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Can you run only 2 of 4 channels on a power amp

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    Posted: 01 October 2019 at 12:44pm
I am about to pick up a MC2 E100 ( lucky me) - I have 2 600 w rms p audio loaded subs currently, and about to get a g sub box unloaded... I would run all 4 subs at 8 ohms , with a shedload of headroom, ( and expand into 4 ohm as I get more speakers) but right now I don't have the cash for the 2 pd 186's to load the g sub...so, I wonder. Is it OK to test eth beastie out using only 2 channels at a time ? Would it be OK to power up only subs for a whole night , or is that not OK.

I know on a valve amp, the output most be loaded, but I am assuming if I don't put an input to the channel, and have it a "zero vol" its not going to be working too hard at all ?

thanks for answering what is probably a dumb question :)

AKA the typo king...bear with me, my hands are big and the keyboard small....
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Post Options Post Options   Thanks (1) Thanks(1)   Quote csg Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2019 at 2:20pm
it will be fine
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Post Options Post Options   Thanks (1) Thanks(1)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2019 at 2:32pm
Yes, and no - it will work, but you could be subject to bus pumping in high power half-bridge topology Class D amplifiers, and that can lead to increased distortion and other issues.

There's a bit of info on this here:
http://data-bass.ipbhost.com/topic/470-amplifier-comparison-speakerpower-sp2-12000-and-powersoft-k20-dsp-aesop/

It's likely not an issue unless you're spanking the amp and running low frequencies. Just one thing to bear in mind.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2019 at 3:18pm
You can also always use the trick of inverting the polarity on one channel, so 'spread the load' a bit.

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Post Options Post Options   Thanks (1) Thanks(1)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2019 at 4:08pm
Originally posted by Earplug Earplug wrote:

You can also always use the trick of inverting the polarity on one channel, so 'spread the load' a bit.



This is already done in almost every Class D amplifier. The pins on the XLR and SpeakOn are inverted too so it's invisible to the end user. Doing it again will decrease efficiency, not improve it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Radius Quote  Post ReplyReply Direct Link To This Post Posted: 01 October 2019 at 6:23pm
YOU guys are the best !

So if I don't go haywire, I should be OK to run 2 subs for a while to test the set up, but I will wait until I have the funds to load a g sub cab so I am running 4 subs at 8 ohmns 1 per channel) which I doubt will tax that amp too much really...

AKA the typo king...bear with me, my hands are big and the keyboard small....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 02 October 2019 at 1:12am
Originally posted by Radius Radius wrote:

So if I don't go haywire, I should be OK to run 2 subs for a while to test the set up,


The amp will run for as long as you want at whatever drive level you want to to push it to with no issues. In general solid state amps have no issues with high impedance loads and "no speaker connected" is a really high impedance so you're good there. This is the exact opposite of what the amps in the bench tests linked above were exposed to... low impedance loads, so you will not experience any of those issues.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 02 October 2019 at 1:49am
Originally posted by Conanski Conanski wrote:

Originally posted by Radius Radius wrote:

So if I don't go haywire, I should be OK to run 2 subs for a while to test the set up,


The amp will run for as long as you want at whatever drive level you want to to push it to with no issues. In general solid state amps have no issues with high impedance loads and "no speaker connected" is a really high impedance so you're good there. This is the exact opposite of what the amps in the bench tests linked above were exposed to... low impedance loads, so you will not experience any of those issues.


The amp in question in my link was connected to a low impedance load on one channel, and no load on the other. The resolution was to full bridge the amp, so both channels were used.
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