Bottlehead Forum

General Category => Tech Tools => Topic started by: xcortes on August 06, 2012, 08:03:38 AM

Title: Negative supply for driver?
Post by: xcortes on August 06, 2012, 08:03:38 AM

I'm thinking of trying a 300B DC amp. To avoid going to very high voltages I was thinking of using a negative ps on the driver tube. I haven't worked the details but let's say I'd go for a 400v plate, 0v cathode (effectively 400v p-k) and -87v on the grid of the 300B and -87 v on the plate of the driver with a 5k ohm load.

Would something like this work?

Title: Re: Negative supply for driver?
Post by: Paul Birkeland on August 06, 2012, 08:49:01 AM

Sure, you can do this, but keep in mind that you will need a cap or a transformer at the input of the amp. 

-PB

Title: Re: Negative supply for driver?
Post by: xcortes on August 06, 2012, 08:50:56 AM

Which negates the benefit of going to DC, I guess.

Title: Re: Negative supply for driver?
Post by: xcortes on August 06, 2012, 11:35:13 AM

On second thought this looks like a good way of going to higher voltages without getting into dangerous territory.

With this approach one could get 15 watts from a 300B XLS while staying at "Paramount" B+.

Title: Re: Negative supply for driver?
Post by: xcortes on August 06, 2012, 02:36:32 PM

And If we keep the cap coupling but use my "idea" of using a negative ps on the grid of the 300B you get to a fixed bias amp! At least I came to the same idea amp designers arrived at maybe 100 years ago! Still a nice way of getting more power without getting onto lethal voltages.