Sunn Studio Lead

[Walt-Dogg]

So I finally got a Studio Lead and I'm in love, it's pretty much exactly what I wanted, a Concert Lead in as a combo amp. But how many ohms is this thing? I wanna make one of HRobert's series boxes (http://sunn.ampage.org/sdp/index.php/topic,5502.0.html) so I can plug into a 4x12 and use the two 10'' speakers it has.

[Walt-Dogg]

Or if anyone knows how I'd go about finding this out myself?

[CLD]

Have you searched the forum? I think this question came up once before.

The '72 and '74 catalogs don't say, and the photo of the back panel in my '74 catalog doesn't indicate anything.

[Walt-Dogg]

Did a search, I've scoured my amp for any evidence of how many ohms its and no luck. What's the tool I need and how do I use it to find out? I know the speakers are each 8 ohms but I'm not sure how they're wired...

[Isaac]

First thing is to ask the right question. What is it you want to know? Do you want to know what the impedance is of the internal speakers? Do you want to know what the minimum output impedance of the amplifier is?

[Walt-Dogg]

The minimum output impedance please. I know the speakers are both 8 ohms, and wired... *checks amp* hmm... I'm not sure how the speakers are wired. There's white and back wires which both come from the 1/4'' male that's plugged into the amp and are snapped onto one speaker then are jumped to the next speaker. The picture explains better, ignore the gray stereo line, that's for the reverb tank, I've never seen speakers wired like this before actually. So I guess I want to know both.

[loudthud]

The speakers are wired in parallel. Based on the rail voltage and a 50W power rating I would say the minimum load should be 4 ohms.

[Walt-Dogg]

Then the amp is most likely 4 ohms as the speakers are wired for 4 ohms?

[EdBass]

Then the amp is most likely 4 ohms as the speakers are wired for 4 ohms?

The speakers are wired in parallel. Based on the rail voltage and a 50W power rating I would say the minimum load should be 4 ohms.

I think the speakers are probably wired for 4 ohms to get the most power out of the amp.

[Walt-Dogg]

Then to be on the safe side, just assume it's 4 ohms not to cause any damage?

[Isaac]

Yes. It's unlikely in the extreme that the amp would be stable below 4 ohms. Use that as your minimum load impedance.