Interesting observations by Lynn Olson

[Rajiv]

Hi,

More interesting posts by Lynn on the long running thread on DIYAudio.

Quote:
Originally Posted by Lynn Olson
Anyway, what I think is going on with sigma-delta converters and Class D amplifiers are new types of coloration we can't describe just yet.

This point needs to developed further. There were many times in the history of audio where a new technology sounded wonderful to the first group of listeners, then a few years later more and more people start noticing unpleasant artifacts, and finally discovered what caused the artifacts.

A quick history: the Williamson amplifier in 1947 swept away other circuits for nearly ten years, then stability problems were gradually discovered and resolved with better, more linear, and more stable vacuum-tube circuits.

The first transistor amplifiers of the late Sixties were dreadful circuits with quasi-complementary output stages with inherently high levels of Class AB switching artifacts, poor feedback stability and overall reliability, and serious problems with slew-rate distortion. It took more than ten years for better, more stable, and higher-speed circuits to appear.

The first pro-level digital tape recorder from Sony, the 1630, used the appallingly bad 741 opamps (which are completely unsuited for any kind of audio), with no dither, no jitter reduction, and ran at 44.1/16 PCM. From a modern perspective, the worst digital imaginable. Yet it was the industry standard for submitting a master to the pressing plant for more than five years. (Even the sainted J. Gordon Holt gave the Crown DC300 and Phase Linear 700 amplifiers a top-rank Class A rating, alongside the Marantz Model 9. I subscribed to the original "Stereophile" magazine back in the early Seventies, and remember reading the reviews.)

I should note that all of these technologies were hailed as the "best sound ever" at the time of introduction, with a few naysayers holding back ... and were eventually proven right when measuring technology discovered the problems. It took several years for digital engineers to admit that dither was a necessary part of digital audio, or that jitter reduction was worthwhile. It took more than ten years for transistor-amp designers to admit that slew rates of more than a few volts/microsecond might be a good idea. It took more than five years for the wretched, high-distortion quasi-complementary output circuit to be replaced by full-complementary.

I think sigma-delta converters and the latest Class D amplifiers fall in the same category. It's a new sound, and a lot of opinion-makers and reviewers like it. But I suspect it's the same thing all over again; the troubles of analog are once again shuffled around into a new place, where they won't be discovered right away.

Like Thorsten, I feel the real drivers behind the widespread adoption of sigma-delta converters and Class D amplification is the holy trinity of lower cost, better specs, and ease-of-application. For most audio engineers, those three parameters are the most important aspects of a new design.

Beyond the Ariel - Page 859 - diyAudio

More posts on his new speakers and the differences between DAC's

Beyond the Ariel - Page 858 - diyAudio

Regards
Rajiv

 

[GeorgeO]

Interesting observations

 

[viren bakhshi]

And this:

"In less diplomatic language, Class D sounds dry ... which to me, is not "accurate" at all, but an electronic artifact that you never hear with acoustic music in a real-world acoustic space. What separates real acoustic music from typical high-end sound is the vividness, sweetness, and dynamic swings of the real thing, along with a completely natural and realistic spatial impression."

And some more wisdom from Olson:

"After several weeks of this, I started to wonder. What's going on here? Is this just me? Have my tastes gotten so idiosyncratic I've completely departed from the mainstream of audio? Well, no.

Karna hears the same thing too, just not using the high-falutin' audiophile language I use. She thinks my setup (with the Monarchy N24) sounds "live", like a performance right in front of you, while the others might be "accurate" as audiophiles understand it, they don't sound "live"they sound canned, electronic, recorded, not real. She thinksand I have to agree 100% - that audiophiles have it all wrong with this obsession with "accuracy". The so-called "accurate" systems almost never sound "live"they mark all the tick-boxes on a checklist, but they just don't sound like real performers playing real instruments in a real space. (This was underlined by hearing two different sets of performers playing outdoors in the Pearl Street Mall in Boulder, Colorado. What we heard didn't sound like an audiophile system at all; the musicians playing a wide variety of acoustical instruments sounded loud, exciting, thrilling, real music, with real people standing around and applauding.)"

Viren

 

[Rajiv]

Hi,

More interesting observations from Lynn.

The Mac's, although legendary in some circles, have serious design issues. The cathode feedback is an excellent way of linearizing pentodes (which they badly need, since they are so nonlinear), but the dirty little secret is that Mac's operate in nearly Class B, and rely very heavily on multiple feedback loops to achieve acceptable low-level linearity. To me, they are very grainy and congested-sounding, a reflection of not-very-good low-level linearity.

Cary amps are optimized for high distortion, and tend to have very weak driver stages. This results in a fat, heavy, slow sound, similar to the jukeboxes of the Fifties, which used low-cost, primitive circuits. Some people, usually too young to remember the sound of the tube era, like this sound. I don't.

