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2 amps...What did I do?


ernieD

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Last nite while fooling around I ran cables from my GK1001rbi send/return to my Peavey Mark VIII and vice versa thru my SWR Goliath 4x10/SWR 1x15 cabs. Then I switched cables into send/ret and each time I could only use one of the amps Gain or Volume controls. I seemed to lose use of the EQ knobs on each amp but had alot of volume. So, what was I doing with my amps last nite? Could I use this setup live to any benefit or could this damage either amp? :confused:
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Without more details, I can't really picture what you were doing, but I assume you were bypassing the preamp on one of the amps (1001rb?), thus disabling that preamp.

 

I get this with my 1001rb when running my SVP Pro into the effects return (which is the power amp "in") The boost and tweeter controls (biamping section) are still active, but otherwise you're effectively bypassing any shaping control the amp has to offer. Not an issue if you're shaping the sound via another preamp or otherwise.

 

Hope that helps,

-Mike

...simply stating.
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Ah, you were not really bi-amping in the traditional sense, but a form of bi-amping nonetheless. Most effects return jacks are post eq, so when you sent a signal from one amp to the other into it's effects return jack, you sent a post eq signal to the second amp. Now, I think that when you adjust the volume you are simply adjusting how loud the signal is that goes into the power amp, so if you adjusted the volume on the second power amp with something else plugged into the effects return jack and nothing in the instrument jack (essentially nothing plugged into the second amp's preamp), the preamp would have nothing to adjust/amplify, but the signal coming into the effects return jack could be turned up and down by the amplifier sending the signal. In that way, you can use one preamp and volume control to control the power amps of both amps. This is intentional and the way most manufacturers suggest chaining two amps together.
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Thanks for the response Mr M Pulsive. I was wondering if running these 2 amps this way would give me the useable power of the 2 amps combined. I thought I was adding about 350 watts, @8 ohm from the Peavey to the 340 watts from the G-K @8 ohm. Thereby using what I thought was aproximately 690 watts total. Was I wrong? :freak:
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Yes, I think you're wrong -- you don't get the power from both amps.

 

If this was your signal chain...

 

bass-->into amp 1 input-->out amp 1 effects send-->into amp 2 effects return-->out amp 2 speaker out-->into speakers

 

...then you get to use the preamp and gain of amp 1 and the power amp (master volume) of amp 2. This signal you're sending from amp 1 is being sent before it goes thru the power amp section of amp 1. I don't think you can send 300W into an effects return. Essentially amp 1 is functioning as your preamp and amp 2 is functioning as your power amp.

 

It would be great, though, if a more knowledgeable techie could confirm, clarify, or correct what I've written.

 

Peace.

spreadluv

 

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Messiaen knew how to parlay the funk.

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Oops, I guess I didn't realize that both amps were NOT connected to speakers. If both amps were, then you would be getting the power of both amps, but Sweets is right when he says you can't send a SPEAKER signal into the effects return jack of a second amp without blowing something. So, if only one amp is connected to speakers, you essentially are using one amp as a pre, and the other as a power amp. If you connect one of your cabs to each amp, though, you would get the power of both amps simultaneously, I believe.

 

Now, if you hooked up speakers to both amps and only one of the speakers worked, then you would need to have a "power amp pass thru" jack or something similar on the first amp hooked up to the effects return jack of the second amp. I am not sure, since I have not tried this, but it may be the case that if a signal goes out the effects send jack of the first amp but nothing comes back into the first amp's effects return jack, then that may be akin to simply bypassing the first amps power amp.

 

So, I could have been a bit wrong in my first reply. D'OH!

 

(Thanks for clarification, Sweets)

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What S-Dub Willie said.

 

Additionally, I'd like to restate something that should be common knowledge, for the sake of fried circuits. DO NOT try to run the 300W output of one amp (or 5 Watts, for that matter) into the input of another amp - attempting to use the combined power of both amps.

One or Both will fry.

 

Essentially, never amplify an amplified signal... only amplify a line level signal.

-Mike

...simply stating.
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