that you posted also.

I will have a 303 to look at on Monday, which reminds me I must take the circuit diagram with me :mental:

[Macca]

I think the 303 only gets bad press because of people who have heard tired ones, or it being run into the wrong speakers. With the right ancillaries they work superbly. Two of the best (i.e musical and easy to listen to) systems I have heard used a 303 for the amplification.

[walpurgis]

I think the 303 only gets bad press because of people who have heard tired ones, or it being run into the wrong speakers.


You could say that about any amp.



Nothing specifically wrong with Quad 303s, but having used them, I find them a bit 'pipe & slippers' much in the same way as the NAD 3020, Audiolab 8000a and A&R Cambridge A60 are too. All safe enough choices, bit a bit dull.


There you go. There'll be proud owners of the foregoing up in arms now. :D

[Arkless Electronics]

You could say that about any amp.



Nothing specifically wrong with Quad 303s, but having used them, I find them a bit 'pipe & slippers' much in the same way as the NAD 3020, Audiolab 8000a and A&R Cambridge A60 are too. All safe enough choices, bit a bit dull.


There you go. There'll be proud owners of the foregoing up in arms now. :D

+1

[Macca]

You could say that about any amp.



Nothing specifically wrong with Quad 303s, but having used them, I find them a bit 'pipe & slippers' much in the same way as the NAD 3020, Audiolab 8000a and A&R Cambridge A60 are too. All safe enough choices, bit a bit dull.


There you go. There'll be proud owners of the foregoing up in arms now. :D

I like all those amps! What I mean is that the 303 is limited on power and current so needs to be matched more carefully than something like my XTZ. Big, modern B&Ws, for instance, are not a good partnering.

[Ninanina]

I ran a 33/303 for years into 57's and loved the sound however moving onto a different system I think the 33/303 lacked a bit of 'sparkle' it's tricky to explain :doh:

I maybe could agree with the 'pipe & slippers' description Geoff gave and I also agree with Geoff on the A&R Cambridge A60 being much the same. In isolation both amps were fine but not when compared to others I have owned

However if I had to 'live' with only Quad gear, as long as 57/63's were being used, I'd be more than happy ;)

[Macca]

I ran a 33/303 for years into 57's and loved the sound however moving onto a different system I think the 33/303 lacked a bit of 'sparkle' it's tricky to explain :doh:

I maybe could agree with the 'pipe & slippers' description Geoff gave and I also agree with Geoff on the A&R Cambridge A60 being much the same. In isolation both amps were fine but not when compared to others I have owned

However if I had to 'live' with only Quad gear, as long as 57/63's were being used, I'd be more than happy ;)

Have to disagree. The 33 was the cause of your lack of sparkle, as it is a stodgy old thing. And stick some Wharfedale Diamonds or similar simple, punchy speakers on the end of an A60 and it will properly rock out.

[Ninanina]

Have to disagree. The 33 was the cause of your lack of sparkle, as it is a stodgy old thing. And stick some Wharfedale Diamonds or similar simple, punchy speakers on the end of an A60 and it will properly rock out.

You have a great piont there Martin..... I was always more impressed with the 303 than the 33 ...

The only other Quad stuff I have used was a fantastic pair of Quad II's which I ran with a Croft Vitale pre... excellent indeed... :)

[walpurgis]

I was going to reply to this thread again. But decided I can't be arsed! :D

[Ninanina]

I was going to reply to this thread again. But decided I can't be arsed! :D

:rfl::rfl:

[Ninanina]

Thinking about it further I have never heard an A&R Cambridge A60 ever sounding that good to be honest

I've heard the A60 with Roger's LS7's, Epos ES22's, and other speakers that I can't remember, and to be honest is was just dull as dishwater....

