Pass Labs INT 60 VS. Primaluna Dialogue Premium HP VS. Arcam A49

I don’t doubt that some tube amps would do very well with this speaker. The ARC REF series would seem like good bets, for example, due to their combination of low output impedance (for a tube amp), robust power supplies, and other characteristics.

However, **if** the output impedance of the Dialogue Premium HP is not considerably lower than the output impedance of the non-HP version (as described in the Stereophile measurements I linked to earlier), and given the speaker’s impedance characteristics as shown in Stereophile’s measurements which Unsound linked to earlier (showing an impedance between 2 and 3 ohms for frequencies between about 60 Hz and 300 Hz, where a lot of music contains a lot of energy, while rising to considerably higher values in the mid-range and treble regions), the result of those impedance interactions **will** be weak bass and over-emphasized mids and highs, ***in comparison with the tonal balances that would result with many other tube amps and most solid state amps.*** The degree to which that effect on tonal balance occurs will be dependent on the output tap that is used and on whether triode or ultralinear mode is used. But it would be a significant effect in all of those cases (if, as I said, the amp’s output impedance is not considerably lower than that of the non-HP version).

That follows from basic EE circuit analysis principles, which of course cannot predict a lot about what we hear or don’t hear from our systems, but can certainly predict some things, including what I said in the preceding paragraph.

Whether or not the resulting sonics would be appealing to some listeners in some rooms is another matter, of course. But why take the risk, unless a meaningful and extended audition in familiar circumstances is possible? And even then, why invest the time that would be required for such an audition, when other candidates can always be found that would not have this issue?

And as Unsound said (rightly, IMO) in his recent posts:

What will work, and what will work best are different things.

When I make a short list, I begin by eliminating those that could be technically compromised....

Best regards,
-- Al

I agree with Unsound and Tls49. And especially in the case of the specific tube amp in question, compared to many other tube amps, given its unusually high output impedance. See the third and fourth paragraphs here (although these measurements are for the non-HP version; the HP version may be somewhat better in these respects given the doubled complement of output tubes).

You may or may not like the sound that would result from the Sasha/PL pairing, but given the very considerable risk of disappointing sonics that is suggested by the impedance characteristics of this speaker and this amp, it would seem to make sense to pursue the much less risky solid state alternative.

Good luck. Regards,
-- Al

Scott, thanks for your inputs. Here is a corrected link to Mr. Potis’ review of the Carissa:

http://www.6moons.com/audioreviews/artaudio2/carissa.html

Interestingly, it is described in the review as being a "no negative feedback" design, but having an output impedance of 1.2 ohms, which is on the low side for a zero negative feedback SET design. While at least in its present version it is described at the Art Audio UK site as incorporating 9 db of feedback, which is a substantial amount, that would tend to reduce output impedance significantly. Both references, however, indicate that maximum power capability has been sacrificed somewhat in order to "double available current" in comparison with traditional designs.

All of these indications (1.2 ohms output impedance, 9 db of feedback, doubled current capability) are consistent with low output impedance, certainly in comparison with most SET designs, and in comparison with JA’s measurements of the PL Dialogue Premium, and I suspect also in comparison with the PL Dialogue Premium HP. (I would assume that the reference to a 10 ohm output impedance that is provided at the Art Audio UK website refers to optimal load impedance, rather than to amplifier output impedance).

In contrast, the interaction of an "unusually high output impedance," such as Scott described for his former 60 watt tube integrated, and a speaker impedance that is low in the bass region and higher at other frequencies, will produce exactly the results he described ("very weak lower mids and bass"), compared to the results most well designed solid state amps (and many other tube amps) would have provided.

BTW, I was one of those who suggested caution regarding the Cary tube amplifier in the thread Charles referred to. I did note in my post in that thread, however, that the output impedance of the Cary amp was unspecified, as was the corresponding damping factor (damping factor and output impedance are inversely proportional), and that measurements of those parameters did not appear to be available.

Also BTW, in saying all of this I’ll add that like several of those who have posted above I personally am firmly in the category of being a fan of tube power amps. But I am also not a risk-taker when it comes to questionable pairings.

Best regards,
-- Al