Input sensitivity, Gain and Preamp matching

Active pre-amp would be the safe bet, even more so with a tube or SET amp, but each active pre-amp will impart a sonic signature of some sort. That's just a fact. So if teh goal is to keep that out of teh equation just don't overpay on the passive and give it a try if you must but be prepared to make tweak from there and make changes as needed. Its the usual routine. These things seldom work out just perfectly after the first crack, especially with more esoteric gear like SET amps and passive pre-amps, but things can be tweaked and refined over time. There are many ways to skin the cat which is what helps make all this stuff fun.

Thank you most kindly, Mofi. I should qualify your statement, though, by saying that at best I'm just an amateur master, while Ralph (Atmasphere) is of course a professional master :-)

Pani, Ralph frequently makes the excellent point he states above that to perform at its sonic best a SET should be operated within just a relatively small fraction of its rated power, such as 25%. Unless, and perhaps even if, your speakers are super-efficient, though, such as being in the 103 db area he mentioned, I personally would nevertheless want to have the flexibility of being able to drive the amp to full power, even if it is only a relatively few recordings having particularly wide dynamic range that might require that.

If you are using the single-ended output of a typical digital source, its maximum output won't usually be much if anything over 2 volts. And it will be less than that for many recordings. So with 0 db of preamp gain (meaning, with the volume control set at max, that preamp voltage out = preamp voltage in) you would not be able to drive the amp to full power. On the other hand I believe that some of the Slagle autoformer-based passive preamps, as in the case of the one-stage tube preamp you are considering, provide up to around 6 or 7 db of voltage gain. That would result in their output being double the voltage they are provided with when the volume control is set at max. That would probably allow you to drive the amp to full power with many and perhaps most recordings, but almost certainly not with some.

Perhaps more significantly, if I'm recalling correctly you use a high quality analog source. Most (although not all) cartridge/phono stage combinations provide significantly lower peak output levels than digital sources, for nearly all recordings (the cannon blasts on the famous and nearly unplayable early edition of the Telarc 1812 Overture perhaps being a rare exception :-)).

So it seems to me that even with 6 db of gain you would at best be introducing a significant marginality into the system, that would probably prove to be unsatisfactory for some recordings. Especially if your speakers are not in the 103 db/1 watt/1 meter area that Ralph referred to, or higher. Personally, my instinct would be to pursue a different path.

IMO. Good luck. Regards,
-- Al

Pani, yes as George indicated it would certainly be relevant to know exactly what your source component(s) is or are.

In the meantime, though, in regard to what I alluded to earlier about the peaks of some recordings leaving margin relative to the maximum volume capability of the medium, my curiosity was sufficiently piqued that I've just made some measurements to shed some quantitative light on that.

What I've done is to use the Sony Sound Forge professional audio editing program I have to examine the waveforms of about a dozen different tracks from about a dozen different CD's, both classical and popular, dating from very recent years all the way back to reissues of 1940's and 1950's material. The Sound Forge program can quickly tell me the level of the highest instantaneous peak on a track.

While several of the tracks essentially reached the maximum possible ("full scale") level of the CD medium, which is identified as 0 db, many others peaked at various points between -1 and -4 db, with one peaking at -6 db and another at -8 db.

A -6 db peak will result for that track in the maximum output of a CD player or other digital source being 1/2 of its rated (maximum) output. So for example a CD player rated to provide 2 volts would never put out more than 1 volt for that track.

As I alluded to earlier, my philosophy is to avoid configuring a system in a manner that might be marginal (or worse) even with just a relatively small number of recordings.

Regards,
-- Al

Hey Al good to hear from you, as you stated, yes a few of the quietest early cd's have low recorded volume and your -6db seems about right for these.

So even if Pani has source outputs 2.5v this will be ample for 90% of the rest of recordings to play at full amp clipping, and if he has 4v from his source/s that will also take care of those quite -6db as well to drive the amp to clipping.
But, and a big BUT, when do we do our listening just below full output (clipping) of the poweramp anyway??? Unless we like blowing amps up to speakers.

All is moot anyway till we find out what source/s Pani has.

Cheers George