EML 2A3-S Tube

[drewh1]

Just curious if anyone knows anything about this tube - the spec claims it can output 9 watts if run at higher plate voltage (400 V).  Curious if it would be possible to adapt it to a Bottlehead Stereomour for a little more juice? Sounds more like a 300b.

[Paul Birkeland]

You could build the Paramount with the 300B audio circuit and 2A3 DC filament supply to use this tube to its potential.  The big JJ 2A3 would also drop in and operate under these parameters.

The Stereomour doesn't have additional voltage to give, but the 2A3-S will work nicely regardless. 

[chard]

  The 9w output is at peak conditions when the tube is biased at 40w, (400vdc x 100ma). The literature on this tube recommends that the tube be run at max peak conditions for no more  then 30 minutes. 28w (375vdc x 75 ma) is the max continuous running conditions recommended for this tube. The literature does not say but I think the tube could put out about 6w run at max continuous operating conditions.
  The internet chatter on this tube is that its sweet spot is at 15w bias with power out of 3.5w same as a normal 2A3. The tube probably hasn't been tried much beyond the normal 2A3 parameters as amp manufactures are not going to make a amp for a single  tube manufacturers tube. I don't know much about the paramount as I have a stereomour but the paramount seems to be a very flexible design, with a few tweeks you could probably set the dc bias at about 28w and get about 6w out with this tube. I plan on buying this tube for my stereomour soon, not to get extra power but because people who have tried or heard this tube highly recommend it and every upgrade I have installed so far has resulted in a very noticeable improvement my sound system.

[drewh1]

Thanks Paul and Clifford - I am not sure I need the extra watts yet, I actually keep turning the Stereomour down! Really enjoying the sound.

Let me know if you try those EML's - Would like to try some tube rolling and maybe will build the Paramounts some day!

[chard]

Thanks Paul and Clifford - I am not sure I need the extra watts yet, I actually keep turning the Stereomour down! Really enjoying the sound.

Let me know if you try those EML's - Would like to try some tube rolling and maybe will build the Paramounts some day!

  I will let you know when I try them. It might be a few months away. I did get a nice improvement in all areas when I replaced the stock 12AT7 with a NOS Mullard CV4024 which is the british equivalent of a 12AT7. I changed out my seduction stock 6922 tubes at the same time with Generex Gold Lion 6922 reissues, so I am not sure how of the improvement is due to the NOS Mullard tube. 

[drewh1]

Yes, I have heard replacing the driver tube is a useful and not as expensive as rolling the 2a3.  think I will try that first.

I need to break things in a bit more before trying anything new though.

drew.

[Paul Joppa]

The Stereomour power transformer is capable of more current, so yes you could increase the current and get more power. You'd have to replace the output transformer (lower primary impedance, 2500 or 3000 ohms), and the plate choke to handle the current, and change the cathode resistor to a smaller resistance, and probably make some small changes to the power supply.

Easier would be to run the tube at 300B points in the Paramount, which runs about 350v at 70mA - 24.5 watts, just a hair under the maximum 28 watts.