Are there ANY Measurements, Signs, or Hints that a Tube amp can PROPERLY Drive an AMP to full Microdynamic Expression? Or purely Experiential?

[caesar]

I wonder if there's something one could check before buying blind or hauling in a demo model...

 

[Duke LeJeune]

"Are there ANY Measurements, Signs, or Hints that a Tube amp can PROPERLY Drive an AMP to full Microdynamic Expression?"

I don't know the answer to your exact question, but obviously that hasn't stopped me from responding.

You see, I CAN think of a seldom-seen measurement which IN MY OPINION [edit: which turns out to be INCORRECT; see Post #6 below by Atmasphere] indicates a tube amp can properly drive a SPEAKER to full microdynamic expression:

Slew Rate, expressed in volts per microsecond, which used to be specified back in the 70's and 80's. The higher the better, as far as responding to dynamic nuance, based on the theory that extraordinary capability implies ordinary demands are effortlessly met. My understanding is that, in theory, something in the neighborhood of 30-40 volts per microsecond is adequate.

High-end audio being what it is, some amplifier manufacturers push well past "adequate" in this area... the highest Slew Rate I am aware of is for Spectral solid-state amplifiers: 650 volts per microsecond.

The second-highest Slew Rate I am aware of is that of Atma-Sphere Output Transformerless tube amps: 600 volts per microsecond.

[dealer hat on]The implication seems to be that Atma-Sphere tube amps are pretty good at microdynamic expression... and in my opinion that's one of the things they excel at, and one of the reasons I became a dealer. To be more specific, I think they do things in the microdynamic realm which are reminiscent of live music, whether or not the sound pressure level itself is reminiscent of live music.

[dealer hat still on] Occasionally you may come across an internet post where someone tried an Atma-Sphere amp and wasn't happy with it. In every such case where I have been able to find the impedance curve of the speakers used, there was an imo fatal mis-match. Speaker matching really matters with Atma-Sphere amps... it's not so much that your choices are few, but rather that a severe mis-match will usually be a step backwards.[/dealer hat]

[humble pie edit] "Regarding 'micro-dynamics' I suspect that is a function of distortion for the most part rather than 'speed' (slew rate), depending on what is meant by 'micro-dynamics'!" - Ralph Karsten of Atma-Sphere, post #6 below. [mmmmm...]

Duke

 

[tima]

The implication seems to be that Atma-Sphere tube amps are pretty good at microdynamic expression...

Implied or not, ime that's true.

 

[bonzo75]

So what's the slew rare for various 45, 2a3, and such sub 5 watt amps?

 

[microstrip]

"Are there ANY Measurements, Signs, or Hints that a Tube amp can PROPERLY Drive an AMP to full Microdynamic Expression?"

I don't know the answer to your exact question, but obviously that hasn't stopped me from responding.

You see, I CAN think of a seldom-seen measurement which IN MY OPINION indicates a tube amp can properly drive a SPEAKER to full microdynamic expression:

Slew Rate, expressed in volts per microsecond, which used to be specified back in the 70's and 80's. The higher the better, as far as responding to dynamic nuance, based on the theory that extraordinary capability implies ordinary demands are effortlessly met. My understanding is that, in theory, something in the neighborhood of 30-40 volts per microsecond is adequate.

High-end audio being what it is, some amplifier manufacturers push well past "adequate" in this area... the highest Slew Rate I am aware of is for Spectral solid-state amplifiers: 650 volts per microsecond.

The second-highest Slew Rate I am aware of is that of Atma-Sphere Output Transformerless tube amps: 600 volts per microsecond.

[dealer hat on]The implication seems to be that Atma-Sphere tube amps are pretty good at microdynamic expression... and in my opinion that's one of the things they excel at, and one of the reasons I became a dealer. To be more specific, I think they do things in the microdynamic realm which are reminiscent of live music, whether or not the sound pressure level itself is reminiscent of live music.

[dealer hat still on] Occasionally you may come across an internet post where someone tried an Atma-Sphere amp and wasn't happy with it. In every such case where I have been able to find the impedance curve of the speakers used, there was an imo fatal mis-match. Speaker matching really matters with Atma-Sphere amps... it's not so much that your choices are few, but rather that a severe mis-match will usually be a step backwards.[/dealer hat]

Duke

Unfortunately the application of the concept of slew rate is poorly understood in audio. It is good to explain why something sounds poor because it is inadequate, but little else. What is meant by "the theory that extraordinary capability implies ordinary demands are effortlessly met" ?

