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Wednesday, October 21, 2020

The Trinity of ELROG 300B Tubes


In August I published a post about the 4th anniversary of Deutsche Elektronenröhren Manufaktur GmbH in which I showed the new molybdenum version of our 300B, the ER300B-Mo. The development did not end there and our 300B line up is now joined by a third model.

Regular readers of my blog know how fond I am of the 46 tube. Unfortunately this tube delivers just up to 1.25W in single ended operation or a bit over 3W in a push pull configuration which severely limits the choice of speakers to go with that tube. So rather than merely developing an ELROG ER46 we decided to attempt to recreate the sound of the 46 in a tube which can deliver more power.

I am proud to announce that we not only achieved to recreate the special sound of the 46 in a 300B compatible tube, but in my humble opinion even surpassed it by adding the neutrality and resolution which our thoriated tungsten 300Bs are known for.

This perfectly suits my own preference for sound. Musical flow, voices and tone with a lot of emotional impact combined with the highest possible resolution and neutrality. Hence the tube received my initials in the type number and is called the ELROG TM300B.

We went through quite a few prototypes with a new filament and grid structure which is very difficult to manufacture. Therefore we can only produce very limited numbers of this tube. Initially it will be reserved to users of Thomas Mayer amplifiers only. But a general release for use in other amplifiers is panned for later next year.

The molybdenum plate ER300B-Mo is released without restrictions and can be ordered now.

But we still have a bit of lead time since the pre orders of the ER300B-Mo will be served first.

We already received some feedback about the sound quality of this tube and general consensus is that it improves upon the qualities of the standard ER300B.

Here a feedback from an early user of this tube:

To me the sound of the ER 300B M are again more gripping. More linear. More solid, locked imaging. Better dynamics. More separation. 
 It feels like the ’transport’ of the sound is more rock solid. It really feels like the same kinda musical step up i experienced going from the my previous set of tubes to the normal ER300B’s. 
But now it’s an even more ’solid’ version. The sound signature is the same as the standard ER300B, but everything is much better. 
I was listening at the new Tool album, from which is not easy to uncover all the details. It can actually sound very flat on a normal system. With the ER300B M, I finally hear way more separation of frequencies, and as a result it sounds way more ‘grunting’ and ‘gripping’. 

Another customer feedback:

They sound spectacular: more of everything, micro detail shimmer on cymbals, bite on trumpets, more nuanced soundstage, bass seems tighten and more defined as well.

I can confirm similar findings in my amplifiers. It is not a subtle difference but immediately noticeable. Of course these new tubes do not render the standard ER300B obsolete. It sill be continued to be offered along these new versions.

We did a minor change in the ER300B. We switched to a different supplier for the nickel used in the plates. The plates are thicker and have better thermal properties. This enabled us to leave out the black coating which we used to apply to the plates. So the plates are shiny now. In terms of performance and sound we did not see any change in this so it is purely cosmetic.

With the addition of the TM300B the ELROG portfolio consists of 13 tube types now. And we are able to offer a choice of different types to 300B users.

Pricing of the ER300B-Mo and our other models can found on the tube site. The ER300B-Mo has the same technical parameters as the ER300B and is also warranted for 1 year.

Best regards



  1. Eagerly awaiting the official release of TM300B, is the gain and RP different than the standard 46?

  2. Commenting to bump this! These sound like they would be heavenly in a Woo 3ES

  3. Would the ER300B-Mo be sufficiently low noise for use in a 300B preamp @ circa 100V plate to cathode, 5V bias? I have a pair of the latest WE300B reissue that I like very much, but they are too noisy to use in the preamp But my EML 300Bs are silent. Would you recommend the ER300B-Mo for preamp use?

    many thanks, Derek

    1. Hi! We have many customers who use ER300B and ER300B-Mo in preamps with excellent results. A 300B is designed as an output tube. It can be used for other purposes like driver or preamp tube if the designer takes the necessary steps so that it can run quiet. A lot depends on the implementation of the filament supply for quiet operation. Different filament materials and coatings can react differently to the filament supply noise. So best to ask the designer of the preamp if he designed it such that thoriated filaments run quietly. Unless it is some microphonic noise it is not the tube which creates it but the surrounding circuitry. 100V / 5V bias is a very odd choice of op point. 300Bs usually are not matched at such op points. In such circuits you will have big differences between tubes not only of different brands but also of different tubes of the same brand.

    2. Many thanks for the response. I probably should have mentioned that the 300Bs are CCS loaded. All tubes other than WE300B reissue are silent - EML, JJ, even Sovtek. From which I conclude that the noise is tube-related. As for strange op, despite that the preamp sounds amazing to my ears. I will ask the designer.

      Thanks again

    3. Hi! CCS filaments can be noisy. If it is a regular hiss you get from the WE it is most certainly caused by the circuit. Tubes do not generate noticable noise except in very low level applications like phono. Especially the thoriated tungsten filaments of our tubes are very sensitive to noise from the filament supply. Please check with the designer exactly how the CCS regulates filament voltage. I have seen many poorly implemented CCS which can kill tubes. You can email me for further discussion

  4. Many thanks again. I would have emailed originally, but I cannot find your email address.

    1. https://vinylsavor.blogspot.com/p/impressum.html

  5. Are the TM300B available for purchase yet?

    1. Yes, but they remain exclusive of owners of my amps since we can only produce very few

  6. Are the only differences between ER and MO is the use molybdenum? Thanks