300b lovers

The Raven was the surprise for me. You see, I’ve been listening to the Karna amps for 20 years, now reborn as the Blackbird. Yes, there are differences, but what’s at the show is very very close to what I know so well at home ... maybe a teensy bit better, with a couple more improvements Don and I are hiding up our sleeve. But the show amps are 95% to 98% of what the shipping amps will be (yes, the production Blackbirds will be even better, Don and I promise that).

But I’ve never heard a Raven before. Hoo boy, is it good. Wow. I didn’t expect that. I knew what it does, of course, because I designed it more than twenty years ago, and Don refined it and took it a few steps further. But I never actually heard it, just other people’s impressions of it. I was quite surprised when I hear it for myself, in what is a very good room.

I’m not all that good at writing puff pieces, but the initial impression is speed and power, followed by vividness, and depth of tone, an impression that grows over the course of a few minutes, and after listening to a few different selections. We keep telling visitors, no, there is no 200-watt subwoofer (or two) tucked away in a corner, and yes, the new Spatial speakers are entirely powered by ONE Blackbird per channel, with passive crossovers (sample on display at the entrance to the room), and no electronic EQ, no active crossovers, no multi-amping, and no DSP. What you see is what you get.

As for source, Don and I are joking around about our favorite DACs. He’s all-in on the LampizatOr family, while I was dazzled by the Bruno Putzey-designed Mola Mola in a nearby room. I was expecting to be bowled over by the Holo May, but nah, it’s not for me. But there’s no way I’m going to cough up the $13,500 the Mola Mola costs, especially considering how fast DACs become obsolete ... five years or less.

Tube amps, by contrast ... the tech never becomes obsolete. For that matter, all of the tubes used in the Blackbird, and the basic circuit, were first designed in the 1930’s! Talk about not going obsolete.

The older preamp is a nice, but conventional single ended tube SRPP circuit with Akido buffer (extra tube per channel).  It uses dual regulated power supplies and dual regulated filament supplies and really good signal path parts, and the wonderful Khozmo attenuator.  The Raven is a completely different approach and  circuit.  It is fully balanced and transformer coupled at both input and output with custom wound transformers from Dave Geren at Cinemag.  It will take either xlr input or rca input, and will happily provide xlr or rca, or even headphone output, and will drive even a 10K power amp impedance.   The Khozmo setup is dual mono because you have to control both halves of the xlr on each channel.  The power supply uses two damper diodes, very high quality transformer and is a true C_- L - C (cap, choke, then cap) that feeds a much higher quality regulator that is used in the previous preamp and also feeds a pair of gas regulator tubes after that.  It is dead quiet, fully balanced, and has very little sonic signature, but provides great drive for the power amp.  I really like it, and those who have been to the show have heard it driving the 300b mono amps.

Don -- can you provide a detailed explanation (without giving away the secret sauce, of course) of the technical and sonic differences between your DS2 preamp and the Raven? Thanks.  

Thanks for the positive feedback from all so far.  The room was a bit of a struggle to get things to sound good, but after a whole afternoon and evening of getting furniture moved out and putting acoustic treatment up we pretty much tamed it.  We have very good image depth, and of course the ceilings and walls limit height and width, but it is a nice sound.   Like every other team here, we work with what we have!  Hope see a few more of you today!

I attended the show yesterday (Friday) and spent significant time in the Spatial room listening and chatting with Don.  I have been a repetitive customer of Don's over the years and was excited to hear the latest.  Wow both the amps and pre did not disappoint!  I'm calling Spatial on Monday to get on the list.  .

My 4+ hour drive to the hotel ended up being a grueling six-hour battle, but I did finally arrive unscathed. After checking in and transferring our luggage to our room, I kissed my wife farewell and went straight to the Spatial/Don Sachs room.

The amps and preamp are beautiful - and have that distinctive D Sachs look IMHO. [I listened to just four songs before getting into a conversation with Don, markusthenaimnut , and his good friend Bob.] How do I describe the music? The first song was a Jennifer Warnes song <not a top 40 song>, and I didn’t analyze it...I mean I so enjoyed the music and her voice without once thinking about the highs, lows, mids, etc. I just sat and enjoyed the moment. How often can you sit down in front of unfamiliar gear; listen to a song, and just enjoy it without analyzing it? And, yes, the songs that followed were excellent.

