300b lovers

@cloudsessions1

Are you guys going to be at the pacific audio fest? I’d love to come hear your Class D amps and hear how it compares to the 300b statement monos

That would be terrific!! Even if not heard in the same system. Still worthwhile to hear the GAN class D amplifiers and how they compare with the new 300b push-pull amplifiers. My sense is that Don and Lynn’s amplifier is something quite special.

Charles

@atmasphere  very interesting Ralph. What are some amps you’ve heard with high feedback that you’ve enjoyed? I’ll have to check them out.  I’ve seen the measurements for the Purifi and its distortion is incredibly low, to the point it’s at the limits of what the AP analyzer can measure. It does have raising distortion in the treble but if I had to surmise, it is most likely low order as I find the purifi a touch sweet in the treble. I do run it without an input buffer as my preamp is up to the task of driving the Purifi module directly. 
I have yet to hear the new Gan stuff that is specifically designed for audio. I know yourself and AGD specifically designed yours for audio applications unlike many of the other brands. Are you guys going to be at the pacific audio fest? I’d love to come hear your Class D amps and hear how it compares to the 300b statement monos. 

@pindac   Exactly my friend, exactly.   Once the power supply is right,  all the operating points are right and there is some serious listening, then the tuning begins.   We are almost there...

When I was having a Bespoke Valve Input/Output Phonostage Built for me.

The designer builder was running two builds parallel, with the only differences being one had more RCA Inputs and my one had a Single RCA Input.

The Designer Builder invited me to listen once more to the design, but I could not get my head around it, there was still too much perception of weight, which was a a assessment put forward during the demo's done prior to what was supposed to be the final demo' prior to completing. 

I told the designer/builder, it was time to introduce Foil Resistors and Alternative Cap's. After some toing and froing, we got there in principle. Z Foils and a selection of Copper Foil Cap's was bought in.

The impact these had on the Sonic was from my assessment something very very special, even the designer /builder was on board and had their eye on this as a Upgrade Package on the Phon's if they were to be produced in increased numbers My later investigations which resulted in the addition of Vintage Tubes selected as a outcome of Tube Rolling experiences, was the addition that is the Cherry Garnish on Top.

The Tuning/Tweaking has the capacity to produce a sonic that is very different in the attraction/likeability generated to a earlier version. 

These amps are still prototypes and being tuned as we speak.  So what Cloud wrote was in reference to the first prototype a year ago.  Spatial Audio Lab had that amp for maybe 6 months.   The mono amps are probably 25-30% better at least.  @whitestix  has a pair, and Lynn and I are still tuning them and have improved them since that pair went out.  What will be shown at the Pacific Audio Fest in Seattle will be very close to the final circuit, but there will probably still be a bit of tweaking after that.  I would expect production and sales to be Q4 of this year and maybe Q1 of next.  We have to see how it goes.   Again, I hope lots of people can hear them in Seattle and give an honest opinion.  They will come to market, I promise, but we want them to sound as good as they can first.

Maybe.  Except that there are things we cannot measure.

@donsachs That was true back in the 1980s. It really isn't now. Measurement technology has really advanced in the last 40 years!

Its the distortion of any amplifier that is its 'sonic signature'.

There are many class D amps I've heard over the years that I had to struggle to take seriously. But I've heard some now that sound every bit like a very good tube amp; just like in a tube amp where arcane subtleties can make or break a design, the same is true in class D (or any design for that matter). I pointed to what is needed to make a successful amplifier (if you're going to use feedback) in my prior post. Most amps using feedback fall short of the GBP needed so distortion is much higher at higher frequencies than the THD measurement suggests!

THD by itself, if that is the only harmonic distortion metric used, allows a lot of problems to be swept under the carpet. When it is the sole metric, it leads to the myth that 'there are things we cannot measure.' The reality is if the harmonic spectra is measured at several frequencies (including above 1KHz) and if distortion is graphed vs frequency, then we start to be able to predict the 'sound' of the amplifier.

Both the 'measurement only' guys and the subjectivist guys hate this! But Daniel von Recklinghausen was right- if it measures well but sounds bad, you measured the wrong thing.

I’m convinced that no feedback plays a role as every amp I’ve heard with feedback doesn’t have that super inky back blackground or perfectly rendered transients.

@cloudsessions1 That is because in most amps employing feedback, its poorly applied- so my surmise is you've yet to hear one where the feedback was really right. Norman Crowhurst pointed this problem out 65 years ago, describing how the feedback node (the point in the amplifier where the feedback signal is mixed with the incoming signal) isn't linear; therefore the feedback signal gets distorted before it can do its job, thus creating higher ordered harmonics that have given feedback a bad rap. Its not the fault of feedback so much as poor application. Amazingly, little has been done in the last 6 decades to fix this; IMO mostly out of ignorance and a lack of will to do so.