I agree that Atmasphere have pretty good micro-dynamic expression. But I have owned several generations of Atmasphere equipment, starting with a first generation MP1 and a M50, all having similar claims of high slew rate and having very different micro-dynamic expression - the Mk3.2 was a big jump over previous ones. IMHO we must look elsewhere for an explanation of their great micro-dynamic expression, perhaps to the particular spectral behavior of the distortion of the Atmasphere amplifiers. Surely, I am just divagating, no proof of any kind of it!

We must remember he can have now ultra fast operational amplifiers with slew rate of 6000V/microsecond! Will they sound great?

Concerning your observation of speaker matching, this can be a serious issue unless we are addressing the M2's. When we look around very few top high-end speakers are fully compatible with those OTLs, narrowing its use to a few speakers.

 

[Atmasphere]

So what's the slew rare for various 45, 2a3, and such sub 5 watt amps?

Between 5 and 20 volts/microsecond

Unfortunately the application of the concept of slew rate is poorly understood in audio. It is good to explain why something sounds poor because it is inadequate, but little else. What is meant by "the theory that extraordinary capability implies ordinary demands are effortlessly met" ?

I agree that Atmasphere have pretty good micro-dynamic expression. But I have owned several generations of Atmasphere equipment, starting with a first generation MP1 and a M50, all having similar claims of high slew rate and having very different micro-dynamic expression - the Mk3.2 was a big jump over previous ones. IMHO we must look elsewhere for an explanation of their great micro-dynamic expression, perhaps to the particular spectral behavior of the distortion of the Atmasphere amplifiers. Surely, I am just divagating, no proof of any kind of it!

We must remember he can have now ultra fast operational amplifiers with slew rate of 6000V/microsecond! Will they sound great?

Concerning your observation of speaker matching, this can be a serious issue unless we are addressing the M2's. When we look around very few top high-end speakers are fully compatible with those OTLs, narrowing its use to a few speakers.

There seem to be plenty of speakers that work with our amps- enough to keep us in business the last 45 years, and some major players, like Wilson, JM Labs, Sound Lab, Quad, Martin-Logan (although the ZEROs have to be used with the MLs), most horn systems and full range driver systems (including ZU Audio), Spendor, Coincident, Audiokinesis (of course), Proac, Silverline, Merlin, Devore Fidelity, Spatial Audio, PureAudioProject and really more names than I can think of right now...

Regarding 'micro-dynamics' I suspect that is a function of distortion for the most part rather than 'speed' (slew rate), depending on what is meant by 'micro-dynamics'! The ear does assign a value to the speed of a system (which means the speakers have to be fast too) as there is a tipping point in the brain where music processing is transferred from the limbic system to the cerebral cortex. If too slow => cerebral cortex as the brain is trying figure out what that sound is, since it isn't obeying normal hearing/perceptual rules.

A high slew rate suggests that a good gain bandwidth product might exist- that can be helpful when trying to get a handle on distortion. As pointed out some opamps have pretty good gain bandwidth product now, which allows them to have really low distortion (using feedback of course- its an opamp) and should be quite musical if used properly.

 

[bonzo75]

Then I disagree that slew rate is an indicator of microdynamic expression, as Duke said. The reason I asked annoy sub 5w amps is that they show the highest micro dynamic expression when matched with extremely sensitive and efficient speakers, and not when matched with harder to drive speakers. So the values given by Duke and what he said about slew rate, if correct, would be only for a certain category of speakers.

 

[Duke LeJeune]

Regarding 'micro-dynamics' I suspect that is a function of distortion for the most part rather than 'speed' (slew rate), depending on what is meant by 'micro-dynamics'!

Thanks for correcting my misconception!

Then I disagree that slew rate is an indicator of microdynamic expression, as Duke said.

So do I. That is, I now disagree with what Duke said.

 

[Atmasphere]

Thanks for correcting my misconception!

So do I. That is, I now disagree with what Duke said.

Not so fast- we don't have a definition of 'micro-dynamics' yet.