You're welcome.

Irony is a must, in all things that are observed in moderation.

Take..er.. your 'give and take', in it's norms. It's ambiguity, and shortness, for some, is designed from the ground up, to speak in ways of inflicted harm, via the least words possible. Trolling without seemingly being trolling. I see you.

Case in point. 

Negative feedback does not work, in the final aspect of looking for perfection in it, in looking for perfection that is reasonably attainable (compared to other possible solutions).

Positive feedback might, if it is programmed correctly. A mighty big if, if there ever was one.

Problem is, that in an entire playback chain, that positive feedback aspect has to be carefully programmed. But some impossibilities remain, or at least seem impossible. Chaos/’infinite variation’ aspects, at least with our normal level of ability to unwind their complexities.

Negative feedback, one might say, is the simplified method of getting past those potentials in error within executing positive feedback. One that fails to take on the fundamental. Rather that it is ’clever’ and sidesteps it all, instead.

I did do a design where I combined negative feedback with a specifically shaped interference in the given amplified signal. It tends to sound like the best of both worlds. People remarked that they’d never heard anything like it before.

An example of this sort of area of thinking is found in Jim Strickland’s Accoustat TN amplifier circuit. It looks kinda dumb at first glance. The trick is that it is dynamically active.  It is transient wave shaping, in it's feedback effects, in the realm of time and level.

I would advise against trying to simplify technical issues like negative feedback.  It won’t work.   The devil is always in the details and how well the experts do things.  That’s why we pay them to design and build things for us. 

New technology sets the bar for what is possible at the various price points. That of course does not mean all new technology is better. Avoid generalizations always.

The issue with negative feedback is tied to the maligning of the micro aspects (in time and level) of transient leading edges.

Since our hearing is based upon this area of a signal, this means that, to overstate it a hair..that..100% of our hearing is in the 1-0.5% (and less) of the signal that negative feedback makes a total mess out of.

Linear measurement wise, this small error is meaningless, as mathematical ratios may go, in mathematical weighting and evaluation.

Which has pretty well SQUAT to do with how humans hear. (the given unweighted and disconnected mathematics)

Negative feedback is, generally, a solution to a problem that humans don’t really understand. at least in the idea of book learned electrical and electronic engineers of audio gear. We have to connect the problem and the solution together and that requires an intimate understanding of the problem. the problem, or question, is the REAL specifics the REAL internal meat and neural and cranial aspects of how humans hear, in the minute and total sum details.

Until then, these methods of making audio, like class D or negative feedback will continue to be the ill ought out abominations that they are. Like idiots on gobos and crutches, trying to run a world class 100 meter dash. Bad attempt, bad understanding, wrongheaded result of dubious value.. looks good on paper, though. works like a bear dancing.

bears don’t dance, they hit the sweet spot in our minds that sees the motions as being akin to dancing so we mentally place a dancing mental envelope of interpretation over the lurching about.

With bad audio we are dealing with the aural equivalent of Pareidolia getting in the way, where we create the shape of the signal in our minds, when it’s actual clarity is not truly there in the most perfect shape it could be. We are wired to fill in, via precognition of all our history in aural ingestion and interpretation.

THAT..is /class D and high negative feedback, in a nutshell.

Some of us can hear past it and recognize these inbuilt filters and correct for them. we can see waldo, aurally.

Some cannot or they feel they see waldo well enough that he’s actually there.

good audio reproduction allows a person to put the mental aural mind scrunching and efforts away, and just listen in a totally relaxed manner to the beauty of it all.

THIS is what Ralph is talking about when he talks about what the atmosphere amps are better at (and others are also better at)

Its the difference between an aware and thinking audiophile getting off on music. Or,on the other side, the linear mind side...getting off and solving a ’puzzle’ of signal recognition and interpretation, which is work. fun for some, but it’s work, hard work. hard, edgy screechy work, work upon a signal that is purposely damaged to make some aspects more aurally obvious, or separated from the whole.. And i hate that sound, like all sane thinking people should. It is horrible and anti-music.

Since we are all individuals with different learning curves, different libraries of internal data, and individual different & differentiated meat packages we are wrapped in...this is not a place where we can lay down a black and white law that covers all potentials.