I've heard amps with very high feedback that sound utterly relaxed in the mids and highs and portray depth with ease.

@cloudsessions1 

I have a purifi amp and it couldn’t hold a candle to the original 300b statement prototype. I love new class D as when you get the synergy right I find it to top any SS class AB I’ve heard. But the 300b just makes everything right

That is quite a tribute and observation.

Charles

I’m not sure how the 300b statements could achieve such great technical performance over some of the “state of the art” amplifiers I’ve had in. Maybe Lynn, Don or Ralph could comment on that. It’s put things into perspective that maybe just maybe we don’t know every way to quantify all measurements to what we hear. 
I’m convinced that no feedback plays a role as every amp I’ve heard with feedback doesn’t have that super inky back blackground or perfectly rendered transients. Although the amps I’ve heard with no feedback trade that off for less extension on both ends of the spectrum and a lack of power/effortlessness. The 300b statement is the outlier in this regard. 

I have a purifi amp and it couldn’t hold a candle to the original 300b statement prototype. I love new class D as when you get the synergy right I find it to top any SS class AB I’ve heard. But the 300b just makes everything right. I find it odd because it does even the technical attributes better. The blackground is soooooo black, the details precisely rendered, and the soundstage depth of the charts. The only system I’ve heard that could compete was a magico paired with ClassE mono blocks. But even that system while the soundstage was mind melting it was very polished sounding. The 300b statement has much more realistic tone with great texture. 
I still snicker 🤭 when bringing a friend over who’s never been a big fan of tubes and putting on Pot by Tool cranking it to 11 and watching his mouth drop. The sheer power and realism the 300b’s presented!

donsachs:

When do you think your new 300b mono-blocks will be available for order? I would want to buy them independently of a package with the Spatial Audio speakers as I have a pair of Daedalus Apollos (sensitivity about 96db) that I am super pleased with. I want to upgrade an integrated tube amp and have been patiently looking for the right 300b amp to drive them.

@atmasphere 

"There are now class D amplifiers that have a distortion spectra that if you had one on the bench you would be completely convinced you were measuring a really well-behaved triode tube amplifier."

Maybe.  Except that there are things we cannot measure.  I prefer the sound of a good tube to any SS device I have heard to date.  Personal preference.  I would not be at all surprised if that Class D amp measures better than my tube amp in every regard.   I bet in a blindfold test I would choose to listen to the tube amp.  Again, personal preference.  Other people would make other choices, as it should be.

I hate the sound of solid state devices.

@donsachs There are now class D amplifiers that have a distortion spectra that if you had one on the bench you would be completely convinced you were measuring a really well-behaved triode tube amplifier.

There are three reasons for this:

1) its really easy to get really high Gain Bandwidth Product values, such as 20MHz with class D, so feedback can be supported across the entire audio band (no rising distortion with frequency- like a zero feedback amplifier in this regard)

2) the feedback node can be very linear so the feedback signal does not get distorted prior to doing its job.

3) the things that cause non-linearities in the circuit tend to generate lower ordered harmonics.

Despite inexpensive power being available, I still prefer higher efficiency loudspeakers for the reasons Lynn outlined above. In addition, the harder you make any amplifier work the higher the distortion. For this reason I feel that higher efficiency and higher load impedance is an advantage to all audiophiles.

@donsachs

I wouldn’t own an inefficient speaker because I would be doomed to SS amps, and I hate the sound of solid state devices

It seems that the latest generation class D/GAN may be addressing this. Time will tell.

Charles

You don't have to convince me, my speakers are 97 dB 8 ohm:)

I wouldn't own an inefficient speaker because I would be doomed to SS amps, and I hate the sound of solid state devices.

@donsachs

I would stick to speakers that are 88+ dB and very well behaved. The spatial audio X4 current model is 88 dB 4 ohm (and very well behaved) and the amps will happily drive them to ear splitting levels in reasonable room

As @atmasphere has made the point eloquently on past occasions, easy load impedance (Higher ohms and less fluctuations ) speakers are less stressful on amplifiers. In addition he has pointed out that they are lower in distortion compared with low impedance speakers.

Charles

As Lynn said, the amps have dual regulated supplies, one for the 300b and one for the input and driver tubes.   IF the specs on that KEF speaker above are really what the review said, then the amp would drive them.   Also, as I said far above somewhere, the first stereo prototype of this circuit with only one power supply per channel drove a pair of experimental Spatial Audio Labs X4 prototype speakers that were approximately 87 dB 4 ohm to insane levels, much as what Thom was describing above.  The monos have dual supplies in each amp, so would be even more capable.  All that said, I would stick to speakers that are 88+ dB and very well behaved.  The spatial audio X4 current model is 88 dB 4 ohm (and very well behaved) and the amps will happily drive them to ear splitting levels in reasonable room.

