I have a Seymour Duncan 84-40 valve amp, and I was wondering if I wanted to plug in a cabinet, could I plug it in at the same time as the internal speakers? There are two outputs on the back, one 8 ohm (for the internals) and one 4 ohm. Am I right in saying I would need a 4 ohm extension cab? (say 2 8 ohm speakers wired in parallel?)
could I plug it in at the same time as the internal speakers?
I lost you right there... I'm not sure what you are asking with this... sorry.
Stairway to Freebird!
I have a Seymour Duncan 84-40 valve amp, and I was wondering if I wanted to plug in a cabinet, could I plug it in at the same time as the internal speakers? There are two outputs on the back, one 8 ohm (for the internals) and one 4 ohm. Am I right in saying I would need a 4 ohm extension cab? (say 2 8 ohm speakers wired in parallel?)
I did a search and found the manual here http://www.seymourduncan.com/website/images/84_40.pdf
looking at the schematics I think you're right, but you might wanna wait for Wes to chime in.
Playing guitar and never playing for others is like studying medicine and never working in a clinic.
They may mean the lowest Ohm rating for the amp. I would try and find out how the jacks are wired. They could mean use either the 8 Ohm jack to run an 8 Ohm speaker or speaker combinations, Or use the 4 Ohm jack to plug a 4 Ohms load, like a 4x12 cabinet thats wired for 4 Ohm's. Another possibility would be an 8 Ohm speaker connected to the 8 Ohm jack and another 8 Ohm speaker connected to the 4 Ohm which would give you a 4 Ohm load.
When using a single 8-ohm speaker, connect the speaker to the 8-ohm jack. If using two 8-ohm speakers (assuming they are wired in parallel), plug them both into the 4-ohm jack. (The logic here is that two 8-ohm loads connected in parallel add up to a 4-ohm total load).
I hope I explained it so you could understand.
Joe
Joe, I noticed before I read your post that the internal speakers were plugged into the 8 ohm socket..then realised that the speakers are both 8 ohm so if they were wired in series that'd mean 16 ohms - but there's no 16 ohm output. There's a 4 ohm however so I've plugged the internal speakers into the 4 ohm output now. It sounds much louder so I take it that's the best impedance. I only bought this amp last week so the amp tech or whoever touched the speaker cord last must've plugged it in the wrong socket (and it wasn't me :lol:).
This means that there's an 8 ohm left, which in turn means any cab I plug in from now on will go in there. I take it that it isn't going to do my amp any harm if I was to plug in an 8 ohm cab in the 8 ohm output. What I really want to know though is why? If you had 8 ohms and 4 ohms being taken at the same time, wouldn't that add up to make a total of 12 ohms on the amp? Or is there some sort of trick wiring I don't know about?
Doug
The amp came in a couple different versions. One version with a single speaker and one version with dual speakers. Here's an example, a Mesa Boogie 50/50 power amp has 4 and 8 Ohm outputs on each channel. It's designed to only use the 4 Ohm or the 8 Ohm outs on each channel, not both. I could run one side at 4 Ohms and the other channel at 8 Ohms.
joe