Once I’ve had a good night’s sleep, and <hopefully> forget about the 6-vehicle smash up on I-5 near Nisqually, I’ll return to this room first thing tomorrow morning and pester Don or whomever is in charge of the music to play my favorite songs, and listen for an hour or more.

@jaytor 

Thanks for your listening impression feedback. Very encouraging to say the least. I hope that others chime in.

Charles

I visited the Spatial Audio/Don Sachs room this morning and again this afternoon.  This was the first room I visited today and I don't think I heard any rooms I liked better today, including some with systems that cost MANY times more. The friends I am with felt the same way, and we often don't agree on what sounds the best. 

Congrats Lynn and Don for building a killer amp and preamp. Very impressive. 

@larryi 

The 300b is not the only contender in the low-power weight class.

True and I don’t believe that anyone on this thread is disputing this. However, Don and Lynn have stated the very compelling reasons why their amplifier was built utilizing the 300b tube. Excellent decision and execution it certainly seems. I’m excited to hear from those who’ll listen to it at the audio show very soon.

Charles

I too am a fan of the 45 tube type.  I also like the 2a3.  But, it is not only triode tubes that I like.  I am a big fan of the 349 pentode; I wish this were not so rare a tube.  Other pentodes I like include the 350B, and thankfully not as rare 6L6.  The 300b is not the only contender in the low-power weight class.

Yes, folks that try the 46 (a direct-heated pentode that is often connected in triode) really seem to like it. By general consent, it sounds very much like a 45.

How different does a triode-connected 6V6 sound from a 45? Good question. The 6V6 was designed as a replacement for the 45 back in the mid-Thirties, and has very similar operating points (by design).

Current production Chinese 45 tubes are about $350 per pair plus shipping.  I may try a quad in my Lampi Pacific DAC.  I quite like the 46 tube there with adapters.   The current production European 45 tubes are twice that price.  That said, if run at sane operating points they may well last 30,000+ hours.  So if you like them, they are really not that expensive in the long-term.

45’s are wonderful tubes. By measurement with a spectrum analyzer, possibly the best tube of all time, with a beautifully clean harmonic structure. Which is why the Mark I Karna’s used them as drivers.

But ... NOS examples are now very rare, so it’s down to a few vendors as a specialty item. I am hoping they become more broadly accepted, though. They really are something special, and are much easier to drive than a 300B or 2A3.

@lewinskih01 

BTW, I'm running 45-type SET on my tweeters above 1 2kHz and absolutely love them. I realize 300b gets more love, though :-) 

Lovely thread. I wish it weren't the exception arou d here!

I believe that both the 45 and 2A3 tubes get much respect and admiration. For a lot of folks the higher power output of the 300b provides more flexibility in choosing matching speakers. I do quite well with the 8 watt 300b Whereas 1 to 3 watt may be a bit shy for my particular speakers.

I certainly don’t think any less of the 45 or the 2A3 tubes. However, they do narrow speaker choices. The 300b push pull amplifier under discussion here has the “potential “ to be an outstanding success given its design and higher power output.

Charles

Undoubtedy individual preference is paramount regarding "best" listening volume. I wonder how certain speaker designs might affect that as well. I'm into DIY speakers and I'm missing the palpable feeling with my 18" open baffle midbasses than I had with smaller sealed midbasses, until I turn up the volume. Midbass definition is better with my OB, but missing some slam/palpability. I run sealed subs below, so slam down low is there. I noticed @whitestix  uses Spatial Audio open baffles so wondering if there might be a correlation there. 

BTW, I'm running 45-type SET on my tweeters above 1 2kHz and absolutely love them. I realize 300b gets more love, though :-) 

Lovely thread. I wish it weren't the exception arou d here!

@ charles1dad 

So true and think my listening levels are contributed to my near field listening; 8 feet from my loudspeakers.

Wig😁

@wig 

I currently do my listening after 8 PM for a few hours and typically my listening sessions never exceed 75 db and I don't feel like I'm missing anything; excellent imaging, sound staging, low level detail, clarity and tight tuneful bass based upon the type of music I typically listen to

Yep! As we all can acknowledge this is purely an individual choice. My listening levels align with you, Don and Thom. @whitestix prefers a higher volume and I understand. Whatever results in more listening enjoyment, go for it.