Like I said, in isolation, it is ok but not when compared against other amps I have heard for not that much more money either.. ;)

It just sounds 'dark' and 'fluffy' to me and not involving at all.. :)

[Arkless Electronics]

Quad 33 is crap. 303 is much better but deficient by modern standards.
I once offered a service upgrading 303's but it was decades before this became trendy and so not a single enquiry....It was £350 for my upgrades!:D
Years later I upgraded a pair of 303 for a friend and took them to a very upgraded and modded spec. Replacement voltage regulators of my own design, new output devices and drivers, huge PSU and output caps etc etc. It sounded much better than standard and completely ended any problems with bass depth and slam, dynamics etc etc... in fact it became a bit of an animal that would drive anything with aplomb to high levels. No pipe and slippers now!
The mods didn't appear to solve the lack of mid range transparency though which was a disappointment... No doubt others will now reply that they think it has good transparency... obviously I disagree!
There was also an amp of my own design there and a Exposure 4 dual regulated (which I had also hugely modded) and these both beat the Quad on transparency but the Quad could match them for "balls" and "drive" :)

[southall-1998]

I would never have a Quad 405/606/303 etc modded!

S.

[Arkless Electronics]

I would never have a Quad 405/606/303 etc modded!

S.

You'd have box swapped them before you had time to:D

[Barry]

Quad 33 is crap. 303 is much better but deficient by modern standards.
I once offered a service upgrading 303's but it was decades before this became trendy and so not a single enquiry....It was £350 for my upgrades!:D
Years later I upgraded a pair of 303 for a friend and took them to a very upgraded and modded spec. Replacement voltage regulators of my own design, new output devices and drivers, huge PSU and output caps etc etc. It sounded much better than standard and completely ended any problems with bass depth and slam, dynamics etc etc... in fact it became a bit of an animal that would drive anything with aplomb to high levels. No pipe and slippers now!
The mods didn't appear to solve the lack of mid range transparency though which was a disappointment... No doubt others will now reply that they think it has good transparency... obviously I disagree!
There was also an amp of my own design there and a Exposure 4 dual regulated (which I had also hugely modded) and these both beat the Quad on transparency but the Quad could match them for "balls" and "drive" :)

If the Quad 33 was "crap", then so too was any other preamp of that era, regardless of it being valve or SS: Radford SC22; Beam Echo; Rogers 'Master' Control Unit; Leak 'Point One'; Kerr McCosh, or Sugden C51. In fact all preamps of that era are woefully deficient by modern standards, however the NET improvements to the Quad 33 are well worth implementing.



The purpose of my thread seems to have been misunderstood - it was not to lionise the Quad 303 per se, it was simply to say that when partnered with the Quad ESLs, the combination is a fine match. In fact, of the amps available of that period, the only power amps I would countenance using with the Quad 57s would be the the Quad 303, Radford valve series using EL34s, Beam Echo DL35s and, possibly, the Leak 'Stereo Twenty' and Quad 50Es.

The Quad 303 was a very good design using a quasi-complementary output stage and transistors, available at the time. I assume you redesigned the output circuit so it was fully complimentary; a service that NET also offer.

As to the sonic attributes of your modified 303 - we will just have to take your word for it.

[Arkless Electronics]

If the Quad 33 was "crap", then so too was any other preamp of that era, regardless of it being valve or SS: Radford SC22; Beam Echo; Rogers 'Master' Control Unit; Leak 'Point One'; Kerr McCosh, or Sugden C51. In fact all preamps of that era are woefully deficient by modern standards, however the NET improvements to the Quad 33 are well worth implementing.


The purpose of my thread seems to have been misunderstood - it was not to lionise the Quad 303 per se, it was simply to say that when partnered with the Quad ESLs, the combination is a fine match. In fact, of the amps available of that period, the only power amps I would countenance using with the Quad 57s would be the the Quad 303, Radford valve series using EL34s, Beam Echo DL35s and, possibly, the Leak 'Stereo Twenty' and Quad 50Es.

The Quad 303 was a very good design using a quasi-complementary output stage and transistors, available at the time. I assume you redesigned the output circuit so it was fully complimentary; a service that NET also offer.