@lynn_olson

 Surprisingly, the 300B survives this gross abuse with no apparent damage, not something I expected.

Well as you said earlier,

Bell Laboratory and Western Electric knew what they were doing.

90 years later and it's still very much admired, appreciated and enjoyed by discerning music lovers. Quite the testament.

Charles

I was there. Thom’s amps did not use interstage coupling (at the time), so 8 watts is pretty much all she wrote. Frankly, I was kind of surprised ... I knew Thom’s NiWatts were maxed out for all they were worth, but audibility was surprisingly low. No flabby bass. No clipping as such, just really loud sound from an absurdly low-efficiency speaker. No screech, but not dull or muffled, either. A shocking amount of punch and bass slam. We both knew in advance that the combination of no feedback (thus no hard-clipping or saturation) and the split supply would protect the amp from things getting really out of hand.

Thom kind of did it on a dare, trying to get the fuse to blow. We both wanted to hear what the NiWatts, still in rough prototype form, did when given an impossible situation. The split power supply really, really came through. The 300B was getting hammered while the rest of the amp just sailed right through. It acts like an 8-watt compressor with surprisingly subtle action.

It reminded me of a little practice guitar amp, which if you have heard one, can get insanely loud, and retain its basic character.

P.S. Yes, Karna Mk II, or Statements, have independent regulated B+ supplies for input+driver and output section, with massive overdrive capabilities. That’s something the Mark I’s, the Statements, and the NiWatts all share. It makes them sound many times more powerful than the nominal wattage rating would suggest. Surprisingly, the 300B survives this gross abuse with no apparent damage, not something I expected.

The speakers appear to be 8 ohm 90 dB from a stereophile review. They dip to 3.2 ohms, which isn’t bad. The amps would drive them with no trouble in any reasonable sized room. I cannot comment on pricing until Spatial Audio figures out all of their costs. I would expect $15,000 - 20,000 per pair with premium tubes, but that might be off a bit. There will be an announcement after the Seattle show in the spatial audio lab website once it is all figured out.

I don’t know Don’s power supply design, although with Lynn’s collaboration, I’m sure some sort of split supply has been implemented - whether via isolation or regulation. It’s one area Don and I haven’t discussed.

Lynn’s original Karna concept (which I’m employing in my NiWatts) runs a separate separate B+ supply for the output section. We’ve already discussed how the sound of a 300B is the sound of the driver.

With a dedicated power supply to run the input and driver sections (separate power transformers and supply circuitry in the NiWatts - 4 transformers in total per channel), an inefficient speaker may whip the output tube’s power supply into submission, while the input and driver stages are just coasting along.

The perceived effect is that of much more power than the specs would lead you to expect.

Lynn was at a session where I drove a pair of Von Schweikerts with my puny, single-ended NiWatts. Until things got rock concert loud (I put in my musicians’ ear plugs - these guys were nuts), the NiWatts were breezing along.

... Thom @ Galibier

It is difficult to predict real-world distortion from idealized triode or pentode models. The models assume tubes with perfect physical assembly and ideal emission characteristics. In practice, grid windings are not evenly spaced, grids are tilted a little bit, coatings on the cathode are not perfectly uniform, and there is always just a bit of residual contamination. Tubes are not built by robots, but skilled technicians, and as a result, they are all a little different from each other. By looking at spectral distortion measurements, patterns that are unique to each manufacturer emerge, and none conform exactly to the tube model. (The map is not the territory.)

Successive stages multiply distortion terms as more and more kinks end up in the transfer curve. Of course, this applies to the entire transmission chain from microphone to loudspeaker, with everything in-between.

Models are useful for finding bias points and the expected high-frequency response, but predictions of high-order distortion can be way off from the tubes you can actually buy. Low-order terms like 2nd and 3rd harmonic distortion may conform to the model, but I wouldn’t trust it further than that, not with real tubes. Think of the models as first-order approximations.

@atmasphere 

I have to admit that the conclusion about SE+PP leads to emphasis on 5th harmonic is a bit counter-intuitive to me from pure math perspective, but I haven’t read his paper and perhaps there are certain situations that contribute to that conclusion (?).

Many report excellent result using a tube pre with a solid state or push-pull tube power amp though. In many cases, such combination includes some SE stages with at least one PP stage. So, SE+PP is not necessarily bad empirically :-)

Hi, CuriousJim!

I am kind of dubious about any KEF speaker being really 91 dB/meter/watt. That’s almost 1% conversion efficiency, and believe it or not, that’s quite high for the mainstream market, and especially KEF. True efficiencies between 85 and 88 dB are much more common. Efficiencies in that range need 100 to 200 watt amplifiers, which is very large for tube amps. When people say XYZ speaker needs 200 watts to "come alive", they are not joking.

