Solid State Amplifier Advancements In A Decade


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What significant advancements in solid state amplifiers have occurred in the last decade?
Specifically in Class A and Class A/B.

No replies regarding Class D please.
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I would read Nelson Pass's writings on the evolution from the X to X.5 to X.8 series of Pass amps, as well as the same for the XA series...
darTZeel NHB-458 monoblocks.

no negative feedback. only 6 active devices in the signal path. astonishingly low noise floor. 500 watts into 8 ohms. all the circuits are suspended inside the chassis for excellent built in isolation from feedback.

amazing first watt; yet very powerful and authoritative.

the best of tubes and best of solid state. sounds like music.

you can have it all. but....there is always a but.....it will cost you.
Mitch-

I think we all owe a debt of gratitude to Mr. Nelson Pass.
Historically, he has given us audiophiles some of the greatest SS power amps. 2nd would be Mr. Mark Levinson.

On the tubed -side, Conrad Johnson and Audio Research comes into my mind. Keep me posted & Happy Listening!
MY Pass 350.8 sounds much better than my old Rowland 8T.
Ebm,
It should sound even better with those new speakers you're building.
THose Datzeels are very interesting. Should be for $150000.

For most people in this world, I'd say advancements in Class D amplifiers is the thing that most people with modest budgets should be looking into. Class D is a different ballgame altogether and the most recent models and technology delivers in spades IMHO and many others as well.
Second note;

Honorable mention to Bob Carver & John Curl.
I am sure there are others that I am missing at the present time. Keep me posted & Happy Listening!
They do a better job of rounding the heat sinks off now so you don't cut your hands when you go to move it.
Mikelavigne-Thx for your insight since your opinions are by ownership NOT speculation!
Great Question. Since my amps are approaching the 10 year old mark, I look forward to the responses.

I think the OP is speaking of technical 'advances' in amp design and performance.

I think the answer is, there have been no advances. Just more of the same with a higher price tag. For the average person, reasonable priced high quality amps, are actually less available today, than a decade ago.

Soon, all we will have is Walmart's selection and the Pass Labs of the world.

He exempted class D.

Cheers
class D need not apply per OP request
Maybe we should talk about cables instead.
Its a good question. I'm sure better is possible for a price but not sure how much SS amps at various price points in general have advanced practically in the last decade whereas Class D is still perhaps the new kid on the block, but growing up fast, and offering new value that did not exist 10 years ago.
If I remember correctly, regarding advances in solid state amplifiers, Soulution was claiming to have developed a new method of eliminating switching distortion, or something like that with a novel and new method. I'm sure someone who owns one of their amps knows what I'm talking about and can clarify, but when I read the explanation in an Absolute Sound, it seemed like something new.
I've noticed much more linear "better" transistor design. Pre-driver and output driver transistors are just better. Replace the older ones with transistors of like specifications, especially the output drivers and you will hear a marked improvement in sound. It is more difficult than rolling tubes, but the same effect.

Also, better internal isolations and shielding for components.

I really haven't seen a major technological improvement in circuit design. regulators, power supply, circuit topology, etc. no real major changes. Just better components, layouts, etc. And as I wrote earlier, better transistors.

The best way to find new technology is to look at the recent patents that have been awarded in circuit design and see if Manufacturers have incorporated those into their new amp designs. I really haven't heard of much lately.

I think that many older amps are just as good as the new amps, if you update the transistors to newer, more linear transistors and maybe remove some extraneous circuitry that really isn't needed. Such as some protection circuitry. Nice to have, but really not needed for amplifications of signals. But, it does effect the sound, because it does touch the signal path.

It is kind of funny to me reading about tube amps and how owners roll tubes left and right with no after thought and people really don't realize that transistors (same specs) do and effect the sound exactly the same way. Just harder to get to on some amps.

Case in point. Mark Levinson 23.5. What a real PITA to work on.

My real point is that if you look at the circuit schematics of older and newer amp designs, you really won't see major differences in the very good amp designs. Just layout, component used and a few tricks.

That said, I haven't seen the Dartzeel amp schematic.

A visit to the patent office is in order.

enjoy
"I really haven't seen a major technological improvement in circuit design. regulators, power supply, circuit topology, etc. no real major changes. Just better components, layouts, etc. And as I wrote earlier, better transistors."

The above statement is pretty much what I believe is the case in the last 10 years, and is the reason that I created this post.

