I have been an owner of Don Sachs gear since he began, and he modified all my HK Citation gear before he came out with his own creations. I bought a Willsenton 300b integrated amp and was smitten with the sound of it, inexpensive as it is. Don told me that he was designing a 300b amp with the legendary Lynn Olson and lo and behold, I got one of his early pair of pre-production mono-blocks recently, driving Spatial Audio M5 Triode Masters.
Now with a week on the amp, I am eager to say that these 300b amps are simply sensational, creating a sound that brings the musicians right into my listening room with a palpable presence. They create the most open vidid presentation to the music -- they are neither warm nor cool, just uncannily true to the source of the music. They replace his excellent Kootai KT88 which I was dubious about being bettered by anything, but these amps are just outstanding. Don is nearing production of a successor to his highly regard DS2 preamp, which also will have a unique circuitry to mate with his 300b monos via XLR connections. Don explained the sonic benefits of this design and it went over my head, but clearly these designs are well though out.. my ears confirm it.
I have been an audiophile for nearly 50 years having had a boatload of electronics during that time, but I personally have never heard such a realistic presentation to my music as I am hearing with these 300b monos in my system. 300b tubes lend themselves to realistic music reproduction as my Willsenton 300b integrated amps informed me, but Don's 300b amps are in a entirely different realm. Of course, 300b amps favor efficient speakers so carefully component matching is paramount.
Don is working out a business arrangement to have his electronics built by an American audio firm so they will soon be more widely available to the public. Don will be attending the Seattle Audio Show in June in the Spatial Audio room where the speakers will be driven by his 300b monos and his preamp, with digital conversion with the outstanding Lampizator Pacific tube DAC. I will be there to hear what I expect to be an outstanding sonic presentation.
To allay any questions about the cost of Don's 300b mono, I do not have an answer.
I should mention SE tuning is not the same as balanced-amp tuning. The dominant coloration with SE are the tubes themselves, and it requires artful selection to avoid heavy additive coloration. The fad for 2-stage SET amps makes this worse, since high-transconductance tubes are not designed for audio, and distortion can be all over the place using tubes designed for RF use. Selecting designed-for-audio tubes in a 3-stage amp makes things simpler and more manageable.
Unfortunately, common design practice in Golden Age push-pull pentode amps is not helpful in designing a balanced non-feedback amp. All of the 1950’s and 1960’s Golden Age amplifiers use feedback as a required part of the design, and the "balanced" part of the circuit (the output section) is typically running in Class AB. You have to reach back to the 1930’s to find useful non-feedback Class A designs.
Once pentodes and beam tetrodes took over, feedback came along with them, and that changed the overall emphasis of the contemporary designs. The search back then was for more power, more efficiency with B+ supplies of 500 volts or less, low measured distortion, and cost and weight reduction.
That search reached an end when high-powered transistor amps replaced tube amps around 1966~1968. Transistors dominated the broad consumer market with the exception of guitar amps, which kept the tube factories going. The decades-long Japanese fascination with triodes finally came West in the early Nineties, where it created a niche market in the high-end sector. (Helped along by Joe Robert’s "Sound Practices" magazine.)
It really helps that tubes are now so popular in the true high-end sector of the market. Transistors ruled the market in the Seventies and Eighties (with the exception of Japan), and the Nineties were an era of transition and growing acceptance of tube electronics. The home theater and 500-watt crowd are still all-transistor because they need the efficiency, and Class D will give them even more efficiency.
In my SET amplifier is IT coupling between driver and 300b and RC between an input and a driver stages.
I think I understand why the tone issue appeared. I played with driver tube B+ voltage and current. The cathode resistors 680 Ohms weren’t changed. The driver is 6f6 in triod mode. In begging, the idle current was 20mA. Then I increase it to 23mA and then to 26mA. So, in the middle setting 23mA, the sound character was faster and rough with flatter musical instruments tone. With 20 and 26mA, the amplifier sounds more like SET, the tone is more reach, and speed is more realistic and natural.
Has anyone that is using Linlai E-6SN7 tubes in 300B amps found them to be noisy? Kind of like a ground hum but not very loud. The system was quiet with the previous RCA VT231 tubes. Sorry if I'm off topic a little. They were favorably mentioned here so I gave them a try. Thanks.
I am pretty much the last guy on the thread to answer your question as "DC heaters" is one of a million design criteria that Don, Lynn, and Ralph understand very well and I think one of them will deign to respond to your question. I think the dead silence of Don/Lynn's amp is a function of a variety of factors... best I can put it.