Generally...the less a person understands all of this, the more the monkey inside senses danger (unknowns!), and henceforth desires a perfect black and white answer to these complexities. So, to self protect, it sits, claws out, in fighting positon..and lays a yes/no black/white beating down on the complexities it does not cognate or understand ...and lays down beatings on audio and music fans, fans that that tell them they’ve got it completely backward.

so, to overstate it slightly to edge enhance the visual on this so the general shape of it can be seen more clearly:

This is what partially encompasses my dislike, my honest and well thought out dislike of the premise and actions of the overall shaped thing called ASR. It’s deep premise is as dumb as a bag of hammers, it is missing the real argument and question, entirely. It is insistent on hanging witches, witches of it’s own creation, witches that don’t exist. It fails to understand the entirety of it’s own core question and answer set.

It also explains the haters and the detractors here on this forum.

No written word set is perfect nor entirely accurate, so don’t take it personally or seek to chase down some minor error in form or whatnot, in with I write here. That would only amply show everyone who is reading and can grok it all...one’s lack of understanding of the issue or the nature of functional discourse.

I will point you to this, the Amp I have is zero feedback design.

RENAISSANCE SEVENTY/SEVENTY Mk. III Dual Mono Zero Feedback All Triode Power Amplifier

FWIW. Attached is the PDF manual.

@retiredfarmer Yes, the Mk III updates were in essence the last version of this amp and preamp, so it is improved upon in their design, their finest version of them if you will.

Let’s simplify negative feedback = taking something ( the AC audio signal aka music ) that has ALREADY happened, flip it around out of phase ( that’s the negative part ) and feed it back into the input where something new and unequal is happening ( unless you think sine ways are music )… then apply some critical thinking….

so you are ditching everything you have espoused (if not self-promoted) on this forum for twenty years in order to go all-in to self-promote your new Class D amps.

Wow. Did you see me promoting our class D amps here? I simply stated the underlying engineering issue that any designer faces if they wish to advance the art.

I'm not stating anything in conflict with anything I've stated before. You'll notice that our OTLs are zero feedback- that was done because applying enough feedback to avoid brightness and harshness was never possible. Personally, I find harshness and brightness to be the biggest sin audio can commit. So they are zero feedback, class A(2), a single stage of gain, all triode, fully differential and balanced from input to output, and output transformerless. This was done to eliminate as many distortion sources as possible. It worked- the OTLs have dramatically lower distortion than any SET, are obviously more transparent on that account and have garnered a lot of nice reviews and awards in the high end press. So we know they work, as if our ears weren't telling us that:

Precisely my point , use your ears and decide. If you genuinely believe that the new betters the older alternatives then case closed as far as you’re concerned, I get it.

 New is not necessarily better. Remember that it is promoted that way by the audio media to help perpetuate the hobby. That's a fact all hobbies go through fads and it gets promoted that you need this not what we told you ten years ago. Get rid of your old stuff buy new! I love currently the idea of stereo pieces that have upper end sparkle. I have listened to some of the pieces that are written about in that way and thirty years ago things like that were called bright! And we're to be avoided. Now it seems like bright is being promoted is that because the average audiofile has gotten older as the hobby doesn't seems to attract the you g anymore and us old audiofiles are losing our high frequency hearing? That's something to ponder. You see the exact same thing going on in hunting magazines the rifle calibres they promote now compared to the past. All hobbies have this promotion directly for sales. 

The other thing I would ask the original posted are you sure when you send your amp back to be modified it will be better? You might get a surprise and that you don't like the changes. Be careful. 

Regards

@jjss49 

+10 for your well stated comments. 3 weeks ago I attended a classical music performance featuring a cello and piano duet. This past weekend my daughter and I went to a local jazz venue . Both experiences were quite different obviously but what they shared in common was the high degree of emotional involvement and listening joy. Both outings were simply wonderful. 

I believe most of us who love music strive to obtain some reasonable degree of this engagement and the stirring of emotions through our home audio systems (At least that's my objective). Newer audio technology  may certainly have the potential to achieve this goal. Time and listening will tell. 

I just do not buy the idea that by virtue of being the next new thing it  by default is superior to what already exists and is performance proven. I've heard the VAC Renaissance amplifiers and know it is quite capable of providing a highly emotionally engaging music listening experience. High NFB solid state may or may not. Actually listening is the true arbiter for better or worse. 

