Using an extension cab with my deluxe reverb

Duane24

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So its two 8ohm outputs wired parallel on there, if I were to keep the internal 8 ohm speaker running and run an extension cab, what would be the right ohms of the cab? I know an 8 ohm cab would make the load 4 and that's not good, so would a 16 ohm cab work out to be 8 in conjunction with the internal speaker?
 

SWeAT hOg

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Stumped on this one. I dunno if it matters, but I owned a Traynor combo with an 8 ohm speaker installed and the ext. speakers had to be min. 8 ohms.
 

Duane24

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Fender amps don't do that like marshalls do unfortunately
 

Six Gun

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Is your amp the old amp or the reissue?

On the old maps you just plug-in any old ext speaker. The OT was designed to accept any 4 or 8 ohm Ext/ Speaker. It will not kill the amp if you use either one. I use a 2x12 at 4 ohms and the 1x12 ay 8 ohms EXt Cab. I have even used a 16 ohm 1x12 Ext/ speaker for a few hours at a clip, with no problem.

Fender made a 12" DR Cab as an option for 90.00.

Deluxe-Reverb-Cab-Extension.jpg


79886-pJqcl5ejk5.km5yVmqU-fender_price.67.jpg
 

Duane24

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It's a new one, I did already blow an OT, not from doing this, they're just crappy, so it does have a mercury magnetics in there now, but I still don't really trust running it that way(4ohms). It may be ok for a little while, but I'm considering all this for pushing more air at a gig, so the amp would be getting pushed hard for a long time.
 

Marshall & Moonshine

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Look into installing a sector switch. You already went with MM, which is commendable; might as well go the distance. Does the new OT have multiple taps?
 

Duane24

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It's only set up to do 8ohm like a stock 65 dr tranny would be. Plus, I wouldn't want to do all those mods anyway. It all works fine as is, just thinking out loud for pushing more air with this amp. I've got more powerful amps at my disposal, but I like this one. I suppose I could just save myself the headache of the math and the wondering if my amp will blow up and unplug the on board speaker, but I figured there has got to be a way to get it to work properly if they include that damn output jack
 

G Man

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Hoping someone comes up with a clear answer, as I have a SFPR and I've always been curious what would be better, 4 or 16 Ohm cab, and assumed 16 would be the answer, but never tried it out of never having read a clear answer.
 

Marshall & Moonshine

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I think the manual says that by unplugging the internal speaker, it will produce no sound. The schematic looks like it has a switching jack that will short with nothing plugged in.
I would contact MM. If the original was built for it, and it's included in the manual. I think you could just go ahead and connect a 16ohm cab to the external jack and go in parallel.
If you only want to run an external cab, you might be able to put a blank 1/4" plug in the internal Jack, which would hold that switch inside, and you could run a 8ohm cab by itself and have the impedances match.
But I'd wait to hear from someone else for that...;)
 

GitFiddle

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The best way to do it is to replace the internal speaker with 16 ohm and add the external 16 ohm and always play with an external cab. I think Mudfinger may be setup this way.
 

Six Gun

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does the 65 reissue come with the ext speaker jack?
 

caljoe

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My 68 CDR has it, I think the 65 RI does too.
 

Marshall & Moonshine

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does the 65 reissue come with the ext speaker jack?

Yes. The internal speaker has to be plugged in or it shorts both jacks together, which I would think would be disastrous to the OT. If someone knows how to post the schematic, you'll see what I mean.
It looks to me like they just intend you to run a lower load. If you want to do it often, then Mudfingers setup is the way to go.
 

Six Gun

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I found a matched pair of minty Jensen C12NA speakers from a Bassman 2x12 cab pull I did over 10 years ago.

I'm putting this one in a DR tomorrow.
79896-pJqcl5ejk5.km5yVmqU-jensen_1966_c12na.jpg
 

NYPV

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Why the heck would Fender offer a set up like this? Makes no sense. You'd think when you plug in the extension it would switch to 4 ohm tap. Freakin stupid. Either change the OT to a 4/8 ohmer or just unplug the internal speaker and run an 8 ohm 212 out of the main I guess. That way at least you still have a grab and go combo at 8 ohms
 

mudfinger

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I gather we're talking about the reissue? You have to match the overall impedance with the OT. Must be 8. That's my understanding.

The originals don't have a switch because they're very tolerant; while nominally designed for 8 ohms, they can handle anything from 2 to 16. This is true of every vintage Fender amp I know of.
 

Marshall & Moonshine

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I bet there's a good chance that the new MM OT is a solid repro of the vintage, which may still make that possible.
Like I said, contact Merc Mag.
 

Big John

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If the OT can't handle the 4Ω load from two 8Ω speakers in parallel (call Fender customer service to find out for sure), then go series for a 16Ω total load. Install and wire a series out jack on the extension cab, then use a male-female speaker cable to go from from the extension cab to the onboard speaker. At 16Ω, at least the OT won't be overheating.
 

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