The preamp and amps use regulated DC filament supplies in all positions
I know there are some DHT amplifier (Particularly with regard to SET) purists who insist that AC heating is sonically superior to DC heating.I have to say though that some of the very best DHT amplifiers I have heard utilize DC heating.
No doubt that either can work fine with excellent implementation.
@charles1dad Well, let's just say I have experimented and know which I prefer:) The 300b amps have a dedicated 5V regulated DC supply for each 300b tube and a 6.3V DC regulated supply for the drivers and input tube. The preamp has a 6.3 V regulated DC supply for the pair of 6SN7 tubes. I value blackness between notes:)
I learn much when reading the rationale of opposing positions. AC versus DC filament heating is one of the classic topics when discussing tube amplifier circuits .
As DIY I can adjust my amplifier to my own taste preference. But compared to experienced Hi-End equipment designers I have less time, money, experience and knowledge. My BCs in Electronic Engineering helps me a little bit. I do digital ASIC design for my living that is far away from analogue electronics.
Regulated high voltage supplies are also a very hot button issue. I know what I prefer from having built the same circuit with multiple power supply topologies and critically listened to each. The way I do it costs more money and certainly has to be worked out so that it is very reliable, but once you get to that point.... As I said, I value absolute blackness between notes and very fast transient response delivered by supplies that are grossly over rated for what they have to deliver. Other people value other things..... to each their own path.
@alexberger Hi. I just tried schottky diodes maybe 5 or 6 years ago and I liked the sound. They have a fast recovery time. They also have very low voltage drop so are good for small filament supplies, but the main reason is the fast recovery. I didn't hear any difference compared to the super high priced hexfreds or other types in the sort of supply I build. The automotive schottky diodes are not expensive and they are available in voltage and current ratings that far exceed requirements of the circuits I am building so there is plenty of headroom, and you can get to-220 versions that fit everywhere. So basically, they work well, sound really good, and are readily available.
For DHTs such as 300B, AC at main frequency is hard to be hum free. But some have tried AC at a high frequency well above human hearing limit with decent result. Sadly this is mostly in DIY world, hence very few commercial offerings with high frequency AC DHT filament supply.
I don’t think DC, IF well done, is any inferior to AC in DHT though. But there are many ways to get DC done. So it gets down to implementation at the end.
I don’t think DC, IF well done, is any inferior to AC in DHT though. But there are many ways to get DC done. So it gets down to implementation at the end.
The commercially available 300b amplifiers seem to bear this out. By a wide margin they are DC heated rather than AC heated. AC is utilized by the DIY crowd more (Relatively speaking) than commercial manufacturers.
There are a lot of little tricks to DC filament supplies that make them sound better too. It isn't rocket science, but you can get a bit more performance and noise rejection by connecting them properly:)
I wouldn't try mixing and matching Ralph's approach with ours. Ralph has his way of doing things, and his own unique taste in sonics, and we have ours. Most designers in this biz have a distinct "house sound" that they aim for, which results from design approaches and parts selection.
FWIW Dept.: We've never had a house sound nor 'voiced' our circuits.
My comments thus far have simply been based in sound engineering practice. Engineering after all made audio products possible, has kept airplanes in the air and provided reliable power when you want light in your house.
It will always work to apply sound engineering practice to circuit design, plain and simple.
We all apply sound engineering practice. We overbuild all power supplies and over spec all parts. But there are choices that affect the sound. If you need a 1 watt 1K resistor you can use any type on a cathode, but different types have different sounds. The cathode bypass cap might need to be 100 uF. Different 100 uF caps sound very different. All will satisfy engineering standards, but parts and layout choices have profound effect on the final sound. We make these choices to achieve the sound we desire. There might be 2 or 3 different tube types that would be appropriate for a place in a design, but can have very different sounds. I can build an amp with entirely different parts and wire and have it be exactly the same from an engineering standpoint, but have a very different sonic presentation. I believe that is what Lynn is alluding to.
I can build an amp with entirely different parts and wire and have it be exactly the same from an engineering standpoint, but have a very different sonic presentation. I believe that is what Lynn is alluding to.
Exactly my take away from Lynn. Most of the builders of Japanese tube amplifiers are degreed electrical engiineers from their native universities. European educated electrical engineers with Nagra, Gryphon, CH Precision etc. No question that although their products are at opposite ends of the audio spectrum, they all adhere and practice engineering principles they were taught.