Charles

Understood.  The Kootenai is a fantastic amp, as I know having one.  Let your pocketbook be your guide, but to be honest, Don and Lynn's 300b monos are in a whole different realm of musical excellence.  Maybe you can come hear them at the Seattle Audio show?  

@ whitesix

I know it would be for sure but it'll have to be a dream for now but one day...My Kootenay is maxed out and had hoped for some upgrades but not much to do other than another brand of boutique capacitors.

Wig👍

Wig,

Dandy system you have, for sure.  You have nominal 4 ohm speakers and if the Kootenai drives them to your satisfaction, then the 300b Statement monos will drive them as well, with an astonishing clarity that will be simply stunning.  Cheers.  

Counting down the days on Don and Lynn 300b debut 😁

I currently do my listening after 8 PM for a few hours and typically my listening sessions never exceed 75 db and I don't feel like I'm missing anything; excellent imaging, sound staging, low level detail, clarity and tight tuneful bass based upon the type of music I typically listen to.

Wig😎

Don Sachs Kootenay KT88 Tube Amp

Radu Tarta 4P1L Transformer Coupled DHT Tube Pre-Amp

Merason Dac 1

ProJect  CD Box RS2 Transport

Liberty Audio X-VOX (PBN) Loudspeakers

Don and Thom,

Gents, with all due respect, an 81-83 db SPL from my speakers conveys none of the emotional aspect of my music so I prefer it more around 88-90 db, thereabouts.  I want a visceral impact to the sound of my system and 83 db does not provide that.   By this, I mean when I am I doing critical listening.  

I participated in a San Francisco Audio Society listening comparison of the totl Coincidence speakers to Andrew Jones' $200  speakers, maybe Panasonic, I forget now.  We initially did an A/B session between the two pairs of speakers at a modest listening level, maybe 75-80 db, and the gathered listeners were totally flummoxed as to which two pairs of speakers were playing.  I personally could not figure out which pair was playing, try as I might.  Well, as you can anticipate, once the volume was turned up, it was 100% clear which pair was which, plain as day.

My best wishes for those that feel they are getting the full measure of their sound of their speakers at 81-83 db, but in my mind, that volume level in no possible way can portray the palpable sense of music reproduction on either my Spatial Audio speakers or my new Cube Audio Jazzon speakers.  Long term listening at 90db is an issue and am aware of that, and I don't listen to music continuously at 90 db, but I do fairly often for short periods of time, and it energizes me. 

If I were to be satisfied listing to music at 81-83 db, there are lots of inexpensive speakers available that sound just fine.  But with more volume, the better speakers begin to shine, which is why we pay the large sums of money for them.  

I know that when I have my system "cranked" and I measure the level it is about 81-83 dB.  I rarely listen at that level.  As was stated above, the hallmark of a good system is that it has enough resolution and balance that it can be enjoyed at low to moderate volumes.  There is a minimum level for the bass to pressurize or load the room, but that isn't all that loud in any house I have lived in.  I generally listen at the level where that has happened and not much higher.

@thom_at_galibier_design

I completely understand the example of your wife’s vocal power/control. At one time I played and studied the trumpet. As with any instrument you have much control over the volume you wish to provide. If I wanted to I could blow people out of a decent size room with just that single trumpet. The thing is that horn sounded just beautiful played at moderate and lower levels.

As you mentioned, audio system resolution seems to be the key factor. As this aspect of my system improved over the years I discovered I could immensely enjoy music at lower SPL levels. I’d say a very good parameter for a system is how satisfying is it to listen to at low and moderate volume?

No question however, to each their own choices. I know that some like to listen regularly at SPL of 90db and above. Their ears and enjoyment be served. It just isn’t for me.

Charles

Hi @charles1dad

Lynn,

Oh yea of little faith...  Very few speakers play nearly as well as the Spatials in less-than-perfect rooms and your front end will be tremendous so great sound is a foregone conclusion.  Your room is gonna sound sensational and I am going to be there to hear it.  Lucky me.  

Hi @carlsbad2, thanks so much for coming to see us at the show! The amp was only pegged like that so that we could then easily control the volume from software - but you were hearing it at a fraction of full output, less than half. It just helps so much with running the room smoothly. Cheers, come see us in Seattle in a week or so! We’ll be paired with a Whammerdyne statement 2A3 amp, it should be pretty special...

