There is SET design trade off - coupling capacitors vs interstage transformers.
Most people tell that transformers are the best solution. But modern capacitors like Vcup, Duelund, Jupiter are better that were available 20 years ago. Technically capacitors give wider bandwidth but transformer put the same driver tube in more linear mode with less distortions.
The question is what do you prefer?
The 300B World
Disclosure: I am not new to Aric Audio, but I am new to the 300B.
I took delivery of my Aric Audio 300B PSET a couple of months ago. Since then, every listening hour has been different than it would have been were I new to both. I want to know who is responsible for what I'm hearing. So, the overriding question every observation is passed through is simply "Was that the 300B or was that the 'Aric Audio Heft'?" Over the years I have purchased a number of different amps and preamps from Aric and have come to identify certain characteristics that can be expected from all of his builds. That's why I keep going back. Examples include the "dead black" background, the solid signal strength delivered by his preamps, the ease with which the soundstage can be mapped, and the raw power resulting from the overbuilt approach he takes in his design work: "The Aric Audio Heft." Knowing what I would get from any Aric Audio amp is instrumental in being able to appreciate the magic of the "show off tube."
I've heard it said that people who go to the 300B never really come back and I've been intrigued by that ever since. It invites critical listening across the broadest spectrum of music one can tolerate. It's here that observations are bagged and tagged, the first being the kind of music I listen to matters much less because I find myself listening differently and hearing so much more. One of my favorites is the leading edge of the lower frequencies and the way every beat reminds me that I'm listening to a 300B. The way I would characterize the sound profile would be to say it's as if the veil has finally been lifted and the distance between the performance and my listening chair closed. You know it immediately even if you can't quite define it yet and it commands your attention.
For some reason I'm surprised by how closely the tonal qualities of SET and PSET modes align. Somehow, I thought there would be more of a "sonic cost" for that extra power. I'm still cautious here though because the quad of tubes I'm using for PSET mode are not topflight tubes. So, the final analysis will have to wait until I can level the playing field. In SET mode I'm listening to a pair of Gold Lions, which I consider to be at least among the heavyweights. The question I'm presently grappling with is which tubes come next? I've done my due diligence researching the various offerings and think it will be a quad of Emission Labs XLS 300Bs. Any input around your experience with 300B tubes I would welcome. Yes, I have my wish list that starts with the Western Electrics (which I'm sure I'll own one day) but the guidance I'm seeking here is the step between now and then. What would be a suitable tube to take an already remarkable experience to a whole new level? Conversely, are there tubes that I should simply stay away from? My thanks to all. Happy listening.
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That is an intriguing question/choice. In the context of this question, if I had to put highest priority on only one, I believe I would choose the interstage transformer. I find it technical advantages more compelling. I suppose that another option to consider is direct coupled. No doubt, like everything else it probably has its pluses and compromises as well. Implementation reigns supreme. Charles |
This statement is incorrect. You can operate any tube using coupling capacitors just as linearly as using an interstage transformer. OTOH the trick with transformer coupling is making sure that the input and output impedances match the transformer properly to maximize bandwidth and yet prevent distortion due to the process of what is known as 'ringing' (which is when the output has an insufficient load). @charles1dad The issue with direct-coupling (Loftin-White) is that you can have signals that are below the LF bandwidth of the output transformer; this can cause saturation (distortion) of the transformer. You also need higher operating voltages to pull this off. If you choose your coupling caps carefully, you can reduce the LF saturation problem and of course the power supply voltage does not have to be so high. |
This is an astute observation. It has been my contention for quite some time that those with thorough engineering and science backgrounds are open minded and do not dismiss what listeners say they hear. Of course engineers and scientists use and rely heavily upon measurements. Yet they willingly concede measurements can’t (Yet) account for all that humans detect while listening.
It seems to me that those who have a lesser level of formal technical education/training are the self declared “objectivists “ who cling so tightly to only what can be test bench measured. Thus a narrow and rigid manner with regard to audio issues. To assert that anything that can’t be proven by current measurements standards is simply expectation bias is lame and foolish. With human beings it seems that the more you actually know, you then are more aware of what you don’t know. This realization keeps one humble and enriches further curiosity and exploration. This is the antithesis of the know it all arrogance of the staunch objectivist. Charles |
@charles1dad back in the 1980s the bit in your last sentence was true. But since the newer analyzer tools have become available, no longer. I’ve noticed though that such has little impact since people doing measurements often don’t do enough or the right ones; manufacturers don’t always publish them and finally, there’s not enough education in the field to be able to interpret what the measurements imply. But if the stars align then you can accurately predict how a circuit will sound, based entirely on the measurements.
