Quad 303 Power Amplifier

Quad 303 Amplfier


Launched by Quad in the late sixties this amp quickly gained a viable reputation as a great amplifier. Like all Quad's hi-fi it is beautifully designed and engineered and indeed won a Council of Industrial Design Award in 1969. The Quad 303 amplifier was Quad's first solid state amplifier after the success of the Quad 22 valve amp, and was the first power amplifier to use triplets in its output stage, a clever and unique circuit design that makes ultra low distortion possible without destabilising the transistors.

The Quad 303 amplifier quickly built something of a cult following and was in production until the early eighties. However it is ony recently that people have been re-resurecting these amplifiers as modern day components allow you to take the performance of these amplifiers to a new level. Indeed with a very reasonable outlay of £200-£250 and the expert advice and improved circuits available from Net Audio, the Quad 303 amplifier can obtain a sound comparable with anything solid state has to offer today. The other thing to bear in mind is that the Quad 303 power amplifier can be bought on Ebay for anything between £100-£150.

This entry was posted on Saturday February 25th, 2006 at 8:47 AM and is filed under Amplifiers, Classic. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response.

44 Responses to Quad 303 Power Amplifier

Jiri nun Says:
March 15th, 2006 at 11:12 PM

I shall buy Quad 303 power amplifier

Robert Says:
October 15th, 2006 at 7:48 AM

Thanks for the heads up!
Now the prices wil go up even more.....;-)

Dewald visser Says:
May 8th, 2007 at 12:49 PM

Ohhh - I cant wait to get my set!!!


Hans Says:
June 21st, 2008 at 6:25 AM

Fine circuits are also available from stefaan Verdonckt in belgium. These boards are superbly engineered and the sound is marvellous!

Geoff fielding Says:
July 10th, 2008 at 8:01 PM

I've just set up a system for a friend with two 303s and an Exposure pre amp, bi amped into a pair of ProAc Studio 110s and it is stunning. To be honest I'm jealous and my amp was well into the thousands. I've now got a 303 that was recently serviced by Quad so I'm on my way to building a system around 303s. What I found amazing, as well as the music, was the information about the room and fingers on strings, etc.

David hembrow Says:
December 14th, 2008 at 9:54 PM

These are a wonderful design both inside and out. The attention to maintainability is something you simply don't see in other designs. They're made to last.

Scotchbrian Says:
December 24th, 2008 at 4:45 PM

i have a mint 303/33/FM3 for sale with cables and a thorens 124 MK11 turntable,made in Switzerland with SME 3009 arm and headshell, not sure on cartridge, also mint any interested parties

Frede kristensen Says:
January 29th, 2009 at 7:26 PM

Perhaps you have allready sold, but I would be very interested.
Please let me know your price idea if you still have the system.

Donavan Says:
January 30th, 2009 at 9:08 PM

Hi Scotchbrian, how much are you selling your set? please email me at yusin79@yahoo.com.sg. thanks


March 11th, 2009 at 2:02 AM

I'm in Toronto, Canada. I have a 303 if anyone is looking.

Joel Says:
March 22nd, 2009 at 9:57 PM

im looking a quad 303 amp......how match youy sell it. pls let me know. e-mail me at jppalma62@yahoo.com

Steve Says:
June 19th, 2009 at 4:42 AM

I am embarassed but I just bought a quad 303 and I cannot wire up the din connector to an xlr-m for the life of me.

Any help would be great.


Shane Says:
July 27th, 2009 at 11:33 PM


I'm a happy owner of a Quad 405 poweramp, very nice midrange and dynamics I will like to call it in soundwise.

Back to the subject, how does the Quad 303 sound compare to the 405? I fancy giving the 303 a try some day. My preamp is a Quad 44, I have to say the Quad 44 phono stage sounds good.

Also, I have been told that Spendor speakers goes very well with the 405.



Alain Says:
July 31st, 2009 at 8:20 PM

Good day All,

I am looking to purchased a QUAD 33/303 set up.
Or wouls consider 44/45 & 303 or 405 combo in good condition.
Please let me know if you have or see anything.


Joel Says:
August 1st, 2009 at 9:37 PM

hello i have (2) 303 and 33 amp fully upgraded good sound , strong bass you dont need a sub woofer

Dave Says:
August 13th, 2009 at 10:15 PM

hello, i have a quad 303 and 44 power and pre amp, with leads and a leak troughline mono valve tuner, all in good cosmetic condition and i think working, also a quad2 valve monoblock in need of repair sadly only one. does anyone know what this lot would be worth as a job lot? im interested in selling and am in the south of uk. maybe px for a fatman amp?? also have a mission turntable to go with ultimo? cartridge. daveoakley2007@yahoo.co.uk

Hamad sheikh Says:
August 24th, 2009 at 9:16 PM

I can repair and upgrade QUAD and LEAK, NAIM Amplifiers. If you'd like yours repaired please email me at computerwala@yahoo.com with the symptoms. Regards, Hamad

George walton Says:
August 30th, 2009 at 4:58 PM

Hi Quad lovers,

've got a Quad 33 with two professionally mono-blocked 303 power amps. I'm the original owner of the 33/303 combo, from around 1969, I think, and bought another 303 to try the mono-block.

