@chngjh,
I would never contradict Ralph. However, I think you may have somewhat reversed what Ralph may have said about amps that operate under the so-called voltage paradigm (i.e., constant voltage at varying speaker impedance levels -- most SS amps which have near zero output impedances) versus amps that operate under the so-called power paradigm (i.e., constant power at varying speaker impedance levels - generally, tubes amps that have high'ish output impedances). Ralph wrote a white paper on this topic.
Just an fyi, the reason the ARC Ref 150 SE operates as though it has "low'ish" (but not zero) output impedance off the 4 ohm taps (.55 ohms in the lower frequency region) is because the amp uses 14 db of negative feedback (NF). Some folks and manufacturers prefer amps that use zero NF.
In the case of a SS amp, voltage generally remains constant at all frequency levels, but power output (wattage) will increase as speaker impedance decreases and amp power will decrease as speaker impedance increases. So, for dynamic speakers that present low impedance levels in the bass region, a SS amp will produce more power than in the frequency regions where the speaker impedance is higher (often at driver crossover points).
The reason the SPL of a good speaker remains relatively flat at most frequency levels if driven by a SS amp, despite the varying speaker impedance levels, is because the speaker was designed and voiced to be driven by a SS amp.
You posted that:
That said, you also posted that:
Rather than me being disagreeable for the sake of being disagreeable, I think what is important in the end is whether a particular tube amp will mate well with your ESLs. Aside from electronic stability issues of mating a particular tube amp (or any amp) with your ESLs, I would expect, if it was my setup, that the amp/ESL combo would produce a relatively flat SPL over the audible sound spectrum.
So returning to your original question, your OP asked for Class A tube amp suggestions to mate with your ESLs. I think there have been several suggestions already offered. I do not think ARC amps are Class A, but some type of hybrid Class A/Class A-B variant. Further, if your ESLs mate better with high'ish output impedance amps, ARC amps may not be a good fit because many of the amps in the ARC line have low'ish output impedances.
In any case, I'll add to the list Atmasphere tube amps, especially if Ralph thinks they would mate well with your ESLs. I would also have a chat with Sound Labs. The manufacturer may have some good suggestions too.
Good luck with your amp search and happy listening.
I would never contradict Ralph. However, I think you may have somewhat reversed what Ralph may have said about amps that operate under the so-called voltage paradigm (i.e., constant voltage at varying speaker impedance levels -- most SS amps which have near zero output impedances) versus amps that operate under the so-called power paradigm (i.e., constant power at varying speaker impedance levels - generally, tubes amps that have high'ish output impedances). Ralph wrote a white paper on this topic.
Just an fyi, the reason the ARC Ref 150 SE operates as though it has "low'ish" (but not zero) output impedance off the 4 ohm taps (.55 ohms in the lower frequency region) is because the amp uses 14 db of negative feedback (NF). Some folks and manufacturers prefer amps that use zero NF.
In the case of a SS amp, voltage generally remains constant at all frequency levels, but power output (wattage) will increase as speaker impedance decreases and amp power will decrease as speaker impedance increases. So, for dynamic speakers that present low impedance levels in the bass region, a SS amp will produce more power than in the frequency regions where the speaker impedance is higher (often at driver crossover points).
The reason the SPL of a good speaker remains relatively flat at most frequency levels if driven by a SS amp, despite the varying speaker impedance levels, is because the speaker was designed and voiced to be driven by a SS amp.
You posted that:
SS output doubles with every doubling of impedance. Therefore my Pass Labs X250.8 SS amp produced about 60W at 30HZ with 30 ohm impedance. On top of that bass frequency takes more power to make the sound than treble.That seems somewhat odd and contradictory if you were using a SS amp with near zero output impedance. This is because your ESLs present 30 ohms of impedance in the low frequency region and just 3 ohms of impedance in the high frequency region. If you used a SS amp, I surmise that bass would be attenuated and treble bright, ... which you kinda indicate in the quoted text below.
That said, you also posted that:
Soundlabs sounds too bright at treble with most SS and sounds better with tubes which don't double output with halving of impedance.On the other hand, it may be that your ESLs were voiced to be driven by a tube amp that has a "high'ish" output impedance. For example, I think many Atmasphere amps have an output impedances in the 4 ohm space.
Rather than me being disagreeable for the sake of being disagreeable, I think what is important in the end is whether a particular tube amp will mate well with your ESLs. Aside from electronic stability issues of mating a particular tube amp (or any amp) with your ESLs, I would expect, if it was my setup, that the amp/ESL combo would produce a relatively flat SPL over the audible sound spectrum.
So returning to your original question, your OP asked for Class A tube amp suggestions to mate with your ESLs. I think there have been several suggestions already offered. I do not think ARC amps are Class A, but some type of hybrid Class A/Class A-B variant. Further, if your ESLs mate better with high'ish output impedance amps, ARC amps may not be a good fit because many of the amps in the ARC line have low'ish output impedances.
In any case, I'll add to the list Atmasphere tube amps, especially if Ralph thinks they would mate well with your ESLs. I would also have a chat with Sound Labs. The manufacturer may have some good suggestions too.
Good luck with your amp search and happy listening.