To the first sentence, I’ve not found that to be the case, although with any kind of inductive coupling good iron is essential! Choke coupling is mostly an excuse to use an expensive inductor when a good resistor will do as well with wider bandwidth. Put another way, if more time was spent optimizing the operating point of the tube and less on fancy inductors that wind up (if you see what I did there) being mostly for show and tell, the circuit would exhibit the same positive attributes. Any circuit that is zero feedback will be affected by nearly everything in it since there is nothing to reject distortion, phase shift and the like. To this end, to avoid phase shift you need really wide bandwidth. To avoid distortion, you need good quality parts, each part of the circuit optimized for the operating point of the active device (since this issue applies to solid state circuits with zero feedback as well) and proper layout to avoid stability problems and noise pickup. |
@calloway. I’ve been sitting on the fence for a while about the WE tubes.I’m also using the ACME matched top shelf 300B and 805’s in my Line Magnetic LM805ia. I’ve been reading about these WE 300B tubes for a long time. In your opinion: Is the ACME to WE tube upgrade worth the $cost? Was it a: "I should have done this a long time ago" or "Meh, they're a little better than the ACME's"?
calloway867 posts
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@charles1dad …”This is an astute observation. It has been my contention for quite some time that those with thorough engineering and science backgrounds are open minded and do not dismiss what listeners say they hear…”.
+1 to your post. Having been a scientist, engineer, and IT executive through my career I have so many times and so quickly broken through the fully described and understood world of science and engineering it amazed me. It is not the big stuff… like dropping a 2,000 pound object. It is important as soon as nuances are important. High end audio, a great example. Hearing is an amazing facility, particularly when a trained ear is involved. |
300b needs carefully matched loudspeakers. Otherwise, it's pushed into higher distortion you want to surf the 1st few watts. Most SET users don't use SET-friendly speaker systems. I have a few 300b amps now. They do best with front horns or full-range drivers that are horn-loaded. The speaker pictured is using a 300b amplifier. |
+1 If you really plan to use a 300b amplifier this is the best advice you can have. |
@atmasphere Stereophile recently reviewed Klipsch La Scalas and measured B-weighted sensitivity of 101/2.83V/m. The impedance dropped briefly to 4 ohms at 70 Hz, 335 Hz, and at length above 10k Hz. Would a 300B amp be capable of driving these speakers? |
I understand your sentiment. Speaker manufacturers recognize that they have to adhere to the demands and needs of current and future customers. Moderate and high power solid state amplifiers are vastly more common and popular than low power tube amplifiers. My 300b SET is simply ideal /splendid for my sonic objectives. I do acknowledge that I occupy a very small niche of the high end audio market. Charles |
Hi @charles1dad , You are right. Small companies still produce SET friendly speakers. On Montreal Audio Show I saw Coherent Audio speakers that use Radian 18" coaxial drivers. They worked very good with 300B integrated SET. They also sound much more alive compared to modern speakers designed for transistor amplifiers.
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Interesting that you reference Coherent Audio speakers (Made in Ontario, Canada). I became aware of them probably four or five years ago. Although I have never heard them, word of mouth with regard to them is consistently excellent praise and feedback. I have mentioned them several times in threads on this forum for people interested in SET friendly speakers. I am glad you had an opportunity to hear them directly. My gut feeling tells me they are terrific sounding speakers. High sensitivity and high/benign speaker impedance load design. |
@tomcy6 Yes. I recommend the 8 Ohm tap. You'll need a sub to be convincing (IMO) since the speaker rolls off sharply below 50Hz.
