Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: xochipelli on February 13, 2024, 05:15:01 am

Title: Using an 8 ohm OT in a 5F1 build Question.
Post by: xochipelli on February 13, 2024, 05:15:01 am

I'm building a 5F1 Champ using a Mercury Magnetics 8 ohm Champ OT since all my speaker cabs are 8 ohms.  I'm trying to figure out if there are any changes to the original 5F1 circuit that i need to make being that the original circuit was designed for a 4 ohm output. Any insight would be greatly appreciated.

Title: Re: Using an 8 ohm OT in a 5F1 build Question.
Post by: sluckey on February 13, 2024, 05:41:11 am

You may want to replace the 22K NFB resistor with a 33K or 47K. This is not really necessary though. So, experiment and let your ears decide which you prefer.

It's popular to use a switch for different resistor values or use a pot for variable NFB.

Title: Re: Using an 8 ohm OT in a 5F1 build Question.
Post by: xochipelli on February 14, 2024, 06:08:21 am

Thanks Sluckey. I was planning on adding an NFB switch so i'll just play around with different rated resistors.