Quad 306 and 909 for ESL 63

[Mandryka]

I’m using a 306 to drive a Quad ESL 63 - there are passive subs driven by another amp. I don’t use a preamp at the moment, I control volume digitally.

I’m tempted, just out of curiosity, to try a 909. There’s one for sale on eBay which I can return if I don’t like it.

Is it a waste of time? How will it change things?

Are there any pitfalls to look for when buying the 909? Are all 909s the same? Does recent servicing make a difference to how they sound?

[Barry]

If I were in the market for a Quad 909, I would look for one that was made in Huntingdon before the company, as part of the IAG group, was bought up by the Chinese, and manufacture moved to China. There have been consistent reports that local Chinese sourced components are now used, especially capacitors, and that these are sonically inferior.

This situation may well have improved, so I wouldn't dismiss a 909 out of hand - especially as you can return the eBay item if you don't like it.

[Mandryka]

If I were in the market for a Quad 909, I would look for one that was made in Huntingdon


And would that be one that says Huntingdon on the back, like this? (Sorry, I can't make this image smaller!)

https://i.ebayimg.com/images/g/tJwAAOSwW4FddfQU/s-l1600.jpg

[Barry]

Well the serial number looks low enough (ignore the initial 909), for it to have been made in Huntingdon.

[Mandryka]

Well the serial number looks low enough (ignore the initial 909), for it to have been made in Huntingdon.

Ah!

[Light Dependant Resistor]

An issue with the 909 amplifier is heatsink compound was not used between the large internal aluminium bracket and
the outer heatsink fins. If buying one you need to spend an hour or so, to do this.

I would in preference purchase another 306, and use one amplifier channel per speaker which is what I do.
Note you cannot combine the 306 channels to make a mono block, rather one channel per speaker from each 306
is quite an improvement. You could though at some later stage purchase another pair of 63's and run them stacked,
with each 306 amp.

[Mikeandvan]

In my system I thought the 909 much better, I think my one was made in China, but it did go back to Quad for a service in 2017. To me the 909 is quite a big step up, the presentation is slightly more laid back, but the gains in detail are worth it. I can't comment on these amps with Quad speakers though, others here will likely have experience of that.

[Mandryka]

I would in preference purchase another 306, and use one amplifier channel per speaker which is what I do.
Note you cannot combine the 306 channels to make a mono block, rather one channel per speaker from each 306
is quite an improvement.

Can someone explain to me how doing this can make an improvement? As far as I can see it shouldn’t make any difference at all, but I’m probably missing something obvious!

[Light Dependant Resistor]

It provides better audio as the power supply is then providing to one channel vs two channels
The 306 does feature separate transformer windings and rectifiers, which you would think was enough separation
but having tried one amp for two speakers vs an amplifier each for each speaker many times- it speaks for itself.

There may be other more intricate explanations, in Quads use of a virtual earth for each channel, perhaps the channel running
is a better circuit slightly where one channel of one amp is running and the other is idle.

To my ears there is no doubt of its superiority

[Mandryka]

It provides better audio as the power supply is then providing to one channel vs two channels
The 306 does feature separate transformer windings and rectifiers, which you would think was enough separation
but having tried one amp for two speakers vs an amplifier each for each speaker many times- it speaks for itself.

There may be other more intricate explanations, in Quads use of a virtual earth for each channel, perhaps the channel running
is a better circuit slightly where one channel of one amp is running and the other is idle.

To my ears there is no doubt of its superiority

Well it's easy to do so I'm very tempted to try, if I don't feel the same as you, I will have lost very little, if I do feel the same as you I will have gained a lot!

Have you really stacked ESL63?

[Light Dependant Resistor]

No not 63's but 57's . No reason why 63's could not be stacked, Peter Walker used to discuss stacking as giving a larger portrayal
and covered as topic here: http://www.quadesl.com/articles/quad_stacking.html

Here is a you tube of comparison of a stacked pair vs conventional speaker https://www.youtube.com/watch?v=ICQM4N4jwbc
... hmm no comparison 63's win hands down even with You tube audio quality. Apparently SME's Alastair Robertson Aikman has 4 x 63's running but not exactly stacked -
I am sure references to that can be found, with a cup of hot chocolate to hand.

Personally i would try to retain the aesthetic look of the 63 if 4 were being used, but 2 are pretty good nevertheless

[Mandryka]

No not 63's but 57's . No reason why 63's could not be stacked, Peter Walker used to discuss stacking as giving a larger portrayal
and covered as topic here: http://www.quadesl.com/articles/quad_stacking.html

Here is a you tube of comparison of a stacked pair vs conventional speaker https://www.youtube.com/watch?v=ICQM4N4jwbc
... hmm no comparison 63's win hands down even with You tube audio quality. Apparently SME's Alastair Robertson Aikman has 4 x 63's running but not exactly stacked -
I am sure references to that can be found, with a cup of hot chocolate to hand.

Personally i would try to retain the aesthetic look of the 63 if 4 were being used, but 2 are pretty good nevertheless

Thanks for that. It's a very interesting paper indeed.

I know someone who argues that the magic of ESL 63s is that the image seems to come from a point source. And that stacking them will mess this up, and hence shouldn't be done.

I'm not convinced by this argument, I use Gradients with mine, and supertweeters, and after experiments I think that the sound is greatly enhanced.

So stacking them may well be a good idea from a sound point of view at least.

[Mandryka]

Well moving the Krell KSA 50 to the ESL 63s was certainly a move in the right direction. I’m starting to hear why these speakers have such a good reputation.

Has anyone heard the Gradient XO amplifier

http://www.gradient.fi/en/loudspeakers/10-gradient-xo-amp.html

I note they use Class D technology, which makes me think that that may well be a good avenue to explore for these speakers, with or without Gradient.