You can certainly follow sound engineering practices and yet have vastly different sounding audio products. I’m sure that Porsche and Ferrari are built adhering to engineering principles and yet drive/feel very differently. A product’s performance can be tailored to achieve a desired goal.
Although I don’t enjoy "tuning", it is an unpleasant necessity for speakers and power amps. For reasons that are not clear, various brands of metallized polypropylene capacitors sound quite different from each other, and there is little correlation with DA and DF parameters. Based on measurements, they should all sound the same.
On a system with moderately high resolution, subjective differences appear that can mimic crossover balance shifts and driver swaps. I found during development of the Ariel, back in 1993, that cap substitutions required 0.5 to 1 dB crossover adjustments to subjectively offset the colorations ... and this was with pink-noise test stimulus, not music.
You can really get into the swamp comparing silver vs copper wire. This should not be audible at all, and I have heard of no convincing argument why any differences are audible. You can go out on a limb and compare silver oxide vs copper oxide, and various weird sources of corrosion, but it’s all very speculative, and again, no useful measurements to be had.
On the other side of the objective/subjective fence, I have heard of well-known speaker designers who never audition their new speakers ... they do it all by numbers, then walk away. I frankly didn’t believe it when I first heard that about fifteen years ago, but other folks confirmed it, so I guess it happens. So it is possible to ignore "tuning" and let the product sound like whatever.
But in the speaker world, it is widely recognized that a "perfect" zero-coloration speaker is impossible at the current state of the art, so it comes down to choosing which set of parameters are most important. Speakers are still very imperfect, compared to any other audio component.
In principle, it should be possible to design and build a zero-coloration amplifier. I started my career in audio design in 1973, and haven’t heard a "perfect" amplifier yet. They all have a sound, and a little bit worse, topologies tend to have distinctive sounds. But that’s my personal experience, not necessarily the experience of others.
If a customer, or reviewer, is in the fortunate position of finding that all well-engineered amps sound alike, that’s great! You can sure save a bunch of money, skip over tubes entirely, and just buy the latest Shenzen-made confection for a few hundred dollars.
Let’s talk technical about DHT filament power supplies. My friend John Atwood built a low-RF filament supply a few years back (100 kHz or so), but he made the discovery that the filament inductance of DHT tubes was all over the place, making it difficult to assess how much power was actually going into the filament. This is a big deal because DHT tubes require very tight control of filament power, preferably 5% of specification, or better. In practice, the RF supply had to be individually tuned for each tube ... and it didn’t sound any better.
An aspect of even very clean sinewave AC heating are "hum sidebands" ... not hum per se, but IM distortion harmonics that are displaced by 100/120 Hz on each side of the fundamental and about 60 dB down. It is clearly visible on a good spectrum analyzer, and is caused by small temperature fluctuations on the filament modulating emission, which in turn modulates the forward gain of the tube ... not much, but it is measurable. (The discovery of hum sidebands led to the experiments with RF heating.)
An aspect of DC heating is where the virtual center-tap appears. If the virtual center-tap is in the middle of the filament, the inherent balance of the filament can give a free bonus of 30 dB or more of additional noise rejection. Considering how difficult an additional 10 dB of noise rejection can be, 30 dB is not to be sneered at. And the whole DC supply has to float, relative to ground, while appearing symmetric from the viewpoint of the filament (mimicking an AC supply in that respect).
But there are choices that affect the sound. If you need a 1 watt 1K resistor you can use any type on a cathode, but different types have different sounds. The cathode bypass cap might need to be 100 uF. Different 100 uF caps sound very different. All will satisfy engineering standards, but parts and layout choices have profound effect on the final sound.
When you run zero feedback, the circuit has no ability to reject things like this. So everything makes a difference. However, for something like an electrolytic bypass, I think you'll find that as long as the part is good quality, the big differences you hear will be more about the part forming up over time: they will arrive at the same place sooner or later.
For reasons that are not clear, various brands of metallized polypropylene capacitors sound quite different from each other, and there is little correlation with DA and DF parameters. Based on measurements, they should all sound the same.
Sometimes you have to do your own measurements because the specs of the manufacturer don't always tell the whole story. If you use a precision differential amplifier to drive the caps in question, you can measure how they behave and differ from one another while in circuit.