Best,

Ken

Yeah, no way of knowing what Seattle will sound like. Might be stunning, might be not-great, no way of telling in advance. Shows are unpredictable.

I like to listen at the volume a live performance would be at.  Obviously, Pink Floyd concerts would be loud, but a jazz combo should sound like you are in the club at normal levels, not screaming at you.   I will try to play at various levels when we demo and I have the remote:)   June 23 is the show.  I know a few folks who say they are attending, so I am sure someone unbiased will post an honest impression.  Listening rooms at shows are often hard to tame as well, so we shall see what we can do when we get there.

@carlsbad2 

Good observation. Over the years I have attended my fair share of high end audio shows. For the most part I have enjoyed these experiences quite a bit. I do get annoyed with the high volume level demonstrations. Personally I do not fine these displays impressive. Even with the very high powered amplifiers driving difficult to drive speakers.

Good quality music sounds better on a good system played at what I consider reasonable listening levels. I do not understand the attraction of the “crank it up”  approach.

The show mentioned in this thread is in 2 weeks.  There was very little at the LA show this past weekend in the way of 300b.  One that had promise was very nice japanese 300b paired with Songer field coil speakers.  But the speakers were only 93dB and every room was playing very loud to keep up witht he volume in the other rooms and the amp was literally turned up to the stop.  It didn't even sound like a tube amp to me.  I would have loved to have heard it at 1/3 volume.

Jerry

Why the radio silence folks??? Where are the impressions from the show? Inquiring minds wanna know!

Don, looking forward to seeing you at the show with your working prototype.

just get yhw alternative 2a3 maybe in paralel

I was proposing "Blackbird" as a product name for the amps, and Don said it is not just black like a raven, but "Intergalactic" black, which cracked me up (literal LOL) when he told me over the phone. Looking forward to meeting him at the show in person.

I can say the Amity, Karna, and the new amps sound nothing like other tube amps, whether SET, OTL, or conventional, or like transistor amps, either. I find them hard to describe, partly since I’ve been so close to them for the last twenty-five years (the first Amity came to life in 1998 or maybe earlier).

I’m trying to think of parallels ... maybe the first time you heard an electrostatic speaker? Kind of like that.

I have had the matching preamp running quite nicely for about 10 days and I will say the combination doesn't sound like anything I have ever heard.  First off, with my 97 dB speakers you literally have to put your ear to the woofer to know the system is on at idle (no hum).  The tube rush (hiss) varies with tubes used, but you pretty much have to have your ear to the HF driver to hear that at idle.  We are talking a Lampi Pacific DAC with DHT output stage feeding a tube preamp, which feeds the 300b amps.  All tubes and at idle it is as quiet as solid state. This gives a totally black background.   Lynn went his own way on the circuits and between the two of us we have turned them into working prototypes that are closing in on production models.   The working prototypes are what will be shown in Seattle.  Again, I hope many folks reading and participating in this lovely thread are able to come and hear them and give an honest opinion.  They do not sound like anything else I have built, or even heard.

Charlie reached out to me and asked if I would like to be Technical Editor of Vacuum Tube Valley, and I happily agreed. First class bunch of people, including the irrepressible Eric Barbour, one of the most notorious curmudgeons in the industry ... he made me look like a mild-mannered moderate. But all of them were, and are, great people.

Back when I was on the Editorial Board of Positive Feedback (a few years earlier), Eric sent in an article so outrageous that we couldn’t publish it, but it was the funniest thing about the biz I had ever seen. No, it still can’t be published, here or anywhere else. We’d get sued for sure. Eric is one of a kind.

Well, OK, there’s Harvey Rosenberg, but his sense of humor was much more gentle. Meeting him in person at the Consumer Electronics Show in the late Nineties was pretty memorable. He would drop the clown act and get quite serious, but if he saw someone he recognized, he do something outrageous right on the spot, then switch right back. The clown act fooled a lot of people, as it was meant to. He was a very sharp observer and knew what was going on.

Once you get away from the oh-so-serious gatekeepers, there are some remarkable people you meet in the biz. The fun thing about Eric, Harvey, and myself is we were outsiders, and we didn’t have to take it seriously.