Can anyone refute the above quote?
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I'm also interested in this questions as I look to replace 15yo Perreaux power amp.

I've done a lot of reading on the interweb, and aside from the disqualified Class D options, this appears to be one of the few more innovative applications of Class AB and power supply design, although I'm not sure how far the apple has really fallen from the tree:

http://benchmarkmedia.com/products/benchmark-ahb2-power-amplifier
Extremely quiet SMPS operating at MHz frequencies and utilizing zero voltage zero current switching. Such power supplies are not only extremely quiet but also have line/load regulation. You can find them in all newest Jeff Rowland amps (including class AB). He also uses SPMS in preamps (Capri) to keep noise low.

Benchmark got rid of linear power supply, used in DAC1, replacing it with SMPS in DAC2, resulting in 10dB lower noise floor. Their brand new ABH2 class AB power amp also has SMPS resulting in S/N=132dB.

Also, in addition to improvements in discrete semiconductors integrated components like OpAmp, Buffers, Instrumentation Amps, etc. got much better.

Many amplifiers are built now using surface mount components. It is significant quality improvement since SMT process is very repeatable making country of origin pretty much irrelevant (that way Apple delivers high quality products, all made in China).
In terms of sonic improvements; nothing what so ever. I had a Threshold T400 in 1995. It sounded magnificent! I haven't heard anything surpass it yet. Joe
11-03-15: Jafant
Mitch-

I think we all owe a debt of gratitude to Mr. Nelson Pass.
Historically, he has given us audiophiles some of the greatest SS power amps. 2nd would be Mr. Mark Levinson.

11-03-15: Jafant
Second note;

Honorable mention to Bob Carver & John Curl.
I'm sorry Jafant but i think you are very ill-informed. An honorable mention to Bob Carver & John Curl?? Are you kidding? Are you serious?? The Mark Levinson amps that you have been enjoying are all John Curl designs. Mark Levinson was a ditz & just the marketing head of his own company (when he ran it) & it was all John Curl designs that were badged Mark Levinson & sold. Some of those older amps still sound superb today. Not to mention that all Parasound amps & the Halo editions are all John Curl designs.
And, as far as Bob Carver is concerned, you can read up on just how much pioneering work he has done in the power amplifier space. You might not like his amps sonically but that's another matter altogether.

In tube amps while Audio Research's William Z. Johnson did some pioneering work (I've read his 1968 patent that deals with partial cathode coupling) towards tube amp development, significant work in tube amp arena was done by those people who made OTL amps viable & reliable. These are people who started NYAL & Atma-sphere (I don't own any of his amps or preamps) & Futterman.
And, before I tip my hat to Audio Rearch & CJ I'd be tipping it before to people like David Hafler who designed tube amp kits to bring tube amplification to the masses so to say.

I really haven't seen a major technological improvement in circuit design. regulators, power supply, circuit topology, etc. no real major changes. Just better components, layouts, etc. And as I wrote earlier, better transistors.
This is also total BS!
There have been great strides in power supply design esp. in making them less noisy, wider bandwidth & having better line & load regulation (like Kijanki wrote before). Additionally, there are a very few power amps that have a regulated linear power supply. This is a very hard thing to do given that it has to be high current & high bandwidth. AFAIK, this design is patented.
Even tho' transistors have gotten better, if you give better parts into the hands of a mediocre or shitty designer, you are not going to get a better power amplifier.
We've seen better power amplifier topologies materialize such as those that use very little global negative feedback & restrict almost all the feedback to local negative feedback. This one aspect of the design has vastly improved today's power amps sonically compared to yester years. Anyone who does not acknowledge this has his/her head buried in the sand.
We've also seen much better thermal management techniques using both electrical circuits to detect temperature rise & quickly deal with it & physical hardware to wick away the heat generated.
We've also seen power amp designers get a much better understanding of circuit theory w.r.t. what makes a power amp sound better & they have been able to use this better understanding to use higher quality parts where it matters most (rather than using high quality parts everywhere & racking up the cost). So, in this case it's a better execution which can be considered as an advance in power amp technology.
We've seen a significant improvement in power amp reliability i.e. much longer MTBFs esp. for solid-state amps. (given that the user doesn't hook up the power amp in some stupid config & blow it up). Even tube power amps have come a long, long way in this regards. For the most part if a tube amp fails the damage is localized & often can be repaired by the owner.

