Help with Impedence

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OdgeUK
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Help with Impedence

Post by OdgeUK » Wed Mar 07, 2012 4:28 am

Hi All,

I sometimes use a 16ohm Hotplate with an 8ohm cab, with my Marshall 4-holer. The problem is, I am not sure what the safest setting is for the head? Should it be 8ohms or 16ohms? I am using the amp in mono, just one lead from one of the speaker outputs, to the hotplate.

Image


The THD Hotplate manual is misleading:
THD wrote:IMPORTANT: WHEN USING JUST ONE OF THE SPEAKER OUTPUTS FROM THE HOT
PLATE, THE SPEAKER CABINET SHOULD HAVE THE SAME IMPEDANCE AS THE
HOT PLATE.
Well this sounds like I should give up right away, as this scenario describes my set up. But.....
THD wrote:Q. Can I still use the Hot Plate if it has a different impedance than my amp?
A. ONLY if the impedance of the Hot Plate is EQUAL TO OR GREATER THAN that of the
amp. However, this will lessen the effectiveness of the Hot Plate’s tone controls.
Hmmm.....well....maybe I CAN use the Hotplate? If I set the amp to 8 or 16ohms then the Hotplate is Equal or Greater to the amp......
THD wrote:Q. If I am using just one speaker cabinet, can I still use the Hot Plate if it has a different
impedance than my speaker cabinet?
A. ONLY if the impedance of the speakers is equal to or greater than the amplifier, AND
the impedance of the Hot Plate is equal to or greater than the amp. Again, this will lessen
the effectiveness of the Hot Plate’s tone controls.
Yes...I am just using one speaker cabinet! Now in my setup, the cab is 8ohms and the Hotplate is 16ohms. So if I set the head to 8ohms then I still match the criteria for this (the impedance of the speakers is equal to or greater than the amplifier, AND the impedance of the Hot Plate is equal to or greater than the amp)
Last edited by OdgeUK on Wed Mar 07, 2012 7:00 am, edited 1 time in total.
73 JMP 1987 w/LarMar
78 JMP 1987
79 2104
Peavey JSX 120
Marshall 1936 G12-65
Gibson LP Custom, Squier CV 50's Strat w/SD '59

OdgeUK
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Re: Help with Impedence

Post by OdgeUK » Wed Mar 07, 2012 4:37 am

I have emailed THD twice but no reply.

I am thinking at this stage that I probably need to use both speaker outs on my head (not possible with one of them as it has a PPIMV in one of the jacks) or swap my 16ohm Hotplate for an 8ohm.....
73 JMP 1987 w/LarMar
78 JMP 1987
79 2104
Peavey JSX 120
Marshall 1936 G12-65
Gibson LP Custom, Squier CV 50's Strat w/SD '59

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Harold
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Re: Help with Impedence

Post by Harold » Wed Mar 07, 2012 9:09 am

Always set the Marshall to the same impedance as the loadbox. Connecting a mismatched cab to the loadbox is far less devastating than mismatching your head.

That said: it's probably best to get it to match 100%.


Are you using the loadbox to lessen the volume just a bit, or to get down to bedroom level?
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OdgeUK
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Re: Help with Impedence

Post by OdgeUK » Wed Mar 07, 2012 9:16 am

Harold wrote:Always set the Marshall to the same impedance as the loadbox. Connecting a mismatched cab to the loadbox is far less devastating than mismatching your head.

That said: it's probably best to get it to match 100%.


Are you using the loadbox to lessen the volume just a bit, or to get down to bedroom level?
Mostly at home to get down to bedroom level but I have used it in a rehearsal situation once or twice to just tame it slightly (maybe by 4db).

So if I went Marshall (16ohm) - Hotplate (16ohm) - Cab (8ohm) it's probably the safest option. This is what I've been doing in the main.
73 JMP 1987 w/LarMar
78 JMP 1987
79 2104
Peavey JSX 120
Marshall 1936 G12-65
Gibson LP Custom, Squier CV 50's Strat w/SD '59

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Harold
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Re: Help with Impedence

Post by Harold » Wed Mar 07, 2012 9:30 am

You could also disconnect 1 speaker so that the cabs is 16 Ohm again. Or are there two 4-ohm speakers in series?
Gibson SG Jr > DP209 > Ross Distortion > JMP 2203, 2204 or 1987x > 1960TV
TANK86 - Instrumental sludge metal!
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OdgeUK
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Re: Help with Impedence

Post by OdgeUK » Wed Mar 07, 2012 9:36 am

Harold wrote:You could also disconnect 1 speaker so that the cabs is 16 Ohm again. Or are there two 4-ohm speakers in series?
It's a Marshall 1936, so yes, you can. If you plug into the "Right" input on the cab, you get one speaker running at 16ohm (sounds a bit different though from memory). Definitely an option for home playing (the cab has 2 x G12-65 so one speaker should happily handle my 50w head).
73 JMP 1987 w/LarMar
78 JMP 1987
79 2104
Peavey JSX 120
Marshall 1936 G12-65
Gibson LP Custom, Squier CV 50's Strat w/SD '59

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Re: Help with Impedence

Post by bdc » Wed Apr 04, 2012 9:11 pm

And or Ed at THD have been great to me....Call them on the phone! They get so much E-mail it's unreal! and it goes through a filtering system....Their busy as hell....but use the phone...They mean well and are great contributers to the guitar playing community....Don't give up...Use the phone...

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