SET AMP'S FOR QUAD. ELS? Is this a no-no?

Pussycat

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I currently run my big 2905s on E.A.R. 509s (100 watts/ch push-pull), but am curious about these other variants of valved monoblocs. SET amp's are usually low(er) powered, but often described as more than adequate for many m/c speakers around 89db sensitivity or more. What are the general parameters regarding amplification and pure electrostatics?

 

AmDismal

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SET amps tend to cope less with difficult loads, and the modern Quads tend to fall into that category. Even the 57s, which were a complex load but don't need (well, handle) that much power, tend to work much better with PP amps IME. You could try one of the monster SET amps, a 211 or 845, but my own experience with an 845 with 57s was not great.

My personal view of SETs is that they are the best way to amplify, but they need the right speakers. Most mainstream speakers are not suitable for SETs - I use horns with mine - indeed only speakers specifically designed for flea powers (Audio Notes, say) work for me. Some here use big SETs like 845s with mainstream speakers, I guess, but my view is that you should choose the speakers you like and then get the right amp for them.

Tim de P reckons that any of his amps will drive Quads, so you could try Bourney's 859, although again I used one and it was pretty easy to get it into clipping...

 

Pussycat

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Tim de P reckons that any of his amps will drive Quads, so you could try Bourney's 859, although again I used one and it was pretty easy to get it into clipping...
Thanks for that, Adam; just the kind of 'gut feeling' I was looking for. T. de P. used Quads whilst designing my 509 mk 2s, he said recently, so there's no doubt about suitability. Just wanted to know if SET amp's were a no-no. Yes, Bourney's (integrated) amp. is lovely, but I've got 509s already................

Crazy pic's, Paul; think I'll pass, though.

 

mighty ant

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I've heard the Quad Classic 11 amps (15w?) powering 2905s and they worked fine if you are not a head banger. The trouble with electrostatics is that they don't require much wattage, but do require to be able to handle large voltage swings. I use 22 watt SET monoblocks to power my 2805s without any problems.

 

paulf-2007

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Feck meChinese OTL's

There's a brave man.
not me Michael, just came across them looking at 6c33c valve amps- - - Updated - - -

Thanks for that, Adam; just the kind of 'gut feeling' I was looking for. T. de P. used Quads whilst designing my 509 mk 2s, he said recently, so there's no doubt about suitability. Just wanted to know if SET amp's were a no-no. Yes, Bourney's (integrated) amp. is lovely, but I've got 509s already................Crazy pic's, Paul; think I'll pass, though.
Just pulling yer whatsit mate

 

Frizzy brizzy

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I am waiting on delivery of my art audio jota, Tom willis is running it in on his 63's , now I know the jota is a unusual beast but I gather it will power some difficult loads.

 

Jazid

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One parameter to watch for is the impedance curve, electrostats often measure with alarming dips in impedance, and depending on where this is it can have a (very) adverse effect on corresponding frequency response. The 63 for instance has a plunging impedance below about 80Hz. This implies that the amp will have to swing more current at low frequencies - not a problem for s/s amps and to a lesser extent for p/p tube designs, but a major problem for SETs which have limited output, higher output impedances and inherently have a limited headroom before they suffer from output tx core saturation, particularly at low frequencies. This might not matter for choral music, but large orchestral or rock/dance will really just work against the strengths of both the amps and the stats; a poor combination. I'd suggest not to bother unless you just want to play or have an itch to scratch, and if so then use an amp with substantial output and beefy output trafos, not a cheap prospect :nup:

IMHO AmDismal is right on the money here :^

SET amps tend to cope less with difficult loads, and the modern Quads tend to fall into that category. Even the 57s, which were a complex load but don't need (well, handle) that much power, tend to work much better with PP amps IME. You could try one of the monster SET amps, a 211 or 845, but my own experience with an 845 with 57s was not great.My personal view of SETs is that they are the best way to amplify, but they need the right speakers. Most mainstream speakers are not suitable for SETs - I use horns with mine - indeed only speakers specifically designed for flea powers (Audio Notes, say) work for me. Some here use big SETs like 845s with mainstream speakers, I guess, but my view is that you should choose the speakers you like and then get the right amp for them.

Tim de P reckons that any of his amps will drive Quads, so you could try Bourney's 859, although again I used one and it was pretty easy to get it into clipping...
 

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Hi Mike, as another very happy user of 509's with ESL63's, I think you'd be hard pushed to find anything valve-based to better them substantially. I've always wondered, mind you, what a pair of the 200w EAR 549's wouls sound like with them and would like to hear Roger Sanders' S/S ESL amps with the 63's as his white papers are very intersting reading. I was very tempted to go and audition a pair of his Innersound Eros speakers that a dealer was selling a little while back, as they were only about £1000 and came with a 200w amp for the bass units. I didnt do so in the end, as I wouldn't have th I wouldn't have had the cash to buy them without selling my current speakers/amps. His speakers and amps get great write ups though.ussycat=Pussycat;1714972]I currently run my big 2lmolmostctempted stctempted 905s on E.A.R. 509s (100 watts/ch push-pull), but

as about these other variants of valved monoblocs. SET amp's are usually low(er) powered, but often described as more than adequate for many m/c speakers around 89db sensitivity or more. What are the general parameters regarding amplification and pure electrostatics?

 

Gizza

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Darn, apologies for the mishmash of text in parts above, my browser on this tablet does really weird things when I'm posting on here!

 

rabski

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The general issue with ESLs is not the power requirement, but the load. Inductive, capacitive and with dips down to near one or two ohm's resistance is enough to destroy many amps.

