RH300B 12W with 1% THD

[Shoog]

Does anyone,

Have any thoughts on a pentode driver RH300B?

Regards
M. Gregg

I would think it a better idea. Thats the last I will say on the matter though.

Shoog

 

[gingertube]

I have power and ouptut trannies (moderate quality from Mabelaudio) and EH 300Bs on the shelf ready to go and have been thinking about a driver circuit for a while.
I'm going shunt cascode.
The Shunt Cascode Driver | Bartola Valves
Rod (Coleman) is a seriously smart engineer so I usually pay attention when I see one of his design ideas.

I'm not going to get involved in the praising or bashing the RH scheme even though I use something very similar in my Baby Huey Push Pull Amps.
Why not?
The designer is not very good at discussing its merits rationally (and has managed to get himself sin binned from most DIY sites) and some of its/his critics are of the "Praise the lord and pass the ammunition" type ratbags (no I'm not talking about anyone in particular and am specifically not referring to anyone posting above).

Frankly I consider that unfortunate.

Cheers,
Ian

 

[Shoog]

I have power and ouptut trannies (moderate quality from Mabelaudio) and EH 300Bs on the shelf ready to go and have been thinking about a driver circuit for a while.
I'm going shunt cascode.
The Shunt Cascode Driver | Bartola Valves
Rod (Coleman) is a seriously smart engineer so I usually pay attention when I see one of his design ideas.


Cheers,
Ian

Looks like a good solution.

Shoog

 

[popa marius]

Mine does nearly 10 W in class A1. You don't need to resort to A2 to get power out of the 300B. You just have to raise the B+ and anode current beyond the commonly used 360 V, 60 mA operating point. I find 400 V, 85 mA, 5 kΩ load to be just about right. That's still well below the max anode dissipation.

The biggest challenge of driving a 300B is that the driver needs to be able to drive the input capacitance of the 300B and deliver a 200 Vpp swing, cleanly.

~Tom

I tested this 430v/90mA/5K static operating point and i think it is correct but only with a driver that can provide the 200Vpp you mentioned with a mu folower configuration with 6E5P and 6P1P wit a THD of 0,3%. In the open loop and at 8W the THD output power is 3,12% wit a good harmonic distribution, the tube used being an Electro Harmonics