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What s the best Class A integrated tube amp over 80W

I am using Sound Lab ESL speakers, which have a very high impedance at low frequency (30 ohms). At high frequency, SL speakers have very low impedance (3 ohms). I loved the class A in Pass Labs amp, but it took too long to FULLY warm up in my small room (9x11)-5-6 hours. I have a thread on Agon on this topic, but now I would like some recommendations on the best Class A tube integrated amp with >80W. Usually, integrated are the budget model of the line, but must be GREAT class A tube integrateds. Any recommendations?
128x128chungjh
chungjh's avatar
chungjh OP
265 posts
 
Here is what Ralph Karsten said about my situation.




11-09-2020 3:48pmThe Sound Labs are a different sort of beast. Like most ESLs, they don't work so well with amps that can double power as impedance is halved, since the Electrostatic principle doesn't rely on a driver in a box...

The impedance curve of the speaker varies by about 10:1 from the bass (peaks at 30 ohms) down to about 3 ohms at 20KHz. But the efficiency of the speaker is about the same though that entire range; for this reason most *but not all* solid state amps will tend to sound bright on them. A Brilliance control is provided to help tone this down a bit, as well as jumpers to allow for more bass, since all solid state amps struggle to make power in the bass region. This is why a tube amp of 140 watts can easily keep up with a solid state amp of 600 watts on that speaker!
Tube amps will stabilize much quicker than solid state (in terms of warming up to get where it needs to go to sound right), so with a good tube amp you should be having the system very near its ultimate warm-up in only an hour, and really sounding quite good in only 15-20 minutes. 
chungjh's avatar
chungjh OP
265 posts
 
What are some highish impedance tube amps? Regardless of Class.
bifwynne
2,206 posts
 
@chungjh, ... if that Q is directed to me, the only brand I know about is Atmasphere OTLs.  I suggest that you make a call to Sound Labs.  They know what electronics are the best fit for their products.

Ironically, most dynamic speakers on the market have fluctuating impedance and phase angle curves, ... but are voiced to be driven by SS amps having near zero output impedances.  Fortunately, most ARC amps have "low'ish" (but not zero) output impedances and mate, for the most part, pretty well with most speakers that have moderate to high sensitivity levels. 

The impedance curve of my speakers fluctuates between a low of 4 ohms in the bass region and have an impedance peak in the high-teens/low 20s in the 2200 kHz mid/tweeter cross-over point.   Because I use my amp's 4 ohm taps, I calculate (as echoed by John Atkinson in his review of the Ref 150) that the SPL delta between the high and low impedance points of my speaker is roughly between .8 to .9 db.  Not too bad for a tube amp.

I would call Sound Labs. 
gilaad's avatar
gilaad
12 posts
 
You may want to look at this amp. 
https://www.bobcarvercorp.com/crimson-raven-features-specs
It may just be the one. 
tweak1
3,561 posts
 
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