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A vintage Quad thread.

I have no real electronics knowledge so you could well be right, I was just extrapolating from where I have seen similar caps in other equipment. My Leak Stereo 20 certainly put a big ‘pop’ out through the speakers on switch-off until, on the advice of others, I fitted a similar cap to it. Same story with the 301 and 124.

Anyway something somewhere is clearly not right here as a 303 shouldn’t make the type of noise described. As I say, nothing more than a quiet ‘flup’ even through 105db Klipsch horns!
 
No. A humongous switch on thump is normal for capacitor output amplifiers unless they have a slow start/anti-thump arrangement built in. Which I assume the 303 does. I can of course repair it for the OP.
 
These little caps suppress the crack sound caused by the momentary arcing across the switch contacts but not the thump or large cone movements. Check the values of the loudspeaker coupling caps - if larger than spec you can expect a louder pop/thump.
 
Thanks all, but as I'd only just bought it it's going to wing its way back to the previous owner who is happy to take it back.
 
Both my 303s have larger than spec coupling caps (4700uf IIRC) and neither get remotely close to a ‘crack’ even through my high-efficiency speakers. The characteristic 303 power-on ‘flup’ I describe is really quiet and deep in frequency, i.e. very much woofer based with no treble content.
 
...Just tried to measure it on the soundmeter on my iPhone one meter or so away from a 95db efficient Tannoy. It is so quiet it is hard to do, the ambient room noise is around 40-45db, the ‘flup’ registered at 56db, though some of that may well be the noise of me throwing the mains switch. It really is not a ‘crack’ or ‘thump’, and no 303 I have ever owned (three over the years) has ever made such a noise.

PS If the one in question is cosmetically tidy and you like the sound otherwise I’d keep it and get it fixed. They are simple and maintainable things, whatever is wrong can certainly be fixed.
 
two class designs period 33/303 34/306 briggs of wharfdale in 1957 said we should get out of speaker manufacturing after owning a pair of 57s 405/2 606 909 great series too
 
I dabbled in some older Quad amps recently after many years with Meridian DSP speakers.

The 303 is nice, the 606 is nicer imho, but for me the 405 is the winner.

I have three, an original 405, one that has new caps and newer OpAmps and a Snook and Net Audi modded one.

The later 2 I still have, the Snook/Net Audio one with dual mono PSU is superb imho.

I am running one with a Meridian G68 pre, and that is such a 'sweet' sounding system, and the other one I am running with a Raspberry Pi and Meridian Explorer 2 as the pre amp, which has blown me away. It has seen off some much higher end kit.


I have had loads of different kit come and go over the last year, Croft, Bel Canto, Unison Research, Quad 909, 303, 606, Meridian G55, 557 are just some, but the 405s have impressed the most.

On thing though, the input sensitivity on them is only 0.5v which is too much, I have changed the dual mono to 1.0v and the I think it was 1.5v for the recapped one. This makes it much easier to mate with stuff.

But all in all, I think the 405 is a wonderful bit of kit, that drives speakers easily and has the prefect balance between warmth and detail.
Plus they can be modded to take them up a level or two for peanuts. What's not to like?
 
I have just read - on another forum - that the Quad 306 is a phase-inverting amplifier, so if used downstream of something other than a Quad pre it is necessary to reverse the two speaker leads for each channel. Anyone know if this is right? Does it matter?
ML
 
Having just got a Lockwoood recone back on a 1955 12 inch Tannoy speaker silent for 20 years i am looking forward to hooking it up with a Quad II set up...
 
I love my ( recently serviced ) Quad 34/303 amplifier.
Having recently acquired a top-of-the-range Sony CD player and running into Harbeth P3-ESRs
I am in ‘Audio Heaven.’
The system sounds superb.
I think I’d have to spend considerably more to better what I have...
 
I'm running one of my 405s into a pair of P3ESRs, but using a Meridian Explorer 2 dac (plugged into raspberry pi as roon endpoint) as the pre amp.

Stunning sounding system.

Oh, I do use a Rel Strata as well, as amazing as the P3s are at bass, I always like a sub.
 
Is it just me, or is there a bias towards the older Quad power amplifiers?
Someone chose the 405 over the 606.
I’ve never heard a 606, but being a Quad I’m sure it’s excellent.
At my time of life I’m staying with my 303...
 
I think I put preferred the 405 to the 606, I actually meant the 306.

I had a 909 which is pretty much a 606MKII isn't it?

The 303 was great, and would probably work well with my P3ESRs?
Just that they didn't have the control I needed with the speakers I had at the time, Quad Z3s and 988s.
It was great with an old pair of Mordaunt Short MS10i's though.

To me the 405-2 with mods crosses that fine line between just enough grunt, detail and sweetness. It feels like a modern take on the old British sound is that makes sense?

I was messing around today with my refurbed 405 and the Snook/Net Audio modded 405-2. The earlier one is smoother, but the soundstage on the later one makes it a winner.

Also, I was trying to integrate my Rel properly, and was amazed that the little P3ESRs still had quite some output at 37hz on a frequency sweep in my 6mx5m room, they then fell off seriously quickly mind. No wonder many say they never feel bass light.
I'm surprised they are rated at 75hz cut off, I suppose if it is -3db then it might be in a chamber if that is how the measurements are taken?
 
As stated earlier assuming an easy load (Tannoys, BBC, ESLs etc) I prefer the 303 to the other solid state Quads I’ve tried, it has a wonderfully lucid midband that is almost tube-like. If you need some heft below 8 Ohms the 303 runs out of steam and I prefer the 306 (and I would assume the very closely related but more powerful 606-909). The 405 is a stunning piece of industrial design with a very clever circuit, but it doesn’t sound as good as the 303 or 306 to my ears (I do technically own a 405-2, but it is elsewhere at present), though I understand it can be tweaked somewhat to bring it more inline with the later current-dumpers. I’d like to try both IIs and 50Es one day!
 
My 909 was no where need as smooth as the 405, felt like a much more 'modern' amp to me, so didn't stay in my system long.

The 405 was the shocker, it sounded more like the 306 than I was ever expecting and mine was modded for 1.0v input sensitivity and had all new caps and op amps so stayed, there was little in it.

Maybe I need to try another 303.
 
I’m always very wary about recommending the 303 as to my ears the magic only surfaces in certain contexts, in others it can sound very disappointing as it does very obviously run out of steam. Really you need to see the impedance plot for the speaker, and if that drops below 6 Ohms or is in any way reactive then forget it, buy one of the current-dumpers. If however you have a pair of fairly efficient ‘tube-era’ speakers that don’t dip below 8 Ohms and can’t be bothered with the faff of a tube amp then the 303 is a surprisingly good alternate. I still prefer my Leak Stereo 20 to it, but I prefer that to any amp I’ve ever owned or tried (again with caveats regarding power)!
 
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