Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Leevi on January 31, 2019, 08:59:24 am

Title: Impedance question
Post by: Leevi on January 31, 2019, 08:59:24 am

The amp is a Vox AC15 based with 2xEL84 power tubes 8 and 16 Ohm output.
Is it ok to plug two 8 Ohm speakers to it i.e. one to 8 Ohm output and one to 16 Ohm output.
I know that it will work but will it change the load impedance (~5K) radically?
/Leevi

Title: Re: Impedance question
Post by: sluckey on January 31, 2019, 09:50:41 am

I would not do that. I don't even know how to calculate the load impedance. I would just connect the cabs in series and plug into the 16Ω jack. Look at page 14 of this pdf to see a simple cable that will do this...

     http://sluckeyamps.com/misc/Amp_Scrapbook.pdf

Title: Re: Impedance question
Post by: 2deaf on January 31, 2019, 11:48:17 am

I believe that would be the same as plugging 2.67 Ohms into the 8 Ohm tap alone.

Title: Re: Impedance question
Post by: Leevi on January 31, 2019, 12:38:56 pm

Thanks for the document Sluckey. There was a 4 Ohm tap in the OT so
I solved the issue by using a switch.
Leevi