Welcome To the Hoffman Amplifiers Forum

September 07, 2025, 12:29:49 pm
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: 50W O-380v PT - Suggested Power Tube to be used with It ?  (Read 2833 times)

0 Members and 1 Guest are viewing this topic.

Offline kagliostro

  • Level 5
  • *******
  • Posts: 7739
Hoffman Amps Forum image
50W O-380v PT - Suggested Power Tube to be used with It ?
« 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
« Last Edit: February 28, 2019, 07:50:05 am by kagliostro »
The world is a nice place if there is health and there are friends

Offline DummyLoad

  • SMG
  • Level 5
  • *****
  • Posts: 5791
Hoffman Amps Forum image
Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
« Reply #1 on: February 26, 2019, 01:46:20 pm »
KT88/6550 in auto bias.


--Pete

Offline PRR

  • Level 5
  • *******
  • Posts: 17082
  • Maine USA
Hoffman Amps Forum image
Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
« Reply #2 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.

Offline kagliostro

  • Level 5
  • *******
  • Posts: 7739
Hoffman Amps Forum image
Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
« Reply #3 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


The world is a nice place if there is health and there are friends

Offline jjasilli

  • Level 5
  • *******
  • Posts: 6731
  • Took the power supply test. . . got a B+
Hoffman Amps Forum image
Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
« Reply #4 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.

Offline kagliostro

  • Level 5
  • *******
  • Posts: 7739
Hoffman Amps Forum image
Re: 50W O-380v PT - Suggested Power Tube ti use with It ?
« Reply #5 on: February 28, 2019, 03:31:06 am »
Thanks also to you JJasilli

Franco
The world is a nice place if there is health and there are friends

 


Choose a link from the
Hoffman Amplifiers parts catalog
Mobile Device
Catalog Link
Yard Sale
Discontinued
Misc. Hardware
What's New Board Building
 Parts
Amp trim
Handles
Lamps
Diodes
Hoffman Turret
 Boards
Channel
Switching
Resistors Fender Eyelet
 Boards
Screws/Nuts
Washers
Jacks/Plugs
Connectors
Misc Eyelet
Boards
Tools
Capacitors Custom Boards
Tubes
Valves
Pots
Knobs
Fuses/Cords Chassis
Tube
Sockets
Switches Wire
Cable


Handy Links
Tube Amp Library
Tube Amp
Schematics library
Design a custom Eyelet or
Turret Board
DIY Layout Creator
File analyzer program
DIY Layout Creator
File library
Transformer Wiring
Diagrams
Hoffmanamps
Facebook page
Hoffman Amplifiers
Discount Program


password