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Quad ESL-63 and low-powered amps; Sun Audio, Atma

Looking for opinions about suitability of low-powered amps with my 63's. I currently have an Audio Note M3 pre, CJ MV-60 amp. Importantly, I cross the Quads at line level at 100 hz, first order with nice Vandersteen MH-5 crossovers to Vandy 2wq subs. So the main amp is relieved of much work below 50 hz or so.

Specifically, I am looking at Atma-sphere s-30 MkII OTL 30 watt amp, and possibly even a Sun Audio 2a3 SET 3 watt amp.

Given my crossover, does this lighten the load (power or impedance) in such a way that these amps would work fine? I imagine the Atma will have no issues, but what about the Sun?

Finally, I would love to hear any opinions about the relative sonic characteristics I might hear between the CJ, Atma and Sun. I listen to 50% acoustic jazz, 25% classical, 25% rock. 60% on vinyl... SOTA w/Grace 714 and Grado Ref Sonata1. CD is CEC transport to Audio Note 3.1 Signature. I value musicality and rich midrange over endless detail and "neutrality".

Thanks all.
montaldo
willemj
1,036 posts
 
No, that is a misrepresenttaion of my position. What I said earlier was that they should be judged within their design parameters. So as long as a well designed amplifier is not driven into clipping it should sound the same as another one not driven into clipping. However, elsewhere I have also argued that you need a lot of amplifier power to avoid such clipping of dynamic passages. And that is precisely what I think was happening with my poor little 303. So again, I don't doubt people hear differences, but it is important to investigate what it is that they are hearing. Beyond insufficient output power, there may also be issues with input clipping due to a gain mismatch at the input stage, or a load dependent frequency response. But those are different issues that I already discussed earlier. So my position is a bit more complex than you may have thought.
As for my experience, well I am not a novice, not at all.
whart's avatar
whart
3,057 posts
 
I had great success using 60-70 watt ARC tube amps when I ran Quad 63s (mine were Crosby modified). I went from the 57, which was augmented with a sub and ribbon tweeters and found the 63 (without the need to supplement) to be the better all around speaker, but it lacked the "magic" of the original 57. Guess which speaker I kept, had restored and still use (in my second system)?
georgehifi's avatar
georgehifi
10,312 posts
 

The 63’s have 4ohm load from 6khz-12khz and then an even lower (epdr) of 5ohms combind with -40 degree phase at 14khz.

This indicates an amp that needs to be able to drive 4ohms as it’s best feature, not as a secondary feature. Which means (for tube if you can get it) an output transformer that’s specifically wound for 4ohms use, not 8ohms with a 4 ohm tap.

https://www.stereophile.com/images/66Quadfig01.jpg
" 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."

Cheers George
douglas_schroeder
3,281 posts
 
willemj, not intending to misrepresent your position. I appreciate the clarification. Aside from the issue of clipping, I see then that we will not agree on the question of amps sounding different from each other. So be it.  :) 
montaldo OP
202 posts
 
Willemj, I also find it hard to swallow that all perceived differences in amplifier sound are due to issues like clipping. My biggest problem with statements like that is the same problem I have with the objectivist camp in general: it assumes we understand why amplifiers sound the way they do to our ear/brain interface. I don't think we know even a small fraction of that. So how can anyone assert that this or that is the sole cause of sonic differences in amplifiers? It presumes perfect knowledge no one has.
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