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Amps for Quad ESL 63s?

I've been using Quad 63s for a few years, but the protection would kick in prematurely and that made amp choices troublesome. What I learned is that these Quads LOVED amps with autoformers instead of transformers (McIntosh 2100, First Watt M2), and to my ear, and my room, they did not like OTL amps (Atma-sphere M60s). Then I discovered that the Zeros by Anticables made amps happier if they were driving higher impedance Quad 63s. Recently I acquired some Gradient subs to pair with the Quads and they 'came with' yet another pair of Quad 63s that work properly and did not have overly-sensitive protection. Now it's back to trying to find the best amp combination. (I learned of the Gradient XO amp/crossover, but it's out of my price range, and was surprised to see that it used Class D amplification). Without the original crossover, and with an MT Audio crossover at the shop now with grounding issues, I'm using a Behringer DSP unit as a crossover. When the power amps driving both the Quads and the Gradients are both of higher wattage the bass is integrated and sound is great. If I try a lower watt amp for the Quads while keeping higher watts on the subs, I can't seem to strike the right balance. Anyone have suggestions for how much to change the sub feed from the Behringer if I have 30 to 60 watts on the Quads and 200 on the subs?
 
I think what you've discovered is that the dynamics are different with different-sized amps. Maybe try adding some subtle limiting or compression to the subs in the Behringer DSP? That should keep the subs from getting up and running away from the Quads when you have a small amp on the ESLs.
 
Gradient recommended identical amps for quads and gradients - Quad 606s. I’ve never had the balance problems urbanshaman describes with the MT crossover, but I did when I tried a single powered sub, which I guess had a very powerful amp built in. I use amps which are quite closely matched I suppose.


I wonder what UK amps have autotransformers like the McIntosh and First Watt M2.
 
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It seems I replied to this thread way back ! I was using a Quad 606II with my OTA Quad ESL 63s at the time, and very happy I was. It gave a big, bold, warm, cuddly sound that was very attractive. However, the chance to try a Primare A30.2 to match the Primare Pre32 and other Primare bits was too tempting, and would allow my to use the Pre's balanced outputs.

The sound was very different. Gone was the warm cuddliness, replaced with much more detail and timbral information. The sound stage was more precise. Bref, a presentation that appeals more to the head than the heart. I wasn't sure at first: I missed the boldness of the Quad, but in the end it was the Primare that won out, and I sold the Quad.

I've very recently aquired a Primare A34.2 at a good price. It's Primare's take on Class D amplification. It's a revelation. I thought it was going to have to be good to beat the A30.2, but it does so so easily. Even more clarity, it's lightening fast and feels nimble on its feet. (What a daft thing to say !, but music just seems to flow and have forward movement in a way that wasn't the case before) Instruments have bags of character, choirs are made up of voices not a mass, choral fugal entries in Bach Cantatas are easy to follow, with each voice part clearly placed in space. I'm listening to some Gigout on a Cavaillé Coll organ and it's got huge character.

I'll spare you the rest of my enthusiasm (Oh, and there's bass, deep, tight bass!). The 63s are remarkable speakers. They've sounded great with all the amps I've used, although the Tag P60 didn't really have the balls to drive them, but they clearly benefit from a really good amp and tell you exactly what's going on.

I'm hearing things I've never heard before ... I'll get my coat !
 
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Thank you all for the replies. Since my previous post I've fiddled with the Behringer and found some good settings. Eisenach mentioned Primare amps and I'll have to add that name to my list of things to watch for - I never really thought about Class D amps for Quads. It's beautiful to hear people so satisfied with gear that creates delight while listening to all kinds of music! Mandryka wondered which UK amps might have autoformers -- I don't know how they are designed, but the early Linn amps, the K2 and K280, worked REALLY well with Quad 63s in a way similar to the autoformer amps I've tried. I had contemplated using the two of them (nearly matched and sitting in a closet) for the Quad/Gradient combo until I discovered that what appear to be balanced inputs are wired in a different proprietary way to work with the K1 preamp; then the speaker wire connection takes a smaller banana plug. I suppose it's not impossible to configure, but it would take the creation of custom cables. I have a working APT Holman amp that drives the Quads or the Gradients very well and I've heard that they have a reputation for working well at dealing with varying impedences -- I'm thinking about having someone check out another one that I have then I'd have two 100 watt matching amps on the Quad Gradient combo. (Clearly I have too many amps from the '80s. And there's an Adcom 555 driving the Gradients at present.)
 