Nothing, other than it was one of the first power tubes used for SETs when they made a comeback in the early 1990s (back then it it was them or the 211...). By the late 1990s, the 2A3 had eclipsed the 300b, which in turn by the mid 2000s was replaced by the type 45. But there really isn't any difference in the performance/sound of these tubes other than output power. The reason the smaller tubes sound better is the smaller output transformers, usually due to wider bandwidth. In any case you need a speaker with enough efficiency to take advantage of that power. The Klipsch La Scala has a good functional minimum for use with a 300b at 101dB in most rooms. Unless you are in a small listening environment, speakers with less efficiency will cause the amp to make too much power (and distortion) to really appreciate what its about. |
It is strictly a matter of perspective and sonic objectives. I believe that a talented and experienced amplifier designer/builder is capable of producing excellent sound quality with virtually any output tube. It’s immensely subjective as to preference of individual listeners. I’ve heard excellent sound from numerous varieties of tube amplifiers. Yet, for my taste, desires and goals the 300b is a superb choice. This assumes a serious implementation and build effort. If this criteria is met, the sonic and musical production can be genuinely great. Tone, timbre, harmonic overtone preservation, musical flow and pace can all be superbly rendered. It has the capability to provide an exceptionally emotionally involving performance that is all inclusive and immersive. I can only attest to my direct listening experience. This is what the 300b has unfailingly done for me. A magnificent tube to utilize if handled by highly gifted hands. Charles |
I find that there are differences in the sound of 300b, 2a3 and 45 tubes based on hearing many different amps employing these tubes. In particular, I've heard amps built by one builder that employs similar designs using these tubes, including the same output transformers (pushpull amp using vintage transformers). To me, the 2a3 has the clearest, most detailed, sound, and is leaner sounding than the other two. The 300b is lush sounding and has a bump up in the upper bass and lower midrange (which I sort of like), but, it is a touch "mushy" sounding (lacking in clarity) and is dynamically soft and polite compared to the other two. I like the 45 for its tight bass, reasonably warm but still clear sound and decent dynamics. It is sort of the momma bear in the Goldilocks story. All three can sound great and can sort of flip this generalization, depending on the specific implementation. The 300b does offer a bit more power. I own a pushpull 45 amp and a PSET 2a3 amp. In my current setup, my only use of any of these three types is quite whacky--I use two 300b tubes as rectifiers in the power supply of my phono stage. The amp in my system is pushpull and utilizes Western Electric 349 output tubes (If you think 300b's are expensive, try finding even used 349 tubes and see what they cost). |
I think you'll find that the differences you hear have more to do with who designed and built the output transformers than anything else. How well the tube works with the transformer; how well the driver circuit and voltage amplifier circuits work all affect the sound. So it seems unlikely that anyone might be able to describe the sound of the different tubes given those variables! |
The way I view it as well. I have heard all three of these sound tremendously good if implemented correctly. Same with the 211 and 845. All of them are very capable tubes in the right talented hands. It just so happens that for my needs the 300b is sublime. I have high regard for all of these tubes. Depending on the speaker in use, I could be thrilled with anyone of these tubes in an amplifier. Charles |
It might well be the case that it is the difference in transformers, or other design factors, that determine the sound and that the tubes themselves have no particular sound. But, whatever the case, I do think their are rough tendencies that distinguish 300b amps from 2a3 and 45 amps--and it is not just power output. If it were power, it would be hard to explain why I like the 45 tube (and it is not just me). But, all three are capable of delivering good sound and I like both pushpull and SET amps utilizing these tubes. As charles1dad mentioned, there are also 211 and 845 amps that sound good too. |
Not only do tubes have their unique intrinsic sonic signature, you can further delineate by brand/manufacturer. A Western Electric/Elrog/EML/Takasuki 300b all sound a bit different from one another I’ve heard all 4 of them in my amplifier. Then one can achieve further distinctions dependent upon choice accompanied wire/capacitor/transformer/resistors etc. Everything has an influence on the sound. This is why One could have six different 300b amplifiers and they do not sound identical at all (Substitute any other tube of choice). For example, someone such as Thomas Mayer can (Does) offer several variations of an amplifier using the exact same tube. Each version will have its individual sonic signature. Again, exactly the same output tube. Audio equipment /components/parts and and how humans hear and interpret them is fascinating. Charles |
Yes, tube brands differ considerably in sound. Even within a brand, different tubes can have dramatically different sound. I had EML meshplate 2a3s and EML solid plate tubes in my Audio Note Kageki amps (parallel SET monoblocs) and the sound was quite different--the mesh plate tubes had a more diffused sound (huge soundstage and an almost phasey sound) while the solid plates had a "denser" sound. I preferred the meshplate, but, others like the solid plate sound more; hence, one was not universally better than the other, and the sound was clearly different. |
Yep! Same impression as mine when I had both in my amplifier. I was captivated by the EML 300b mesh but truly enjoyed both tube versions. Unfortunately the mesh plate suffered premature failure in my amplifier. The operational points in my amp are too aggressive for the more delicate mesh plate. On the other hand a piece of cake for the very robust solid plate EML XLS 300b. A genuine rugged work horse beyond all doubt. 11 years of heavy frequent usage in my SET mono blocks. In the right 300b amplifier the EML mesh plate is a very intriguing option. Charles |
As I explained earlier, the big challenge of SET OPT design is bandwidth. Its pretty easy to get bandwidth using a 45! Wider bandwidth means less phase shift, so the sound stage is recreated more accurately and there's less coloration at the bandwidth extremes (for example, phase shift in the bass region can rob it of impact, even if the transformer is flat to 20Hz). |