Emergency Amp Swap

K

Kip Conner

Junior
Mar 13, 2011
370
0
0
Athens, GA
I lost and an amp that I power the mid range band in a three way system on a rental recently. The amp is at service and the tech is a little behind so there's a possibility that it might not be ready for the next engagement. I don't have a spare of that particular type that isn't in use, but I do have two amps that I can put in it's place to cover the bands. However, the amps would have to be bridged mono to get enough power and then it would be too much power.

I'm trying to determine where I'm going to drop the gain to match the correct power requirements. Either I can do it on the Omnidrive or do it on the amp gains themselves. I typically like to do it in places where I lock it in such as the processor and not front panel trim gains.

Any advantage to either solution (correcting in the processor or the front panel)?

My tech thinks that he'll have it fixed barring any back ordered parts, but I need to start thinking about a plan b
 
Re: Emergency Amp Swap

If the gain is the same (remember you pick up 6dB from bridging), how much power the amp is capable of doesn't really matter, you're not likely to use any more midrange drive that you were previously. I'd not change your DSP *if* you have a reliable way to use the amp's front panel controls (and then gaff them over). If not, use the DSP output level.
 
Re: Emergency Amp Swap

It's easy to dial back the DSP, considering that I'm using the same series of amp in theory the tone shouldn't change, just the level. The current amp produces 1200W per channel for Stereo Mids. The the substitute would be 2 lesser power amps, one per left mid and one per right mid. They would produce 2000w each so I would have to dial the input gain back a considerable amount in order to not damage the drivers.

I'm going to use my smaart files from the original tuning session to match up the levels so I would be able to see tone differences as well.
 
Re: Emergency Amp Swap

Kip Conner said:
It's easy to dial back the DSP, considering that I'm using the same series of amp in theory the tone shouldn't change, just the level. The current amp produces 1200W per channel for Stereo Mids. The the substitute would be 2 lesser power amps, one per left mid and one per right mid. They would produce 2000w each so I would have to dial the input gain back a considerable amount in order to not damage the drivers.

I'm going to use my smaart files from the original tuning session to match up the levels so I would be able to see tone differences as well.
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Dialing the gain back on the bridged amps will change the tonal character of your boxes. You're better off using limiters on your DSP for each band if you can accurately measure or calculate amp output, or better yet bringing enough rig for the gig so you aren't into the limiters, and therefore it won't matter.
 
Re: Emergency Amp Swap

Kip,

Dialing back the gain will not change how much power the mids can receive, it will just change how much drive level it takes to deliver that power. It will also mess up the tonality of your boxes. However, if you weren't blowing up the mid woofers before, you are no more likely to do it now. The increase in potential power is less than 3dB, and unless they were massively underpowered before the previous amp should have been just as capable of blowing them up. I would match actual gain and call it a day. If you had power limiters set before they can also stay at the same level.
 
Re: Emergency Amp Swap

I agree with Bennett. My rig uses all old Crest x001 series amps which all have the same gain. I keep an 8001 and use it for a spare for even for the smaller model 7001s and 4801s in a pinch as my processing is setup to not allow more power out of the amp regardless of the maximum output capability. In theory I could use all 8001s for all the band passes so long as the rms and peak limiter settings on the XTA processors were left alone. But that would make my 300lb. amp racks weigh double and be 3RU taller ;)
 
Re: Emergency Amp Swap

Bennett Prescott said:
Kip,

Dialing back the gain will not change how much power the mids can receive, it will just change how much drive level it takes to deliver that power. It will also mess up the tonality of your boxes.
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I'm confused by this statement. How does changing the gain on the front of an amp have a different tonality versus changing the gain in a DSP? Maybe I'm reading this wrong. (I do agree with the first sentence).
 
Re: Emergency Amp Swap

Tony Williams said:
I'm confused by this statement. How does changing the gain on the front of an amp have a different tonality versus changing the gain in a DSP? Maybe I'm reading this wrong. (I do agree with the first sentence).
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I think Bennett meant that doing EITHER, will mess up the mid/high blend that is meant for the cabinet, thus messing up the tonality
 
Tim McCulloch said:
So what about the 6dB of gain (not output current capability) he'll pick up when he puts the replacement amp in bridge mode?
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Unless the amp compensates internally... This is one of several reasons I dislike bridging. Now your amp gain is "read the manual", and set those front panel knobs right, and get the dip switch right, and change your wiring, and check your impedance... Also, call me crazy, but I don't think it sounds as good.
 
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