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Old 10-21-2012, 06:17 PM   #1
NordicThrasher
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Amp Technical Help (ohms question)

I have a Line 6 Spider III cab and on the back, it says 150 watts. I'm looking into getting a Marshall DSL 100H and I was wondering if it's possible to match it with the aforementioned cab. I don't know much about ohms, so if someone could fill me in on the gist of it (I only know very basics about this stuff, so forgive the noobie question!).
Thanks!

Last edited by NordicThrasher : 10-21-2012 at 08:39 PM.
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Old 10-21-2012, 07:23 PM   #2
Dave_Mc
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what impedance is the cab? (in ohms)

but odds are it'll work, the dsl has 4, 8 and 16 ohm speaker outs, and I doubt your cab is anything other than one of those 3 impedances.

you just plug into your cab (the mono socket if it's a stereo cab, i have no idea if it is or not) and then plug into the amp and set the amp to the same impedance the cab is in mono mode.

that being said, it's probably not an amazing cab. but it should "work".
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Old 10-21-2012, 07:36 PM   #3
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Quote:
Originally Posted by NordicThrasher
I have a Line 6 Spider III cab and on the back, it says 150 watts. I'm looking at getting a Marshall DSL 100H and I was wondering if it's possible to match it with the aforementioned cab.


man, line 6 makes it hard to tell what the impedance of their cabs is. it seems like a line 6 cab can do 4 or 16 ohm mono though (correct me if i am wrong).

it seems the marshall DSL 100 can do either:
- one 16 ohm cab through the 16 ohm output
- two 16 ohm cabs through both the 8 ohm outputs
- one 8 ohm cab through one of the 8 ohm outputs

so, i'd set the line 6 cab to 16 ohms and run it out the 16 ohm output on the marshall.

Quote:
Originally Posted by NordicThrasher
I don't know much about ohms, so if someone could fill me in on the gist of it (I only know very basics about this stuff, so forgive the noobie question!).


'ohms' are a unit of measure for resistance in direct current. a simple, if fairly inaccurate, analogy would be to think of a river or stream. the water flowing down the stream would be the electricity, the amount of water passing a given point of the river would be the electrical current. anything the slows down the electrical current, like a rock in the river, would represent electrical resistance.

the electricity that is dealt with in a guitar amp to guitar cabinet is not direct current though, it is alternating current, and that above analogy completely breaks down when discussing AC. resistance in AC is called 'impedance', because it has to account for resistance and reactance.

just knowing the idea of resistance and knowing impedance is more complicated than resistance is probably more than you need to know. the important part is that a tube guitar head will want to see a 'load' (an electrical impedance, aka a speaker cabinet) when the amp is operational. not providing a load can damage the most expensive part of the amp.
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Old 10-21-2012, 08:02 PM   #4
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^ maybe you looked up the newer dsl? i got a manual from the marshall site (i think it was the older one, i assumed he has the older one) and it had 4, 8 and 16 ohm options.

other than that, agreed
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Old 10-21-2012, 08:17 PM   #5
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Originally Posted by Dave_Mc
^ maybe you looked up the newer dsl? i got a manual from the marshall site (i think it was the older one, i assumed he has the older one) and it had 4, 8 and 16 ohm options.

other than that, agreed


yeah, i was gonna say something about that, i got a shot from a website of the back of what looked like the new DSL. even marshall's site doesn't have a pic of the back.
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Old 10-21-2012, 08:46 PM   #6
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Quote:
Originally Posted by Dave_Mc
what impedance is the cab? (in ohms)

but odds are it'll work, the dsl has 4, 8 and 16 ohm speaker outs, and I doubt your cab is anything other than one of those 3 impedances.

you just plug into your cab (the mono socket if it's a stereo cab, i have no idea if it is or not) and then plug into the amp and set the amp to the same impedance the cab is in mono mode.

that being said, it's probably not an amazing cab. but it should "work".


