80s ODS Half Power 50/100 Switch Diagram

[Tonegeek]

i tried a half power switch on my Twin but never liked the way it sounded, but I also did not compensate for the spkr mismatch.

[glasman]

I could be wrong but its' possible HAD didn't care either, aren't there "real" combo style amps out there with 4 ohm iron and an 8 ohm speaker?

Hi Henry, you are very correct. Most of the 100 watt 6L6 Dumble combo used a twin tranny with a single 4 ohm tap. Most were loaded with either EVM's or Altec's (8ohm).

According to comments I have seen from Steve Kimock, he likes to run a mismatch on his Dumble (8 ohm load on 4 ohm tap).

Gary

[glasman]

Seems you could also just disconnect input signal from the grids of a pair of tubes, leaving them idling. Then the impedance doesn't change.

You could, but would have to add two additional coupling caps to the design and break the signal before the caps. This would allow you to keep the bias voltage on the tube. Just disconnecting the grid connections would not be a pretty sight .

Gary

[Funkalicousgroove]

Alot of those amps had Dual Showman OT's (8ohm), some had Music Man Iron which would have had both 4 and 8.

[glasman]

Dual Showman OT's (8ohm)

??? Only Duals I have I've seen were 4 ohm. Maybe I am mistaken.

[Funkalicousgroove]

Sorry, My bad, Regular Old Showman OT's, not "Dual" Showman.

the difference between a Showman and a dual showman is the OT,
Showman ran 1 15" at 8 ohms
Dual Showman ran 2 15"at 4 ohms.