THD claims of audio signal generators

Since the cartridge you use has it's trackability limits, and the cutter lathes also have their limits, there is still a finite limit to what you will ever get from a vinyl disk. This can be ascertained. OTOH, CD's have differing average levels, so you cannot "set and forget", only ascertain the peak level setting for clipping for Dfs. Admittedly the peak levels on all modern CD's come close to this, whereas the peak levels for individual vinyl disks cover a wide range. Knowing the maximum gain setting in both cases allows you to set a volume control level below the maximum required for amplifier induced clipping however.

MrT.

too,

unlimited

Yes, but there's a massive variation in maximum groove velocity, from say EMI 'Music for Pleasure' at one end, to the Sheffield Track and Drum records at the other. Setting your system gain to avoid clipping at 30cm/sec will make for very quiet listening to most commercial output!

forget",

Simply that the apparent SPL level will be different using different CD's in a "set and forget" position regardless of Dfs. I think it's simply bad terminology saying "set and forget". It is actually ascertaing the *maximum* gain setting, and one *often* varies the system gain below that level.

Which I agreed with, vinyl too. Also FM etc.

Nearly all are these days.

Quite so.

MrT.

Are you saying that just because most modern CD's have peak levels very close to Dfs, you *always* listen to them at the exact same peak SPL, day or night? Or do you actually use the volume control like most people, based on your knowledge of recorded levels and the system gain structure that you have already ascertained?

I simply refuse to believe that more than a handful of people do actually "set and forget" the volume control, even with CD.

MrT.

Agreed! (assuming a rather broad definition for "little" :-)

MrT.

No, but I know where to set the volume control (-6dB, to be precise) to *ensure* no clipping.

Yes.

Me, too! :-)

What? No explanation? Just no?

It was a tongue-in-cheek response to Arny's comments. That was what the ":-)" thingie was all about. However, I think it is rather pointless to compare two circuits that are as completely different as a direct-coupled, transformerless transistor power amp and a typical iron-laden tube amp. I would expect a direct-coupled, transformerless tube amp to sound much more like a transistor amp, if such a design is even practical.

In article , Karl Uppiano wrote: [....]

I've heard one and it sounded very good, if that's what you mean.

It isn't.

Whether any tubed hifi amp design is practical is open for debate, but only if the tubie wants to lose the debate.

In fact a goodly number of transformerless tubed audio amps have been built and sold

Here are some schematics:

Do what? First of all, there will be many conditions where the 20 watt amplifier will be well into gross clipping while the 250 watt amp is loafing along. Next, even assuming 50% final stage efficiency, which is a stretch for most tube implementations, there's no way in hell the tube amp will draw merely 50 watts at full output.

Let's assume 6BQ5s - they'll deliver 17 watts wound out, but that's in the ball park and we want to use the lowest-dissipation tube for this examination: each tube's filament eats 6.3 volts at 0.76 amps, so a pair takes 1.5 amps at 6.3 volts. That's another 10 watts there, plus another

On the other hand, even assuming Hamm's paper is still relevant 32 years after publishing and several generations of amplifier designs since, and comparing amplifiers which he claims would have more-or-less equal resistance to overload, 60 watt tube amps have a quiescent dissipation around 70 to 90 watts: that would bias the SS output stage at 0.7 ampere. Note this is enough to maintain class-A operation into several watts. The extra dissipation all goes into the output stage, as opposed to warming up an armada of tube heaters; one could argue that a transistor amplifier dissipating as much heat as a tube amp half its size uses that heat more efficiently!

In any event, the core of the argument here is not so much the thermal efficiency of various amplifiers (which is a hell of a way to defend tubes), but how they _sound_, and I can come up with any number of scenarios for which a 20 watt amp, no matter how liquid its midrange*, will be Not Enough.

• which I suspect is a function not of transfer characteristics but more of non-zero output impedance changing frequency response when driving a loudspeaker.

Francois.

