Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on February 26, 2019, 01:41:00 pm

Title: 50W O-380v PT - Suggested Power Tube to be used with It ?
Post by: kagliostro on February 26, 2019, 01:41:00 pm

I've this PT (50W 0-380v no filament winding - a separated one is to be used for it) and would like to have suggestions about a Power Tube to be used with it


No tube rectifier will give 380*1.4 = 530v B+ @ around 90mA (I think)


Thanks



Franco

Title: Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
Post by: DummyLoad on February 26, 2019, 01:46:20 pm

KT88/6550 in auto bias.


--Pete

Title: Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
Post by: PRR on February 26, 2019, 09:45:41 pm

500VDC 80mA DC suggests a 40 Watt tube at 6K load or two 20W tubes at 12kCT load. Expect 15W-20W output.

A single winding and tube rectifier leads to half-wave at much lower current or three rectifier tubes and three filament windings, usually an excessive bunch of bottles for loads this size. Or one dual vacuum rectifier and two Silicon rects in a full wave bridge.

Title: Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
Post by: kagliostro on February 27, 2019, 02:36:35 pm

Thanks Pete & PRR

About the use of a tube rectifier (that would have the advantage to lower B+) it will be a problem about the filament supply for the Tube Rectifier

so I was thinking to use a Solid State rectifier (4 diodes configured as a bridge)

Franco

Title: Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
Post by: jjasilli on February 27, 2019, 05:56:55 pm

One of the 6V tube rectifiers might work, with a SS diode tail. 


Also: Power resistor and/or bucking tranny can drop voltage if you want.

Title: Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
Post by: kagliostro on February 28, 2019, 03:31:06 am

Thanks also to you JJasilli

Franco