Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Paramount => Topic started by: xcortes on July 08, 2013, 09:25:11 AM

Title: c4s 2A3
Post by: xcortes on July 08, 2013, 09:25:11 AM

Could I convert my 2A3 Paramounts to direct coupled and c4s the 2A3? Trade an extra cap for active loading the 2A3? A simple, heatsinked c4s at 54mA.

Not enough compkiance for full power, right? How much power would I get?

Thanks

Title: Re: c4s 2A3
Post by: xcortes on July 08, 2013, 11:07:07 AM

Now I see, the mje5731A max is 375v so no good ?

Title: Re: c4s 2A3
Post by: Paul Joppa on July 08, 2013, 11:30:12 AM

Quote from: xcortes on July 08, 2013, 11:07:07 AM

Now I see, the mje5731A max is 375v so no good ?

Well, high risk for sure! For a 3k load impedance, 3.5 watts is about +/-150v peak, i.e. 300v pk-pk.

But of course that means a B+ margin of 150v. Add in 275v plate to cathode, 55v bias, and 175v for the driver plate (direct coupled) and you need a 655v power supply. Add 10% margin for a shunt reg supply and it's 725v.

Now you might get 470v from the Paramount supply, so (scaling everything down) maybe 1.5 watts from a 2A3 would be possible. It doesn't sound like a big-selling product to me  :^)  but maybe an interesting experiment.

Title: Re: c4s 2A3
Post by: xcortes on July 08, 2013, 11:37:00 AM

Can you help me scale it down?

What would be that magical 1.5 watt op with a 3k opt, sr, dc and c4sed? I could go lower power if required, maybe as low as half a watt but 1.5 would be awesome.

Thanks!


Thanks

Title: Re: c4s 2A3
Post by: xcortes on July 09, 2013, 05:03:19 AM

Also, I can definitely skip the driver section so there's no need to calculate voltages for direct coupling nor currents for a driver. Just a simple SR, C4sed 2A3 spud for 3k opt and around a thousand milliwatts.

This is going to be a game changer for me!

THANKS Paul!

Title: Re: c4s 2A3
Post by: Paul Joppa on July 09, 2013, 07:19:13 AM

I'll PM you. It will take some time; I really need to get the SR45 project going first.