Elrog 300B vs Takatsuki 300B tubes

Ecx123 2-25-2017
The Franks use 5U4GB and Isreal says they are different than even 5U4G. I believe he said 5U4GB takes more current.

A 5U4GB can **handle** a somewhat greater output current load than a 5U4G, but their specs are otherwise pretty similar.  The website description of the Franks Mk II indicates 5U4G, however.  Perhaps the description isn't up to date.

A 5U4GB will just about always be a suitable substitute for a 5U4G.  A 5U4G will be substitutable for a 5U4GB in some designs but not in others.

Charles1dad 2-25-2017
To the best of my knowledge the Millard GZ37 is a drop in replacement rectifier tube.  

The GZ37 is equivalent to a 5AR4.  It will often and perhaps usually be a suitable substitute for a 5U4G, and it will be a suitable substitute for a 5U4GB in some designs but not in others.  There was some discussion of the 5AR4 near the bottom of page 9 and near the top of page 10 of this thread.  (Those page numbers apply if posts are sorted most recent last).

Best regards,
-- Al
 

In the Coincident manual for the Franks, it specifically says uses 5u4gb and don't use 5u4g. Before reading the manual I did roll some 5u4g tubes in because they looked cooler with their bottle shape. One amp stopped functioning shortly after but luckily it was just a blown fuse. When I inquired with Isreal he referred me to manual and said use 5u4gb only. Was blown fuse the result of the 5u4g?Cant say for sure. Interestingly on EML spec on note 4 it says they are not the same:
http://www.emissionlabs.com/datasheets/EML5U4G.htm
I guess it is a case of it works until it doesn't.

Very much loving the Coincident Franks and CSL. Actually got the Statement Phono first and loved that, then decided to go all in. Big improvement on CSL and Franks w PSVANE WE replicas. Will be ordering the Elrogs next week to see how much better it can get.

Ecx123, thanks for the additional info. I see what you are referring to in EML’s note 4, which states in part:

Replacing 5U4G with 5U4GB may result in higher rectified voltage, so should never be done. Replacing 5U4GB with 5U4G may result in lower rectified voltage, and may result in damage of the 5U4G rectifier.

However, here are vintage datasheets for the 5U4G and the 5U4GB. Note the statement in the first paragraph of the 5U4GB datasheet that:

The 5U4-GB ... may be used as a replacement for either the 5U4-G or 5U4-GA.

Also, while the detailed parameters indicated in the datasheets do suggest that substituting a 5U4GB for a 5U4G will result in higher rectified voltage, the difference does not appear likely to be major.

Finally, my older Sam’s Tube Substitution Handbook lists the 5U4GB as a direct substitute for the 5U4G (while of course not listing the reverse). I have never known its listings to be inaccurate, and I have often found them to be overly conservative (i.e., to err on the side of caution) if anything.

In any event, all of this is of course superseded by the indication from Israel and in the manual that the 5U4GB should be used in the Franks. He should update the website description of the Franks, though, which indicates 5U4G as I mentioned.

Enjoy!  Regards,
-- Al

Well I have EML 300B XLS in my Ruby amps for several years and the sound is superb. These are more rugged and reliable and you can get more power from them if you design an amp around it.
- IMO they are among the best 300B's that can be had at any price and run around $750/pair