The best Fifties-era vintage amps were the Brit models (Quad, Leak, Radford), the Scott LK-150, and some of the Fishers. The Marantz Model 9, although legendary, is not really better than the Brits, just more powerful.

What's more shameful, or embarrassing, depending on how you look at it, are the American "high-end" tube amps of the Seventies and Eighties. By and large, these are warmed-over Fifties designs, with bad-sounding and instability-prone solid-state B+ series regulation. The worst of both worlds: solid-state failure rates, the necessity for frequent output tube replacement due to over-running the tubes beyond their ratings (more POWAH!), and worse sound than the originals they were copied from. I was startled to find out the single best-selling model of Audio Research was the monstrous Classic 600 ... even in the tube world, more POWAH sells big.

Many of the high-dollar high-end tube amps have egregious design errors, and it's hard to tell if they are intentional or not. For example, a high-powered design might have all four or six power pentodes share a common cathode resistor, or share a common bias point if the circuit uses fixed bias. If one of the power pentodes is just a little more efficient than the others, it will run away and current-hog, with the plates glowing red. Imminent failure is only seconds away; the user doesn't usually catch this until too late.

Now you've got a set of three or five power pentodes in a circuit where all of them must match or it will fail. Guess what? The amp vendor will be happy to sell you another factory-matched set of four or six output tubes. The vendor will tell you it was your fault one of the tubes ran away and cooked itself, or the power supply regulator blew a transistor and wiped out the output stage.

I frankly think this is grossly unethical behavior. Another pet peeve is correcting a design fault, typically with two or three resistors, and making that the "new, improved Mark 3.2 model", and charging a fat fee for "updating" the existing products.

There are well-engineered PP-pentode amps out there, but I don't stay on top of that market. I've heard some pretty decent examples, with sonics not far from the DHT ideal ... but there's almost no correlation between price and quality at all. Things I avoid: driver circuits with less than 8 mA of standing current, circuit boards, which make no sense for simple tube circuits (and create unwanted stray capacitance), and solid-state rectifiers, which have more hard-to-filter HF switch-noise than tube rectifiers.

The classic Mullard has been around since the early Fifties. Not many were imported into the USA, but they were all over the Commonwealth countries in the Fifties and early Sixties. I remember seeing them, along with the Quad II, at Radio People in Hong Kong, so they were around, usually with "Tropicalised" plate on the back.

Modern vacuum-tube designs, at least the ones aimed at wealthy audiophiles, go all-out for power and bass "slam", which magazine reviewers are always obsessing about. High-end manufacturers mimic solid-state techniques: regulation, more regulation, very large capacitance in the power supply, multiple feedback loops, and large arrays of output tube running in Class AB.

A conservatively operated PP-pentode amp will give an honest 35 watts RMS per channel. If you want 60 watts from the same output pair, you can back off the bias, decrease the Class A operating region, and increase the Class B region. This increases power at the expense of more low-level distortion. In practice, 60 watts doesn't sound any louder than 35 watts, since overload behavior and recovery dominate the perception of loudness.

The only reason to use more than two output devices is more power; quality goes down, not up, since multiple devices inevitably have slightly different Class AB transition points, which substantially degrades low-level distortion. This applies to pentodes, direct-heated triodes, bipolar transistors, and MOSFETs.

Solid-state rectification has the advantage of cheapness, cooler running, much higher current capability, and much less voltage sag under peak loads. It has the disadvantage of 10x more switch-noise (we're talking about 1000V peaks here), which radiates into the circuit and down the power-line, to contaminate other equipment. Yes, snubbing techniques help, but there's a big difference between a diode that has a rough on/off action spread across 0.7V and a diode that has a very smooth action spread over 12 to 30V.

I could go on. The tube amps that have gotten the glowing reviews from the hifi press over the last thirty years are usually overpowered behemoths that are substantially inferior in sound to pretty ordinary tube amps from the Fifties. Part of the reason that SETs took off in the Nineties was that mainstream high-end amplifiers sounded so nasty ... and rogue audiophiles made the discovery that old junk, barely restored, sounded better than the latest-and-greatest $7000 confection from Audio Research.

This is exactly what happened to me and the intrepid band of Tek guys who were working on our little MOSFET project for three years. We went to one of the first Oregon Triode Society meets back in 1991, and one of the members demoed an especially foul and rusty-looking Dyna Stereo 70. The chrome on the chassis was so badly pitted it looked like it had been dug up from a hole in the ground.

The so-called "mod" was a Triode Conversion, which consists of moving the screen connection of the EL34 from the transformer winding to the plate pin. The fancy version of a Triode Conversion is putting a 100-ohm, 10-watt resistor between the screen pin and the plate pin of the socket. Not exactly rocket science.