I wonder what UK amps have autotransformers like the McIntosh and First Watt M2.

The M2 has direct coupled MOSFET outputs. It uses the transformer as coupling between the input stage and the outputs, not on the output like the McIntosh.

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Thank you for the clarification, Yank! I understand less of the technical details than most of the guys on here, but I'm having to learn more after adopting these Quad 63s. Previously I thought very little about amp design -- tube or SS, more watts or less watts were the only considerations. Speakers were in a box with impedance marked on the back. Now I've experimented with McIntosh, First Watt, Atma-Sphere, Curcio, etc. amps with different designs that interact with the Quads differently; adding the Anticables Zeros changes each interaction. (Boy I really need to sell some of these amps.)

After adding the Gradients to the Quads it's potentially another set of options for the Quads only going down to 110hz. How might a First Watt M2 function when possibly pushed to it's last watt - should I even consider a 25mpc amp or even a 35wpc Stereo-70 (Curcio version) to power the Quads while using the Gradients below 110hz? Could they handle dynamics properly? I'm about to try, but I'd welcome input.
 
MiniDSP plate amp for the subs, I have mine set to -3db at 50Hz, though mine are 989's which have a little more bass extension.

80/100 Wpc for the quads of the lowest distortion you can find.
 
It will be interesting to see if the Icon Audio MB90 Mk.IIs I have ordered will be a good match for my 2805s (which are basically 63s in fancy clothes). I have realised that my room really doesn't suit the Quads, but I'm trying to get the best out of them. I should have stuck to making my own speakers, at least then I could tune them to suit!
 
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What are you using now?

Used to use Class D Hypex N-Cores then moved to Class A/B Neurochrome amps, similar vanishingly low distortion but a slightly sweeter sound. Tried 60Wpc at first then bridged them to around 100Wpc. That gave a lower noise floor and better dynamics.

I would like to try these.
https://neurochrome.com/products/modulus-686 I would steer clear of using DSP on the Quads as that will only add distortion.

I now use a DAC with 0.000070 THD +N, best sound yet, totally holographic.

The reason the Quads are so highly rated is because they are one of the lowest distortion loudspeakers and they have no Xover or 'box'.
 
Yes I saw your posts about the DAC.


I wonder if I should ask someone to build me a neurochrome amp. Any takers out there?
 
Yes I saw your posts about the DAC.


I wonder if I should ask someone to build me a neurochrome amp. Any takers out there?

This is what I did (and it worked out very well)
I am clueless on electronics but found someone who built a neurochrome amp for me.
I use the neurochrome power amp on the 63's and a separate Gradient XO/Power amp for the Gradient subs.
happy to share details if you want to PM me.
 
The reason the Quads are so highly rated is because they are one of the lowest distortion loudspeakers and they have no Xover or 'box'.

Quad 57s have a three-way crossover, and the 63s and subsequent concentric models have the delay lines. Plus the step-up transformers. There is definitely "stuff" between the amplifier and the panels.
 
Here's One Thing Audio's essay on why the 63 is special, from their new (prototype) website -- http://www.onethingaudio.net/

Over the years we have made no secret of the fact that we consider the Quad ESL-63 (and its many derivatives higher in the range) the best transducer on the planet. It is superb because it was designed properly in the first place. It was a less hectic world in those days: not many producers now would spend a decade perfecting a design with all the cost and time involved. There were minor modifications: one being a redesign of the audio step-up transformers to improve the speaker’s efficiency (this occurred in the successor to the ESL63, the 988 series). Beyond that – except some improvement in the protection circuitry – the design remains unchanged.

