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Exposure IV or Quad 303/33

Yes that's right so the 2N3055H is an exact drop in replacement but an ordinary 2N3055 isn't.

The trouble is that the H suffix wasn't adopted from outset since they were all "H" up to about 1977 and were just labelled 2N3055
 
I agree entirely with Tony about the merits of the Quad 33. I have a home built passive volume control / input selector that uses a high quality stepped attenuator bought from Hifi Collective. I've used it with my 303's but I much prefer using them with the refurbished 33's. More weight to the music with no audible loss of detail. The 33's offer more facilities too of course. Years ago I bought a refurbished 33 and it was so good I bought another and refurbished it myself as a spare / back up using a Dada kit. Quad 33's are so underrated .... which is a good thing if you're looking to buy because it makes them cheap. Making judgements on their sound quality on non refurbished units will not do them justice.

Making them usable with modern sources is dead easy too as you can solder in a few components onto one edge of the disc input board. There's lots of info on the web about that, including from Quad. Alternatively, you can adjust the tape input sensitivity as stated above. I did the former simply because using the 'disc' input selector on the front panel is more intuitive for CD replay than pressing 'tape'.
Units with a serial numbers in excess of 100,000 used the better gold plated contacts on the boards.
 
Oily Rag said:
I agree entirely with Tony about the merits of the Quad 33. I have a home built passive volume control / input selector that uses a high quality stepped attenuator bought from Hifi Collective. I've used it with my 303's but I much prefer using them with the refurbished 33's. More weight to the music with no audible loss of detail. The 33's offer more facilities too of course. Years ago I bought a refurbished 33 and it was so good I bought another and refurbished it myself as a spare / back up using a Dada kit. Quad 33's are so underrated .... which is a good thing if you're looking to buy because it makes them cheap. Making judgements on their sound quality on non refurbished units will not do them justice.

Making them usable with modern sources is dead easy too as you can solder in a few components onto one edge of the disc input board. There's lots of info on the web about that, including from Quad. Alternatively, you can adjust the tape input sensitivity as stated above. I did the former simply because using the 'disc' input selector on the front panel is more intuitive for CD replay than pressing 'tape'.
Units with a serial numbers in excess of 100,000 used the better gold plated contacts on the boards.
Click to expand...
Case in point ... One has just been sold on PFM for £80.00!! That's a steal.
 
The first time you take a 33 away from the 303 in favour of a passive, you’ll notice a cleaner and initially more detailed sound. Then as time goes on you lose the detail as your ears become worn out early in the listening session. Chuck the 33 back in and you get more weight, fullness, lushness etc. It’s like getting out of the pool and getting cold so you can enjoy the warmth when you jump back in.

My 33/303 is freshly serviced by Amplabs and is to my taste far better to listen to than my Sugden A21 Signature. People talk of a veil or lack of dynamics but nah.

People also talk of hassle with modern sources and gain. I personally found impedance matching with a passive preamp far more irritating!
 
Indeed and the benefit of tone controls is that you have an infinite number of sound profiles at your finger tips! I wonder how many cables and box swaps could have been solved with a quad 33!
 
I suspect a lot depends on the specific source component (impedance etc) and the quality of the passive preamp (they are far from equal).
 
Gosh! Interesting stuff, at least the bits I understood :)
Are there any thought on a Quad 34/306 with 57s…?
I’ve discounted the 405 and 405-2, from what I’ve read…
 
VinylRadio said:
Gosh! Interesting stuff, at least the bits I understood :)
Are there any thought on a Quad 34/306 with 57s…?
I’ve discounted the 405 and 405-2, from what I’ve read…
Click to expand...

34/306 is nice to look a bit more modern than 33/303.

306 is based on a similar circuit to the 606, and good on newer speakers also.

Have to me careful when hooked up to 57s think it will go past the 33v max for 57s.

Have every quad amp now and swap em about regular, Cant really beat a 303 with 57s for the money,if u are not going for a valve amp in the future.

Another route is 306 for everday,bit livier than 303.
The best sound ive had with 57s is with the leak st20 .

Have the preamps but use a passive khmozo and a schiit saga plus (remote control)

405 are 405.2 are underrated and good when u need cheap power amp for complicated crossovers and low sensitivity speakers,no need for with 57s....
 
I don’t like the 34/306 with my ‘57s. Too flat. But maybe that’s just me (I have two 34s though, a DIN and an RCA).
 
Thanks so much for your replies, again! What a super-helpful, friendly bunch you are!

Not a bad shout, the 306/34 then. The Boss does prefers (notice I didn’t say like!) the look of the 306 combo, which given she allowed me to keep my new 57s, might just have to swing it that way. Incidentally, she says it must be you, Chartz and it’ll be fine…!
 
VinylRadio said:
I had just read that they weren’t really a suitable match. Good to know then :)
Click to expand...
The 405 replaced the 303 in the Quad lineup and was a common upgrade. Have a guess what they would have used to test the thing. Have another guess as to the chances of it not working very well when a then current owner of a 33/303 and ESLs came into a shop and said "well I really like what I have and I hear that the new 405 is better, can I listen to it?" They're not going to say "We don't recommend it sir, to be honest, you stick with what you have and keep your money in your pocket" , are they?
 
Obviously not, but things are never so simple. The 405 is simply not as good as the older 303 with ESL57 panels. Well that’s my experience anyway with completely restored but unmodified examples.
The 303 matches the ESLs in a magical way, which our very own Jim Lesurf attempted at explaining years ago.
The 405 I like best on cone speakers in wooden boxes.
 
As ever synergy is everything. The 405 was released into a market of entirely different speakers, most based around heavier plastic cones and lower impedances than the 303. The 303 is an exceptional amp of its era, one that sits exactly on the pivot-point between valve and solid state and belongs with the speakers of its time. The 405 is another exceptionally clever design, but unlike the 303 it took Quad a few goes to really nail down. The 405/2 is better, the 606/707/909 better again. The 306, a baby 606 is a great amp too. If I needed more power than a 306, which is certainly more powerful than a 303, then I’d go for a 909 (purely to avoid the Nextel finish of the 606). I love the look of the 405, aesthetically it is a perfect slab of 70s minimalism, but sonically I’d take the other current dumpers with modern speakers, and the 303 or IIs with vintage speakers.
 
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