Welcome To the Hoffman Amplifiers Forum

April 14, 2026, 09:42:55 pm
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: Tweed pre with XLR out  (Read 2196 times)

0 Members and 1 Guest are viewing this topic.

Offline J3ona1

  • Level 1
  • *
  • Posts: 57
  • I love Tube amps
Hoffman Amps Forum image
Tweed pre with XLR out
« on: April 01, 2026, 09:52:12 pm »
Hi good people. I'm putting together a fender tweed pre with XLR out and wanted some eyeballs on the XLR out portion of the circuit. I have a cathode follower feeding a Hammond 1:1 line matching transformer (Model 1140-LU-B) https://www.amplifiedparts.com/products/transformer-hammond-line-output-1140-series to get the balanced feed for the XLR out. Will this schematic get the output impedance to a good enough place where it can drive a long run to a mixing console. Schematic attached. Thanks in advance for your help.

Offline J3ona1

  • Level 1
  • *
  • Posts: 57
  • I love Tube amps
Hoffman Amps Forum image
Re: Tweed pre with XLR out
« Reply #1 on: April 02, 2026, 08:20:19 am »
Updated schematics to reflect actual pt and xlr pinout

Offline Merlin

  • Level 3
  • ***
  • Posts: 642
Hoffman Amps Forum image
Re: Tweed pre with XLR out
« Reply #2 on: April 03, 2026, 04:30:50 am »
Looks OK. The output impedance will be roughly 1/gm, so less than 1k for a 12AU7. The ground lift switch is kinda redundant, just tie XLR pin-1 to chassis.

Offline J3ona1

  • Level 1
  • *
  • Posts: 57
  • I love Tube amps
Hoffman Amps Forum image
Re: Tweed pre with XLR out
« Reply #3 on: April 03, 2026, 07:09:10 am »
Thanks Merlin!

 


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