Found resistors on non functional ext speaker out , on twin reverb

Hi
Wanted to hook up an extra cab on my twin reverb.
No sound from the ext speaker output.

Opened it up and found this:

Two resistors on the speaker jacks

6k8 from speaker tip to ext speaker tip

810 ohm from ext speaker tip to ring

Will rewire it to stock, so not a big problem, but a bit curious to know what it's for, or what it does?

Kind regards

Kasper
 

Attachments

  • IMG_20250215_132417.jpg
    IMG_20250215_132417.jpg
    495.4 KB · Views: 44
  • IMG_20250215_132408.jpg
    IMG_20250215_132408.jpg
    398 KB · Views: 44
I've added the resistors before, but added a cap to roll off the highs to closer approximate the sound coming from the speaker. The direct out includes the power amp section (and it's distortion), where the line out is probably before the power amp.
 
It could possibly a headphone output. But only for one ear. Might be good for a play along with some form of recorded music, that way you can hear both. If you are listening to recorded music, you might as well use the amp through the speakers.

The complicating factor is that to be useful, you need to unplug the existing speaker. Output transformers need a load. A tube amp transformer would rather see a shorted output than an open output. It is possible to generate internal arcing with a open output.