ELROG ER300B into BeePre?

[bombay317]

Background: I have the limited edition BeePre with the BeeQuiet modification and the XLR input modification.

Question: What modifications would be necessary to run ELROG EL300Bs in place of the current 300bs?  I saw some other threads that talked about that, but then in a separate thread advice was to not follow those ones.


ER300B info from https://www.elrog.com/products/

Filament Voltage................................................................5 V

Filament Current ............................................................1.2 A

Amplification Factor ..........................................................3.3

Transconductance ........................................................3.3 mS

Plate Resistance ........................................................950 Ohm

Max. Plate Voltage .........................................................600 V

Max. Plate Dissipation ....................................................40 W

[Paul Birkeland]

I will take a stab at guessing what PJ would do, but he'll be along shortly I'm sure to weigh in.

If you plug the Elrog into the BeePre, you will probably find that the plate voltage is higher than we'd like, and precariously close to the regulated B+ voltage. 

To address that, you could dial back the plate current by 10mA.  (17.1 ohm R1 instead of 14 ohm R1)  This will leave 10mA extra rolling through the regulator circuit, which will drop the Kreg voltage a little bit, but I can't see real issues with doing that.  If you use the balanced outputs, you will need to replace the 604 ohm resistors with something closer to 1K.

On the filament side, everything should still work just fine with the stock circuit.

-PB

[johnsonad]

I am on of the few that has tried this and posted on them in the past.  They are very microphonic and IME, where not a good match for the BeePre.  They worked very well in the Parmount/Kaiju's until they died, from poor workmanship and a poor product in general....  They sounded amazing but if I could go back in time, they weren't that great for the price.  My EML Mesh plates have lasted 3 times as long and are going strong still. 

[bombay317]

I was sent the plate curves for the tube.

I'm still thinking about doing this, though not yet sold on it. 

[m17xr2b]

I used the elrog 300B for a while in the beePre, no issues on my side.