I agree with much of Bombaywalla's post just above, but I want to make a factual correction: While the earliest designs produced by the Mark Levinson Audio Systems company during the years it was owned by Mr. Levinson were indeed the work of John Curl, subsequently his chief designer was the late Tom Colangelo. Who subsequently followed Mr. Levinson to Cello Ltd., and as far as I know probably also to some of Mark's later companies.

I believe that the ML-1 preamplifier, ca. 1977, marked the transition point between the work of John Curl and Tom Colangelo for Mr. Levinson, with that design borrowing heavily from Mr. Curl's work on earlier Levinson products, but with Mr. Colangelo's work also being reflected in the design, especially in the external power supply.

Also, while the characterization of Mr. Levinson as a "ditz" is perhaps not entirely unfair, my impression is that he does deserve a good deal of credit for many of the important (and ultimately very influential) philosophical concepts which underlied the products of his original company. Namely keeping the signal path as simple as possible, eliminating controls and functionality that would usually do more harm than good, and implementing everything that remained to very high standards.

Regarding amplifier progress in general, though, I can't help but recall the pair of 1950's Marantz 2 monoblock tube amplifiers I owned (and unfortunately sold) during the early 1990's. When operated in triode mode and in conjunction with a benign and efficient speaker load, still among the best sounding amps I have ever heard.

Regards,
-- Al
Al,
I believe Tom Colangelo and one or two other associates started Viola Labs some years before he died.
It is significant to me that you mention the Marantz 2 amplifiers, (which I never heard), because I often compared the sound of more modern amplifiers in my system, with more up to date circuit topologies with my old Mac 2105, and then realized why they still command silly prices. They just sound really good. When all of the technology and casework is complete, it still comes down to what sounds good to the listener.
That said, I'm using an 8 watt 300b now, but I'll keep the Mac.
Almarg,
thanks for your post & factual corrections.
maybe i should have given Mark Levinson some more credit but I lost a lot of respect for him when he lost control of his own company esp. after doing pioneering work in the field. which kind of designer doesn't want to regain control of his company & continue the pioneering work?
Bombaywalla, I really enjoy your contributions here, and more often than not agree with them. But, a lot of what you have attributed to happening in the last 10 years has been available for much, much longer than that.
In further defense of Mark Levinson, he's just one of very many, that for what ever reasons lost control of what once was thought be their companies.
I agree with Unsound. That was the basis of my response earlier. I do agree with some of what Bombaywalla wrote. However, in my opinion as an Engineer, much of what he has described has been around for quite some time.

I agree that class D amp design has come quite far, but, we weren't talking about that.

in my opinion, a major technology change will have to happen to supplant the current technology.

Maybe recording, processing and playback based on something other than electricity.

Having designed and worked on circuits, amps, pre-amps, filters, etc. for some time, I can say that good amp/circuit design is just that. There are some very good older designs out there that can definitely stand with the latest and greatest of today. They also managed to squeeze the best out of some not so great components. Sometimes one is limited by the technology of the era.

What I'm finding is that current Japanese transistor technology is also really amazing. That is a step forward.

Look at cars. How long has the internal combustion engine been around? We've greatly improved the efficiency of internal combustion engines, but they are still just that. Controlled explosions turning some machinery. We should be wayyyy past that by now. Don't get me started as to why we aren't.

But, I can tell you that the circuit/amp designers mentioned and many that weren't are absolutely amazing. I still go back and re-read some of Nelson Pass' early papers. Still relevant today. But, if this "hobby" was a popular as automobiles, we would see some major technology breakthroughs. In my opinion.

Look at what happened to phone and computer design/technology. It is changing on an exponential scale.

Who is stepping up to take over for excellent audio designers and move the industry a step or two forward?

I tell you. I count myself as fortunate that I can sit and listen (and still hear) my system/music with a good book, company, and a good glass of wine and appreciate it.

I love it.

enjoy
Benchmark AHB2. http://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier#buJbikdLh7dJAfBo.97
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Kr4, thanks for the link. I read the review. I wonder if that technology can be scaled to create an amp that can play at 500 wpc or 1,000 wpc at 8 ohms at attainable prices.
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I think we are going backwards in audio solid state wise. The death of the discrete transistor is upon us. All the fabs that used to produce great discrete transistors are now owned by third tier players. Take Motorola, for example. Or Toshiba.

