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Question for Sylvia: Splitting AV output

to

of

musical

and

transistor/mosfet amps then

**Utterly and completely untrue. THD figures (comprehensives ones, which include the spectrum of distortion components) can tell us a great deal about an audio product. That said, it is also true that beyond certain limits, further reductions in THD may not be useful for humans. Such reductions may cause other problems, which can introduce other artefacts which humans can respond negatively to.

Make no mistake: An amplifier which exhibits (say) 10% THD _IS_ introducing it's own signature into a system and is not acceptable for a high fidelity reproduction system. An amplifier which exhibits less than (say) 0.1% THD is not likely to be so compromised. An amplifier which exhibits less than (say) 0.001% THD is unlikely to be differentiated from the 0.1% example.

--
Trevor Wilson www.rageaudio.com.au
Reply to
Trevor Wilson
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to

of

musical

and

transistor/mosfet amps then

I obviously refered to the *non*-comprehensive ones which yaputya quoted (but you snipped), i.e. "@XXW THD < 0.YY% at 1kHz". By definition the "T" in THD makes the THD meaningless if not accompied by a slew of other relevant/related data. But I know that you know that.

But to be [f|F]rank, it was mainly flame-bait. Sorry that you we're the one that bit / got hooked.

[...]
Reply to
Frank Slootweg

have to

notion of

distortion

musical

and

transistor/mosfet amps then

So you are a troll

Reply to
yaputya

amplifiers?

have to

notion of

distortion

musical

sound, and

transistor/mosfet amps then

Nope, it was a somewhat provocative response to a rather meaningless specification. People who talk back to/at you aren't neccessarily trolls. So why the ad Hominem? Don't you have a real argument?

BTW, do you think that a troll would have let Trevor Wilson get away with his "**Utterly and completely untrue." statement?

Reply to
Frank Slootweg

amplifiers?

have to

notion of

distortion

musical

sound, and

transistor/mosfet amps then

to

Amplifier manufacturers nearly always quote the THD at 1kHz, it is a perfectly valid way to compare amps as the other distortion measurements will reflect the quality of the 1kHz result. The manufacturers of the Altitude amp I quoted do the same:

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Note that is the only distortion measuement they mention.

SC measured and plotted the THD vs power and THD vs frequency for the Altitude and their 200W amp module. Since this is not a binary NG I cannot post them here, but they clearyly show that the valve amp is vastly inferior in distortion at all frequencies and powers.

What's the difference between a provocative response and a troll, then?

Reply to
yaputya

amplifiers?

have to

notion of

distortion

musical

sound, and

transistor/mosfet amps then

to

THD is only a reliable measure of amplifier quality and performance if it is quoted as a maximum over the audio bandwidth at a reasonlble power output level. eg. 0.01% max THD 20hz - 20Khs @ 40w RMS per channel both channels driven

--
rgds, 

Pete 
------- 
"If Julia is the answer, then what was the stupid question!"
Reply to
felix_unger

Yes, I do know what manufacturers quote, but, as I said, that does not make them particularly useful.

*If* it's a very good amp, the 1kHz at XXW THD number will be representative for other frequencies and power levels.

The point is that most amps are *not* "very good amps", so it's silly to trust some non-representative single THD number.

*That* is the kind of distortion data I'm referring to, for the complete frequency and power range.

And then we haven't even touched on crossover distortion and clipping distortion, nor on the issue that the equal weighing of all harmonics in THD is a matter of debate.

(IMO (and in my case)) A provocative response is on-topic and intended to trigger an on-topic response. A troll is just intended to trigger heated responses, anger, etc., i.e. just the emotions matter, not the content.

Thanks for your response.

Reply to
Frank Slootweg

Crossover distortion will clearly be shown in THD specs at low power, and is just as bad (or worse) for any Vacuum tube amp as solid state using the same amplification class. Easier and cheaper to build a decent class A solid state amp of the same (or more) power as a similar VT one these days if low power distortion is your prime consideration.

No need to go anywhere near clipping with a modern solid state amp of course, unlike low power VT amps, since you can get about ten times the power output for less money.

If *ALL* harmonics (individually and in total) are below the threshold of human hearing, as with any good modern solid state amp, (but not with VT amps) what does it matter? Why in hell put up with increased even order distortion, just so it makes the odd order distortion figures look relatively lower, even when they are actually far higher is absolute terms for example? Only nutbags think like that. Plenty of those of course :-( There are plenty of effects processors to digitally add even order distortion these days if that is what you prefer to clean audio, no need to buy a valve amp to do it any more.

Trevor.

Reply to
Trevor

amplifiers?

have to

notion of

distortion

musical

sound, and

transistor/mosfet amps then

to

quoted as a maximum over the audio bandwidth at a

channel both channels driven

It is preferable to display the data as a graph which shows THD over the frequency range for a given power, and THD over the power range for a given frequency, usually

1kHz. Creating a 3-D plot showing all combinations would be even better, but would require automated testing. AFAIK nobody does this, since the 2D plots are adequate. . SC published 2D graphs for both the Altitude valve amp and their 200W module.
Reply to
yaputya

You should be able to see the SC measurements here (zoom in)

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These are scanned from SC who hold all copyright etc.

Reply to
yaputya

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