Seriously considering tube preamp…opinions?

@tvad , all: I went back and read the last few pages of this long thread and really appreciate all the advice. I do regret that in some ways, my posts occasionally ran people in circles — reiterating good advice to me that had already been given, with sufficient clarity! My apologies.

* I now have a very, very short list of tube amps to drive inefficient speakers.
* I now have a very, very short list of solid state amps to drive inefficient speakers.
* I have some very powerful advice to reconsider buying inefficient speakers.

Since I am not fiscally committed yet, I can keep this in mind as I audition the Salks vs. Dynaudios.

Given the above lesson that "tube speakers love efficient speakers," the only question I'm left with as I keep the inquiry into more efficient speakers is a simple question:

At what *starting* level of db sensitivity does the choice of quality all-tube amplification open up? 88db? 92 db? more? (I suppose I'm not thinking of the tiny-watt tube systems, but things that are up to 35-40 wpc)
[Context for the question are the earlier parameters: listening at modest volume (85db), room (450sq ft), genres (classical/jazz/rock), digital sources, comfortable headroom]

Regarding the PrimaLuna EVO 400, I don’t know about that specific model but Stereophile’s measurements of several other PrimaLuna amps reveal them to have very high output impedances, even for tube amps. That stands a good chance of resulting in tonal imbalances when paired with many small two-way speakers. As well as with some larger speakers, depending on how their impedance varies as a function of frequency, and especially if the speaker was designed with the expectation that it would be driven with solid state amplification.

Regarding VTL, over the years a number of members have reported in threads here that they had customer service experiences with VTL that were, shall we say, less than ideal.

To add to Tvad’s comments about VAC amplifiers, with which as a former VAC owner I entirely agree, a nice thing about them is that they usually include a 2 ohm (or "1-2 ohm") output tap, in addition to the usual 4 and 8 ohm taps. The lower the impedance designation of a given output tap the lower the corresponding output impedance will be, and that additional tap adds significantly to the amp’s versatility with respect to speaker matching. The VAC models that were mentioned above include that third tap.

Regarding ...

At what *starting* level of db sensitivity does the choice of quality all-tube amplification open up? 88db? 92 db? more? (I suppose I’m not thinking of the tiny-watt tube systems, but things that are up to 35-40 wpc)

... Answers to that question will vary considerably among different listeners. And IMO a major reason for the variability is that it depends on the dynamic range of the kinds of recordings that are listened to (i.e., the **difference** in volume between the loudest notes and the softest notes). As I think I mentioned earlier in one of your threads there are some classical symphonic recordings in my collection that have been engineered with minimal or no dynamic compression which can reach brief dynamic peaks of 100 to 105 db at my 12 foot listening distance, while being listened to at average levels in the 70s, and with the softest notes being in the low 50s. And lest that amazing 50+ db dynamic range be questioned I’ll add that I have verified those dynamic ranges on a few such recordings by examining their waveforms on a computer, using a professional audio editing program.

Tvad’s suggestion of 90 db or more as the answer to your question is certainly reasonable. Beyond that the only things I can suggest are to try plugging various numbers into the SPL calculator I linked to earlier, and preferably to obtain an SPL meter which provides fast response time and "c-weighting." I use an older Radio Shack model 33-2055 digital SPL meter, which may be findable at eBay.

Finally, as a Daedalus owner I certainly agree with Tvad’s comments regarding them. However all of their models are floorstanding, and their prices may be discouraging. There is a used Daedalus Athena for sale here presently for $6K; with the possible exception of some particularly old models I doubt that other models are likely to appear for sale for much less than that.

Best regards,
-- Al