300B Stereomour

[Thoburn]

Just curious, but I was wondering if the Stereomour would ever have a 300B option?

 

[Paul Joppa]

I have a couple ideas in mind ... it's a bit tricky to get the higher voltage needed, but it IS under consideration...  :^)

 

[Thoburn]

Very cool. I have a DIY 5 inch back loaded, rear firing horn project in mind. It would be about 94 Db/W/M, so I think the 300B would be a good match.

 

[Dr. Toobz]

Without changing transformers or squeezing in one just for filaments, wouldn't one be limited to a 2.5v 300B?

 

[Paul Joppa]

Without changing transformers or squeezing in one just for filaments, wouldn't one be limited to a 2.5v 300B?

Heh-heh! No, I have planned ahead - the 2.5v winding is quad-filar, two independent bifilar windings. I can ask the supplier to make a bifilar winding of two independent single windings, which will supply 5v at 1.25 amps. A very small change to an existing design. Hum might be 4-6dB greater, so we'll have to try it and see - like I said, I have some ideas but they need to be tried out.

The good news is that we can do the experiments with a 2.5v 300B, and not mess with the power transformer before we know whether we have a good basic design.

There are a few more things in the pipeline before we get to this, though.

 

[Dyna Saur]

The J/J 2A3-40 is very close to being a 300B with a 2.5V filament.  At the Stereomour's  existing "2A3" B+ voltages and currents, it would still behave more as a 2A3 would.  At those voltages / currents, the 2A3-40 should last a VERY long time (the "-40"  refers to the 40 watt plate dissipation rating, as compared to 15W for a 2A3).    I've put the 2A3-40s in Paramour IIs and they sound very good, though they do not deliver any higher power output.

HTH

/ed B in NC