The 300B World

If it were power, it would be hard to explain why I like the 45 tube (and it is not just me). 

@larryi 

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).

@larryi

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

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

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.

@larryi

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

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

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.  

@larryi 

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

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

A large difference in the power output of those SET tubes 45 about 1.5 watts, 2a3 about 2-3 watts, 300b about 8 watts. This you will hear if running high eff loudspeakers but transformers and overall design matter much in SET.  I tend to use 300b but have owned almost all types.

I find that there are differences in the sound of 300b, 2a3 and 45 tubes based on hearing many different amps employing these tubes. 

@larryi 

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!

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).

@emergingsoul

So what makes 300b so special?

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

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?

@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.

So what makes 300b so special?

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.

@alexberger

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.
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.
https://www.coherentspeakers.net/coherent-audio-the-eighteen

@alexberger

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

It is sad, that most of famous producers that made tube and SET friendly speakers in the past like Tannoy (Silver, Red), JBL (model - L200. drivers - LE15, 2234) and now Klipsch build speakers and drivers that designed for transistor amplification and for very high maximal power.

So what makes 300b so special? What are the more noteworthy amplifiers that use this?

@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?

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.

Tango Hashimoto ,monoliths Electroprint. Lundahl each one has its own sonic signature Tango transformers are top shelf big sonically some have lower bass output , master vacuum tube builder ,Radu Tarta has said Monolith is a great European  company and the chokes are also very important .

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.

@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.

@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"?

calloway

867 posts

02-12-2023 at 06:06pm

My SET monoblocks use 300B as the driver tubes. I have used Psvane ACME 300B and the new WE 300 B tubes. the WE tubes are better but you have to let them burn in for about 300 hrs before they reach their best.I use 845 tubes as my output tubes and use Psvane ACME 845s their also

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.

@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.

Even in the case of capacitor coupling, loading the driver tube with a choke instead of a resistor will sound better - more dynamic and immediate sounding. No escape from good irons!

SET amps are simple, yet there are many circuit design and part choices that affect sound.

@atmasphere 

I don't think so- for teh last 65 years audiophiles have been hearing this problem despite the measurement camp touting its all 'expectation bias'; IMO/IME the measurement guys that think this don't have the engineering knowledge to understand why its happening. This in particular with solid state since its inception

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

Technically capacitors give wider bandwidth but transformer put the same driver tube in more linear mode with less distortions.

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. 

@alexberger

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?

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

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? 

I think some tweeters are going to expose that more than others.In my experience higher sensitivity ones like compression drivers seem to be much more fussy about amplifiers than less efficient ones using say soft dome tweeters.Or perhaps they are just masking this rising distortion less?

@jtgofish I don't think so- for teh last 65 years audiophiles have been hearing this problem despite the measurement camp touting its all 'expectation bias'; IMO/IME the measurement guys that think this don't have the engineering knowledge to understand why its happening. This in particular with solid state since its inception.

It really doesn't seem to matter about the tweeter (tweeters with breakups will make it worse).

IME this is why tubes are still in business 65 years on from being declared 'obsolete'.

Fortunately class D is offering a solution; just in time since in the next 10 years tubes will get a lot harder to find.

Thanks for that Ralph.Rising distortion with rising frequency due to decreasing feedback seems to make sense.I think some tweeters are going to expose that more than others.In my experience higher sensitivity ones like compression drivers seem to be much more fussy about amplifiers than less efficient ones using say soft dome tweeters.Or perhaps they are just masking this rising distortion less?

Perhaps the most beautiful and pure treble I have heard came from a zero feedback SET.It was a Kondo Ongaku though.

A typical 300B SET with zero negative feedback. Frequency response .The green line represents a simulated 8 ohm speaker.

@jtgofish FWIW the kind of speaker in the simulation is rarely used with SETs. They are low power and so speakers used with them tend to higher efficiency; also designed to expect a higher output impedance of the amplifier, with no expectation that the amp behave as a voltage source!

Most tube amps with zero feedback will act more like a power source than a voltage source. So the standard ’simulated speaker load’ is irrelevant if the user has his SET set up correctly.

In @charles1dad ’s case, the speaker he is using was designed specifically for tube amps with higher output impedance and no feedback.

