Hooking up a single speaker to a Stewart World 1.2 amp

Tony Glassman · From: The Great Northwest

I've been using a Rev plus Stewart World 1.2 amp with two black widow speakers for several years. I recently got a Sarno V8 which has a mono output and I would like to use it with just a single speaker for small gigs

The question is, how do I hook up a single speaker to the World 1.2 if I only want to use one. Will leaving the second speaker output unplugged cause damage to the amp?

Lane Gray · From: Topeka, KS

Unbridge it and only use one side?
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2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

Dickie Whitley · Posted 22 Jun 2014 1:03 pm

Ok, since you used two speakers, I'm assuming you used it in "stereo" mode with a cable going to each speaker. If you want to use one speaker, then you could put in "bridge" mode and just be careful not to "overload" it (depending on the number of watts the speaker will handle verses what the amp will deliver).

I use an ART SLA-1 amp in bridge mode with a single Peavey PR-15. The SLA-1 can deliver up to 260 watts to the 8 ohm PR-15 speaker in bridge mode, but the PR-15 is rated at 400 watts, so no worries there.

Hope this helps.

My 2 cents, YMMV.

Mike Wheeler · From: Delaware, Ohio, USA

[quote="Will leaving the second speaker output unplugged cause damage to the amp?[/quote]

No problem using only one channel and leaving the other with no speaker attached....you will get less total power, obviously, but there's no harm to the amp.
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Best regards,
Mike

Tony Glassman · From: The Great Northwest

Thanks all.

Mike W - You answered exactly what I was concerned about.

Mike Wheeler · From: Delaware, Ohio, USA

Glad I could help you, Tony.
_________________
Best regards,
Mike

Tony Glassman · From: The Great Northwest

Somebody mentioned mono "bridging" of the Stewart World 1.2. I've read the amp manual, but still can't visualize exactly how to hook-up the speaker & amp outputs using a single 4 ohm BW speaker.

Is any one familiar w/ doing this?

Lane Gray · From: Topeka, KS

I'd just use either the right or left output of your preamp, disconnect the other one. Completely disregard the other channel.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

Mike Wheeler · From: Delaware, Ohio, USA

Tony, if you Google "Stewart World 1.2 manual", you'll be able to get the manual. It explains how to do the Bridged output. It's simple. But be aware, at a 4 ohm load, the amp will put out about 1000 watts! At 8 ohms it still puts out 700 watts. That's pretty extreme for a single speaker.

You're probably batter off using one channel only (350 watts at 4 ohms) as mentioned earlier.

Edited to add the link to the manual....

http://www.stewartaudio.com/manuals/World%20Series%20600-1.2%20-%20Manual.pdf
_________________
Best regards,
Mike

Lane Gray · From: Topeka, KS

I had mentioned bridging, but in the course of urging the UNBRIDGING. It never occurs to me that someone will run stereo in live situations, even though the Rev is stereo.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

Mike Wheeler · From: Delaware, Ohio, USA

True, Lane, one could run the Stewart in true stereo, but it's just as true that one could feed a mono signal into both channels of the amp and thus have true mono from the speakers. I preferred doing that (instead of bridging) just in case one of the speakers goes south on me during a gig. (big bummer) Oh Well

I know you know this...I just wanted to clear up any misunderstanding. Wink

_________________
Best regards,
Mike

Lane Gray · From: Topeka, KS

Mike, given that Tony asked about bridging, I chose to assume that he ran the Revelation with right and left identical, and each channel to a side of the Stewart, and then on to a cab.
Stereo outputs of a mono source.
If that's what he does, then just unplug one side.
The current configuration isn't fully known, but the current configuration tells one how to change to the new.
Tony, assuming you never bridged it, I'd do the following:

Guitar-preamp (configure effects and volume pedal as you wish)- left channel Rev output - left channel Stewart input - left Stewart out to speaker.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

Mike Wheeler · From: Delaware, Ohio, USA

Tony, I just re-read the above posts and realized I didn't answer the question you asked...instead I pointed you to the manual...which you already have. duhh!

First, make sure the amp is powered off, and switch the "Mono/Stereo" switch to "Mono" (this puts the amp in bridged mode). The speaker load (whether 1 or more speakers) goes to the two red posts. One speaker wire to one red post, the other speaker wire goes to the other red post (polarity isn't important in this case). The black posts are not used at all for bridged mode....in fact, you want to be sure the metal part of you speaker wire's plug doesn't contact any grounded connection at all...ever...while in bridged mode.

Use the left signal input of the amp for bridged mode operation.

If you want to switch back to stereo operation, double check that you have turned the power off, and that you put the "Stereo/Mono" switch back to the "Stereo" position, or you could blow the amp.

Hope this isn't confusing to you.
_________________
Best regards,
Mike

Lane Gray · From: Topeka, KS

Mike, given that his speakers can't take the full load, wouldn't it make more sense to use one half and stay in stereo? That way, he can't fry the speakers.
AND it must be a quieter gig since he only wants one...
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

Dickie Whitley · Posted 27 Jun 2014 3:28 pm

While there may be no scientific basis for my belief, I just would not disconnect a speaker from one side so I could go mono, I think it's better to go bridged and turn the volume down to achieve some speaker protection or better yet, fuse the speaker line for even more protection.

Sorry, I just can't agree with the "one side" only operation. My 2 cents, YMMV.

Mike Wheeler · From: Delaware, Ohio, USA

Yes, that's true, Lane. I think running the amp in stereo mode, but with a mono signal, would cover a lot of situations. One speaker for moderate sized venues, and both speakers when big guns are needed. That's what I'd advise.

Even with that setup the speakers are getting 350 watts each, so beefy speakers would be needed.
_________________
Best regards,
Mike

Mike Wheeler · From: Delaware, Ohio, USA

Dickie, your method will also work, if that's what you want to do. But there is no technical reason to not run with only one side. This way Tony won't have to change his rig around to accommodate either stereo, or mono operation. Seems like the best solution for his situation, though. All he has to do is decide how he wants to run his inputs, and how many speakers he needs. Nice and simple, it seems to me.
_________________
Best regards,
Mike

Tony Glassman · From: The Great Northwest

I understand the "bridging" now. You are basically running the signal through both channels, sort of in series. The signal enters the left channel and is shunted to the right channel, where it ultimately exits. The speaker is hooked to both channels so it gets the increased power.

Using a single speaker (one side of amp in stereo mode) @ 8 Ohms: the amp will put out 200w. At 8 oHms in "bridged mode it puts out 700 watts. That seems a bit "heavy handed" and risky for both the speaker and the amp (runs hotter).

I got an email from Brad Sarno re: running one channel only in stereo mode. He said that will not be a problem for the Stewart amp.

Lane, Mike and all - thx for your input

Lane Gray · From: Topeka, KS

Tony, think of "bridging" as the 240V that enters an American house. You have 120 left and 120 right.
And 240 comes by ignoring the tap in the middle and using left and right together.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects

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