Frankly, that was part of my motivation to design the Amity and Karna ... to show, by example, that things could be done differently. At the height of the SET mania in the Nineties, Harvey was the only one who (very strongly) encouraged me to follow my own path. That encouragement, from an old pro like Harvey, made all the difference.

Lynn,

My local tube tech was good friends with Charlie who lived near Sacramento and he had immense respect for him.  He published a magazine which I am sure you aware of, 100% tube centric.  I never met him but he was a legend in this neck of the woods for his tube knowledge. 

Ralph, it seems curious to me that knowledgable audiophiles would rely on anything but sound to be the arbiter of their purchase decisions.  Tube gear is a hassle and costly, but to my ears, it is the price to pay for such magnificent sound. I think buyers buy tube gear because it sounds better, pure and simple.   

There’s nothing quite like twiddling with a speaker crossover or the critical components on an amplifier. That brings the guesswork to an end. You know what increasing the slew rate of an amplifier sounds like ... it’s a pretty distinctive sound, actually. Likewise, if the tweeter crossover is screwed up, you hear tweeter distortion ... lots of it.

Which makes show-going by and large an unpleasant experience (although I love to meet people). I walk by a room, without going in, and I hear problems. Big ones. Multiple problems. And yes, I know how to fix them. But I’m not going to do it for free, and besides, most exhibitors really don’t want to hear unsolicited advice from a notorious busybody like me. So I just keep on walking. There might be one, two, or three rooms where the equipment is working OK, and I’ll spend most of the show there.

This might sound cynical, but seriously, I’ve been designing speakers since 1975. I can’t stand speakers with wonky response, multiple resonances, or gross distortion. And that’s most of the famous-name speakers, so they’re out. And they certainly don’t want to hear my wisecracks at first hand.

I got into tube-amp design around the early Nineties, and joining the staff at Vacuum Tube Valley was a fabulous learning experience, especially from Charlie Kittleson, a great guitar player, and John Atwood, an engineer’s engineer, having worked at Intel, Tandem Computing, and Apple. Sadly, Charlie passed on around 2000, but I’m still good friends with John Atwood. We’re both big fans of the history of technology, and can talks for hours on end about AC distribution systems in Japan and the arcana of NTSC, SECAM, and PAL color television. His current project is restoring a TeleType machine ... because why not? He’s also a ham radio enthusiast who builds vacuum tube rigs from scratch.

At any rate, those of us who do this for a living (although I am technically retired) can spot design errors pretty much immediately. My background is speakers and electronics, which also means I cannot ethically review anything, because all I would do is criticize, which isn’t fair to the manufacturer. Besides, the various designers all disagree with each other ... my designs are completely different from Atma-Sphere, or Audio Research, or Krell, etc. etc. We are all very opinionated.

Are you at the point where you feel your Class D amps are equivalent to your best tube amps?

@whitestix Yes.  After extended listen sessions as you put it I don't find that our tube amps bring anything to the party that the class D doesn't. I really doubt that we're the only ones that can do this so this has led me to thinking that tube power amps are on borrowed time at this point- that is if sound quality is the only arbiter. People do like the glow of tubes- so do I. But I've found also that I don't miss them in the slightest, despite liking tubes so much as to make a business of them.

Lynn…. I really appreciate two comments… illusion generator… and the layman disadvantage of not hearing individual part changes…. both of which help explain why many of us go through a bunch of gear trying over and over to improve the illusion. 

Ralph,

Your comments on this this thread, as on any thread, are extremely informative.   I have not had the pleasure of hearing your new affordably-priced Class D monos and maybe they will be playing at the Seattle show later this month so I could hear them then.  

You have had a career as a designer and builder of tube gear.  You now are selling a Class D amp with the new GaN technology.  Don and Lynn of course are solidly tube amplification adherents, make no mistake about that, but you seem to be straddling the line between an affinity for tube gear as well as Class D amplification. 

Are you at the point where you feel your Class D amps are equivalent to your best tube amps?  I have long anticipated that the day will come where the march of technology might render tube gear obsolete, but in the main at the moment, my experience with Class D amplification is somewhat akin to the unwarranted adoption in the 60s of lousy sounding solid state gear (everybody made a variant of it) over tube gear that took a very long time for the industry to recover from.  Tube gear, like vinyl sales, are better than they have been for a long time, but I remain dubious that Class D amps yield the same sonic goodness after extended listen sessions, than the better/best  tube amplifiers.  But then I have not heard your new Class D monos. Comments?