The proliferation of integrated circuits and operation amplifiers has killed the discrete transistor. Everyone waxes about John Curl and Nelson Pass, but most of their designs cannot be built today. At least not on a mass scale. Talk to John Curl about one of his later designs for Parasound, the JC3 phono pre-amp. He wanted to build it with discrete JFETs like his other designs, but was forced by Parasound management to use IC opamps because Parasound believed they could not get an adequate supply at a reasonable price.

There is no question that IC opamps allow simplification of circuit topography and lower costs. But at the cost of sound quality. Like the CD, we have given up quality for convenience in the solid state design or amplifiers.
Forget Class D ban imposed here then. Class D is where the real progress is in SS amps. I've owned gear for years and miss very few SS amps. My old Tandberg receiver at home and Nakamichi in teh car maybe. I'd probably own a tube amp by now if not for having tried Class D first.
Please forgive this trespass; perhaps the future of ss will be Class D:
either by D evelopment or D efault?
What about the capacitors in amps - have they improved in the latest decade (or more) with regard to sound quality/longevity?
Capacitors and or other electronic parts alone make no sound and therefore have no inherent sound quality.

Its how you put all the parts together in the design that results in "sound quality".

Some parts are better than others though and operate within a smaller tolerance range ie more accurately to spec as a group overall.

So a good designer these days has access to better parts (perhaps for lower cost than in the past) and if he does his thing well, voila, the result can be better sound/performance.

OR many may take it upon themsolves to replace parts with better parts which if done properly should produce better results to some degree overall. If you replace a part with a better quality one but it is not the right kind to start with, well anything can happen.

Experts in all fields tend to become better over time so no doubt in my mind there is more expertise in designing good gear out there today than ever before. That's called progress and is probably the biggest difference. Today's experts have the expertise of all those in the past to draw upon. They may still innovate but there is a better body of knowledge available for them to start with so the good ones will likely produce even better products. That's progress.....
Capacitors and or other electronic parts alone make no sound and therefore have no inherent sound quality.

Its how you put all the parts together in the design that results in "sound quality".

Implementation is key, sure, but I guess the case could be made just as well that implications into sonics are inherent to the components themselves.

Experts in all fields tend to become better over time so no doubt in my mind there is more expertise in designing good gear out there today than ever before. That's called progress and is probably the biggest difference. Today's experts have the expertise of all those in the past to draw upon. They may still innovate but there is a better body of knowledge available for them to start with so the good ones will likely produce even better products. That's progress.....

Progress.. I see what you mean, but most of the progress made today and through the last decades appears to be working around how to keep costs at bay through mass production, convenience (i.e.: size, consumption, etc.) et al. and hereby lessening the impact of such factors. Oftentimes "developments" resemble a rewrite in disguise in the effort to wow and lure its costumers into ongoing purchases with the promise of better and better sonics. If one were to read all hifi magazines through the last 30-40 years and follow the development of how the reviewers reflected progressively positive on the coming iterations of, say, Mark Levinson amps, the current versions should almost sound as good as to cure severe illnesses as a side effect. It's symptomatic to much of the hifi industry at large: reveling so locally, and navel-gazingly, as to miss the bigger picture.

It's not that I don't see a progression into making amps sound better, but it seems the class-D segment is more or less the sole beneficiary without raising the bar in absolute terms, although getting closer to the best out there. That's definitely progression and exciting in many ways (also as to accommodate the environment, not least).
Interesting thread, the comments by John Curl are a disappointment for me. It reminds me of a vintage Sansui receiver from the early 70's that I acquired. I could not believe how good that old thing sounded, I preferred it over my near flagship Onkyo AVR.
"Progress.. I see what you mean, but most of the progress made today and through the last decades appears to be working around how to keep costs at bay through mass production, convenience (i.e.: size, consumption, etc.) et al. and hereby lessening the impact of such factors."

There's a difference between mass market products and high end audio components. What you are talking about here, applies mostly to lower end gear.

"If one were to read all hifi magazines through the last 30-40 years and follow the development of how the reviewers reflected progressively positive on the coming iterations of, say, Mark Levinson amps, the current versions should almost sound as good as to cure severe illnesses as a side effect. It's symptomatic to much of the hifi industry at large: reveling so locally, and navel-gazingly, as to miss the bigger picture."

Then how would you have them write the reviews? Its not like they can see the future and hold off on giving a component a rave review because future models will sound better.