I ran ESL 57s for a while and tried a fair few amps. IME, push-pull tube offers the best compromise. With decent output transformers, the PP design is reasonably immune to the effects of the load and maintains decent performance across the frequency range. SETs are a mixed bunch, but most couldn't cope and those that could were rather compromised.

OTL might just be perfect. I never tried it, but those who have report good results. Trouble is, you need a few watts and that means some compromises in the design.

PP KT88 or similar seems to work just fine.

 

MUJI

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Agree with Gary that Roger Sanders White Papers are very informative.

I had a pair of Martin Logans and I spoke with RS a few years ago to locate dealers of his products. At that time, he was happy to ship his amp for me to have a trial. I am not sure if that is being offered now but there is no harm giving him a call and ask what he thinks. I have found him to be most helpful in all aspects and always willing to answer every dumb question I had to ask about electrostatic speakers.

 

Gizza

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The 63's appear to be a better load than the 57's and certain other stats. The early Stereophile review of the 63's measured the minimum impedance at 3.5 ohms rather than the 2ohms of certain other stats - " ... Dropping below 6 ohms below 50Hz and between 5kHz and 18kHz, with minima of 3.5 ohms at 10Hz and 13.85kHz, this represents a reasonably demanding load for an amplifier to handle. Tube amplifiers would be best used from their 4-ohm tap (if they have one), though any solid-state amplifier that more or less doubles its power output into 4 ohms compared with 8 ohms would have no problems driving the Quad." The measurements can be found here http://www.stereophile.com/content/quad-esl-63-loudspeaker-measurements

Interestingly, after spending alternating periods running between the 4ohm and the 8ohm taps on my EAR valve amps, I much prefer the 8ohm taps. Looking at the measured impedance vs. Frequency graph that stereophile published, more of the frequency range falls closer to 8ohms than to 4ohms, so I don't really understand why they recommend using the 4ohm tap.

Mike, have you tried both the 4ohm and 8ohm taps from the 509's to the Quads? If so which do you prefer?

One parameter to watch for is the impedance curve, electrostats often measure with alarming dips in impedance, and depending on where this is it can have a (very) adverse effect on corresponding frequency response. The 63 for instance has a plunging impedance below about 80Hz. This implies that the amp will have to swing more current at low frequencies - not a problem for s/s amps and to a lesser extent for p/p tube designs, but a major problem for SETs which have limited output, higher output impedances and inherently have a limited headroom before they suffer from output tx core saturation, particularly at low frequencies. This might not matter for choral music, but large orchestral or rock/dance will really just work against the strengths of both the amps and the stats; a poor combination. I'd suggest not to bother unless you just want to play or have an itch to scratch, and if so then use an amp with substantial output and beefy output trafos, not a cheap prospect :nup: IMHO AmDismal is right on the money here :^
 
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RobHolt

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There are few strict 'no no's' in amplifier/speaker matching since much depends on what you expect to hear, what you like in terms of balance and how loudly you listen.

So a SET will drive any Quad ESL but the reactive load, exhibiting wild swings in impedance will mean these designs sound clearly different when driven by a SET design compared to a typical high feedback SS amp, or PP valve amp.

Based on my experience with ESL63s I wouldn't run them on anything less than a good 50wpc amp, and you really want a solid 100w/8R to make them go loud without obvious strain. They aren't particularly sensitive, and the relaxed strain-free sound encourages turning up the wick. I have them running experimentally on a vintage 25w Marantz at the moment and it audibly clips when I go from loud-ish to loud. Sounds fine at lower volumes but just runs into the buffers too easily for comfort. If you're a low level listener with the occasional louder blast then 20-30w will do ok in a small room or if you listen in the near-field.

All of the Quads from the 63 onwards have similar sensitivity and drive requirements.

The 57 of course can't take power so works great with small amplifiers, but the same warning wrt to tonal changes applies when going from SET to SS, or high impedance PP valve to SS.

 

John (big)

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Interestingly, after spending alternating periods running between the 4ohm and the 8ohm taps on my EAR valve amps, I much prefer the 8ohm taps. Looking at the measured impedance vs. Frequency graph that stereophile published, more of the frequency range falls closer to 8ohms than to 4ohms, so I don't really understand why they recommend using the 4ohm tap.

Mike, have you tried both the 4ohm and 8ohm taps from the 509's to the Quads? If so which do you prefer?
Whilst my Rogue Audio Atlas Magnum has output transformers I also prefer the 8 ohm taps to 4 ohm

 

Pussycat

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Mike, have you tried both the 4ohm and 8ohm taps from the 509's to the Quads? If so which do you prefer?
Thought I'd answer this before catching up on posts, so apologies if others have commented. My 509s sounded best into my ginormous ProAcs on their 4 ohm tappings (NAC A5 speaker cable), but it didn't take long after my 2905s were set up (again with NAC A5) to realise that they were better on the 8 ohm tappings.

They've very recently been serviced and re-valved by Tim, who suggested that the 4 ohm tappings would be better. Later he said that he'd mentioned this more from a safety standpoint, but that's over my head. I kept them on 4 until the new valves had settled down, and it sounded very good. Two weeks ago I reverted to 8 ohm taps and suddenly the whole room lit up !

That, for me, was/is the difference; not s.q. particularly, but holographics and emotive involvement; all probably based upon an improvement in dynamics, but whatever, I'm a happy bunny !

Oh, and thanks all for the interesting input. There are lots of upgrades to aspire to, so not replacing or supplementing my 509s suits, and is entirely rational after a £600 refurb.

 

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