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To recap, you correctly pointed out that I was all wet in suggesting that an amp could exceed the amount of current given by P=IV *at maximum gain (voltage)*. But that was the only mistake in my rationale - at max gain, the amp can't put out more than P/V amps, but only at max gain is there such a restriction - and when are we ever listening at max gain?
Much more important is an amp's current-delivery capabilties at less than max gain, and this is theoretically (and, in practice, often substantially) completely unrelated to its maximum RMS wattage rating. This is how we get very powerful amps that are rated for a rather meager amount of constant power delivery.
Typically, amplifiers using a single 845 output valve per channel achieve a 24-26wpc power rating. By applying less voltage instead but drawing more current, we have designed an amplifier with less rated power. Operating in pure class 'A' to full power rating, we achieve lower-than-customary distortion specs across the whole bandwidth. Equally audible, we achieve far superior dynamics. Additionally, the lower plate voltage prolongs tube life.
this particular SET amp was built for low distortion across the entire audio range - under 1% at full power
As far as whether this amp is appropriate for these speakers or whether I'd be better off with more power, let's run some numbers, assuming we want 85dB at the listening seat:88 dB/W + 3dB for having two speakers -6dB for distance gives us exactly 85dB/W - thus, we need 1W continuous power from the amp for 85dB. If we allow a factor of 15 for transients, the Carissa is still within its *continuous* RMS delivery capability, <1% distortion across the board. We're not even considering the biamping now - we can assume at the very least another 3dB effeciency with 500W of solid-state power on the woofers.
1) There is definitely something to the "tube power > SS power" arguments. It's due to current delivery.
2) *I* prefer the sound of tubes, in general, and that sound is defintely *different* than SS amps. (No arguments there, I'm sure.)
3) Bi-amping, with tubes (even SET) on top with SS muscle on the bottom for bass, is definitely a scheme that offers lots of advantages. If you like tube/SET sound.
Sorry, but I don't understand the concept of max gain. My understanding is that an amp has a fixed gain, not a min nor a max gain. If you are talking about an amp's input sensistivity -- the input voltage that will cause the amp to produce its max power for a given load -- then I don't see how that's relevant. Since the gain is fixed, any input voltage lower than the input sensitivity spec of the amp will produce an output voltage less than its max and for the same load the current being delivered will be less.
Here is a quote from Art Audio's web site on the Carissa:Typically, amplifiers using a single 845 output valve per channel achieve a 24-26wpc power rating. By applying less voltage instead but drawing more current, we have designed an amplifier with less rated power. Operating in pure class 'A' to full power rating, we achieve lower-than-customary distortion specs across the whole bandwidth. Equally audible, we achieve far superior dynamics. Additionally, the lower plate voltage prolongs tube life.My interpretation of this is that the designer has designed the amp with a greater amount of dynamic headroom than typical 845 designs by not running the tube as "hot". This does not imply that the maximum current delivery of this design is any greater than any other 845 design. It can't be. The fundamental limitation of current delivery is the 845 tube.Since he's not pushing the tube as hard as in other designs his distortion specs at max power will of course be better (his max power will also be much lower). I doubt that they will be substantially different from any other 845 design at say 10 watts or 20 watts.
Sorry, but I'm not following the +3dB for two speakers nor the -6dB for the distance. For a point source (your speakers), the sound decay follows an inverse square law. Please provide more detail here, thanks.
Agreed. There is no argument against personal preference. When I replaced an NAD C320BEE integrated amp in my office system with a Decware tube amp due to not having any level control (the NAD amp had way too much power), I expected to hear quite a bit of difference. I heard essentially none and honestly, was disappointed. My guess is that as long as the load on the amp is moderate (say 1/2 of its max power so their distortion figures are comparable), I doubt that tube vs SS could be determined blindly.
3) Bi-amping, with tubes (even SET) on top with SS muscle on the bottom for bass, is definitely a scheme that offers lots of advantages. If you like tube/SET sound.Gee, if tubes have so much more current available that SS, then you'd really want a tube amp on the bass, right? Seriously, I'm a fan of bi-amping and as long as the gain is matched (by electrical measurement not by ear), you should reap some benefit.
1st, the amp does have better distortion figures across the board than most single-ended 845 designs. There are other factors at work there.As to the rest of what you said, I think that's accurate (that the 845 has an inherent max current capability). I don't see how that's terribly relevant, tho. You're certainly right that their able to able to provide more current because they lowered the voltage, but I don't believe that's the whole story.
Hmm. I agree that some of the best SS amps can sound a lot like tubes. From what I hear, the new FirstWatt F3 sounds exactly like a good SE tube amp. However, in the more usual class AB SS vs. PP tubes, I personally can hear a different within a few seconds, every time. I've done a lot of A-Bing.
I don't think we're really "arguing" about much here, Bob, though it does surprise me that you don't hear much different in SS vs. tubes.
There's no SS amp in the world rated at 15W, or even 40W, that would sound as good (BE as good), as this tube amp I'm using now.
It's not the peak RMS number that's so important, but the instanteneous current delivery at lower voltages.
Max wattage is about as useful a metric of amplifier power as total harmonic distortion is of sound quality. That's the way it is - in the real world, amplifiers are complex devices with a lot of other, usually unmentioned, performance characteristics.
I was happy to see, reading the Gallo SA sub amp manual, that they specifically discuss (and recommend, if you like it) using a "low-powered SET amp" on the Gallos as long as you're bi-amping to take most of the bass load off that amp. (And, I still don't know EXACTLY how the Gallo scheme breaks up the load, because the top pegs do still drive the woofers, but if you've got a bass amp on the 2nd coils and especially if you turn up the crossover a bit, most of the load is assumed by the bass amp.)
Thought I'd let you know I was pushing the Carissa tonight and found that it does go into clipping at levels not too far beyond my usual listening levels. Every once in awhile, I do like to push it to 95dB+. Based on how wonderful it sounds at 10dB lower, I wasn't expecting it to fall apart as quickly as it does, but it does.
Maybe. I am not sure what to do now... frankly, I am TIRED of auditioning amps for the Gallos. The Gallos must stay because I love them.
Actually, I have already taken the bass load off the Carissa using the 70hz highpass filters. The Gallo sub amp handles the bass on its own. Sounds very, very good this way - the Gallos do spectacular low bass, as tight and clean as you could imagine, down to 22hz.
Somewhat oddly, using the filters seems have very little effect on the loudness at which the Carissa clips. Also amazing, the Carissa all on its own (no bass amp) does wonderful bass as well up to its limits.
I'm back looking at switchig amps again. I didn't like the NuForces, but many ppl seem to like the CI stuff much better.The utter simplicity of SET appeals to me intellectually very strongly but perhaps that is just something I need to get past. :-}