The ugly little Stereo 70 cleaned the clock of the top-reviewed Audio Research. Not even close. It sounded better than any amp the dealer was selling, and not by a small amount. It made the other amps sound broken. Not surprisingly, the dealer did not welcome any more OTS meetings. Bad for business. It was a wake-up call to everyone at that meeting: don't trust the reviewers, listen for yourself, and get serious about building your own.

After that meeting, our group of three abandoned the MOSFET project.

and rogue audiophiles made the discovery that old junk, barely restored, sounded better than the latest-and-greatest $7000 confection from Audio Research.

I guess he is talking about guys like me.

I am in agreement with Lynn having experienced the same with tube amps in my audio journey.


Regards
Rajiv

 

[viren bakhshi]

Hello everyone,

I'm addressing this especially to the young folk in the forum. These quotes may seem reactionary to some, seeing that they are diametrically opposite to what the mainstream audio press says. Just be aware that they are the observations of one of the most astute and respected of audio designers - Lynn Olson.

Lynn Olson, and some of us elderly members of this forum, have been through a generation change in audio reproduction. Home entertainment in audio practically began in the late 40's, early 50's, about when we were born. And changes since then have been tumultuous. Observing the fits and starts of the audio industry all along, doing design work on our own, these comments are based on personal, and very educated, experiences. Take them with some skepticism, but in all seriousness.

Meanwhile, develop some skepticism of your own. Don't take anyone's word, but find out for yourself. Listen for yourself. You'll find a lot of the big names falling short. And, there's no excuse for it. They have taken us for a ride for far too long!

Regards,
Viren

 

[Thad E Ginathom]

Much of this stuff is, technically, way beyond me, but, as so often happens, referring to links and browsing leads to new discoveries. I never had the least clue how single-bit digital could possibly work until yesterday, and thanks to this thread.

Even though I am of the age that Viren refers to, I don't know valves. I have no idea about the systems being spoken of and their technical ins and outs, ups and downs. But who knows? What I read here might save me from an expensive mistake one day!

 

[GeorgeO]

Well said Viren, no substitute for listening for yourself. I'd like to rephrase one word though, and refer to us folks "seniors" instead of "elderly", if you don't mind!

 

[Thad E Ginathom]

"seniors" instead of "elderly"

Ha Ha... speaking as one, I'm not sure it is any better!

Anyway, in many aspects of hifi I am a mere baby

 

[keith_correa]

<snip>I'm not sure it is any better!

It may be not but the connotation is different. As in "Junior!!! Shut up and listen to your seniors when they are speaking"

 

[square_wave]

I have always been intriqued by what Arthur Salvatore says about THE WEAKEST ELEMENT OF HOME AUDIO - IDR.

Can we achieve high IDR in a complex system ?

The weakest area in audio at present is the same as it was back in 1960...


The INability to reproduce lifelike "dynamics"

This is the capability of the system "to change its volume at the same speed, scale and intensity of real live music".

I refer to this as: Instantaneous Dynamic Response (IDR).

Most audio systems are simply pathetic when it comes to imitating what occurs in real life. Any live concert, even for a solo flute, or just a passing high school band, makes this unavoidably clear.

Part of the problem is that none of the existing musical software is yet capable of storing the entirety of this information, but most systems couldn't begin to reproduce realistic IDR even if it did exist on available analog or digital sources.

Instead, systems will routinely compress the IDR to varying degrees, or even seriously distort. The best I've heard are some "horn systems", but only at certain frequencies, and they still have their other, unique problems. Some conventional systems are pretty good at reproducing IDR, but only at lower volumes. Why is this so, and what is at fault?

The Causes of Compression
The causes are many and various, but the two main culprits are amplifiers and speakers. For an amplifier to reproduce IDR, it must have high voltage and power swing, and this gives the advantage to tube designs, which should be no surprise to experienced audiophiles. However, amplifiers with truly high voltage swings are very rare because of their extra difficulty and expense to build.

On the speaker end, the ability to move large amounts of air is critical, which consequently requires a large, total driver area and also larger cabinets to house them. The subsequent problems are that accurate, large drivers are very costly, and so are their required, large dead cabinets.

If that wasn't enough, if the drivers are too large, they will then have unavoidable problems with transparency, purity, delicacy and refinement etc. This is why there has never been an easy and obvious solution to this problem. (However, if a listener prefers rock, or any other poorly recorded music, he/she will not be as unhappy with those compromises.)

 

[arj]

Rajiv, Santosh and I were discussing on this a few days back. on how we seem to be going back to older days.
This issue , result of perhaps overspecialization ,and is prevalent in many areas including medicine where the Big picture view as a starting point seems to be forgotten and now we are more stuck in details trying to make the big picture...perhaps like joining bits of the mirror to make the big mirror ?

in getting more details/resolution and other individual parameters we seem to have lost the essence of music