Aric Audio? First Watt? PrimaLuna?

I run my Unlimited with a First Watt F5. I find the sound completely addictive. I unfortunately have never had the chance to hear Aric's tube amps,however,after living with his pre,I'm sure they're magic as well. 

According to measurements performed by the National Research Council of Canada and published in SoundStage the sensitivity of the speaker is somewhat less than specified, at 85.4 db/2.83 volts/1 meter. Consequently I would be concerned that some of the amps you are considering won’t provide enough power. Possibly including all of the First Watt models, but especially the SIT-3 and the F6, which are unlikely to be able to provide enough power into the speaker’s extremely high impedance peaks in parts of the frequency range. (See the impedance curve near the bottom of that page).

Also, the SIT-3 has extremely low gain for a power amp, which together with the speaker’s low sensitivity might cause you to have to operate the preamp’s volume control at or near the top of its range, especially when using your phono source.

Also, given the wide variations of the speaker’s impedance over the frequency range I suspect that the very high output impedance of the PrimaLuna DiaLogue Premium would not be a good match in terms of tonality. From Stereophile’s review of that amp:

The output impedance varied widely, from an extraordinarily high 15 ohms with EL34s and 14 ohms with KT120s from the 16 ohm tap, both tubes in Ultralinear mode, to 2.4 ohms with EL34s and 2.15 ohms with KT120s, both tubes in Triode mode, from the 4 ohm tap. The output impedance from the 8 ohm tap was lowest with both tubes in Triode mode, at 4.6 ohms (EL34s) and 3.9 ohms (KT120s). Changing to Ultralinear mode raised these impedances to 7.9 and 7.4 ohms, respectively.

With these high output impedances, the DiaLogue Premium’s frequency response will be altered to a significant extent by the Ohm’s law interaction between these impedances and the manner in which the loudspeaker’s impedance changes with frequency.

I have no particular knowledge of the Aric Audio amp, although it appears that it would be sufficiently powerful in its higher powered configurations.

A very well regarded tube amp that I suspect would be a fine match sonically, **if** you feel confident that 35 watts per channel would be sufficient, is the Music Reference RM-10 MkII, purchased used. Its power tubes are not expensive, and according to the description at the website tube life is estimated to be "5,000 to 10,000 hours if the amp is played below clipping at the recommended bias setting." And while I see that you would prefer an amp with non-adjustable bias, in this case the adjustment pots and test points required to bias the amp are easily accessible, right on the top panel. And regarding heat generation, note that it consumes only 70 watts of AC when idling.

http://www.ramlabs-musicreference.com/rm10mk2.html

http://www.ramlabs-musicreference.com/rm10design.html

Good luck. Regards,
-- Al

Thanks rocray.  Can I ask what speakers you are using?

almarg, I was wondering about the power myself.  I rarely go over 12 noon on the volume.  I confess to not understanding this completely.  From what I have read 16w will produce 100db for 88db speakers.  Which is ....ok.  Not rocking out loud, but ok.  I read a review (audiophilliac) on the J2 where he used it  with 805D3's.  Similiar impedance from what i saw on stereophile.  But admittedly, I would HATE to plop down 3-4k and not have enough power.  Which is one reason why I posted.

Thanks to both!

Sorry, it was the F7, not the J2

From what I have read 16w will produce 100db for 88db speakers.

16 watts is 12 db greater than 1 watt, and 88 + 12 equals the 100 db figure you cited. However that is at a distance of 1 meter, and that assumes the 88 db spec is accurate, which as I mentioned it is not.

To get a better handle on that, I suggest using the following calculator, plugging in your listening distance, speaker placement, and using 85.4 db for the speaker’s sensitivity:

https://myhometheater.homestead.com/splcalculator.html

For example, based on 16 watts, 85.4 db, a 10 foot listening distance, two speakers, and speaker placement within 2 to 4 feet of the walls the result is a maximum SPL at the listening position of 93.8 db. And only 90.8 db for speaker placement further away from the walls.

Also, as I indicated the speaker’s impedance rises to very high levels at various frequencies (42 ohms in the vicinity of 2 kHz, more than 20 ohms in much of the upper midrange and lower treble, and 32 ohms at about 85 Hz), and comparing the 8 ohm and 4 ohm power capabilities of the F6 and SIT-3 suggests that they will not be able to supply much power into those high impedances. That will be compensated for to a significant degree by the speaker’s presumably greater efficiency at those frequencies, but still ....

Regards,
-- Al