Charles 

technological advancement is not always for the better in a subjectively driven, aesthetic pursuit where criteria people care about are highly complex and multi-variate

well worn example of sports/performance cars... new cars are better technologically in so many ways, but are boring to drive, lacks soul, involvement -- computerized/robotic perfect in some ways, as appliances and easy speed machines, but for those seeking thrills, man machine involvement, emotional engagement, development and sharpening of skills, they are sorely lacking

similarly, machines we buy to make music for ourselves to enjoy should, at their best, stir the senses, invigorate the soul, transport our spirits, connect us with beloved artists at the height of their artistry... technology in such devices makes for more choices, an expanse of possible presentations -- but different may/may not be better... we all strive to experience, and decide for ourselves....

The vintage amplifiers still sound good but parts quality has definitely improved over the years with Capacitors and other low noise parts. IMHO, it's possible to build a superior amplifier now but it will be at a cost!

My ears tell me things are possible today that were not in years past with amplifier technology. There are some very good older amps but I would have no interest in moving backwards

Precisely my point , use your ears and decide. If you genuinely believe that the new betters the older alternatives then case closed as far as you’re concerned, I get it.

For other fellow music lovers who also listen and compare, their outcome and conclusions may tell them otherwise. The epitome of individuality. No consensus correct or incorrect but rather what sounds best in each unique listener’s case.

Charles

I am running a 20 year old BAT VK-60SE that destroys everything I compare it to (that I can afford).  Of course that is kind of the point of this hobby…finding those relatively affordable gems, new or used, that just break the mold for years to come and stand the test of time of musical enjoyment, if not also technical accuracy.  

I recently listened to some vintage Fisher gear, having had a Fisher 400 as a kid but not realizing what I had.  My part-time paycheck replaced it with an Onkyo separates and CD player.  I thought it was broken when I hooked it up…but I digress.

Listening to that amp 35 years later I remembered the lack of extension and warmth, but was floored by the textures, image and musicality, remembering that moment when I realized SS then, as now, just cannot compete with tubes, for me at least.

However, my 20 year old BAT has none of those shortcomings and the qualities in spades.  I only have, for heat issues, a less vintage Ayre SS amp that while very good in its own right and a fantastic, reliable, great sounding amp, is a disappointment every time I turn it on.

I have two pieces of gear that I will never sell: the BAT and my LS-50s.  Not because they are faultless, but because they so fundamentally make the music sing that ‘better’ ceases to be relevant.  Now or in 20 years.

Enjoy your VAC.

Lancelock mentioned the Altec Lansing 1570B (170 Watt mono). I have a pair of the Altec 1568A (40 Watt mono), also about sixty years old and they sound beautiful.
These Altec theater amps had some of the finest transformers ever put in audio amplifiers but the power supplies were primitive. Tightening up the PS with new, larger electrolytics and poly bypass caps, maybe adding a choke, turned these into some of the finest sounding amplifiers, tube or SS, money can buy -

But not quite up to the level of a (modded) Harman Kardon Citation II (Stereo 60/60), again with superb transformers, probably THE best ever, which I am currently using and which replaced the Altecs.

There’s probably something to be said for vintage Audio Research and Marantz 9’s but those get crazy expensive and I haven’t had them in my system.

I have copious notes on the mods for both the Altec and HK which I’d be pleased to share if you’re interested.

Marc Stager
New York City
https://stagersound.com/silver

Technology only moves on one direction.   My ears tell me things are possible today that were not in years past with amplifier technology.  There are some very good older amps but I would have no interest in moving backwards. 

@fsonicsmith

Let history be the judge! Over 60 years time has proven that the basics continue to be valid and that the newest ground breaking production is two steps forward and three steps back. So go ahead and make a fool of yourself. I will sit back and eat popcorn. With extra butter.

I understand new technology is introduced and time marches on, No problem with accepting that. My point is simply everything new is not necessarily better. Can it be?Sure, but it is not a given.

The wonderful thing about audio endeavors is you have the ability to listen to music being reproduced and deciding which truly is better sounding and convincing to you the individual.

