Other Amps

Why is it that Fender and other Amp Manufacturers Have Ext. Speaker…

1

When you plug a external speaker into an amp like a Deluxe Reverb, the output transformer doesn't change to a 4 ohm secondary...it still uses the 8 ohm one even though it's now seeing a 4 ohm load.

This could easily be fixed by using Jack like this one and an output transformer with 8 and 4 ohm taps:

http://www.ebay.com/itm/152...

2

Yes, back then I guess impedance just went out the window when it came to using the extension speaker jack... it wasn't seen as any big deal.

3

You are supposed to unplug the internal speaker when using another 8 ohm speaker or 2 16 ohm speakers.

4

You are supposed to unplug the internal speaker when using another 8 ohm speaker or 2 16 ohm speakers.

– Pt

Totally right. And IIRC the "ext" on Fenders is for 'external' speaker in contrast to 'extension' on most other amps.

5

That's lame. For one thing who wants to lose the internal speaker?

For another, why bother with two jacks on the back? Just unplug the internal and plug the external into the same jack.

6

....why bother with two jacks on the back? Just unplug the internal and plug the external into the same jack. (guitarcapo)

Now THAT is a GREAT question! Fender owners' manuals have never been very explicit about connecting "ext" speakers and impedance issues.

7

Yes, you do NOT want to use a second speaker cabinet with a Super Reverb or other amp with a 2 ohm secondary. If zero ohms is a dead short, you can't go much lower than 2!

8

Ext. Speakers are more about filling a room, or sending something back towards the drummer and band, generally used well below the amp's total Volume and Power output...

Even while diluting total ohms, never meant to be an Electrical Engineering challenge.

If you like or want to try different speaker cabinets, just match up and plug straight into the main speaker jack.

9

Yes, you do NOT want to use a second speaker cabinet with a Super Reverb or other amp with a 2 ohm secondary. If zero ohms is a dead short, you can't go much lower than 2!

– JBGretschGuy

Not really a good analogy, and not really true. But I probably wouldn't plug in another 2 ohm 4x10 cabinet into the Extension cab jack*. I mean if you're going to do that, might as well run a second Super Reverb.

*If it wasn't "Extension," why would Fender have made them?

https://reverb.com/item/250...

10

Not really a good analogy, and not really true. But I probably wouldn't plug in another 2 ohm 4x10 cabinet into the Extension cab jack*. I mean if you're going to do that, might as well run a second Super Reverb.

*If it wasn't "Extension," why would Fender have made them?

https://reverb.com/item/250...

– Kap'n

Fender amps take a mismatch pretty well. Using that extension with a Deluxe would be fine at 4 ohms. It would drop a Twin to 2.6. Probably OK. It would drop a Super to 1.6. Mayyyybe OK.

But running another 4 or 2 ohm load with a Super Reverb is asking for trouble.

It's your choice though, so do what you want.

11

If your know you're gonna run a second cab, put a speaker into your combo with twice the impedence as the OT secondary. Plug the second cab (with a speaker same ohms as the first) into the EXT jack and you have a perfect match. Never had a combo with an 8 ohm secondary pushing a single 16 ohm speaker pop. Seen it go bad the other way though.

12

Yessir, up, is a whole lot safer than down! Past 100% mismatch, it may start to sound a little constipated, but you won't smoke your tubes or transformer.

Similarly, attenuators manipulate the impedance of the load, and they generally go up in impedance as the attenuation increases. So the more you attenuate, the more you get that constipated tone.

13

Yes, you do NOT want to use a second speaker cabinet with a Super Reverb or other amp with a 2 ohm secondary. If zero ohms is a dead short, you can't go much lower than 2!

– JBGretschGuy

You're right about tube amps. Lots of modern PA gear is 2 ohm, where Classic Altec was 16 ohm. Tubes prefer a higher impedance, transistors can handle lower impedances. Bose/Delco auto sound speakers half 1/2 ohm voice coils. There are always exceptions to any rule.

14

The amount of misinformation in this thread is astounding.

16

What good does it do to be adversarial and passive aggressive? This is a discussion board. Not an argument board. We generally respect one another around here, unlike 99% of the other forums on the Internet. And, respectfully, the tone of your discourse sucks.

17

Later 70s Super reverbs actually do have another tap form the OT which is used when you plug into the external speaker jack.

18

Totally right. And IIRC the "ext" on Fenders is for 'external' speaker in contrast to 'extension' on most other amps.

– sascha

Ermm, no. That's not quite right. Fender always uses a shorting jack on the main speaker output to save the output section from a numpty powering it on with nothing connected. For a short time, it'll survive, especially with controls zero'd. Never not have anything plugged into the main jack, or you risk presenting a 0 ohm or dead short to the output transformer. Apparently, allegedly, EVH left his brown Tremolux unplugged for years which partly explains his 'tone', with a cab plugged into the extension and it didn't blow - I wouldn't want to risk that personally.

On vintage Fenders, they were always rated for a 100% mismatch on the impedance. So you could plug a 8 ohm speaker in parallel with the existing one and get 4 ohms, a Princeton, Deluxe Reverb or similar could cope. Similarly, a Vibrolux, Pro Reverb, Twin can cope with a 2 ohm total load. With modern plastic former trannies? I wouldn't risk it. But I've seen many old paper Schumachers with wax melted out of them, that keep wailing. The guy winding transformers for me told me he sees almost no old 70's Marshall or Fenders unless a power tube fails and shorts. He sees the newer ones all the time.

19

I have seen a few old Super Reverbs go up in flames from running second cabinets. One was also feeding a Leslie, and a tube shorted plate to filament and it caught on fire. I think the Leslie was 16 ohm, so I would have assumed that safe.

I guess it's like anything else - YMMV.

20

I have seen a few old Super Reverbs go up in flames from running second cabinets. One was also feeding a Leslie, and a tube shorted plate to filament and it caught on fire. I think the Leslie was 16 ohm, so I would have assumed that safe.

I guess it's like anything else - YMMV.

– JBGretschGuy

Yep, if you need more volume than a Super puts out, plugging a second cab in and diming it is asking for it. You're probably just sailing that one too close to the wind, especially as you may be outdoors in heat. Nothing other than a fuse on the output transformer ct can save it in total tube flameout scenario. The transformer may saturate, or just get too hot and melt. A friend's Laney 100 (Marshall 100 Plexi bass clone) flamed several tubes and the output tranny - eventually we traced it to one hyper-microphonic 12AX7 causing ultrasonic clip. Turning it off standby and then turning channel vol up, I was watching the current draw on the tube skyrocket! Then the tube started sparking internally!


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