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Quad 33 revisited

NeilK

pfm Member
Conventional wisdom is that the 33 is a pretty poor pre-amplifier. I have 2 (well,3, but one is non-functioning at the minute). The first is an 'avondaled' item from Les's early days when he worked a little magic on MF and Quad as well as Naim. This is a lovely little pre', it has an external PSU (nothing too special) and some modifications to the output boards. I really like it.

The second is a bog standard unit which had seen no tlc for many years and lived up to it's reputation as, well, just lacking something - detail and dynamics mainly. I sent this off to Rob at Amplabs for a full service and the addition of his modified back panel.

Since it has been returned to me I've done a fair bit of listening - with the exception of the phono stage - average :-( - it seems, to my ears at least a very nice little pre.

Just thought you'd like to know.
 
Conventional wisdom is that the 33 is a pretty poor pre-amplifier.

It may well be the most successful preamp ever made in the UK, IIRC they sold 120,000 of the things, and you just don’t do that with a poor product that isn’t cheap! Can anyone think of any other UK preamp that sold more? The 33 was around from 1967-81 and barely altered in that time (better edge connectors and a safer back panel).

The 33’s main issues IME are gain related, it was just designed for far lower output source components than the 2V digital kit we use today, plus no one has any real use for filters etc anymore. I have got a very nice serviced example and it is pretty decent, though I prefer either a Audio Synthesis passive preamp or better again my Verdier valve pre with my 303s, as in fairness one would expect. Plus I hate DIN plugs! A properly serviced 33 is definitely better than people expect though, as is the later 34. As ever with Quad gear it is worth remembering that they designed it to partner some of the finest and most revealing loudspeakers on the planet, they are so even now! ESLs will unquestionably tell you if something is awful, yet they sold huge, huge numbers of complete systems to discerning music lovers.

PS IIRC the 33 MM phono stage (both of them) is set by default to 68k, which is a bit odd to put it mildly. If using it myself I’d replace the appropriate resistors with a more normal 47k. No idea what the capacitance is, but I think very little as SME used to add capacitance for the usual V15/III, and the Ortofons sounded better with the add-on ‘Cap 210’ card on the back of the cart. It is certainly all documented and configurable if you can solder.
 
I modified my Quad 34 because with my cartridges I like the 68k better, with a brighter sound that I enjoy so much with my 33, with zero capacitance on its module.
I’ve never used the 33 with anything else than a 303 or a 405 (less liked).
I think you really can’t judge the unjustly maligned 33 with other amps.
It will also gladly take CD with the tape input set on the lowest gain.
As a matter of fact, the position of the volume potentiometer for a given volume is the same on both disc and tape, which is perfect.
Oh, and I’m really fond of good DIN plugs, and rather dislike RCAs. Correctly implemented, they will run the ground separately from audio modulation.
I use an old Naim DIN to RCA I was given to connect the Arcam 70.2 to the 33.
Like you Tony, I have a valve preamp (not a Verdier, a Hiraga of the same parish!) and it sounds really good with the 303 I must say.
 
I sent this off to Rob at Amplabs for a full service and the addition of his modified back panel.
Since it has been returned to me I've done a fair bit of listening - with the exception of the phono stage - average :-( - it seems, to my ears at least a very nice little pre.
Neil, Can you elaborate on the differences you heard on the 33 after Amplabs service? Thanks. I've always been curious about any changes to the sound quality from their work.
 
@ampedup, following the service there was a distinct improvement all round, previously the 33 could have been described as ‘overly polite’ but the service brought out the missing sparkle/dynamics. I was very happy with the quality of the work - and Rob is very interesting to chat to.
 
Interesting thread. I'm seriously thinking of having one of my QUAD 33/303/ FM3 sets fully serviced by Amplabs including new front and back panels with updated socketry etc. for use in my upstairs office system. I'm not too fussed about the phono stage performance as I doubt I'll use it, but there are supposedly better aftermarket upgraded phono stage boards available.
 


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