I hope that the OP is able at some point to compare his beautiful and timeless (In my humble opinion) VAC Renaissance 70/70 to a modern high NFB circuit design solid state amplifier and draw his own conclusion. Just listen to the music, which amplifier  is the more compelling and promotes more listener engagement and emotion/passion? That’s the better amplifier.

Charles

OK Ralph, so you are ditching everything you have espoused (if not self-promoted) on this forum for twenty years in order to go all-in to self-promote your new Class D amps. Fine. Let history be the judge! Over 60 years time has proven that the basics continue to be valid and that the newest ground breaking production is two steps forward and three steps back. So go ahead and make a fool of yourself. I will sit back and eat popcorn. With extra butter. 

I would sincerely suggest to the OP to listen to an example of a modern high negative feedback solid state amplifier as described above and compare its sound quality to the Renaissance 70/70 and be your own judge. I’m not convinced that the "modern " high feedback would be  superior sounding.

Emphasis added

I completely agree with this advice, although not his conclusion :)

IME the distortion spectra (the distortion signature) has to be right; too many designers ignore this simple fact.

Most speakers today are designed assuming that the amplifier is able to behave as a voltage source (meaning it can make the same voltage output regardless of load). Some speakers in high end audio are not designed for this behavior- and for those few, sometimes an amp with a high output impedance will sound better.

some modern super low distortion amps can produce a somewhat harmonically lean, clean-white, antiseptic kind of sound that may be not be favored by listeners used to a more saturated, rich, bloomy type of sound that some tube amps deliver...

Once any frequency response issues are sorted, the differences we hear between amps is the distortion signature. You can think of any amp as having a perfect amplifying aspect and also a distortion aspect thru which the signal travels. That distortion aspect is the 'sonic signature' of the amplifier. SETs have a pronounced 2nd and 3rd harmonic, which masks the higher orders (SETs actually have more higher ordered harmonics than any other kind of amp, but when masked you don't hear them), giving them a lush, smooth sound. Some amps which do not have such pronounced 2nd and 3rd have unmasked higher orders, which contribute to the description in the quote above.

That's not just a subjective thing; these aspects are easily measured; and if the proper distortion spectra results in the amplifier design, no matter if solid state or tube, the amp will be easy to listen to, involving and relaxed. So an SET might have the right distortion signature, but imagine two or three orders of magnitude less. you'd hear more detail with no downside (no brightness or harshness).

I know how hard it can be to understand that this is so- for the last 70 years we've simply had to listen to know if an amplifier was going to be musical and satisfying in our systems. That's a lot to overcome! But also for most of that time, building an amp with enough GBP wasn't possible, and the industry really didn't want the market to know that. Heck, that wasn't too hard to sweep under the carpet because of how hard it is to explain what gain bandwidth product even is!

People can argue about design in amp, and i am with atmasphere about the evident technical progress that have been made here like in any other field...

But dont forgot that the sound impression is not only created by the design of an amplifier but also with the speakers relation to a room...

And our preference each of us differ much because our listening history differ also...And our acoustic condition differ too...

There is no ABSOLUTE here...

The only rule is the ratio S.Q. /price for most of us....And the way we can optimize some system to reach the minimal satisfaction threshold...

Here acoustic control help a lot....More than upgrades half of the time...

I will live happy with my 1978 Sansui and will nor buy the superior Berning or any other very superior new design...

😁😊

«Why do you keep this old gramphone Groucho? Acoustic is timeless brother»-Groucho Marx audiophile 🤓

«Music too brother»-Harpo Marx

agree with @charles1dad

modern amps have technological advancements which allow them to reproduce sound and interact with speakers differently (and perhaps measureably better) than older amps, and especially tube amps where impedance match with driven loads can be highly variable... all this said, what combinations of amp and speaker, modern or aged, and what sound quality and character would be produced for the owner trying to enjoy music is still subjectively determined...

some modern super low distortion amps can produce a somewhat harmonically lean, clean-white, antiseptic kind of sound that may be not be favored by listeners used to a more saturated, rich, bloomy type of sound that some tube amps deliver... all subjective in this hobby, which is what makes it all the more fun...

So based on Atmasphere's response with "SS low feedback" designs being superior, does the Peachtree Audio Gan400 qualify as an amplifier that fulfills this description?