For more on this topic see:

The Voltage and Power Paradigms

Since loudspeakers of all types typically have much wider frequency variation than amplifiers, the theory is that the tonality imparted by distortion figures more importantly than tonality induced by FR error. This is because the ear/brain system converts all forms of distortion to tonality and pays more attention to that as a result. SETs produce innocuous distortion so can be fairly neutral in this regard.

The brightness and harshness of traditional solid state is an example of this: you can’t measure it on the bench in terms of FR error, since the brightness is caused by distortion interpreted as a tonality. Its really hard to get away from this problem with amplifiers using feedback, since what usually happens is the the distortion vs frequency starts to rise somewhere near 1KHz due to a lack of Gain Bandwidth Product.

Ideally distortion vs frequency should be a flat line across the audio band, and with any zero feedback amplifier with sufficient bandwidth that’s exactly what you get. Alternatively this can be fairly easily accomplished with a self oscillating class D amplifier, since obtaining super high GBP values is fairly easy with them so feedback is properly supported across the entire audio band. See

The F word

for more information.

When distortion rises with frequency, its because the feedback is decreasing with frequency and so distortion is going up. This usually does not show in THD figures; in effect sweeping this problem under the rug. So the actual distortion at higher frequencies where the ear is more sensitive can be quite a lot higher than the THD values suggest!

So while I’m not an SET fan by any stretch, picking on them due to FR errors due to output impedance is not the way to expose their real problems!

I'm using the Sophia Mesh 300b (2.5V version).  Didn't see them mentioned.  I think they are a great tube and is underpriced compared to the competition.

I think rectifiers are as important at the output tubes.  For a GZ34 designed amp, you can't beat Mullard or Matsushita (same equipment).  I'm currently using a radio shack that sounds excellent.  Probably cost $2.99 new.

Jerry

I definitely agree that NFB amplifiers need appropriate matching speakers. If this is achieved then extraordinary sound quality can be the outcome. NFB adjustment is a very reasonable and useful idea.. It would widen the range of speakers deemed suitable for the amplifier.

In my audio system the 300b SET, 101D preamplifier and 6080 tube DAC are all zero NFB and the combination sounds remarkably emotionally engaging and sonically captivating. For sure the speakers are designed from the ground up to be very compatible with zero feedback amplification.

Charles

Yes you can certainly achieve good sound with a zero negative feedback SET but that will require more than a hint of two wrongs making a right.And some good luck.

Many SS and Class D amps also overdamp rather than underdamp speakers so they produce a dead flat frequency response but also sound dry and flat.

I believe all SETs should be fitted with a variable negative feedback control which will help you to better match them to different speakers.When I owned an Almarro 318B I had it modified to include one of them and it certainly helped .I never liked it with zero negative feedback and the default factory setting had slightly too much for my speakers.

A typical 300B SET with zero negative feedback. Frequency response .The green line represents a simulated 8 ohm speaker.This was a Mastersound but is typical for the breed.Tube selection is unlikely to make much difference.

Technically I understand the point. The last transistor amplifier I owned was a very fine German make called Symphonic Line. To this day I haven’t any doubt that it produces superior FR graphs and probably every test bench measurement one would care to see compared with my 300b SET mono blocks.

Playing field changes to actually listening to music and the 300b amplifier went to where my Symphonic Line couldn’t follow or render. So,of course  it depends on what one is seeking in their audio systems.

Charles
 

A typical 300B SET with zero negative feedback. Frequency response .The green line represents a simulated 8 ohm speaker.This was a Mastersound but is typical for the breed.Tube selection is unlikely to make much difference.

Ralph, the current draw is constant averaged over one cycle of the lowest frequency present. Otherwise the current is rising and falling with the input signal.

This of course is what filter capacitors are for.

If the last capacitor in the power supply is properly sized the power supply voltage should stay constant even in the presents of changing current draw on the power supply.
 

Actually if the design is competent, this can also be said of the filter capacitor at the output of the filter choke, assuming a capacitor input supply.

Properly designed power supply + well chosen operating point will lead to much less sensitivity to the choice of rectifier tube in SET. The flip side is such design often needs a lot of space: multiple chokes with decent inductance each as opposed to just one choke used in many one box amp designs.