1% efficiency is 92 dB/meter/watt. 0.5% is 89 dB/meter/watt. 0.25% is 86 dB/meter/watt. This raises the question ... where does all that power go, if not making sound?

It heats the voice coil, which eventually radiates its heat to the magnet structure, which radiates its heat into the cabinet. Copper increases its resistance with temperature, which leads to a type of dynamic compression as the voice coil heats and cools. In addition, voice coil heating eventually damages the cylindrical former it is wound on, leading to driver failure over time. That’s why Nomex and other fire-resistant materials are commonly used for VC formers.

This is the charm of high efficiency speakers: for a given SPL, much less power is wasted in heating the voice coil. More is turned into sound, which is the goal.

P.S. I agree, it is somewhat annoying to realize that 99%, or more, of the expensive watts we buy do nothing more than heat a voice coil, but that’s what’s really happening. It’s kind of shocking: hundreds of watts from the AC wall socket end up as milliwatts of acoustic power. The rest ends up as heat, and not in a great place, either.

@curiousjim 

The speakers appear to be 8 ohm 90 dB from a stereophile review.  They dip to 3.2 ohms, which isn't bad.  The amps would drive them with no trouble in any reasonable sized room.  I cannot comment on pricing until Spatial Audio figures out all of their costs.  I would expect $15,000 - 20,000 per pair with premium tubes, but that might be off a bit.  There will be an announcement after the Seattle show in the spatial audio lab website once it is all figured out.

A good way to visualize the difference between even and odd-order distortion harmonics is to imagine a sine wave ... a perfect, happy little sine wave. That's the original signal.

* Now, use a single diode to clip one side of it ... say, the positive side. In addition to generating a DC offset, if you run a spectral analysis of it, you'll see a series of harmonics ... 2nd, 4th, 6th, etc. etc. If you look at the "transfer curve" ... a curve mapping the input/ratio at different levels ... you'll see a diagonal line that is perfectly straight (the linear portion) that also has a sharp bend in it at the top, with a flat-topped region beyond the bend. The transfer curve is actually the true distortion mechanism; the spectral analysis of it is an indirect indicator that is (relatively) easy to measure.

* Let's use two diodes to clip the top and bottom sides, both positive and negative. This is known as symmetric clipping. If the flat-topping is at exactly matched levels, there will no DC offset. Similarly, if the clipping is precisely symmetric, the spectral analysis now shows no even-order terms (2nd, 4th, 6th, etc) but only odd-order (3rd, 5th, 7th, etc.). The transfer curve now has TWO kinks in it, at matching plus and minus signal levels. If the levels precisely match, there will be no even-order terms, but odd-order terms are abundant.

The diodes create hard clipping. Vacuum tubes, properly biased, create a softer "knee" region, but rest assured distortion is still there, just not as much, and with less high-order content. The property of symmetric circuits is they cancel transfer curves that are precisely opposite in shape ... a "C" shape that is inverted in the other phase of the circuit. But that depends on symmetry and precise phasing that tracks as levels go up and down.

@donsachs 

Hi Don,

I have always wanted a 300B system. Two quick questions. I currently have a pair of KEF Reference 5 speakers @91db. How well will your 300b power them? And can you give me a ballpark price so I can start groveling to She Who Must be obeyed?😁

Thanks in advance.

Jim

True, push-pull substantially reduces distortion, but in reality it only reduces even-order distortion ... 2nd harmonic, 4th harmonic, 6th harmonic. etc.

@lynn_olson This statement is not correct. If the circuit is fully differential and balanced (in effect, PP from input to output) distortion is compounded less from stage to stage. The result is less 3rd harmonic than you would otherwise see if only the output section is PP.

In addition I should point out that the 3rd harmonic is innocuous in the same way as the 2nd as long as it is at the same level or less as seen in an SET, which as you pointed out in most cases (except for the example I just gave) it will be.

A properly functioning tape recorder makes a dominant 3rd harmonic that is actually higher than seen in most PP tube amps at full output. No-one really seems to complain about the ’sound’ of tape; rather people seem to like it quite a lot!

How about using SE as opposed to PP in the first stage and a SE to PP interstage transformer between the first and second stage?

@ffzz When you combine single ended and PP in one amplifier you get two distinct non-linearities (since neither circuit is perfectly linear). PP circuits generate what is known mathematically as a ’cubic non-linearity’, while single ended circuits generate a ’quadratic non-linearity’. The cubic or quadratic function describes a lot about how the higher ordered harmonics behave in the circuit. This is important because higher ordered harmonics can contribute to harshness and brightness, as that is the tonality assigned to them by the human ear.