Aberyclark: is spot on. IMPE I have stayed with "Vintage" High End equipment. Re cap and re tube. In some cases will provide todays equipment with a respectable comparison .

I would sincerely suggest to the OP to listen to an example of a modern high negative feedback solid state amplifier as described above and compare its sound quality to the Renaissance 70/70 and be your own judge. I’m not convinced that the "modern " high feedback would be  superior sounding. Hard to know which you will find musically preferable without an actual listening experience.

Charles

I agree too because he know what he is talking about ...

We cannot reduce technology progress to embellishment only for sure...

IMO, I totally agree with atmosphere...well written and it just magnifies how stupid that statement "amp is an amp" is...

There is always progress.

But to answer your question:

Can a Amp be "timeless" and compete with todays amps?

The correct answer is ’no’. The single thing that has held back amplifier improvement is something called Gain Bandwidth Product (GBP). Over the years you may have noticed that feedback in amplifiers has gotten a bad rap. This is because limitations in GBP have prevented enough feedback from actually being applied. The result has been that the application of feedback has resulted in added distortion on account of the feedback itself, and increasing distortion with frequency above a certain point.

This has caused feedback to be conflated (and rightfully so) with harshness and brightness.

What happens if there is insufficient GBP is that the feedback starts to fall off at higher frequencies and so with less feedback comes greater distortion. If you graph distortion vs frequency you can see this in almost any amplifier made in the last 60 years employing feedback. Since the ear converts distortion into tonality and since the ear is keenly sensitive to the higher ordered harmonics generated by feedback itself, the result is harshness and brightness over the last 60 years.

That is why there are many zero feedback amplifier designs. Zero feedback is about the only traditional way of getting around this problem.

If you can manage about 35 dB of feedback in the amplifier design and there is sufficient GBP, the result is that the feedback can ’clean up’ its own mess, resulting in less higher ordered harmonics. Since the feedback is consistent at all frequencies, the distortion and the distortion signature (the spectra of harmonics) does not change as frequency is increased.

Its a simple fact that no tube amp is capable of this! You need a lot of gain and a lot of bandwidth; the former is simply not available in tube designs without associated phase shift, which would cause the amp to oscillate at some higher frequency.

There are now designs that satisfy these goals, designs that were not possible 20 or 30 years ago because the amplifying devices didn’t exist.

What this means is its possible to build a solid state amp that is every bit as smooth in the mids and highs as the best tube amps and leave nothing on the table in terms of detail, sound stage and the like, in such a way that vintage amps simply cannot compete (not that they sound bad, just they don’t sound as good). This is one of those things that is easy to hear and easy to measure.

My Sansui Au 7700 so good it was and so good it is right now will not compete in sound quality ( his versatility is unmatched though) with the Berning ZOTL technology which is  a bargain it seems in Audio offerings...

My exemple is valuable for other brand name for sure...

But my Sansui is enough for me twenty times less costly .... 😁😊

It was a legendary product and it is enough to reach heaven  especially in a controlled  acoustic ...

Hornets 🐝 nest

There are some notable newer designs:

Lavardin - low memory 

Halcro - low distortion

the thing is that class a amps haven’t changed in essence

many classics they just got right. Some old components were just better:

old valves

old jfets 

some say tinned copper wire

But there is a lot of rehash of various topologies

@elliottbnewcombjr  I still have the Golden Dragon 6sn7's and I have  back up complete set of tubes for the amp (8-300 Bs and 4 6SN7 Golden Dragons), they came with it when I bought it, but I bought all new tubes for it when I got it to start out with "freshies". It was used but gently with little time on it as I remember. I am looking into some Tung Sol USA black base but trying to predict a sound signature of a tub cab be tedious. 

fthompson251

you are a man with a plan, impressive.

It's very nice to get a vintage piece back that has been properly checked over by competent people you trust. I visit a friend who lives a few miles from Audio Classics, I feel they are in my back pocket!

I see your amp has 6SN7. My Cayin has 6SN7's and 6SL7's. I mixed em up by mistake, blew one. Researched, picked a matched pair from Brent Jesse, I was very surprised at how much difference in sound they made, in my case not good. I was able to send em back, try another pick, they sound equally wonderful as the ones Cayin used whatever they are. Just saying, I would ask VAC some advice about recommended 6SN7's for yours while they have it. 