Yeah, it probably wouldn't even provide the full tonal quality and potential of the head (the cab), but it will do for now. Anywho, the back says "150 watts (each side)" with "8 ohms left and 8 ohms right" for Stereo, and the Mono is 4 ohms.
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Old 10-21-2012, 08:49 PM   #7
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Quote:
Originally Posted by gumbilicious
'ohms' are a unit of measure for resistance in direct current. a simple, if fairly inaccurate, analogy would be to think of a river or stream. the water flowing down the stream would be the electricity, the amount of water passing a given point of the river would be the electrical current. anything the slows down the electrical current, like a rock in the river, would represent electrical resistance.

the electricity that is dealt with in a guitar amp to guitar cabinet is not direct current though, it is alternating current, and that above analogy completely breaks down when discussing AC. resistance in AC is called 'impedance', because it has to account for resistance and reactance.

just knowing the idea of resistance and knowing impedance is more complicated than resistance is probably more than you need to know. the important part is that a tube guitar head will want to see a 'load' (an electrical impedance, aka a speaker cabinet) when the amp is operational. not providing a load can damage the most expensive part of the amp.


The last part about damaging the amp I did know, and a very important fact it is!
Thanks for putting in perspective, though, I pretty much have the essential idea of it now.
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Old 10-21-2012, 08:49 PM   #8
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Originally Posted by NordicThrasher
Anywho, the back says "150 watts (each side)" with "8 ohms left and 8 ohms right" for Stereo, and the Mono is 4 ohms.


well, that is an issue. the DSL can't take a 4 ohm load. you can technically just use one of the '8 ohm, 150 watt' sides, but you will just be using 2 speakers.
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Old 10-21-2012, 08:52 PM   #9
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Quote:
Originally Posted by gumbilicious
well, that is an issue. the DSL can't take a 4 ohm load. you can technically just use one of the '8 ohm, 150 watt' sides, but you will just be using 2 speakers.


If you wired up a y cable the right way you could run each side together in series to the 16 ohm jack. Or you could rewire the cab to run 16 ohms mono. Given that the cab is almost certainly wired with spade connectors that wouldn't be hard.
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Old 10-21-2012, 09:09 PM   #10
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Quote:
Originally Posted by gumbilicious
well, that is an issue. the DSL can't take a 4 ohm load. you can technically just use one of the '8 ohm, 150 watt' sides, but you will just be using 2 speakers.

The DSL100H?
Cause I know the old DSL was the JCM 2000 so I'm just making sure we're talking about the same amp x)

EDIT: I use Stereo currently, with the head I have now, a Spider III HD75. Not sure if that matters or not. So I have two cables for that. Does the head come with cables of its own (Marshall)? (Assuming it does...)

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Old 10-21-2012, 09:28 PM   #11
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Quote:
Originally Posted by NordicThrasher
The DSL100H?
Cause I know the old DSL was the JCM 2000 so I'm just making sure we're talking about the same amp x)


http://www.sweetwater.com/store/detail/DSL100H

the back pic only shows 8 and 16 ohm outs

Quote:
Originally Posted by NordicThrasher
EDIT: I use Stereo currently, with the head I have now, a Spider III HD75. Not sure if that matters or not. So I have two cables for that. Does the head come with cables of its own (Marshall)? (Assuming it does...)


your head is a stereo head, the marshall is a mono head (the marshall only effectively send out 1 signal that can be run in parallel).

if you cab only has 8 ohm stereo or 4 ohm mono, then you can only run one side of your stereo cab (barring kevin's advice).

marshall will prob not come with it's own speaker cable.
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Old 10-21-2012, 09:30 PM   #12
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^Yep. Like I said, your best bet is to rewire the cab for 16 ohms mono. Its not hard. Since the cab is 4 ohms mono and 8 ohms stereo that means it has all 4 ohm or 16 ohm speakers, so its possible to wire it for 16 ohms mono.
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Old 10-21-2012, 09:35 PM   #13
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Quote:
Originally Posted by gumbilicious
http://www.sweetwater.com/store/detail/DSL100H

the back pic only shows 8 and 16 ohm outs



your head is a stereo head, the marshall is a mono head (the marshall only effectively send out 1 signal that can be run in parallel).

if you cab only has 8 ohm stereo or 4 ohm mono, then you can only run one side of your stereo cab (barring kevin's advice).

marshall will prob not come with it's own speaker cable.