When you combine both circuits in the same amp you get both non-linearities. Norman Crowhurst (one of the technical gurus that wrote about tubes and other technical/engineering topics related to audio) wrote about this 65 years ago, stating that the result is a more prominent 5th harmonic. With this understanding I’ve not found it surprising that SET owners prefer their amps over PP simply because the PP amp combined both types of circuits with the result described.

Link not working, no.  There are some monos on ebay with no tubes for $2-3K per pair.  SE amps.  Typical Chinese amp in that you have no idea what is inside that transformer box.  Could be ok, could be $99 transformers.  A tube amp is the sum of three things.  How good is the circuit?  How good is the power supply?  How good is the iron (transformers)?   The circuit might be a faithful reproduction, the power supply and iron are suspect.  Ali Express brings to mind two words:  caveat emptor🙄

Any thoughts on the Chinese Western Electric 91A mono amps on Ali Express?

https://www.googleadservices.com/pagead/aclk?sa=L&ai=DChcSEwiN6byo24j_AhVOmmYCHQQiD3cYABAHGgJzbQ&ohost=www.google.com&cid=CAESbeD2kzDOBRl7ASZAHvWHTgobJGiZNfpAe6oelPNUukMAUBmgSMVLgoIjFmfJxhMcqAhBfGLF56d-nyLRvKe5Co9pyCuqGar44aWI17sxz3Is5R8_eg2whK82LJ0j6EcxbFoaBV1Vkqe1jm0ao2M&sig=AOD64_01fjBQQqjPvkqlxFoGJ6k9oENBUg&ctype=5&q=&ved=2ahUKEwjfqLao24j_AhWWTGwGHTz0AYwQ8w4oAXoECAcQDw&adurl=

Link will not post for some reason.

@lynn_olson

IT-coupled PP DHT’s have a power and majesty unlike anything else in audio. Bell Labs and Western Electric knew what they were doing back in 1935.

Western Electric is also pioneer of "Ultra Path" circuit design for SE amplifiers which removed local feedback which is evil in true audiophile amps.

Long tailed symmetric push pull is another WE originated design.

Only modern circuit design which enhanced WE golden edge SE DHT amps is solid state CCS which a magnitude better than tube CCS.

@markusthenaimnut  I have no idea.  I think Lukasz at Lampizator was.  Yes they will be pricey because the power supply topology is something that I have not seen in any commercial amps that I haven't built, and there are custom wound transformers throughout.  So even if someone would build a similar concept, these have a lot of features that probably wouldn't be in something else.  Hence the cost.....  Again, this was essentially a cost no object (within reason) project to see what was sonically possible.  I am pleased with the outcome.  There are certainly many decent quality tube amps out there for under $5,000 including the Kootenay that I used to build.  None of them are this good though.  Doesn't mean you cannot have a really satisfying and enjoyable stereo for less.  Just that if you want this level of performance it costs this much to do correctly.

Is anybody else building IT-coupled PP DHT amps these days?

Kinda' seems like these amps are going to be (justifiably) pricey when they come out.

@lynn_olson

IT-coupled PP DHT’s have a power and majesty unlike anything else in audio. Bell Labs and Western Electric knew what they were doing back in 1935.

A compelling point. I do believe that if implemented properly the DHT tubes are difficult to equal or surpass in terms of music reproduction purity. Nothing is perfect but they have considerable  intrinsic sonic value and ability.

Charles

The house I lived in back when I was in Portland had a ceiling like that, with a panoramic picture window overlooking the Oregon Coast Range behind the speakers. The very first PP 300B amp, the Amity, had a vast, CinemaScope soundstage. Once I heard that, no more SETs for me, nor PP pentode. All done.

That’s when I contacted Harvey Rosenberg back East and told him that interstage transformers were The Way. He never did get to hear my amps, but he got his hands on the Japanese Sun amplifiers (with ITs) and never looked back. Harvey was powering his gigantic Tannoy Westminsters, but from what he told me, the Sun amplifiers took charge of the big Tannoys. No surprise there.

IT-coupled PP DHT’s have a power and majesty unlike anything else in audio. Bell Labs and Western Electric knew what they were doing back in 1935. It probably didn’t hurt they had Leopold Stokowski as an in-house musical consultant.