McIntosh has always been a leader in solid state amplification, and they have moved recently from the double balanced to the much more expensive quad balanced designs. I see them continuing to push the engineering forward for there solid state amps of the future. So, I am not disappointed by JC’s statements, his designs have had no personal effect on me or my system. That’s my choice indeed, It is all about the company you choose to get behind. I for one don’t like mass produced junk, or expensive products that don’t hold the test of time. John Curl and Parasound...(way overpriced IMO) . Also, Class D amps are not the future for true audiophile systems, class D amps are used in specialty type situations. For instance Multi channel home theater recievers, car audio amps, sub woofers, wireless speakers. I have never heard a full range class D amp that I could listen to loud for more than a minute! The words, Harsh, uninvolving, abrasive, hammering come to mind, really.  


Regards,


Matt M 

11-06-15: Mapman
Capacitors and or other electronic parts alone make no sound and therefore have no inherent sound quality.
c'mon Mapman, I did not expect you to make such a ludicrous statement!!! You know that electronic parts have a sonic signature (look at the myriad of capacitors available) & check out this 56-page thread if you haven't already!
http://forum.audiogon.com/cgi-bin/fr.pl?cspkr&1211428524&read&keyw&zzcapacitor

And, here's a resistor thread for your reading pleasure: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1223946120&read&keyw&zzresistors
Well they definitely do not make any sound alone but some parts definitely seem to get certain sonic attributes associated with them over time so there you go.

In a decade of reviewing I have seen implementation of some good ideas; banks of smaller capacitors massed vs. a few larger ones, Power Factor Correction, and bridged integrateds like the Musical Fidelity M6500i that I reviewed for Dagogo.com (Note, such a design outputs speaker voltage and current on ALL speaker posts, so it must be handled carefully with certain types of speakers. I have not done a retrospective on these technologies, so I don't know offhand whether they have been brought back from earlier designs or newly developed. Regardless, they seem to be in vogue now.

Despite these advancements I do not think the larger, heavier and much more costly class A and A/B amps will thrive long term.
There's a difference between mass market products and high end audio components. What you are talking about here, applies mostly to lower end gear.

Then, I'd say, you've only proven my point; progress is made mostly with mass (market) products in the context of their production methods and the demand for more size-convenient and power-efficient products. I'd go further though and incorporate the high-end market into the need for convenience and profit maximization which, I'd wager, "borrows" a lot from the cheaper section of audio components, one way or the other. This is less (if at all) about raising the sonic bar in absolute terms and more about working around constraints whose impact is, again, sought lessened.

Then how would you have them write the reviews? Its not like they can see the future and hold off on giving a component a rave review because future models will sound better.

Simply put, I don't need for them to have crystal balls but to put their sonic impressions into perspective. I've heard dealers say, quite often, how a new or more expensive product would "blow away" another (cheaper) ditto, only to feel myself they've exaggerated wildly. It's not only about exaggerating though, but perhaps mostly about feeling they're being mislead by factors that would influence what is sonically perceived. Essentially the same goes with many reviewers.
There is only so much human ears can hear. We are limited in frequency response and SPLs. I suppose progress can be made with lower noise and distortion levels that truly approach 0 more, but what will be the audible difference?

So amps can continue to improve but for what reason other than offering better sound for lower cost and maybe smaller size? One might argue good quality amps already produce all that most can hear as accurately as needed. Not to say that there are not many differences case by case within those limits, but those could attributed to objective design decisions in order to provide a different or particualr kind of sound but not one that can be clearly measured as "better".

So maybe we've hit the proverbial wall for now not in terms of what's possible, but what's audible. Especially when it comes to resolution of modern digital audio formats used but that is not an amp issue.

Most new technology tends to get it mostly right after a period of time. Amplifiers have been around for quite a while now. Most of the bigger practical problems have likely been solved fairly well. Time to tackle other fish maybe?

Could be the end of progress in high end audio amplifier technology as we know it for the foreseeable future. Except for things that can continue to offer better results in a clearly smaller and more afforadable package (like CLass D) Of course no one vendor will ever say their product cannot be improved upon in some way. Not many sales in that! Small distinguished niche vendors might broaden their niche perhaps. Improve the digital source formats as well while at it! Storage space and network bandwidth is getting cheaper.

Just saying...
Good thing I got my waist high waders on.