Stereophile | January 2017 Issue

[LL21]

Thanks Lloyd, I also remember well your interesting and thoughtful questions which made the other 'side' of the 'tango'.



I don't believe there are such things as 'correct' measurements. There are helpful ones, and less helpful and lastly, largely irrelevant ones. There's a spectrum of usefulness.




In my experience yes, its more straightforward to build a low wattage transparent amp than a high wattage one. I've been working on such a thing for the past few weeks, turns out to be about 15W per channel. Getting more power without losing quality is the next design challenge. Its a widely appreciated observation that high efficiency speakers sound more dynamic than low efficiency ones, I put this down to the difficulty of building high powered amps with the highest level of dynamics. That in turn stems from the physical/electrical limitations of capacitors which are the primary power source in practically all amps.

Thanks, Opus...once again, very interesting reading!

 

[microstrip]

Hi...i am very intrigued by Aries Cerat. That aside, the reason i am interested in SETs and distortion is because:

1. the cliche is that they have high distortion and those who love them dont care...but in fact, proponents argue that at low wattage, they are not only very low distortion, but can compete or be superior [AT 1-3 WATTS] to that of many SS designs.

2. the kinds of distortion SETs produce...plus the physiological way the human ear perceives/processes sound...combine to possibly make a different kind of scientific case for SETs

If the good things of SET were only due to their distortion we would not need SET amplifiers with all its limitations - we just would need a preamplifier recreating these distortion figures and spectra, and a decent solid state power amplifier with a two ohm series resistor in the output. Same thing to OTL or DartZeel amplifiers ...

 

[bonzo75]

Hi...i am very intrigued by Aries Cerat. That aside, the reason i am interested in SETs and distortion is because:

1. the cliche is that they have high distortion and those who love them dont care...but in fact, proponents argue that at low wattage, they are not only very low distortion, but can compete or be superior [AT 1-3 WATTS] to that of many SS designs.

2. the kinds of distortion SETs produce...plus the physiological way the human ear perceives/processes sound...combine to possibly make a different kind of scientific case for SETs

Whenever I have looked at the meters of Mike's Dartzeel, Justin's Accuphase on Apogees, and Luxman, they do way more than 1 - 3 watts.

The avant-garde engineer was asked to design the amp that would best run the speakers, he chose to do a class A 150w. Mike at AS has been selling a few demoing them with Vitus. One designer recommends his 80w valve SET for his horns. It all varies. No one agrees.

 

[Mike Lavigne]

Whenever I have looked at the meters of Mike's Dartzeel, Justin's Accuphase on Apogees, and Luxman, they do way more than 1 - 3 watts.

The avant-garde engineer was asked to design the amp that would best run the speakers, he chose to do a class A 150w. Mike at AS has been selling a few demoing them with Vitus. One designer recommends his 80w valve SET for his horns. It all varies. No one agrees.

and even though you almost never see continuous output of much more than 5 watts or music peaks over 20 watts on the dart 458's in my system, the authority and scale of the music has much to do with the grip and headroom of having plenty of power. lesser amps with limited power sound limited in my system.

everything involves compromises somewhere. it's all about the whole system balance.

 

[Aries Cerat]

Thanks Lloyd, I also remember well your interesting and thoughtful questions which made the other 'side' of the 'tango'.



I don't believe there are such things as 'correct' measurements. There are helpful ones, and less helpful and lastly, largely irrelevant ones. There's a spectrum of usefulness.




In my experience yes, its more straightforward to build a low wattage transparent amp than a high wattage one. I've been working on such a thing for the past few weeks, turns out to be about 15W per channel. Getting more power without losing quality is the next design challenge. Its a widely appreciated observation that high efficiency speakers sound more dynamic than low efficiency ones, I put this down to the difficulty of building high powered amps with the highest level of dynamics. That in turn stems from the physical/electrical limitations of capacitors which are the primary power source in practically all amps.

Hello opus.100% correct about the 'correct' measurements,what they really mean and if are helpful.Measurements are what statistics are for politics.On official way to lie.

Now,the easiest thing when designing an amplifier,is to make one with low THD.Just add gain,and feedback.and there you have it.Designing a good sounding amplifier is another story.
So the question should be,is it easier to design a good sounding amplifier or a low THD amplifier?Answer is of course the latter.A 50 dollar chip amp measures great.So what?

