I have recently been testing an old 306 (no upgrade yet) but man, is it good. The bass is immaculately defined and the detail outstanding. Why is it that this amp lives in the shadows. There is so much talk about the 406 and tube amps but I have been side by side comparisons with tube amps, an upgraded 406, and a Cayin tube amp and a Rogue Audio tube amp and this little wonder, blows them all away... a snip at 200EUR from e-bay!
https://www.facebook.com/photo.php?...o.303923949727300&type=1&theater¬if_t=wall
https://www.facebook.com/photo.php?...o.303923949727300&type=1&theater¬if_t=wall
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It only lives in the shadow of it's bigger brother, the 606, which is still popular for cloning. Perhaps you meant to compare it with the 405 model.
Yes, the 306 does sound great and it has been hailed as the best of all Quad current dumpers technically and sound-wise, at a few Quad interest sites and various forums discussing commercial products. It has no vices and uses cheap parts but being small amps with a dismal appearance, they have limited appeal, so guys think...nah, it can't be very powerful and I want something in black or silver. 'Their loss
Yes, the 306 does sound great and it has been hailed as the best of all Quad current dumpers technically and sound-wise, at a few Quad interest sites and various forums discussing commercial products. It has no vices and uses cheap parts but being small amps with a dismal appearance, they have limited appeal, so guys think...nah, it can't be very powerful and I want something in black or silver. 'Their loss
It did not really take long for smart engineers to better tube amps. Sounds like this is proof. I guess what is sad is how many have been built since that are not it's equal. Funny, I always liked the packaging of the Quad gear from that era. Putting the heat sink out where it gets air seems quite reasonable to me. Alas, this was from the power meter days.
There were quite some small improvements made between the QUAD-405 and QUAD-405 II (improved op-amp, halved dead zone of the class-C stage, some tweaks to the protection circuitry), but I don't think they have much to do with whether the loudspeakers are electrostatic or magnetic. Anyway, this has little to do with the 306.
From what I gather a number of QUAD amps have inrush limiters and weeny power supplies so they don't go up in smoke when driving ESLs.
With that in mind and in my experience the best amp they made was the 520.
According to the late Peter Walker it is basically a 606 with a pair of output transistors missing but in return it got a 3 times larger PSU. In an interview Peter was very proud of every aspect of that amp but it was designed for professional use, not to drive electrostats.
With that in mind and in my experience the best amp they made was the 520.
According to the late Peter Walker it is basically a 606 with a pair of output transistors missing but in return it got a 3 times larger PSU. In an interview Peter was very proud of every aspect of that amp but it was designed for professional use, not to drive electrostats.
Do you mean when you trigger the loudspeaker's protection? The Quad ESL-63 has an input protection circuit that more or less shorts the input when it is overdriven. As long as you don't trigger the protection, it has a very well-behaved impedance characteristic that shouldn't be difficult to drive.
Often people describe emotions and memories from Quad amplifiers ...Emotion and memories is strictly tied up with time thaaaaaaat time loooooooong ago .....
Today we have spectrum analyzers ( far more honest than simulators ) and thank God better safety rules ( no 220 tied up with input output V+rails+V- rails and so on and on and on )
Still i take it as a fact like anything else illegal 220 tied with rails input and output will add to the sound a certain warmness !!!
Safe regards
Sakis
Today we have spectrum analyzers ( far more honest than simulators ) and thank God better safety rules ( no 220 tied up with input output V+rails+V- rails and so on and on and on )
Still i take it as a fact like anything else illegal 220 tied with rails input and output will add to the sound a certain warmness !!!
Safe regards
Sakis
yeah, but the 33/303 appearence is pure design art, and master piece of its time
actually I have never considered the inside layout of the 303 mono amps
but looks real great on the pics I have seen now
actually I have never considered the inside layout of the 303 mono amps
but looks real great on the pics I have seen now
I have 2 303's driven by DCB1 Mez. The 33 is a distorsion generator...
Regards
I guess whenever we talk about Quad amplifiers, only the very popular models mean much, so people post their experience with the older Quad 303 or 405 models - the big sellers from long ago. Quad Electroacoustics - Wikipedia, the free encyclopedia.
The 303 is an iconic piece of art really, but nothing like any of these current dumpers.
The 306 design is electrically close to the 405 but like the OP says, blows it away, even the later 405 revisions.
Models 606, 707 and 909 are essentially super-sized 306 amplifiers as they are electrically very similar but have 3 output transistor pairs rather than 1, making them near bulletproof.
The 303 is an iconic piece of art really, but nothing like any of these current dumpers.
The 306 design is electrically close to the 405 but like the OP says, blows it away, even the later 405 revisions.
Models 606, 707 and 909 are essentially super-sized 306 amplifiers as they are electrically very similar but have 3 output transistor pairs rather than 1, making them near bulletproof.
I concur- the amp is excellent.
I am currently using a 306 with a small self designed ribbon based speaker driven by a Krell Pam 5 and fed by a Yamaha CDS 3000 and the sound is excellent. Bass is super-tight but the amp tends to get a bit warm if you play it too loud.
I just need to replace the 20 year old power caps...
I am currently using a 306 with a small self designed ribbon based speaker driven by a Krell Pam 5 and fed by a Yamaha CDS 3000 and the sound is excellent. Bass is super-tight but the amp tends to get a bit warm if you play it too loud.
I just need to replace the 20 year old power caps...
The 57s impedance looks like this:
http://www.audiomisc.co.uk/57and303/57imp.gif
The 63s look very similar and it is not exactly what I would call well behaved.
Either way apparently early SS amps struggled with this, I've heard a few stories of ESLs turning BGW 750s into smoke machines.
Hence Peter Walker installed aforementioned bits and pieces into some of his amps.
Spectrum analysers have been around for some time, my favourite museum has one from around 1880:
Teylers Museum | The Cabinet of Physics of the Teyler Museum
Regarding the ESL-63 impedance characteristic, I only knew the part up to 20 kHz, which doesn't drop below 4 ohm anywhere and is rising at 20 kHz. Looking at some web sites, apparently it has a deeper impedance minimum just above 30 kHz.
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