Basically twice the power and the same quality, and theoretically even more discreet separation. They've been maintained either by Bay Bloor Radio or American Sound (where I bought my second 303).

Every so often I go into a high-end stereo shop and tell them what I have. Then I ask what they've got that might be better. And they look at me and say, "Nothing that'll beat that." They don't even try to sell me something.

Nowadays I mainly listen to my computer, at my iPod. So not much use for the Quad stuff any more. Interested?



(Toronto) 416-505-9523

Jonathan wade Says:
September 3rd, 2009 at 11:22 AM

Hi. Do you still have the quads for sale. Regards

Eric jackson Says:
October 3rd, 2009 at 8:11 PM

Interesting stuff - I have had a 44 control unit and pair of monoblocked 405-2's for some years which have always sounded great. I had the lot serviced by Quad last year (a hum from one of the 405-2's) and the difference in clarity, imaging and dynamics was unbelievable - the source is Linn Sondek etc. and I have a pair of SL6's on purpose built granite stands.
I've had the same kind of comments from hi-fi shops, saying that it would cost me an absolute fortune to make even a slight improvement - it's unbelievable how the quads make the SL6's sing.
Unfortunately I no longer get the use from the quads as most of the music played in our house these days is mp3's through Ipod or computer and the tv surround sound system.
I think that's the way with youngsters these days - I may have to think seriously about selling my stuff too.

Leo de kam Says:
October 6th, 2009 at 4:42 PM

My old and extremely dirty 303 and 33 was recently restored by a Quad Specialist in Bavel Netherlands.
The result far beyond my expectations. The sound is sparkling and fresh and hardly no hiss at all. Allthough I was more into sony v-fet gear I am now a Quad fan aswell.

Louis Says:
October 19th, 2009 at 6:04 PM





Wigan Says:
November 5th, 2009 at 8:41 PM

Hi all, my own setup is a 33 and FM3 with a pair of mono Quad 303J amps (I think these were built as mono amps by quad, and not a later conversion.)

There's a bit of hum and crackle creeping in - is this a diy job, or do they have to go back to Quad for repair?

Any advice welcome



Charles Says:
November 7th, 2009 at 6:05 AM

Wigan, maybe you just need to spray your potentiometer or switches with a bit a of contact cleaner for some crackle, hum sounds like a short or ground problem.

Any way I now have a pair of 303/33's and one Quad Fm tuner, my original teen stereo. Had it rigged up in a big high ceiling wooden Panabode living room with a pair of Acoustic Research AR2ax's bolted up over the sliding door. Never heard a finer disco in my many many days and travels, and they are still cranking it out today. I'm about to reconstruct the above at the cottage.

Computers and mp3's are great, but I still thrill when I can FEEL it - and not hear my own caterwauling to boot! Course you gotta place where you can do that, and a need to do it.

Wigan Says:
November 21st, 2009 at 5:30 PM

...and it works... There are small slots on top of each of the pots under the wiring connectors. Just need to be careful to spray only a tiny amount at a time.

The guys at NET Audio recommended the same treatment, and an ebay seller of SERVISOL-SUPER-10-SWITCH-AND-CONTACT-CLEANER which cost almost nothing.

Thanks for that - now to wait until the neighbours are out...


Neal madden Says:
November 24th, 2009 at 11:20 PM

I have 2 303`s and would like to connect them as 2 mono blocks to 1 pre-amp, can I do that ????, thanks for your help, Neal

Wigan Says:
December 12th, 2009 at 5:37 PM

Hi Neal, there's a circuit diagram on Dada electronis site. Just google +quad +monoblock and see where you get to? I think there are conversion kits available too, if you can do some diy electricals.

good luck


Chris broster Says:
December 17th, 2009 at 3:42 PM

Have just dug my 33/303 out of the loft as was thinking of selling them. Connected them up to the system to check if working ok and was blown away at the sound quality. Is it worth having them upgraded by Net as some people recommend. My Cd player is an Arcam 72 and my speakers are JM Labs Chorus 710's.

Neal madden Says:
January 8th, 2010 at 2:48 AM

Thank`s Wigan, Itry that, I live in Chile, South America and here this amps are like an UFO, they were my Dads, and still sound lovely, thanks for your hints, cheer´s NEAL

Charlie Says:
January 30th, 2010 at 12:00 PM

I've had one for 30 years - bought it 2nd hand with the 33. Recently I connected it direct to the Airport Express (not through the 33) and the huge improvement in presence surprised me. (on Spendors)

Now, I'm looking for another 303 for my vacation home...

Alain Says:
February 8th, 2010 at 6:35 AM

hello everyone,
you will find my original post somewhere in august 2009.
I am please to report that I have purchased the Quad's from George in Toronto.
An absolute gentleman who patiently waited while my life was turned upside down with 5k miles relocation etc just because i signified I was interested to his units.
George if you are out there thank you, your units were as described or better and you patiently reassured me on a long distance transaction.
thanks also to this site for alowing us to connect and afterward express my thanks.

