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Jaganath

Controlling Ohm Impedance

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I have a POD HD PRO X and now that I have a tone I'm happy with, I want to run it into a cab. I understand that I need a power amp to do so, and I understand that I use the effects out and in to connect the pod with the power and I use the Pod's own line out into the amp, but how do I control the amp's Ohm impedance so that it matches the cab?

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you don't really control it, you just get an amp that can handle your cab (or vice versa)

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Bottom line.  Best if impedances are the same but if not, make SURE the cab impedance is greater than the amps impedance. Burnt out amp will result if you don't.

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Most power amps will have a range of ohms that it can run at.  You will certainly want to match your wattage and ohm up correctly.  you will want your power amp to run at the same ohms as you cab and have a little more wattage than the cab (never under power it, it can damage the speakers).  As an example I have a 8 ohm 120 watt cab.  My power amp, when running at 8 ohms puts out 150 watts per channel.  There isn't really a set equation for how much more powerful than your cab you want your amp to be but I would keep it at a small fraction above, like 15-20%.

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I have a POD HD PRO X and now that I have a tone I'm happy with, I want to run it into a cab. I understand that I need a power amp to do so, and I understand that I use the effects out and in to connect the pod with the power and I use the Pod's own line out into the amp, but how do I control the amp's Ohm impedance so that it matches the cab?

Some power amps will have a selector switch that allows you to use cabinets with different impedance ratings, but not all have that option. I have a Carvin TS100 that I can run at 4,8, or 16 ohms. And since its a stereo amp, I also have the option of running at 50W per side, or 100W bridged mono. That pretty much covers all the bases. Others are less versatile and may only give you one option.

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If this is true, then why does every amp In the world come with higher wattage speakers than the amp wattage? Never seen one the other way around. Please clarify.

 

Most power amps will have a range of ohms that it can run at. You will certainly want to match your wattage and ohm up correctly. you will want your power amp to run at the same ohms as you cab and have a little more wattage than the cab (never under power it, it can damage the speakers). As an example I have a 8 ohm 120 watt cab. My power amp, when running at 8 ohms puts out 150 watts per channel. There isn't really a set equation for how much more powerful than your cab you want your amp to be but I would keep it at a small fraction above, like 15-20%.

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If this is true, then why does every amp In the world come with higher wattage speakers than the amp wattage? Never seen one the other way around. Please clarify.

 

Yeah...I didn't feel like being the first one to wade into this pool, but it doesn't make any sense to me either.

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Just chippin' in here - personally I'll always rate my speakers at or above the amp rating, BUT - if there's a serious difference (with the amp rated lower) than if you push the amp into square wave clipping you can easily blow your speakers.  In this case it's not a question of wattage, it's the signal being put out - conventional speakers don't take kindly to being hit with right angles.....

 

So - make sure the amp is strong enough to get you where you need to be at, say 60% of rating, and size you speakers accordingly.  Like I say, I always rate my speakers at 50% or so more than the amp.  I dunno, works for me.....

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So I am certainly no sound technician but... Just like Ricstudioc said... it works for me.  I do have some friends in the biz that used to run sound for national stage acts and they still do for some of the bigger local named bands around here.  The rule of thumb of making sure you amp is a but more powerful than the speakers it is pushing comes from his years of experience.  The rig that I have put together sounds great and works well so it didn't steer me wrong.  Do some reading out there and see what others say or try to match them exactly (good luck there).

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I can appreciate your "friends in the biz" and their experience, but I'll tend to listen to the guys who have built amps and speakers for almost a hundred years instead. I generally aim for what seems to be the norm in guitar amps at least, and have a speaker rated for roughly double my watts. Same for PA.

 

 

So I am certainly no sound technician but... Just like Ricstudioc said... it works for me. I do have some friends in the biz that used to run sound for national stage acts and they still do for some of the bigger local named bands around here. The rule of thumb of making sure you amp is a but more powerful than the speakers it is pushing comes from his years of experience. The rig that I have put together sounds great and works well so it didn't steer me wrong. Do some reading out there and see what others say or try to match them exactly (good luck there).

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