@atmasphere First off, this thread was started by a fellow who has a rough first prototype of a zero feedback push pull 300b amp, so of course we are discussing that. I agree that in that circuit you hear everything. I will tell you that even in circuits with feedback I will not use electrolytic caps in the signal path. I also do not use them in my power supplies, but only in the filament supplies. In my experience electrolytic caps make circuits sound grey and hazy compared to a very top quality film cap. You can wait forever for a lytic to run in, you can bypass it with small film caps, and whatever else. When I replace them with a very good film cap I hear the difference. To each their own. I also hear differences between resistor types in key spots in circuits, whether the circuit has feedback or not. Again, my experience, so I build amps with the parts types that I favor.
As I read the last few posts, it seems like objective approaches contain a subjective element (the proverbial yin-yang). Designers can perform the same experiment and draw different conclusions based on what they hear or don't hear. Perhaps the ultimate audiophile is the guy who designs his own gear and seasons to taste. :)
Well, Hawkrising, your last sentence might be correct but I studied Economics, not electronics, so I rely on excellent designers and fabricators like Don and Lynn for my front end gear and, in exchange, I compensate them for their efforts.
Aspirationally, the ultimate audiophile could take a stab at recreating the something akin the stellar Lampizator DAC's, like the $20K Lampi DAC in the Spatial room in Seattle which was the source for the music they presented. Totally stunning sound, but likely far beyond the skills of most audiophiles. I am not sure even Don or Lynn want to tackle building a DAC.
Don/Lynn vs. Ralph seem to have somewhat different notions of how these tube amps might be best designed and fabricated, which reflects different design criteria. That's cool. Lots of designers have different design philosophies... probably all of them. I haven't heard Ralph's 300b amps which might at some point be an interesting comparison to my 300b amps. ;-)
Don sent me his pre-pro 300b amps a few months ago which I have been using to power my very efficient Cube Audio Jazzon speakers and the sound is simply ethereal, like nothing I have every heard in my 50 years of audiophilia... a remarkable improvement even in comparison to Don's KT88 amp, which is outstanding, a legacy amp for sure, and the 300b mono's are better in every way. The musical notes simply hang in the air, suspended in the room in front on my listening seat. Matching of speakers is required for the 300b monos, but I drove some 86 db efficient standmount speakers with alacrity... my ears gave out long before the 300b amps did, with not a hint of distortion so as Don says, the 27 wpc amps rather sound like a 100 wpc SS amp. That is what my ears tell me so the amps will drive a wide variety of speakers that many other 300b amps simply will not.
If you have followed this thread, Don and Lynn have made significant enhancements to the performance of the pre-pro mono's I have, yet I just can't imagine how much better the SQ will be after Don gets them back and updates them to the final production version. However, I have no doubt that I will have one of the finest 300b amps possible at any price so always with Don, it is "promises made and promises honored."
The final point I'd like to make is that Lynn envisioned this employment of 300b tubes in an earlier iteration of it and he and Don put their collective wisdom together to update the design with these new mono's. Just as with fleawatt 2A3 power tubes, the 300b power tubes have a sonic signature, to my way of thinking and to my aging ears, are unlike any other tubes in power amps and I have had many of them over the years. Once you have heard them, you can't unhear them... so long as they are matched properly with compatible speakers which in fact will include a lot of speakers that many other 300b amps will not drive properly . Cheers.
If you have followed this thread, Don and Lynn have made significant enhancements to the performance of the pre-pro mono's I have, yet I just can't imagine how much better the SQ will be after Don gets them back and updates them to the final production version
I eagerly await your listening impressions of the updated mono blocks. You certainly have terrific speakers to judge what you hear.
Once and alway, no participant on this forum has more erudite and encouraging responses to all things audio related than you. Charles, thanks as always for your upbeat posts, alway a pleasure to read. Mark
My first experience of a 300B amplifier was back when I was writing reviews for Positive Feedback magazine back in 1993. It had grown from a 4-page mimeographed club magazine for the Oregon Triode Society to a fat 100-page periodical with cartoons, editorials, and a staff of reviewers.
I was one of them, after submitting a series of construction articles for the Ariel twin transmission line loudspeaker. I was listening to a whole string of amplifiers when David Robinson, the magazine editor, dropped off not just the Audio Note Ongaku (which cost three times the price of my car) and the Reichert Silver 300B’s. So now I’m in the reviewing business, too. Oh well, not one to look a gift horse in the mouth, away I go, with a month’s free use of entirely new amplifiers on my brand-new speakers.
