Quad ESLs - your amplifier experiences

As a 57 owner — no expert, but I worked inside a dozen of them — I urge you to send your Grandson and his "popping noises" to rehab. It takes so little to damage the panels, especially the treble below 100Hz. Even way back when I had mine (over 25 years ago) repairing such damage was nearly impossible, but now...?

It's not just the diaphragms that "arc and burn": so do the stators. Diaphragms are just Mylar; making them conductive is possible but hard work, and getting them 'right' even harder. But repairing the stators? The voltage is 1,500V and the arc may re-strike on each half cycle of the current. The stators don't burn in a brief flash like the ultra-thin film, they can melt: they aren't made of steel. I had one treble panel that looked like third-degree burns on skin, both sides melted and bubbled-up like mozzarella in a too-hot pizza oven.

I assume you use the limiter circuits. But with the aging of components in both the Quads and amp, I'd still be wary. Eternal Vigilance (and fear) is the price of 57 ownership.
 
One of 4 speakes that have left a lasting impression was a single Quad 57, the other one was back for warranty work, dbSystems gear.
 
... I assume you use the limiter circuits. But with the aging of components in both the Quads and amp, I'd still be wary. Eternal Vigilance (and fear) is the price of 57 ownership.
I am planning on restoring the Grandson before using it again. The popping noises were the amp, I believe - they weren't that loud, and the treble panels seem undamaged. Lucky me.

I have the limiter boards, and will install them when I replace the HT power supply boards, this spring.

Meanwhile, I'm back on the Marantz MM9000, which sounds very nice, just a little short of what's possible.
 
A fair amount has happened since I last posted. The Marantz MM9000 took exception to its on/off switch actually being used - I had it in an always-on state in my HT setup for 10 years, but now it needs a new switch.

You would think that the pandemic would have been a great time to get those new high-voltage power supply boards installed, and the limiter boards installed, too. But instead of doing that, I've been riding my bicycle. :) A Rotel RMB 1076, another home theater amp replaced the Marantz. It is class D, with six B&O ICEPower modules inside, iirc. It runs cool, and gave a serviceable sound without an edge. Perhaps that lack of an edge is why the Rotel was spoken of as one of the first 'listenable' class D amps; I don't know. But it was no standout sonically, at least with the Quads.

Had to switch out my Promitheus TVC magnetic passive preamp after the source selection switch got flaky, dropping the left channel, on one, then two inputs. Propping the knob up worked for awhile, but I can't see how to remove the knob - what look like set screws aren't. Anyway, after removing the TVC preamp, I notice the left sub is unplugged - maybe that was why I had no left channel at all. That stupid source selection switch on the Promitheus has confounded me enough however - I will hardwire one input and use a separate switch box if I have to.

But for now, the Luxman L-505u is serving as my preamp. That really throws a wrench into comparable amp evaluations. With the Rotel, I was listening to everything a fair amount louder than before, after changing to the Luxman as a preamp. The MC phono stage was not nearly as good as I remembered, so I put my Bob's Devices Cinemag 1131 SUT back in instead. Much better.

Meanwhile, while still getting used to the Luxman as a preamp again, I go and get another amp, a Chi-fi unit that uses a public-domain Class A design by J.L. Hood, published in 1969: https://audiokarma.org/forums/index.php?threads/1969-hood-amp-repro.794345/

The combination of the Luxman and the Hood Class A is the closest I've come to the Promitheus/PrimaLuna combo, so far (with the possible exception of the Promitheus/G.A.S. Grandson, whose popping noises may have been that infernal switch! Grr...)

I'll get it sorted, eventually. :)
 
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