As to the sonic attributes of your modified 303 - we will just have to take you word for it.

Sugden C51 best of those you mention but yes all crap.

The best I've ever heard 57's, and in fact one of the best sounds I have ever heard, full stop , was with a Stereo 20 which I had very extensively modded for the same guy who got me to mod his 303's and Exposure 4 Regulated.

I considered going fully complementary but didn't go through with it. just better and more robust outputs and drivers. Later simulation I did showed no improvement from this anyway but it would need to be tried in practice. They (2 of em) were highly modded though, even to the extent of no longer regulating the negative supply but the positive instead! As I say the finished article sounded very modern but just didn't quite cut it for me in terms of transparency and filigree detail but the owner was delighted!
I no longer offer mods to Quads as a "standard" service as I can't compete on price with Dada and Net Audio... I do still modify ALL amps though (with exceptions.. no class D or SET's).

[spendorman]

Just connected up a Quad 303 to Rogers BBC LS3/6, sounds wonderful, the midrange is so clear. Had an A&R A60 connected for an hour or so previously. 303 sounds better, more dynamic, more detail than the A60 (a late model one).

The 303 is one of four that I have, a fairy early model, completely original.

[Barry]

Just connected up a Quad 303 to Rogers BBC LS3/6, sounds wonderful, the midrange is so clear. Had an A&R A60 connected for an hour or so previously. 303 sounds better, more dynamic, more detail than the A60 (a late model one).

The 303 is one of four that I have, a fairy early model, completely original.

I have a 'standard' 303 as well. I only used the 303 "K", as most of my system cabling is balanced and uses XLR connectors. Returning to the 4-pin DIN of the standard Quad 303 would have been inconvenient.

Glad you're enjoying the Quad 303 powering your Rogers BBC speakers. I heard similar (though it might have been a 405) many years ago, shortly after the Speaker was introduced.

[spendorman]

I just have a cable that I made up, 4 pin din plug to phono, so easy to connect up. This older 303 has the mains Bulgin input. Made up a mains lead with Bulgin at one end, in line switch, and an IEC at the other end.

The 405-2 that I have, I bought new as a 405 about 1976, never got on with it, converted to 405-2, much better, then much later fitted Burr Brown op amps, not much difference.

[walpurgis]

I heard the newly released 405 compared to the 303 back then driving ESLs and thought the 405 clearer and having more grip. This was for maybe an hour or so at London Sound, when Mike Solomons had his shop in Eastcote for a while.

[spendorman]

Perhaps Mike's 303 was not set up recently, makes a lot of difference. My first 303 was purchased second hand, not that old, in good condition, sounded rough. Sat on the shelf a while as I did not like it. Decided to follow the setup instructions, made a big difference.

Only been to Mike Solomons shop when it was at Harrow on the Hill. That must have been a long time ago. He used Sinclair speakers for some testing.

[walpurgis]

Perhaps Mike's 303 was not set up recently, makes a lot of difference. My first 303 was purchased second hand, not that old, in good condition, sounded rough. Sat on the shelf a while as I did not like it. Decided to follow the setup instructions, made a big difference.

Only been to Mike Solomons shop when it was at Harrow on the Hill. That must have been a long time ago. He used Sinclair speakers for some testing.

The 303 and 405 were new 'demo' items. The Eastcote shop was before Mike later moved to Harrow on The Hill (Just around the corner from me at the time). London Sound eventually relocated to Rayners Lane, where it still is as far as I know. It took a VTL pre-amp to him about ten years ago for a service and was not best pleased with his (overpriced) work. I should have done it myself.

[spendorman]

A friend had similar problem with servicing, I had to remake some joints and cables. It was a Rogers valve pre and power amp combination.

[Martyn Miles]

Perhaps I'm 'Old Fashioned', but my Quad 34/303 sounds lovely with Harbeth P3-ESRs.
The 303 was recently serviced by Amplabs ( excellent customer relations ) and the 34 worked on by Keith Snook.