"My experience over the last forty years of owning top level amps… although in the past mostly solid state (but my preamps and phono stages have been tubed) is that, ten years is a significant improvement in performance… and twenty is in a completely different league.". --. ghdprentice.

I would be the other dissenter then because my experience is the same as yours. Even really great equipment 10 or 20 years out has been surpassed, even in the amp category. I also tried to upgrade a top of the line tube amp and preamp 20 years old, 15 years old by having them be rebuilt and upgraded with the latest and the greatest parts. Unfortunately I ended up selling them and buying newer high-end amps and preamps. 

Now the upgraded equipment was much better than the original and there were obvious sonic improvements but just not as good as the latest and greatest equipment. 

Even the very idea people on this form are saying you should upgrade and tweak the equipment you've got to modern day standards should tell you that modern day equipment will be better. Of course modern day equipment at the equivalent purchase price of the old equipment.

Genesis was purchased years ago and Gary (forget his last name) still runs he company.  All components can be repaired or upgraded to complete with todays products as long as the parts are available and the part numbers are                     there.  Been doing repairs and upgrades for years.

I would send them in ... let us know!

David Hafler was designing Amplifiers in the 50’s under Acrosound and then Dynaco The Hafler DH-200 was introduced using mosfet outputs, a feature that was way ahead of the rest of the pack. In the late 80’s Hafler hooked up with the Rockford Corporation where they took on the challenge of creating high end amplifiers. The 9505 by all accounts was one of the most musical power amps ever made.

Many timeless designs that still can compete with amy new models or brands.

I believe So,

Ralph Karsten of Atma-Sphere commissioned an OTL Amplifier with no Compromise on parts, Design or Circuitry. It was built using all his 45++ Years of knowledge, Amps like these will become timeless collectors' art. I just put it up for sale for the reason of downgrading our building and rooms but it's been hurting me last few weeks to see it go.

@pdreher 

out of curiosity, what was the failure/issue that required you sending it out?

Who ever claims Amp is an Amp lacks experience.

I think he might lack more than that.

Our late great member Almarg owned the VAC 70/70 for many years. With all of his knowledge, that says something for it. I loved the looks and the fact that it used 300b's. I never had the pleasure of hearing one.

@styleman

 An amp is an amp?  Julian Hirsch has been resurrected on this Easter Sunday.

I could not agree more.👍

Charles 

Who ever claims Amp is an Amp lacks experience.

@aberyclark

I would send in your components and let VAC give them a go-over. IMO, you have endgame equipment

I agree with this assessment.  The VAC Renaissance  70/70 is a superb tube power amplifier built to a very high standard. You can undoubtedly find different sounding current production amplifiers, better sounding? You’d be hard pressed to find find that IMO. Despite much hype and marketing efforts "very little" has changed with high quality tube amplifiers that were well built and have excellent implementation.

@fthompson251 , your amplifier is an example of a timeless audio component if pure quality of sound is the over riding priority. Much can be rendered with the KT 150 tube but 8 300bs in well executed push pull is just different. 

Charles

An amp is an amp?  Julian Hirsch has been resurrected on this Easter Sunday!

Like Tim de Paravicini said :(30 y. ago. )It Will take more than 50 y. when  one even comes close to the sound that was then designed with tube amps. Class D will never reach that level. And he is right ! Look at the EAR 509 : more tha 30 years still the same… what a sound ! I have the VAC phi 300.1 : never heard a sound so beautiful like that. The emotion, “feeling” the music, placements…a lot of new amps.are very to the point , but cool, well detailed ,but without soul or emotion……

I always thought that the VAC Renaissance 70/70 was just a bad ass looking amp!

@gregp858   +1!   For real!  I used to experience sexual feelings when I saw it advertised in Stereophile!

I always thought that the VAC Renaissance 70/70 was just a bad ass looking amp! VAC is outstanding equipment! Personally I would go for the upgrades and enjoy absolutely timeless equipment! Always lusted over that line! Also talked with the president at the Florida audio expo. He still has one in his closet! Very cool gear indeed! Enjoy!😎🎶

If you enjoy it, then yes it can!

Amp is an amp?....ridiculous