I am using a Raytheon Ceramic base  274b in my amp.   I also have some Ken Rad circa 1945 5r4gy that are great .

late to the thread, I see the topic has turned to rectifiers.  I find the rectifier to be almost as important as the output tubes (and don't forget the input/drivers).

There are a lot of interchangeable rectifiers and I'm an ardent tube roller, but when it comes to rectifiers, I always end up back witht the tube that the amp was designed for (maybe a much better one, but the same tube). 

Jerry

274B is commonly used with 300B SET amps.

For 300B tubes I like PSVANE 300B-T Mark II. Best tube in its price range. Not a fan of the silver coating but It supposedly makes the tube sound better.

Best transformers I have heard in a production amp are from Icon Audio hand wound by them in UK. Very resolving. But you need to do a coupling cap upgrade in the amp so you can actually hear how good they are if you buy a base model. Their upgraded amp versions come with Mundorf EVO SGO which sound good enough.

"In a traditional single-ended 300b amp the current draw is constant, from idle to full power. "

Ralph, the current draw is constant averaged over one cycle of the lowest frequency present. Otherwise the current is rising and falling with the input signal.

If the last capacitor in the power supply is properly sized the power supply voltage should stay constant even in the presents of changing current draw on the power supply.

The last cap in a power supply filter should be thought of as a bypass cap (like a cathode bypass cap) for the whole circuit.

Tre'

The rectifier tube should be a consideration in 300B SET build.

In a traditional single-ended 300b amp the current draw is constant, from idle to full power. That means the voltage drop across the rectifier is constant too. If you are hearing differences, there can be only 2 causes; the first being that the amp isn't biased class A1 so at higher power levels the current varies (there is a class A2 and A3 operation where grid current is present at full power).

The second reason is you are hearing the difference due different voltage drops across the rectifier tube itself.

One advantage of tube rectifiers is that don't interact with the power transformer to create 'diode noise'. However, solid state rectifiers can be set up properly so the diode noise is properly taken care of; they can be as quiet as a tube rectifier. The nice thing about this is that they don't go downhill over time and hold up better. If this is done correctly it will outshine any tube rectifier. With DHTs you don't need to worry about cathode stripping since there's no cathode coating.

Fun thread. And yeah, it would be great if there was a website where 300B owners could share, obsess and research information on various amps and brands and vintages of tubes.

BTW, Brent Jesse now includes the JJ 300Bs on his website and speaks pretty highly of them.

A comment about the Cary SE-1; yeah, that's a really nice amp. I have one back in my system right now and it sounds good.

I'm not trying to derail this thread, but I'll reiterate a point I've made elsewhere - I think it is essential to know what sound pressure level you are listening at, and by inference, how much power you're using. I have 93dB efficient JBL monitors and ~99dB efficient Altec Magnificent A7s in my system. I listen around 70dB most of the time. I've found that I can get by with 1.5 watts, and there's a pretty audible difference between the 300B and the vintage 45 tube. So I've switched over to Alan Eaton 45 monoblocks. I still think the 300B tube is a wonderful thing. I used to think "nothing could sound better than this". Now I understand why people talk about 2A3s and 45s and so forth. I love simple, low parts-count amplifiers.

My thanks to everyone. There's been a lot of material put forth that will be very helpful in my quest.

My SET monoblocks use 300B as the driver tubes. I have used Psvane ACME 300B and the new WE 300 B tubes. the WE tubes are better but you have to let them burn in for about 300 hrs before they reach their best.I use 845 tubes as my output tubes and use Psvane ACME 845s their also

AudioAsylum.com has a good SET forum and tube diy. Great info can be had over there. I just changed out my EH Gold after 14 years,  for some Gold Lions, nice improvement. 

Haven’t tried these tubes yet, but hear great reviews about them.

Decware had released their new Zen Sarah SEWE300B amp.

Very curious, but long waitlist at Decware for their products.

I recently purchased one of only 2 Don Sachs 300b class A amps he has made, and the only one with custom wound CineMag IT transformers.  Four 300B tubes.  Four NOS Tungsol 6V6 from the 50's.  And two 6sn7's.   I've owned a lot of equipment in my life but, for the first time, I've got an amp that checks all the boxes.  A truly great sounding piece.  No need to look any more.  This is it for me.