Sid Says:
March 21st, 2010 at 5:04 AM

Am a music lover. I am willing to look up for offers on quad monoblocs.

Shall be kind of u to advised back if u hv a pair to sell or any offer u get to know of.
Would only prefer well working and mint condition pieces.

New Delhi, India.


Allan Says:
March 26th, 2010 at 7:42 AM

Hello all
I live in Denmark, and am looking to purchase another 405 block, to try to establish them into two mono blocks by bi amping.
The oneI have already is a 405-2
Do I have to find another 405-2 for a match ? or will just a 405 do nicely?

Hans Says:
April 20th, 2010 at 3:32 PM

Hi everyone,

I just purchased a quad 303 / 33 in excellent cosmetic condition on ebay. I think that the amp/preamp were made or last serviced in 1985 according to a small sticker I found on the 303 transformer, the components looked okay but really dusty. I have also bought brand new speaker cables and plugs as well as replaced the old power cords that were provided. One important note is that I live in an old flat and the plugs are not grounded. Now here's my issue: everytime I turn on the 33/303 I can hear a loud crak on the right channel clearly visible on the LF driver and then a constant hiss. I have repeated the operation with the 4 pin din cable detached from the amp and preamp with the same result. This leads me to believe that it's a power issue. I've been looking on the web for a solution but nothing comes up. Could someone help me please. It was a rather costly investment and I'd hate to return it if it's something easy to fix. Thanks a lot.


Bernasmeister Says:
May 7th, 2010 at 2:43 PM

Hans, have you tried connecting it somewhere which is grounded (at a friend's place or something).

My Quad 33/303 set-up was not grounded originally (and that’s for 20 years or so) and I never had a problem with it. It is grounded now and I found no difference in its performance.

The hiss may be a leaky capacitor on one of the amp boards. I would try and replace all caps if possible. Plenty on offer online with the likes of Net-Audio (in the UK) and Dada Electronics (Belgium).

You have a fantastic amp set in hands, but they need a bit of work (not much) to bring them to the 21st century. Enjoy it!

Will g Says:
May 30th, 2010 at 8:52 PM

hi there im looking to purchase 33/303 has anyone got an up todate pair for sale let me know pls. willow101010@yahoo.com

Chris Says:
June 27th, 2010 at 9:02 PM

Hi Quadies

I visited my local carboot this morning and happened upon a stall with a 303, 33, fm3, Thorens TD 125/SME3009 and a par of Rogers bbc monitor speakers for £100.
Well they were there on my second walk passed so my boss alowed me to make the the purchase.
Question! Should I power them up or are there some tests I should carry out first, they don't look to have been powered up in a while.
I have tried the speakers and I suspect the cones have gone - very distorted low range - compared to my old mission speakers.

Any recommendations greatly received.

Michel gauthier Says:
September 11th, 2010 at 7:49 PM

Hi Quadies,

I have a full Quad stereo system for sale. The 303 Power Amp, the 33 Pre-amp, the FM3 Stereo Tuner, a walnut cabinet for the 33 and FM3, and two Quad electrostatic loudspeakers, instruction booklets and cables. Sole owner, purchased in 1977.

Buyer must pickup at my place in Gatineau, Québec. Call 819 684-8978

Bruce linde Says:
October 25th, 2010 at 2:50 AM

i have a full quad stereo system for sale: 303 power amp, 33 pre-amp, fm3 stereo tuner, two quad electrostatic loudspeakers, original owner manuals, schematics, and cables. not immaculate, but recently serviced and fully functional. located in san francisco bay area.

if you're interested, drop me an email at blinde@5happy.com

Raymond st-pierre Says:
October 30th, 2010 at 8:57 PM

M. Michel Gauthier, Bonjour,

I have been trying to join you by phone for a couple of days, and all i get is that the number is not in service.

Could you correct it or give me another way to get in touch with you, please...

I am interested in your Quad set up!

Thank you very mutch.

Dirk van der merwe Says:
November 23rd, 2010 at 2:09 PM

I'm on the lookout for a Quad 303 or 405 Power amplifier. Mine was blown out by lightning. I do have the Quad 33 pre-amp in excellent condition. Please let me know. I'm staying in South Africa. Will pay shipment costs. Looking forward to hear from you.

Adam atkinson Says:
September 7th, 2011 at 2:26 PM

1968 Quad 33, 306 and FM3 in excellent condition. Barely used since serviced by Quad in 1995, as I've never had the space to truly appreciate this marvellous system.
Pictures at http://tinyurl.com/Qu4d33

Estate agents in peterborough Says:
June 9th, 2015 at 11:36 AM

I haven't come across this amplifier before. I wanted to ask based on what I've read here, what's the best setup to accompany this to maximise amplitude and sound quality?


Gerald ware Says:
February 9th, 2016 at 2:36 PM

I have two Quad 303's, matching pre-amp and tuner bi-amped with a Passover unit to my Magneplaner 6 ft. 3 panel speakers and there is absolutely to my hearing not a home sound system that compares to it. This is pure original un-adulterated sound, having my controls set on flat the bass is a thud not a thunk, which is pure and that is across the board! As an avid jazz listener, my reproduced sound must be excellent and it is!

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