The fact that low efficiency speakers sound more compressed than high efficiency speakers like horns,have nothing to do with what is driving them,but the physics behind the transducers themselves.

Example.A flea 2W amplifier with minuscule PSU capacitors,coupled to a 100Hz flare tractrix horn,will blow away a conventional cone driver driven by an SS amplifier with welding spec output stage,and there are many SS like that out there.

The 100Hz-flared horn,will present 0.2% H2 at 115db for the two octaves it covers,where as the conventional driver will be near meltdown at that levels,let alone measuring distortions.

It has nothing to do with what amplifier is used.The energy transfer efficiency for the horn is couple of magnitudes higher than a typical midbass cone driver.Imagine a compression driver's voice coil barely moving inside it's magnetic gap,producing much higher acoustic energy than a conventional cone driver moving at it's Xmax limits (gross distortions) and it's voice coil dissipating triple digits Watt(dynamic compression).

Best
Stavros

 

[Believe High Fidelity]

Hi...i am very intrigued by Aries Cerat. That aside, the reason i am interested in SETs and distortion is because:

1. the cliche is that they have high distortion and those who love them dont care...but in fact, proponents argue that at low wattage, they are not only very low distortion, but can compete or be superior [AT 1-3 WATTS] to that of many SS designs.

2. the kinds of distortion SETs produce...plus the physiological way the human ear perceives/processes sound...combine to possibly make a different kind of scientific case for SETs

I am happy to hear that you are intrigued. More and more the temptation to turn to the dark side grows in the WBF community

Many moons ago when I was a Jolida dealer I ended up carrying to satisfy the market request. To my ears many of the lower priced tubes were not at the same level as their SS equivalent. In spite of my disagreements with the sound they would sell because of what F1 stated the "euphonic" sound did provide a very lovely blanket of coloration to the sound many did enjoy.

It wasn't until I did a tour of duty in Colorado that I heard back to back higher end tube designs (and horns) that turned my life around. One in paricular was a V8 designed push pull amp powering Hansen Kinight speakers had so much tonality I was blown away.

Then I heard the SET's on horns (Cessaro's IIRC) and Game Over. It is also what started to get me away from analog. Of course once I setup a few Linn Sondeks as a Linn dealer I swore off analog again. I still have bad dreams working with that table...

 

[LL21]

If the good things of SET were only due to their distortion we would not need SET amplifiers with all its limitations - we just would need a preamplifier recreating these distortion figures and spectra, and a decent solid state power amplifier with a two ohm series resistor in the output. Same thing to OTL or DartZeel amplifiers ...

Hi Micro...well, i guess the reason i ask about SETs is because (in your example), the SS amp would go because it's generating higher distortion/or whatever the right measurement/metric is than the SET (AT 1-3 watts). I fully understand that 1-3 watts gets you almost nowhere with a Celestion SL6si which was 84db efficient or with an Apogee Scintilla, and hence the reason why powerful amps exist.

But if there is truth to the concept that SETs can produce extraordinarily clear signal at 1-3 watts (and I think Ralph Karsten has suggested performing better than many SS amps)...then as long as there is a 105-109db efficient speaker on the other end...that certainly is a compelling alchemy (i wont call it chemistry!).

 

[bonzo75]

Lloyd, you want the 105 - 109 for almost ALL drivers

 

[amirm]

I actually don't feel that strongly about it, just playing devil's advocate really.

On that note, please allow me to express what a great debate you and morricab had. Both of you put meat on the table and demonstrated learned ability to explain your point of view. I don't think I have seen so much objective evidence to back one's opinion in a long time here. As such, I hope you both walk away with respect for each other for a job well done.

 

[microstrip]

and even though you almost never see continuous output of much more than 5 watts or music peaks over 20 watts on the dart 458's in my system, the authority and scale of the music has much to do with the grip and headroom of having plenty of power. lesser amps with limited power sound limited in my system.

everything involves compromises somewhere. it's all about the whole system balance.

Power is a function voltage and current. Unless we separate them debating power - and then we have to include the speaker in the equation - it is a meaningless debate and only goes on feeding the myth that grip comers from plenty of power and that the headroom that is not used is a miraculous need.