@atmasphere 

So the cap is not as efficient at the new voltage when new. It takes time for the cap to 'form' to the new voltage. Its important to understand that electrolytic caps have some properties in common with batteries and so are fundamentally different from film caps in this regard. Charging them and polarity are two examples of this similarity. Forming is one way they are unique.

Anyway, when the cap forms up to the new voltage used inside the amp or preamp it will be a more efficient bypass. Its my theory this is what people hear during break-in. I've found it measurable too- the voltage once the caps are formed is every so slightly higher and the supply is less noisy.

Ralph, this is believable and logical.

I recently had a DAC built and delivered to me from Ukraine. The builder (Abbas Esoteric Audio) told me that it will require roughly 200 hours minimum of burn-in time to sound its best. He specifically cited the Blackgate capacitors utilization as the reason. He explained to me that it takes time for these excellent electrolytic capacitors (His opinion) to form.

Sounds right to me based upon my experience with his DAC.

Charles

 A Cornell Dublier engineer once explained to me that the difference between a 150V rated cap and one rated at 175V was the way the cap was formed up and nothing else. Forming is a process where voltage is applied to the capacitor with a target of the rated voltage; something that is done only once in the factory.

But the cap is almost never used at the forming voltage. Usually for best reliability, they are to be run at about 80% of the rated voltage.

So the cap is not as efficient at the new voltage when new. It takes time for the cap to 'form' to the new voltage. Its important to understand that electrolytic caps have some properties in common with batteries and so are fundamentally different from film caps in this regard. Charging them and polarity are two examples of this similarity. Forming is one way they are unique.

Anyway, when the cap forms up to the new voltage used inside the amp or preamp it will be a more efficient bypass. Its my theory this is what people hear during break-in. I've found it measurable too- the voltage once the caps are formed is every so slightly higher and the supply is less noisy.

My concern for the customer experience might sound big-hearted, but actually it’s purely selfish. Neither Don nor I want ’em coming back. I am 100% retired, Don is thinking about it, and we both want the preamp and power amp to be reliable and good-sounding right out of the box. People tell their friends, etc. etc. So every part going in has to earn its keep in terms of reliability and sonics.

My concern is reliability and unknown, undocumented processes going on in critical components. This is just bad engineering. Imagine an expensive car where the horsepower and handling changed from day to day, and the manufacturer had no idea why. Cars are 100x more complex than an audio product ... the average car has 35,000 parts, 5,000 of which are moving parts, nearly all of which are critical to performance, reliability, and safety. A single-part failure can make the entire car useless.

What’s the capacitor manufacturer’s excuse? "This is how we’ve always done it" isn’t good enough. "We don’t understand what we are making" is even worse. There’s good engineering, making reliable products that people enjoy, and bad engineering, where mysterious things occur and nobody knows why. Regrettably, this is the situation for much of high-end audio.

For all I know, Don, Thom, and I might end up designing a capacitor conditioner for one of the cap companies. Back when I was working with Gary Pimm, he came up with a gizmo that did that ... pushing through 10 kHz square waves at 1/4 of the cap’s rated breakdown voltage. After twenty minutes of that, it either survived or not. Actually, nearly all survived, and they were "broken-in" for sure after that treatment. And it weeded out the parts that were going to fail anyway.

By contrast, using the cap in a normal circuit, with music stimulus, is barely tickling it. No wonder it takes forever.

I've lived through many new equipment break-in events over the years. As my experience level increases and the resolving capabilities of my system increases, it has been easier to track changes through the duration of the event. In a moment of judgement, it can be difficult to make statements of progress or regression as we aren't very good at making absolute comparisons, unlike numerical measurements. It's always relative and our powers of perception are better at establishing trends over time than snap judgements. It is possible to fool yourself in a single session. More valid impressions form through multiple sessions.

Here are several notable examples where break-in from new was significant and long in duration.

Antipodes K50 Server. From new, un-listenable for 9.5 days of continuous power up. Utter dreck. By two weeks of on time the performance was quite good. After 1 month, exceptional. After 6 months, fully plateaued. My experience, corroborated by others, and the manufacturer. The reason - power supply capacitor break in.