Watch which petard you have in your own back pocket, Mr. Ludwig, a'fore you make such comments.

You made absolutely NO such claim, Mr. Ludwig. You're claim was VERY simple, unambiguous and wrong:

"Subjectively tube amps of a given specification often (not always) sound better than solid state amps of better spec. Russ Hamm proved it in 1973 with his paper which appeared in JAES and it has not been contradicted."

Hamm's article makes NO such claim, it deals SPECIFICALLY with operation under conditions of sever clipping when THD amounts are on the order of 30%.

Absolute nonsense. Hamm's article makes no such statement. You have not provided a single shred of evidence to support such a claim.

Further, NO one here ever made such a claim, save you. The statement was VERY simpe: ANY solid state amplifier with substantially more power than 20 watts is going to sound MUCH better than ANY 20 watt tube amplifier when both are being asked to deliver more than 20 watts.

That means a 50 watt SS amplifier will do better at 35 watts than a 20 watt tube amplifier trying to do 35 watts,.

So what? What on earth does class B operation have to do with it, since almost NO audio amplifier since that time ran class B. There is but one or two such examples, and all are LONG off the market.

Further, what on earth does power consumption and efficiency have to do with it?

Just like a class AB solid state amplifier, which comprises MOST of the solid state amplifiers on the market. The only difference is the SS amplfiier doesn't have to provide power for filaments..

This is utter and completely irrelevant claptrap, Mr. Ludwig. We're not talking about efficiency, we're simply dealing with the fact that ANY higher power amplifier will sound better than any LOWER power power amplifier when trying to produce more power than the lower power amplifier is capable. It has nothing to do with bias class, it has nothing to do with amplfiier efficiency.

Your numbers are WAY off and completely irrelevant.

The concept that is clear is that you made a specific claim which was wrong:

"Subjectively tube amps of a given specification often (not always) sound better than solid state amps of better spec. Russ Hamm proved it in 1973 with his paper which appeared in JAES and it has not been contradicted."

and now you're making further claims which have only solidified the fact that you were wrong to begin with.

What is evident is either your inability or dogged refusal to deal with the fundamental tecnnical errors behind your assertions, not to mention the fact that your cited an article which utterly fails to support your, ahem, "thesis."

"(null)"

The final stage efficiency of a *class B* amp is NOT a number but a curve on a graph.

The *maximum* efficiency, with sine wave drive and a resistive load, is

At 1/2 power, efficiency falls to 55%.

At 1/10th power it is 24 %.

At 1/100th power it is only 8% !

So, a 100 watt class B amp dissipates over 12 watts when delivering only 1 watt to the load ( aside form any idle dissipation due to the bias setting).

OTOH:

A class A amplifier has a maximum efficiency of 50% at full power.

So, a 100 watt class A amp will dissipate 100 watts when delivering 100 watts.

At 1/100th power, efficiency falls to a mere 0.5% !!

It will dissipate 199 watts when delivering 1 watt !!!!

......... Phil

I have it, actually. It's in a book published by Newnes, isn't it?

I may have given the wrong HP part number. (Didn't I say 204C? I think that's right.) It's transistorized and does not contain a light bulb.

The name of the article is:

"Max Wien, Mr. Hewlett and a Rainy Sunday Afternoon", included in the book "Analog Circuit Design: Art, Science and Personalities" . See Amazon, etc.

I wholly agree. However what happens when both are asked to deliver

Actually very little, juice is cheap.

Yes, that filament power is a deal-breaker. How many watts do four

To the extent you never clip your amp, that is true. Hamm et al dealt not at all with reasons for hobbyists (not studio owners) in 2006 (not

Any recording medium saturates at a reasonable, but not extreme, level above average program level, CDs run out of bits, vinyl runs out of groove width, mag tape saturates, even live FM is deviation limited.

John

A 36dB transient ? You are joking yes ?

Graham

No, he's simply thrashing about in defence of a lost argument - as usual.