Preamp is an amplifier too, right???

When I was studying electronics I was never introduced to such component as preamp. The whole section in electronics were dedicated to amplifiers and they are only realy different with output power.
If preamplifier is basically an amplifier than it certainly have an output power only you can't use it to drive speakers since the output impedance might require matching
I'm not familiar with 2a3 monos but pretty familiar with the bulbs' output characteristics. It realy seems to me that by cranking volume on your SS-pre you're getting these tubes onto clipping. Since they're working far away from their specified region, they might end life pretty quick.

You have to much money, Cary 2A3 monoblocks with solid state, no way. Just for the info: How did you learn about a company like Cary and not know anything about audio.?

Tube preamps typically have a far higher maximum output level than the mass majority of SS designs. As such, the only thing that i can think of is that the tonal balance has shifted due to different power transfer / loading conditions and you seem to like those changes.

Other than that, a preamplifier is nothing more than an amplifier designed to work with a lower input signal and a lower output signal. Think of a preamp as an "intermediary gain stage". It can take a weak signal and boost it enough to drive the next gain stage or it can regulate a signal that may otherwise overdrive the next gain stage through attenuation. Pre-amplifiers got their name as they are nothing more than an amplifier stage prior to the main amplification stages, hence "pre" ( before or prior to ) amplifier. As such, most do not consider "passive units" to be pre-amps as they have no amplification stages. However, one "could" say that they go "before the amp", so in effect, it is still a "pre" amp.

Other than that, there are preamps with enough voltage swing and a low enough output impedance that they can drive speakers. They will typically sound like tin cans vibrating when doing so, but you might be surprised what comes out of the speakers if you were to try doing this. This is NOT a suggestion to try driving the speakers via a preamp even though i have. For the record, i did this as a "yout" ( pronounced "youth" ) when i didn't know better. Sean
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Preamps do not increase power, only voltage. A preamp drives a load of thousands of ohms, which is far larger than its own output impedance, and that, along with a smaller power supply, decreases the power produced and transferred. Instead, it increases the voltage, so it is a small signal (voltage) amplifier not a "power" amplifier. A power amp drives loads of less than 10 ohms, which require a lot of current at a given voltage - so there is substantial power transferred. That's the basic difference - one amplifies voltage and the other power (voltage and current).