Which was quite a revelation. When you design a speaker, and you’ve been doing it for decades, you get to know them pretty well. What they can and can’t do, and what the overall character of the speaker sounds like. Nothing new to me, and the Ariel was my eighth speaker design, after my time at Audionics during the Seventies.
One of the last stages of a near-commercial design is auditioning the speaker on many different amplifiers, keeping in mind the impact of output impedance (damping factor) on the bass alignment and the crossover. The Ariels are designed to have low sensitivity to output impedance: transmission line bass with no impedance peaks, low-Q 2nd-order crossovers, very flat drivers that don’t need equalization, and a tweeter that is running flat out, with no attenuation, since the paired midbass drivers have matching sensitivity. So all amplifiers see an equal playing field, with a minimum of power disappearing in resistors.
The shock with both DHT amplifiers was a radically different sound than Class A transistor, Class AB transistor (with high slew rate), and push-pull pentode. Much higher transparency and much more vivid tone color ... out of a speaker that I knew very well, and was my own brainchild. This is what led me to design my own DHT amplifier, but not following the path of either the 211-based Ongaku or the Reichert Silver 300B. But definitely using the 300B for sure; no 2A3 came close, and 211’s and 845’s (with plates running at 1 kV) are extremely difficult to use.
Don has brought me up to speed on modern power supply design, things I didn’t know about in 2003, when the Karna was designed. That takes the Karna to a new level, and reduced it from a ridiculous four chassis setup with high-voltage Amphenol connectors to a much more sensible pair of monoblock chassis. One pleasure of working with Don is he will chase down every possible variant, build it, audition it, and let me know how it measures and compares to all the rest. Fortunately, we have gone full circle and have arrived at a Karna Mark II with far superior transformers and power supplies.
Yes, we are pretty much back to an updated Karna circuit with more modern power supply topology, and custom wound iron everywhere. I listened to every possible variant of the circuit and it is obvious that removing all coupling caps and going with all transformer coupling walks all over any other variant in pretty much every way. We are now using custom wound Monolith Magnetics iron for power and output transformers, and Cinemag interstage transformers. The chassis is much wider than the shoebox amps displayed at the Pacific Audio Fest in Seattle. Spatial will change the look slightly, but the layout and size will be the same. There are reasons for the layout, which makes for very short signal path at all sections and also has complete isolation of the power supply from the signal part of the amp. They are just about ready to build in quantity and I would expect them to be available in November or December if all the vendors meet their production schedules for parts. I will say that I cannot listen to anything else now. I am spoiled..... everything else sounds dull and coloured to me now and I have pretty much cleared my house of all other amps and preamps. We shall see what others think!
I cannot seem to post a photo of the final prototype, but will upload to my old website and see if I can post a link to that photo eventually.
This thread, with over 500 posts I think, has allowed interested people to understand the evolution of their 300b amps design compared to other designs. A rare insight into the machinations of amplifier design, which to be honest Roger Modjeski from RAM was stellar at doing as well. Lynn astounded me with an earlier post that some designers, maybe it was with speakers, design to specs and that's it. What Don and Lynn have done is an endless process of swapping not only components, but topologies, a very interactive process, subject to both measurements and equally or more important, endless comparative listening observations. This to me is the optimum process to design gear and the process has to be exhaustive, but both Don and Lynn have done this for decades... this iterative process. And, to wit, they have shared their excursion on this thread in masterful detail to inform all of us.
My pre-pro 300b amps are a glimpse of heaven with my Cube Audio speakers and it is hard to imagine how much better they will sound when Don updates them to the final version, but I am certain his promises will be fulfilled.
I managed to update my ancient website with the beginnings of 300b project page. There is a photo of the final prototype of the Blackbird 300b monoblock amp at the bottom of this page. Spatial will change the look a bit, but dimensions and layout will be the same. The amps are optimized for sonics and short signal path.
This is very close to the production version. It is simpler and more straightforward to build than the shoebox format shown at the PAF show ... more spacious, more direct layout, and the power supplies are confined to their own section of the amp, on the right side of the chassis. The vent holes for the twin B+ regulators are visible on the right side of the amp, next to the VR tubes.
The audio-only circuit is on the left side, with very short signal paths from 6SN7 -> interstage 1 -> matched balanced 6V6 -> interstage 2 -> matched balanced 300B -> Monolith output transformer -> speaker jacks. The input selector switch bypasses the input transformer when XLR is selected. Compared to the show amps, there are actually fewer parts in the production version, with a very simple signal path from input to output. From input to output, there are only wires, transformers, and triodes, in a fully balanced circuit. No coupling caps, no plate-load resistors, no plate inductors, and no dynamic loads.
