Quad amplifier buyer guide?

[spendorman]

Just a point on the 303, I have four of them but the latest one has the IEC mains connector, which I find a bit more more convenient, compared to the Bulgin connector of the older models.

[DSJR]

The 500 and 600 current dumpers (possibly the 306 as well?) took the op-amp out of the signal path - to advantage I think - and should drive anything out there within reason. I had my wake-up call at KJ in the late 90's when a customer brought a mk1 606 under his arm in because he thought it was faulty. Connected 'cold' into Wilson Witts it sounded amazing and better than a Chord 1200e, let alone the Krell KAV's we used often. Go figure.....

Shane, the 303 is just fine, it's just that I played music with very powerful bass lines that are quite out of keeping with the era in which the amp was designed. Average bass levels on contemporary recordings have increased quite a bit since the 60's and 70's and the 303 used with a wide open source and passive pre couldn't quite handle it. One reason why the 33 preamp is so heavily low-filtered (roll off starts at 35Hz I believe) is to help the 303 do its job better with then wayward vinyl and tape sources..

Here's my 303 naked... It started life as a late model in all-over green, as the last ones were apparently. I suspect it did it's working life in Our price records, who bought hundreds apparently...

[Juha]

I am running a Quad 522 here.
This is a version with balanced inputs and input transformers.

The input transformers add a special shene and texture.
Like the great U.K. audio guru Rupert Neve has said: "The sound is in the iron"

Also, friends that have heard this amp have praised the authoritative bass on Quad 522.

[r100]

Just a quick question...

is there a fundamental sound / technical difference between the Quad 606 and 909 ? There is a 909 for sale here.

Thank's
Ru

edit: Just saw Dave's comment about the 909..

The 606 and descendants are readily available and in my opinion, really good and better power wise, than the 500's which now sell for at least as much (I know, I prefer the looks of the 500's too and they're more imposing again in the flesh ). Mk1 606's had 10,000uF supply caps and mk2 caps were 15,000uF, together with a toroidal transformer. I believe the amp boards were all but identical (I think!). The mk1 606 needed an hour or so to open up sonically, where the mk2 was 'there' straight from switch-on. The 707 was also delightful, although I hated the Speakon connectors. The 909 is potentially at least as good, but Chinese ones will need the caps looking at, as bad ones ruin noise and distortion and sadly, this affects music reproduction a little

[Barry]

Barry - Thank you very much for the info on the Series 5, I've only really seen these discussed here, there's very little information about them. A little reading up suggests the Series 5 does not use OP Amps, is this true and if so what effect does this have on the sound? Looking at the photo you uploaded of your 510's here: http://theartofsound.net/forum/showt...iday-tinkering, servicing seem pretty straight forward? From the point of view of servicing the 520 has the added complication of the regulated PSU, what if any difference would you say the regulated PSU brings?

Your correct in that no op-amps are used in the signal path. There is an IC used to provide DC control, but this is not in the signal path. I'm not an electronics expert, but common opinion is that descrete circuitry is better as regards sound quality. Certainly a large improvement in SQ can be made in the 405 amp by replacing the op-amp with a better quality item.

Servicing ought to be straightforward and Dada have some ideas for upgrading/fettling these amps.

Again, I can't really comment on the desirability or otherwise of using a regulated power supply. Some say that an unregulated supply, being simpler, can respond more quickly to sudden current demand and thus the amp has a better dynamic response.

[Barry]

I am running a Quad 522 here.
This is a version with balanced inputs and input transformers.

The input transformers add a special shene and texture.
Like the great U.K. audio guru Rupert Neve has said: "The sound is in the iron"

Also, friends that have heard this amp have praised the authoritative bass on Quad 522.

That's good to know Juha.

The 522s are quite rare. Most of them being used by the BBC, so appear on the market infrequently.

[DSJR]

It's also countered that a good op-amp is better than an equivalent discrete layout due to the miniscule signal paths and so on... The end of the day, I think that correct supplies are fundamental and in my current NVSA work, I've been shocked at how a couple of chips can be made to sound 'better' by hugely increasing the size of the power supply amongst other things. So I don't think it's as cut and dried as some would make out.

The 909 can be a very fine amp indeed and maybe all the hoo-ha about capacitor quality was confined to a small final batch for all I know. There's no doubt that a good one is one of the best 'fit and forget' options out there in my opinion..

Interestingly, I heard the Elite 909 replacement with the matching preamp and the pair, run for some hours at hifi dave's place, did everything I don't remember vintage Quad amps doing as well except for the most important thing of all... Everything was so controlled, precise and 'matter of fact' it was almost as if the 'soul' in the recording had gone. A Croft integrated didn't have anywhere near the headroom, but vocal diction seemed so much better and you could hear what the acoustic guitars were actually strumming musically, rather than just being backing instruments that were 'there' in the recording. 'My' 33/303 also did this musical 'thing' with ease in direct comparison and I know from past experience that the 405-2 in good fettle can do it too, as well as the 66 and 77 series...

Interesting thing, this 'subjective' vibe.....

[Barry]

How does the Elite 909 differ from the stock 909? Are there any changes to the circuit and/or components?

[Martyn Miles]

Which speakers work well with the 303?

S.

LS3/5as.
I run them from a 34/303 and it all works superbly.

[Arkless Electronics]

I was just having a listen to a pair of Quad II monoblocks which I rebuilt for a customer... Much better than I remembered! A touch bass light maybe.... Closer to my Leak Stereo 20 than I expected and remembered the last ones I heard to be.