300B/EL156 Amp

[avico78]

Hi,

Is it possible to build an PP monoblock amp that can be support both EL156 tube and also 300B?

I can't find many project based on EL156 - but i heard one amp that sounds amazing but from the other hand want the 300B alternative to be avialble just in case...

Thanks All

 

[kstagger]

different sockets, different tubes (EL156 pentode, 300B triode).

You could build something 'generic' enough where you could re-use the output and power iron, possibly the driver/input stages, etc but change the sockets, change the filament supply, bias, etc etc to switch to the other tube. I'll also note that the EL156 is easy to drive compared to the 300B.

 

[avico78]

Is there a reason there's no many amps based on el156? Both diy and industrial amps?

 

[danFrank]

Is there a reason there's no many amps based on el156? Both diy and industrial amps?

This tube came out late and had a funky socket. The new Chinese ones have an common octal socket but they are pricey even for chinese tubes. I have 20 of the Chinese ones and they look well made; I'll know more when I build something with them.
The original Telefunken EL156 was a great audio tube who's cathode could provide massive amounts of current for an audio tube. 150 watts can be had from a pair of them, which is pretty impressive.
The funky socket (10 pin) made it unattractive for amp manufacturers, especially guitar amp makers. The reason they used this funky socket is that the pins were situated where you can put 800 volts on the anode without a plate cap. Octals for the most part can't take that kind of B+ without arcing.
Daniel

 

[kstagger]

I've built a SE amp using the Shuguang EL156. Very nice sound though I did have one tube fail. The 50W plate can certainly make some power.

Probably not many amps out there since there is only the Chinese version - perhaps not much chance for tube rolling? It's pretty hard to introduce a 'new' audio tube to the market though the KT90 has its followers.