I am not sure the of the adjective @whitestix would use to describe the amps, but "trippy" is pretty much spot on.  It is funny, because when I first wrote Lynn after building the initial stereo version with the CCS on each 6V6 plate I told him that it was so clean and clear and threw such a soundstage that it sounded like you were high every time you listened to it.  He was amused and wrote back and said that he and Karna described the sound of the first amps as "trippy".   That indeed is how they sound.  They are unlike anything I have ever heard, and with each improvement, they get "trippier".  Adding the Raven preamp with XLR connection directly to the input tube grids pushed them to new "highs" 😉 

I have an old timber frame house and the ceiling slopes upward from about 10 ft at the speakers to at least 20 ft overhead at the listening position.  So there are no ceiling reflections.  The sound stage is huge, and as I said earlier, it is akin to Omnimax theater for the ears.  Sometimes you are sitting inside the recording if that makes any sense.  Trippy indeed, and once you hear it, you just cannot unhear it and go back to some other amp.  It sort of blows the lid off of things.

@gavin1977 

No, sorry.  The 2A3 is 2.5 V filament and 300V plate max.  The 300b is 5V and the plates are at about 395 V in this amp.   Not ever going to happen.  What you have to realize is the 300b is a better tube for this purpose and people who make comparisons may not be doing it in amps where the 300b is actually driven by a driven section that can show what it can do.   The best 300b I have heard in the amp is the Linlai WE300b exact copy.  It is just superb and can be had for under $800 per matched quad.  The "new" WE300b is $1500 per pair.  I have not heard them, and at that price I probably won't when I can get a quad of absolutely superb tubes for half of that.  These amps deliver about 27 watts/ch and can drive most rational speaker loads.  A 2A3 amp would be limited to more efficient speakers.  That may work for some, but we wanted an amp that could drive a much wider variety of speakers.

I forgot to ask, will the new amp also take 2a3?  The LINLAI 2a3 apparently sound better than Elrog 300b, so high praise indeed.

What’s odd is that I have trouble describing the sound of my own gear ... this applies to Shadow Vector, my loudspeakers, and my electronics. I aim for natural, open sound that is free of electronic artifacts. If there is a residue of coloration, I’d like it to be pleasing, but as low as possible.

That’s the goal. What I hear is a very spacious sound, no surprise there, but also an unexpected "trippy" kind of feeling that slowly deepens over the first ten to twenty minutes of relaxed, non-critical listening. I have no idea what causes it, to be honest. Many don’t experience this, but some do, and it’s fun to watch them process the experience. My only guess is the disjunction between the auditory experience and the visual experience is so strong that secondary emotions are invoked.

My degree is in Psychology with a focus on Perceptual Psychology. I grew up in Japan and Hong Kong, which gave me a cultural experience different than most Americans, and am a bit familiar with Buddhist, Taoist, and Vedanta Hindu world-views. Partly as a result of that, I take Western audiophile pronouncements about what can, or can’t, be perceived with a lot of skepticism. Different cultures experience the world in profoundly different ways, and there’s a lot of individual variation, too.

The task of the audio system is to get out of the way of what can be a profound emotional experience for the listener. "Accuracy" in this context is absurd, since the goal is to facilitate a trance experience, a dreamlike state of consciousness. Artificiality (colorations that do not occur in nature) is distracting and can prevent the experience from happening.

By minimizing coloration at the level where it originates, the device itself, there’s less need for post-facto processing, which can induce dynamic colorations that are unnatural and a signature of "electronic" sound.

This discussion is kind of "meta", but it is my experience audio designers need to have a goal they are aiming for, otherwise you will never get there. And not a mechanistic goal, but a perceptually subjective goal.

Whitestix I can tell you are astute and have a sense of humor.  When I came up with that name in 2002 I was thinking of my family name and probably at that point didn't realize ss is an abbreviation for solid state amps.  Funny :^)

I too have been almost exclusively a jazz listener since junior HS in 1964.  Listening to Joe Pass, the Compete Pacific Jazz Years right now.

I hope to meet you at PAF

I rather think that there is inherent magic in the employment of 300b tubes, which I discovered with my Willsenton 300b amp with all of 8 wpc.  It drove my Spatial just fine... until it didn't.  With these monos, there is no such limitation on db levels vs distortion which stands to reason.  Easily end-game amplification which will be added to with Don's new preamp, designed from the get-go to pair optimally with the monos via XLR connections. 

You have great 300b amps, and you like Barney Kessel (I am almost solely a jazz listener for 50 years) so you and I are on the same sheet of music.  Your posts are always informative and upbeat, which I value.   

@whitestix 

He clearly knows the sonic splendor of 300b gear.  

Sonic splendor is true. 300b SET mono blocks owned since 2009 and as happy with them as I’ve ever been. Listening to the great jazz guitarist Barney Kessel as I write. Reading the comments from Lynn and Don on the how and why of their PP 300b amplifier convinces me your description of its sound is dead on the mark. I have no doubt that it is sublime.