The “secret” to this marvellous design is the novel and ingenious panel design. Most models in the range use four of these panels (the taller versions six). The annular designs of the audio electrodes (sometimes called stators) enable sound to reach the listener which closely imitates the way sound reaches the human ear in the real world. That is the pure genius of the design – or rather that and some clever electronics which govern the amplitude and frequency the annular “rings” and bass areas receive.

To achieve transparency and accurate information retrieval, it is necessary for the perforated stators to be very thin (just 0.5mm). Down the centre of these two drive stators is a diaphragm which utilises a special coating. The object is that the diaphragm only moves – not the stators which are glued to a solid grid. This latter requirement is perhaps the single weakness of the design, because over the years the diaphragms are required to vibrate billions of times and at different frequencies and amplitudes in response to audio signals generated by the stators. In time, this can result in failure of the glue which holds the stators firm. This usually causes the stator to lean into the diaphragm and “sparking” will occur, causing severe crackling in the speaker. Protection circuits are quick to shut the speaker down but usually the damage (to the delicate diaphragm) has already been done. It should be possible in an age where glues can be developed and “stress-tested” to cope with most situations and conditions, for this weakness to have been addressed (the car industry is the major consumer here and an industry has grown up to meet these requirements). However, Quad’s panel – while it can last for many years – seems to have missed out on the theoretically “indestructible” glue and visually declares the end of its life-span by turning into powder form.

So what is our solution to the problem? We are currently working on the ultimate solution but in the meantime we remove the residue of the old glue and substitute a glue which boasts a certain flexibility. Admittedly we have had only nine years to collate our findings, but so far we haven’t come across a single panel where our glue has failed – the glue merely having hardened somewhat in the passage of time. Only a powerful glue solvent will get rid of the glue that we have used.

So what’s the point of this discussion ?

The point is this: the 4 or 6 panels operating in a Quad speaker are all subjected to the same stresses. The wear-and-tear on them is approximately equal. So the common-sense factor must be applied very stringently: if your car tyres had clocked up fifteen thousand miles, would you insist, for reasons of economy, in changing the one tyre which is now illegal? “I’ll change the others when I can afford it.” That seems pretty idiotic and certainly the most expensive way of dealing with the problem in the long run. Yet time and time again, we get Quad owners who will instruct us, “Just do the work that is necessary”. (Thus implying that some of the work we undertake is unnecessary!) The question is also sometimes asked, “If your glue is so superior, why can’t you use it on the other panels that might still have some life in them?” The problem here is a purely technical one: When our glue is applied to a rebuilt panel, weights are applied for 24 hours to ensure that the delicate stator lies perfectly flat. Obviously this can’t be done on an “in-situ” panel – and even if it was attempted, some of the glue would find its way onto the diaphragm. Not good! In short, there is no effective solution that does not involve replacing all the panels. Yes, there is a cost: but it’s nothing compared to the cost of returning the speakers to us every few months when yet another panel gives up the ghost! Changing single malfunctioning panels is false economy in the extreme. Some of our customers have learnt this the hard way.

The above applies to speakers that have their original panels and have been in use “from new”. In some instances one or two panels have been changed over the years. If, after tests, these meet our criteria – these are panels you won’t have to pay for (obviously). So it’s not all bad news!

Good listening to the world’s most accurate sound transducer!

Ron Best, June 2019
 
This thread has lasted a long time! Looking back through it I had a Jadis DA50S with the 63's. Now have a DA88S and like a lot of others on this thread the extra valve watts especially with KT120's has delivered sounds from the 63's that I didn't think possible. Nobody has mentioned the source and for me that is also very important. Currently and hopefully forever I have a diy dac with dual mono burr brown TDA1794 chips. Power supply is supercaps. It also has an SD card player.
 


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