# ohms??



## wvr013 (Nov 28, 2014)

I have a randall KH-120 that i use as my main amp... I was wondering about which output(?) would serve me best and give me the best sound?

I have an input for 4ohms or 8ohms. I don't understand the difference I have read a few articles on it but I can't seem to grasp the concept.


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## Guitar101 (Jan 19, 2011)

http://colomar.com/Shavano/speaker.html

You need to figure out the ohm rating of your speaker cab and choose the proper input on your amp.


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## hardasmum (Apr 23, 2008)

wvr013 said:


> I have a randall KH-120 that i use as my main amp... I was wondering about which output(?) would serve me best and give me the best sound?
> 
> I have an input for 4ohms or 8ohms. I don't understand the difference I have read a few articles on it but I can't seem to grasp the concept.



Your speaker cabinet has inputs for 4 or 8 ohms?


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## GTmaker (Apr 24, 2006)

first, your amplifier needs to see the same ohms settings as the output calls for.
So if you plug into the 4 ohm jack, your total speaker ohms needs to be 4...

The is a corolation between the power your speakers see and ohms.

use the following calculator to input your amp power and your specific speaker cabinet .
You will then see what power is going into each speaker.

This is particulrly usefull if you speaker cabinet has unmached speaker ohms ratings.
I found that usefull.
http://www.speakerimpedance.co.uk/?act=two_parallel&page=calculator

I hope this helps...
G.


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## greco (Jul 15, 2007)

If this is your amp, it appears to be rated for 4 ohms minimum.

http://www.randallamplifiers.com/th_product/kh120rhs/

Giving us information about the speaker cab (i.e., number of speakers and ohms/impedance rating of each speaker and how the cab is wired ...if there is more than one speaker) is essential. This impedance matching stuff and cab wiring can get very confusing and your type of question comes up on this forum quite frequently.

There are many knowledgeable members on this forum that will be able and pleased to help you.

Cheers

Dave


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## keto (May 23, 2006)

Given the amp is solid state, I wouldn't mismatch - they're *generally* not built to take it.


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## Guitar101 (Jan 19, 2011)

hardasmum said:


> Your speaker cabinet has inputs for 4 or 8 ohms?












I think he's talking about the 4 ohm & 8 ohm outputs on a KH-120 head.


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## greco (Jul 15, 2007)

Guitar101 said:


> I think he's talking about the 4 ohm & 8 ohm inputs on a KH-120 head.


I might have linked to the wrong amp...Thanks for this pic.

Dave


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## cavemusic (Jul 8, 2013)

Guitar101 said:


> I think he's talking about the 4 ohm & 8 ohm inputs on a KH-120 head.


Those jacks are speaker _outputs_. The 4 ohm output will drive an external speaker and that speaker should be a minimum of 4 ohms impedance. Using a 4 ohm speaker cabinet connected to the 4 ohm amp output will give you the maximum rated power output of the amp. The 8 ohm output will drive an external speaker and that speaker should be a minimum of 8 ohms impedance.


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## greco (Jul 15, 2007)

@wvr013...Welcome to the GC forum!

Looks like your first thread is getting a lot of attention and offers to help. That is what this forum is all about ...and more (IMHO)

Cheers

Dave


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## jb welder (Sep 14, 2010)

Owners manual doesn't explain that part? :smile-new:


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## greco (Jul 15, 2007)

jb welder said:


> Owners manual doesn't explain that part? :smile-new:


Not a lot of detailed info in their 2 page manual....but I guess it is enough to help with the issue at hand:
http://www.randallamplifiers.com/manuals/KH75 KH120RH_Manual.pdf

Cheers

Dave


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## bluzfish (Mar 12, 2011)

greco said:


> @wvr013...Welcome to the GC forum!
> 
> Looks like your first thread is getting a lot of attention and offers to help. That is what this forum is all about ...and more (IMHO)
> 
> ...


Sorry but I couldn't _resist_...


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## cavemusic (Jul 8, 2013)

bluzfish said:


> Sorry but I couldn't _resist_...
> 
> View attachment 11172


Impedance is futile?? :congratulatory:

Or measuring resistance is futile if your multimeter leads aren't connected??


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## Steadfastly (Nov 14, 2008)

This may help to explain it. If they are not matched you are either going to get poor performance (under powered) or possibly damage your amp.

http://www.prestonelectronics.com/audio/Impedance.htm


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## jb welder (Sep 14, 2010)

greco said:


> Not a lot of detailed info in their 2 page manual....but I guess it is enough to help with the issue at hand:
> http://www.randallamplifiers.com/manuals/KH75 KH120RH_Manual.pdf


Thanks Dave, and the manual is not very helpful so apologies to the OP.
The rear panel is labelled for the combo version and they didn't bother to change it for the head. With the combo, using the 4 ohm jack cuts out the internal speaker, using the 8 ohm out does not.

For the head, if you run an 8 ohm cab you will get about 100W output power. With a 4 ohm cab (or two 8 ohm cabs) you will get the full 120W output power.
Do not run the head into less than a 4 ohm load (example two 4 ohm cabs) as you could damage the amplifier.


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