IMHO perhaps one of the greatest contributions is due to the power supplies of high power amplifiers, that have intrinsically better regulation than low power ones. But a good designer can easily overcome this situation.

For many reasons high powered amplifiers can give us "the authority and scale of the music ". But I have seen many high powered amplifiers that could sound anemic and small, irrespective of being very powerful in the specifications.

Mike, you have masterly tuned your system around the NH458. IMHO any amplifier will sound limited in your system, irrespective of being low or ultra high power!

 

[microstrip]

Hi Micro...well, i guess the reason i ask about SETs is because (in your example), the SS amp would go because it's generating higher distortion/or whatever the right measurement/metric is than the SET (AT 1-3 watts). I fully understand that 1-3 watts gets you almost nowhere with a Celestion SL6si which was 84db efficient or with an Apogee Scintilla, and hence the reason why powerful amps exist.

But if there is truth to the concept that SETs can produce extraordinarily clear signal at 1-3 watts (and I think Ralph Karsten has suggested performing better than many SS amps)...then as long as there is a 105-109db efficient speaker on the other end...that certainly is a compelling alchemy (i wont call it chemistry!).

IMHO, no. As far as I know technically you can now have solid state amplifiers that have much lower THD and noise than any tube amplifier, irrespective of power. Modern ICs, such as the LME49710 are hard to beat. For example see this application adding a LME49710 to an "horrible" sounding LM3886: http://www.neurochrome.com/modulus-86/

Again, IMHO debating sound quality of SETs just in terms of THD is misleadingly reductionist.

 

[microstrip]

(...) Then I heard the SET's on horns (Cessaro's IIRC) and Game Over. It is also what started to get me away from analog. Of course once I setup a few Linn Sondeks as a Linn dealer I swore off analog again. I still have bad dreams working with that table...

Nice to know that vinyl is not the exclusive land of horns. My only excellent exposition to horns was also digital.

 

[amirm]

IMHO perhaps one of the greatest contributions is due to the power supplies of high power amplifiers, that have intrinsically better regulation than low power ones. But a good designer can easily overcome this situation.

With the exception of class D amplifiers, regulated power supplies in a power amp output stage is very rare. Vast majority of them use unregulated power due to huge cost (power loss) in attempting to regulate them. Fortunately these topologies are pretty tolerant of voltage variations in the output stage until such time you hit their peak current limiting.

 

[KeithR]

Whenever I have looked at the meters of Mike's Dartzeel, Justin's Accuphase on Apogees, and Luxman, they do way more than 1 - 3 watts.

The avant-garde engineer was asked to design the amp that would best run the speakers, he chose to do a class A 150w. Mike at AS has been selling a few demoing them with Vitus. One designer recommends his 80w valve SET for his horns. It all varies. No one agrees.

Yes, believe Mike at AS has said 300B Tri monoblocks are great but have nothing in reserve on his 104db sensitive Duos - in fact, I believe he prefers Vac 200iq P/P monoblocks on them.

I believe DDK on this forum has said Lamm 2.1s aren't enough power for AGs as well (18 watts). Ralph (Atmasphere) runs his 60 watt OTLs on 100db Classic Audio Reproductions speakers.

There clearly is variance of opinion.

 

[LL21]

On that note, please allow me to express what a great debate you and morricab had. Both of you put meat on the table and demonstrated learned ability to explain your point of view. I don't think I have seen so much objective evidence to back one's opinion in a long time here. As such, I hope you both walk away with respect for each other for a job well done.

absolutely agree...i have particularly followed this thread and sought to add the 'no clue audiophile' faction's two cents' worth of questions for that very reason. Extremely good to read and follow.

 

[morricab]

Power is a function voltage and current. Unless we separate them debating power - and then we have to include the speaker in the equation - it is a meaningless debate and only goes on feeding the myth that grip comers from plenty of power and that the headroom that is not used is a miraculous need.

IMHO perhaps one of the greatest contributions is due to the power supplies of high power amplifiers, that have intrinsically better regulation than low power ones. But a good designer can easily overcome this situation.

For many reasons high powered amplifiers can give us "the authority and scale of the music ". But I have seen many high powered amplifiers that could sound anemic and small, irrespective of being very powerful in the specifications.

Mike, you have masterly tuned your system around the NH458. IMHO any amplifier will sound limited in your system, irrespective of being low or ultra high power!

