#1
Hi all, i have a marshall jcm 800 100w head with a marshall 1960a 4x12 cab.

I have always set my amp to 16ohms but this is a bit to loud for home recording and causes my amp to hiss a lot. So i was going to change the output to 4ohms but dont really know what to do and the manual isnt 100% convincing.

So do i have to set the output of my head and the cab to 4ohms or do i just have to set the cab to 4ohms and can i leave the head at 16ohms? Sorry if its a daft question i just really dont want to damage my amp.

Thanks in advance. Si
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#2
I THINK you have to make them match up, so head at 4ohms and cab at 4 ohms as well. But someone else should really answer, as I have never owned a head/cab.
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Last edited by bartdevil_metal at Nov 1, 2007,
#3
Quote by bartdevil_metal
I THINK you have to make them match up, so head t 4ohms and cab at 4 ohms as well. But someone else should really answer, as I have never owned a head/cab.


What he said. I think they have to match up too, but don't own a head/cab.
#7
Yea, you've gotta match it, and it won't make any volume difference I don't think.

You need an attenuator, or a bigger house.
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#8
Quote by R_H_C_P
Yea, you've gotta match it, and it won't make any volume difference I don't think.

You need an attenuator, or a bigger house.


Oh right, how come it doesnt make any difference in the sound if its reducing the ohms then?? How much does an attenuator cost then, dont think i can afford a bigger house, cant even afford pay my mum board lol.
www.myspace.com/bluecollars

My Gear
Fender telecaster deluxe 72
Fender squire strat
Crafter acoustic
Boss ME-50
MXR 10 band EQ
EHX DMM
Marshall JCM 800 100w head
Marshall 1960a cab 4x12
Boss BR-1600
#10
All this stuff about matching isn't always true. You only have to have a cab with an equal or higher impedence, so if you plug you 16 ohm cab into a 4 ohm output you will have a quieter amp but the tone might suffer slightly, I'd still get an attenuator but it is possible to have a quieter amp without.
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#11
It's for current I believe, not power. Different attenuators at different prices. THDs Hot Plate, Marshall Powerbrake, Rockman Power Soaker, Dr. Z Air Brake Weber Mass, Gibson FXPA Power Stealth, TAD Silencer are just a few.

I'm not sure which is the cheapest...I think the range I've found, not including ones I've listed is from 40 to 600. I did find these ebay exclusive ones called Tube Squeezers. Those are forty, but I believe aren't really as good.
#12
The loudness depends on the Wattage, which is a measure of power, not the impedance (Ohms). As someone said, you need an attenuator, or a lower wattage amp.
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#14
Quote by Zaphod_Beeblebr
All this stuff about matching isn't always true. You only have to have a cab with an equal or higher impedence, so if you plug you 16 ohm cab into a 4 ohm output you will have a quieter amp but the tone might suffer slightly, I'd still get an attenuator but it is possible to have a quieter amp without.

that can get just as dangerous as mismatching the other direction with tube amps. You can get flyback voltage from the transformer, where the energy stored in the magnetic core has no where to go with the high impedance, and causes a voltage spike which can short the transformer windings. Keeping within one step "should" be ok either way, but you can't say mismatching to a higher impedance is always safe, because it's not.
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#15
Unless your going to be gigging alot any time soon it might be time to trade for a smaller amp. You will never get the tone out of a tube amp if you cant turn it up. Kinda defeats the purpose of getting one. Some amps can be modded to use only 2 of the tubes at a time instead of 4. But still far louder than you would need for a house. They make alot of 30 watts that are much better for in a house. And can still be miked for a gig. The wall of marshalls you see at a concert are for show. The switch for ohms is usually so you can hook 1 or 2 cabinets up at one time. Or use different speakers.
#16
Quote by Erock503
that can get just as dangerous as mismatching the other direction with tube amps. You can get flyback voltage from the transformer, where the energy stored in the magnetic core has no where to go with the high impedance, and causes a voltage spike which can short the transformer windings. Keeping within one step "should" be ok either way, but you can't say mismatching to a higher impedance is always safe, because it's not.


Oh...Ok then, I stand corrected; I've never owned a tube head so I wouldn't know.
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#17
Quote by Zaphod_Beeblebr
Oh...Ok then, I stand corrected; I've never owned a tube head so I wouldn't know.

lol, I kinda sounded like a dick there, didn't mean to. Yeah, solid state is much more forgiving about impedance mismatches in that direction. No output transformer trying to match a high impedance circuit.
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#18
Quote by Zaphod_Beeblebr
Oh...Ok then, I stand corrected; I've never owned a tube head so I wouldn't know.

What you said was true for solidstate heads, but tube heads have to match.

Threadstarter:
They have to match, and it won't make any difference in volume.
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#19
Quote by chase312
What you said was true for solidstate heads, but tube heads have to match.


Well that's the problem, I've got a solid state bass head and a tube guitar combo

Erock503: You didn't sound like a dick, I was genuinely admitting fault
R.I.P. My Signature. Lost to us in the great Signature Massacre of 2014.

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