Mid-70s Fender Ultralinear Amps

[fuzzonaut]

They also did something weird with the speaker jacks; plugging into the external jack puts the two jacks in series and connects to the 8-ohm tap on the OT. So you can use one 4-ohm load, two 4-ohm loads, or one 8-ohm load and still be matching.

This reminds me of my MusicMan HD 130. Speaker jacks wired in series with a 4/8 ohm switch.

I don't know if the MusicMan amps are ultraliner, but I use mine for bass, there's plenty of headroom, and it takes pedals like a champ.