One subtle difference is each single grid is driven by a pair of balanced plates, so distortion and noise are minimized in every stage of the amplifier. In the show amps, each 6V6 grid was driven by the corresponding 6SN7 plate. In the production amp shown here, each 6V6 grid is driven by a balanced pair of 6SN7 plates, thanks to interstage 1. I was doubtful a good interstage could be made for the 6SN7, but our transformer designer came through with performance from 18 Hz to 32 kHz. Close collaboration with modern transformer design is what made this possible.
Don did a marvelous job here. It’s actually quite functional, with a clean and direct front-to-back signal path, and with all wires in the balanced circuit equal length (yes, he went to that much trouble). You can infer that from the top plate.
The power supply side is equally tidy, with two independent B+ regulators, one in front of the other, and the three low-voltage regulators on the other side of the power supply section, all supplied by the custom Monolith power transformer. The soft-start circuit in the back of the amp keeps incoming AC power away from the front-panel power switch, as well as protecting the tubes and regulators from AC line transients.
The amp is considerably simpler to build, because signal flow is obvious, and color-coded wiring is used to keep track of polarity. It is also the same 18"/457mm width as the matching Raven preamp.
I really like Thomas Mayer's 300B amplifiers, but I don't have deep enough pockets for that. You two seem to be on the right track with your 300B, and it's more affordable than his.
@alexberger Spatial Audio Lab will be in charge of presentation at shows. I know we are returning to the Pacific Audio Fest in Seattle again next summer. Beyond that I don't know. We are focusing on getting the preamp and amps into production by year end. They are also finishing work on their Q series speaker. A prototype of that was shown in Seattle and they expect to release that by the end of the year. So lots going on. Spring shows may be a bit soon. Given they are in Salt Lake City, I suspect they will focus on American shows though, so probably not Montreal. You never know though:)
I have long admired Thomas Mayer audio products (Particularly his power amplifiers). Given what I have learned regarding the Blackbird 300b PSET mono block amplifiers it’d be most interesting and informative to hear a comparison. Two very different approaches. I have no doubt that both are genuinely sublime products.
@charles1dad when Thomas Mayer first started building tube amps for his personal use, he built them for 3 phase power. He also loves vinyl, even though his regular job was digital electronics.
Thomas Mayer builds seriously good amplifiers:) I have his octal phono circuit saved, and one day I will build myself another phono preamp with my power supply and his signal circuit. I bet it will sound very good. His tube blog is wonderful.
I met Thomas Meyer at the 2004 European Triode Festival (I was the invited keynote speaker). He’s a lot of fun, and super knowledgeable about tube history. He, too, is a transformer enthusiast, particularly with modern transformers.
I’m super happy that he made the transition from hard-core hobbyist to the ultra-high-end commercial world. He’s set an example for all of us. It helps that Europe has a fine tradition of artisan-built audio, with wealthy patrons who appreciate the arts.
When I was Switzerland as the guest of Christian Rintelen (host of the 2004 ETF), I visited the museum in Zurich, and astonished to see wooden clocks that were a thousand years old ... and still in working order. The traditions of technology in Switzerland and Germany are ancient, and a deep part of the culture.
I met Thomas Meyer at the 2004 European Triode Festival (I was the invited keynote speaker). He’s a lot of fun, and super knowledgeable about tube history. He, too, is a transformer enthusiast, particularly with modern transformers
Spot on! Definitely transformers in addition to tubes. I’ve learned much reading his site over the years. I bet that he’d admire the Blackbird amplifier effort and result.
Charles, I am not sure what Meyer would think of the Blackbird! There are some elements of it that are aligned with his thinking and others that are radically different. I would be interested to hear some amp of similar power that he has built in the same system as the Blackbirds. It would be fun:) As I said above, Thomas Meyer builds SERIOUSLY good amps. The man has his own tube factory! I would love to try a quad of his 300b tubes, but they cost serious money. Maybe one day.... I bet they are really good though.
Yes, I would not mind a matched quad of Elrog 300B's with their thoriated-tungsten filaments. That would be something quite wonderful. The Mark I Karna's thrived on a matched quad of Emission Labs 320B-XLS, but that was also a serious investment. The European super tubes are something else.
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