Daedalus Apollo 11 speakers. Pretty rough on arrival. Grainy HF. Over days the bass would come and go. By 110 hours the sea began to part. The grain and hearing fatigue began to lift. Bass came in. By 150 hours they were quite good. The manufacturer claims 400 hours for full break in. Guess my hearing isn't that good. Mundorf capacitors are the main culprit here.

Taiko Extreme music server. Sounded OK on arrival. After a couple weeks, quite good. After 1 month exceptional. Here's the rub on this one, even after fully broken in. If you shut it down for 15 minutes, unpowered, it takes 4 hours to recover. If you unpower for over 1 day, it takes 4 days to recover. All of a sudden the drapes open and it's a nice sunny day. These experiences are corroborated by the manufacturer too. Cause - power supply capacitors.

The common ingredients in these events are the capacitors. I suspect that these parts are the special sauce that makes this level of performance possible.

I have not heard a power amplifier exhibit this extreme of behavior from new, but that does not mean these parts don't require break in and overall performance will benefit from more run time.

If you are throwing parts in the bin after 30 minutes, I think you are missing out on some opportunities.

I've read plenty of attempts at explaining why parts, particularly capacitors change during break-in (they do plateau, they don't keep changing) but it doesn't matter unless you are a capacitor designer/manufacturer. Results are results. The reasons why don't matter for users.

Engineering is the prostitution of science. Even scientists don't have all the science worked out yet. Not even close.

I understand that you are referring to the approach you use with judicious application of negative feedback. I was referring to Lynn’s comparison to the “golden age “ PP amplifier which typically used 20db of NFB. Your current class D amplifiers do not fit this description.

@charles1dad 

They don't! However, Futterman claimed 60dB of feedback in his OTLs. That was during the 'golden age'... Also Kron-Hite made a transformer coupled tube amplifier (UF-101) that claimed even more feedback! It was built for laboratory use but works great for audio as well. Its specs are astonishingly impressive and having had a set (they were single channel) I can say they sounded quite decent. That was a long time ago but we compared them to an ARC amplifier which got its doors blown off.

If feedback is applied properly it is really beneficial. If its not then it will mess things up with the amounts normally found in tube amps (12-20dB...).

In the last couple of years, I had the VTV Audio EVO 1200 Class D amp with the Purifi module, with the aftermarket ministrations of Ric Schultz, and while the sound was as Ralph describes it,

@whitestix I'm going to contest this; I was not describing those amps at all and haven't heard them. You can tell something is up that isn't right since when you go on the web, you see really variable reports about their 'sound'. I notice that doesn't happen with tubes- everyone agrees that tubes sound smoother and often have more detail and so on. To what degree and what emphasis is the differences between the tube amps. I'm saying I've been playing a class D that you would think is in that category if you heard it. Going back to tubes you don't find that tubes are bringing anything more to the party. I get that seems like a tall statement. Keep in mind that OTLs have ruled the roost in the transparency department of the tube amplifier world and I've been building them since 1977 or so. During that time I've heard many tube amps; I repaired audio for a living as I put myself thru college and afterwards until Atma-Sphere was able to keep me busy full time. So I know what tubes bring and I'm telling you there's at least one class D out there that does the same thing. I suspect there are others.

Sorry I won't be able to participate in this thread for a while- I'll be out of town for 4-5 weeks. Y'all have fun and be well! 

I have had situations with break-in on my own amps, which are very revealing of parts quality, where the sound got better and worse on a two-hour cycle. While there was an overall upward trend, the up and down kept going on, with the cycle timing varying between a half-hour and two hours. At the twenty-hour mark, I finally lost patience and threw the questionable parts in the trash. That experience has made me wary of all parts that require subjective break-in.

My rule now is twenty to thirty minutes, tops. If the part can’t make up its mind in that time, in the trash it goes, no matter how expensive, or what the reviews say. I don’t want unstable parts in my system. Now if the fancy audiophile part requires a half-hour on a burn-in gizmo, fine, but I will regard it with some suspicion.

I think audiophiles and reviewers are too tolerant of this hokum. If it sounds bad for days on end, it is bad. Something is wrong. There is a design or fabrication error.