Charles

@jeff_ss

Being an owner of Don's Vahalla tube integrated, might your "handle" more appropriately be "@jeff_tubes"?   ;-)  

 I have the Triode Masters and heard the Sapphires and was not compelled to upgrade.  However, the X-series is a different kettle of fish so I am enthused to hear them with Don and Lynn's newest electronics, presented in their best possible light.  Oh, and the excellent Lampizator DAC which will clearly complement the rest of the gear.  

I reiterate and amplify my love for these new mono's, which sounds cliche, but they sound like no amps at all, just masterful reproduction of the music in such an effortless and ethereal way... the sound is suspended in the air in the room with a completely realistic manner.  The amps just completely get out of the way with a sonic signature that I would not describe with adjectives like "warm" or "cool", just completely realistic to the source of the music.  This uncanny sound reproduction you will hear when you visit the room, of that I am confident.   I hope I run into you and others on this thread in the room to get acquainted and share our impressions of what we hear.

I wish Charles would be there so I could meet him and applaud him on his excellent contributions on this forum, a paragon of audio knowledge and the utmost of civility.  He clearly knows the sonic splendor of 300b gear.  For me, hearing these mono's, it is a bell that can not be unrung.  I think other attendees to the room might come to the same conclusion.  

@jeff_ss 

I don’t mind.😊

I am interested in your listening impressions of this amplifier  at  the upcoming Pacific audio show.

Charles

What a great thread!  Reminds me of the early 2000’s when I was on here more often.  I love how charles1dad said it back a ways so I’d like to repeat it, hope he doesn’t mind: “If a thread topic generates quality insight, information and perspectives from genuinely knowledgeable and earnest contributors then this is what happens.”

In January 2021 I bought from Don Sachs a Valhalla integrated amp.  I couldn’t be happier with the sound of my system.  After years in the “pursuit” I have felt no desire to change anything.   The Spatial Audio X3 speakers have a lot to do with what I love about my system now.

Don mentioned in an email last month that he was working on some 300B monos for the Seattle show.  Immediately I was interested and have been looking forward to hearing them in the Spatial room since I’ll be there.  Although much of the technical info in this thread is over my heard it is fascinating to read.  I’ve gained so much further insight into Don’s expertise, learned about Lynn Olson and how the two have worked together with their combined knowledge on this amazing project.  I think anyone who has enjoyed one of Don’s masterpieces would probably feel these new amps are a must have, including me.  It’s fortunate I’m so happy with the Valhalla since the new amps might be out of reach.  Hearing them in the Spatial room could be dangerous.

Looking forward to meeting Don and Lynn and would be nice to see Clayton again this year like last.  Hope he can make it.

Jeff S.

Gig Harbor, WA

@lynn_olson 

I did check catalog of one European manufacturer for SE to PP interstage transformers. Within the limited offerings, it does seem that a tube with low Rp is needed in the SE stage - if not a DHT, ones like 6EM7 (the half with 750ohms Rp) may work. The gain will be less, but can still work with an active preamp. 

Ultimately, I agree that it all depends on the design goal - I wonder whether having some 2nd order harmonic would end up being a good thing for someone who prefers sound of SETs. But there is a lot factors to balance in such a design that uses SE in the first stage.

To simplify.. All tubes have distortion. The higher orders are what are like fingernails on a blackboard to your ear. DHTs have lower levels of higher order distortion than other types of tubes, and good indirectly heated octals like the 6SN7 and 6V6 are reasonable regarding distortion in the higher harmonics. When I rebuilt a ton of vintage tube gear I instantly could hear that pieces using small signal tubes, particularly the 12au7 were not very good. If you see a 12au7 in a piece of gear other than a tuner, go buy something else. I always preferred amps with octal tubes as drivers. Anyway, to keep upper harmonic distortion down we choose a great DHT, the 300b for the output tube. Traditional feedback approaches can keep higher order distortion down, but phase split circuits and the usual coupling methods, and the feedback itself rob the amp of clarity. Push pull amps have lower levels of distortion. Class A is the way to go. If you can build an amp with no feedback at all and solve all the problems it will sound cleaner and clearer. The driver stage has to be able to really push a 300b. There are numerous forms of coupling, but interstage transformers (if really well made and designed for the circuit) solve a lot of problems. Recovery around clipping is really important for the driver stage and the transformer coupling aids that considerably over traditional RC coupling. LC coupling sounds very good for an input stage where an interstage transformer would have to deal with the higher impedance of the input tube. Power supply topology and design is critical and the output stage should be isolated from the input and driver stages. Of course the quality of the output transformers is a key as well as the power transformer, which should have good regulation. I am sure I am leaving some things out, but those are some key points of the design.

Don, Lynn

Like many have said, there is a lot here that is technically beyond me...so, I'd like to see if I've understood the essence of what you are saying..which I believe is....

That by eliminating all harmonic distortion above 3rd...and by driving 2nd and 3rd harmonics to extremely low levels you have achieved an amplifier that is not "tubey" in the classical sense but absolutely open and clear that gets out of the way resulting in truthful musicality.