Odd that even though the back of my cab has two inputs for 8 ohms and so does the back of the Marshall, it still will only input through to one side of the cab . This is why I like to get a second opinion, so to speak, for this stuff. Thanks guys! A little disappointing but I'll keep searching for that perfect amp that will work for me.

EDIT: I don't suppose the JCM 2000 is any different, as far as its ohms requirements and matching my cab. I'll check but it probably isn't

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Old 10-21-2012, 09:37 PM   #14
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Quote:
Originally Posted by Kevin Saale
^Yep. Like I said, your best bet is to rewire the cab for 16 ohms mono. Its not hard. Since the cab is 4 ohms mono and 8 ohms stereo that means it has all 4 ohm or 16 ohm speakers, so its possible to wire it for 16 ohms mono.


Eh, but I'd be too afraid of ****ing up the thing because I've never done anything like that before. Plus if I wanted to use the old head for anything, it probably wouldn't work and I'd have to rewire it, wouldn't I?
I mean, if I could do it and knew how I totally would but, I dunno, man. Too risky?

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Old 10-21-2012, 09:46 PM   #15
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It would still work if the cab was 16 ohms mono. And trust me, there is nothing to mess up. Just take a clear pic of the wiring before you start, so you'll have a reference to go back if need be. After that, show us the pic and we can tell you exactly which wires to move. When you see these spade connectors (assuming thats what your cab has) you'll see why its silly to worry.
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Old 10-21-2012, 10:01 PM   #16
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This is what the back of the cab looks like on the inputs. I'll work on unscrewing the back panel now.

EDIT: Can't even figure out why this back panel's not coming off. I've removed all the screws on it. Do the cable jack frame screws need to come off too? I just didn't want to rip any wiring out by accident.
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Old 10-21-2012, 10:37 PM   #17
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If I did what Dave said, it should work, at least the with JCM 2000, because that has an ohms selector. the DSL100H doesn't appear to. I could just go with the older model. It'd probably sound better anyway. It would save me ****in' around with my cab's wiring, too.
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Old 10-21-2012, 10:49 PM   #18
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Originally Posted by NordicThrasher
If I did what Dave said, it should work, at least the with JCM 2000, because that has an ohms selector. the DSL100H doesn't appear to. I could just go with the older model. It'd probably sound better anyway. It would save me ****in' around with my cab's wiring, too.


you are correct.
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Old 10-21-2012, 11:12 PM   #19
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Originally Posted by gumbilicious
you are correct.

So, basically, I select 8 ohms and hook it up in stereo format, as I normally would, like with my current head, or are all Marshalls mono and I would just put one cable in the mono jack in the cab and select 4 ohms, on the head, since that's what I have for mono on the cab? Just clearing it all up, sorry! x)
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Old 10-21-2012, 11:29 PM   #20
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Originally Posted by NordicThrasher
So, basically, I select 8 ohms and hook it up in stereo format, as I normally would, like with my current head


technically, you could switch the JCM2000 over to 4 ohm operation and run it into both sides of the cab and that would be acceptable because each side of the cabinet is 8 ohms and:

1/Rtot = 1/R1 + 1/R2 = 1/8 + 1/8 = 2/8 = 1/4
take reciprocals and
Rtot = 4 ohms

that is just how you add up resistance in parallel.

but the simpler way to do it is just to switch the JCM2000 over to 4 ohm and plug one of those outputs into the mono input on the cab.

Quote:
Originally Posted by NordicThrasher
or are all Marshalls mono and I would just put one cable in the mono jack in the cab and select 4 ohms, on the head, since that's what I have for mono on the cab? Just clearing it all up, sorry! x)


yup, that is dead on.
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