Impedance question

[Bernardduur]

Tried to search for the answer but the term is sometimes too widely used


When you use an amp with two dedicated speaker outputs from the same OT (so for example the Orange AD200 which has 2x 4 ohm outputs and 1x 8 ohm output; both outputs (the 4 and the 8 ohm) are 'dedicated' as they originate from 2 places of the OT with a shared common ground) can I use both speaker outputs at the same time? So can I hook up an 8 AND a 4 ohm speaker to those outputs at the same time?

[olddawg]

Tried to search for the answer but the term is sometimes too widely used


When you use an amp with two dedicated speaker outputs from the same OT (so for example the Orange AD200 which has 2x 4 ohm outputs and 1x 8 ohm output; both outputs (the 4 and the 8 ohm) are 'dedicated' as they originate from 2 places of the OT with a shared common ground) can I use both speaker outputs at the same time? So can I hook up an 8 AND a 4 ohm speaker to that output?

Nice to see you on this board bro. It's an interesting question and I've never done it. Never had a reason to. It's not like using 2 separate OTs because one speaker load would use the whole secondary winding and the other would be using half the same secondary winding at the same time. I haven't a clue. Enzo probably does though.

[MWJB]

They probably share a common ground. If they do, when you plug into the 8ohm output, you are using the whole winding, fine. But if you plug into the 4ohm ouput too, you now have the 2 loads in parallel and the speaker load will effectively drop...not good. The amp will see the mean impedance accross the whole winding, pullling down your primary Z, blowing your tubes damaging the OT.

If you wired the jacks so that the 8ohm jack & the 4ohm jacks, used together, switched out the 4ohm tap & put the 2 loads in series, you could use 2x4ohm loads...but then it's easier to wire 2x4ohm loads in series & just plug into the 8ohm output.

[Enzo]

I am more the troubleshooter than the theorist, but we did have a big discussion of this not terribly long ago. A search should bring that up. If you use both, then your loads are in parallel back at the tubes.

[Steve Conner]

Yeah, so to load the amp properly you need a 16 ohm load in the 8 ohm socket, and an 8 ohm one in the 4 ohm socket.

[tboy]

...we did have a big discussion of this not terribly long ago.

Here's the link to that thread: http://music-electronics-forum.com/t20950/

[Wilder Amplification]

Yeah, so to load the amp properly you need a 16 ohm load in the 8 ohm socket, and an 8 ohm one in the 4 ohm socket.

Yep...very good trick when pairing up a 16 and an 8 ohm cab on the same amp.

[Bernardduur]

Here's the link to that thread: http://music-electronics-forum.com/t20950/

Tnx!

I had some issues with searching on the term as it is kinda widley used .

All clear now!