Obviously, this is an extreme simplification of what you've achieved and how you've achieve it...but is this a correct interpretation or have I over simplified or missed some key discoveries?

Well, I tried that with an amp I once called the Aurora. SE input, and if memory serves, the conversion to PP prior to the driver, which was PP. The problem is the input tube has a high output impedance, which enormously complicates the transformer operation.

You see, the input transformer of the new amplifier, as well as the Mark I Karna’s, is driven with a low source impedance ... the preamp. There are a handful of ancient preamps with a Zout of 8k or so, but they are hard to use because a Zout that high makes them very susceptible to rolloff from cable capacitance. Most tube preamps have cathode follower outputs in the 400 ohm range, and if feedback is used, quite a bit lower. Transistor preamps can be as low as a few ohms.

Transformers like to see a low impedance on either the primary (input) or secondary (output). It doesn’t matter which end. The problems start with an interstage, where the secondary is driving a grid, which has a near-infinite impedance that is somewhat unpredictable, and a primary connected to a plate. The nicest sounding tubes tend to be the old octals, or even the true antiques, the five-pin tubes from the Thirties.

They all have pretty high output impedances, 7.7 k or higher. This is a really high impedance for a transformer. The lack of bandwidth wasn’t a problem back in the day, since AM radio bandwidth was never higher than 8 kHz, optical movie soundtracks the same, and shellac 78’s were mostly noise above 6 kHz. And program sources didn’t go lower than 50 Hz. Modern bandwidths of 30 Hz to 15 kHz didn’t arrive until the mid-Fifties, with magnetic tape, modern LP’s, and FM radio. By then, transformers were used for line level applications in studios, and for output transformers in power amps. This was the all-analog vacuum tube era, of course.

Interstage transformers are a very special use case. We are reviving a 1920’s and 1930’s technology to modern high-bandwidth applications, but there are still limitations, mostly the result of using high impedances. I did use what I call "Interstage 1" in the Karna amplifier, but that was really putting the transformer right to the edge of what can be done. Adding phase splitting to its task list means I will likely see phase spread at the top of the band due stray capacitances not matching between sets of windings. This is a solved problem for studio line-level transformers, but asking interstage transformers to do this results in a not-very-good interstage transformer.

And frankly, for what benefit? It isn’t like a SE input tube is all that awesome. In phono preamps, sure, SE circuits make things easier, what with RIAA compensation combined with noise considerations. But for the input stage of a power amplifier? Where’s the benefit, except for tradition?

So I restrict phase splitting to the easiest location, the input, where it isn’t doing much else. This is proven studio technology that’s been around since the 1930’s, and well-refined by the 1950’s. The interstage, a far more difficult task, is confined to the driver/output interface, and is fully balanced on both ends.

Yes, there are interstage transformers on the market that are SE to PP. I would not use them. It is very difficult to get HF symmetry on the secondaries, but modern transformer designers can do a lot that wasn’t possible even ten years ago. I wouldn’t be surprised to see a 300B SET driver interfaced to PP 300B outputs through such a transformer. I won’t be the one designing it, though.

A power amp with three 300B’s would have a certain visual appeal, and you could weave a fun story around it to match the visuals. At the hifi shows, you could hang pictures of famous trimotor airplanes, like the Ford Trimotor.

@lynn_olson 

How about using SE as opposed to PP in the first stage and a SE to PP interstage transformer between the first and second stage? 

@whitestix 

I am very happy for you. What you wrote expresses genuine joy and satisfaction listening to music. Isn’t this the ultimate objective? You are fortunate to have received this early opportunity. I know you are very grateful.👍

It’s been so much fun and interesting reading about the development of this new 300b push-pull amplifier and what it took to get here.

Charles

Since rolling out of bed in the morning, your amps have been filling my room with amazing sounds, and I appreciate greatly the design thought that went into them, the technical derivations of which is way over my head.

The amps, now with the excellent new Linlai WE300b tubes also run in, create a sheer wall of sound, effortless in its presentation, heft in the LF, delicate highs, and a mid-range to that sounds exactly right.   Even compared to Don's excellent Kootenai KT88, these monos are in a whole different realm.  The sound with my Spatial Audio speakers just hangs effortlessly the room.  

This thread, with both the participation both you and Don, has been most informative, and I am an early beneficiary of your design which as been to elevate my listening enjoyment to degree to a level that I never anticipated possible.  With your monos, there is no amp at all... just joyous music, heard in a way I never thought possible with no sonic signature at all... just pure clean vivid sounds.  Perhaps that ought be the design goal for all... create front end gear that sounds like nothing at all...  You gents have succeeded in that respect.