You make some very good points here. I have not heard this vaunted "authority" claimed for high powered amps compared to good quality lower powered ones...as long as both amps are running below clipping. This is an audio myth IMO. If a speaker is cruising at < 5 watts with peaks to 20 watts, then a good 50 or 60 watt SET (an expensive proposition to be sure) will have ample head room to deliver those peaks without sounding stressed.

I also agree that hte power supply is of key importance in making sure the amplifier is delivering as it should regardless of demands...as long as it does not exceed its absolute demands. I have seen this also with preamps where a highly regulated preamp will deliver more precise sound with more "balls" than other preamps...despite the argument that not much current is needed to be delivered.

I have had a number of experiences where the low powered amp sounded at least as powerful as the "beast" amp. The best example was a KR VA350i on an Acapella Violon speaker where it sounded far powerful and authoritative (especially in the bass surprisingly) than a 225 watt Electrocompaniet amp, which totally thinned out the bass...we were shocked. I have also heard a 30 watt PP Class A tube amp out muscle 130 watt Class AB tube monos on the Thiel CS3.7...another shock.

 

[morricab]

With the exception of class D amplifiers, regulated power supplies in a power amp output stage is very rare. Vast majority of them use unregulated power due to huge cost (power loss) in attempting to regulate them. Fortunately these topologies are pretty tolerant of voltage variations in the output stage until such time you hit their peak current limiting.

That is true but I know of two notable exceptions: One is the Lamm ML2 18 watt SET monos. They use one 6C33C as an output tube and the other as a regulator. The other is the NAT Symbiosis SE that I had. I used a single large MOSFET per channel (each had its one huge heat sink!) for the output stage (it was single ended) and ANOTHER identical MOSFET, also with its own identical huge heatsink per channel, as a regulator. That meant 800 watts of continuous consumption from this monster. But what a cool concept.

Most other amps, as you have pointed out, simply don't regulate the output stage. Input and driver, increasingly common.

 

[Believe High Fidelity]

On that note, please allow me to express what a great debate you and morricab had. Both of you put meat on the table and demonstrated learned ability to explain your point of view. I don't think I have seen so much objective evidence to back one's opinion in a long time here. As such, I hope you both walk away with respect for each other for a job well done.

+1 Here, here!

 

[morricab]

Yes, believe Mike at AS has said 300B Tri monoblocks are great but have nothing in reserve on his 104db sensitive Duos - in fact, I believe he prefers Vac 200iq P/P monoblocks on them.

I believe DDK on this forum has said Lamm 2.1s aren't enough power for AGs as well (18 watts). Ralph (Atmasphere) runs his 60 watt OTLs on 100db Classic Audio Reproductions speakers.

There clearly is variance of opinion.

FWIW, I have had no problem getting plenty of umph from my 97db Odeons with everything from 18 watt PP tubes and 15 watt PSET to 50+ watt SET. My JJ322 works great (15 watts at 1% THD and a nice spectrum to boot), the PureSound A30 in triode mode worked well (18 watts), the VAC 30/30 worked well (32 watts), the Wall Opum M50s worked well (35 watts), the KR VA350i works well (30 watts), the Ayon Crossfire works well (30 watts), the Aries Cerat Diana works well (25 watts), the NAT Symbiosis SE worked well (100 watts) and the Ayon Vulcan Evos work well (55 watts). None of these ever sounded strained in any way on my speakers at the levels I listen at (peaks around 100db). Nor should they. At the levels I listen I am probably pushing no more than a couple of watts peak.

The Tri monos are probably around 8 watts with 2 or 3% distortion...1 or 2 really clean watts. For a 104db speaker that should be ok unless the room is huge and you sit far away...or you listen truly and distressingly loud. That amp would probably be borderline on my 7db less sensitive Odeons.

 

[morricab]

With the exception of class D amplifiers, regulated power supplies in a power amp output stage is very rare. Vast majority of them use unregulated power due to huge cost (power loss) in attempting to regulate them. Fortunately these topologies are pretty tolerant of voltage variations in the output stage until such time you hit their peak current limiting.

Thanks for the compliments...just want to make sure that people realize that there is a lot more to good sound than "text book" engineering in particular because human perception is involved and it is not like designing car tires...