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Unread 05-18-2011, 10:28 PM   #1 (permalink)
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JCM 2000 DSL 100 watt

I am absolutely beside myself!!

I have a 2000 DSL and I have a 412 Cab the has 4 - 16 ohm speaks in it. The cab has 2 inputs, 8 ohms a side. I have been running my Marshall with 1 speaker wire in each of the 4 & 8 ohm Paralell Jacks to each of the 8 ohm inputs on the cabinet...WITH the OHM switch on 8 OHMS!!

Let's see, since I got it 4 months or so ago!!

I JUST happened to DL the Owners Manual today, and it said that for the load to be 8 ohms with 2 speak cabs they are 16 ohms each. I was like WTF!!! I thought I was so smart too everytime i checked the switch to make sure it was on 8 ohms!

So basically if I am running 2 x 8 ohms speakers (or 1 - 4x12 split stereo 2- 8 ohms) and using both jacks I need to have the switch on 4 OHMS??

Does anybody know?

I am almost sure now that is the way it is supposed to be NOW!

Can anybody tell me what I might have F'd up in my amp head??

It still works, but It was cutting out when it first fired up. IDK I am just furious with myself!

Please any input would be appreciated, I would really want to discuss this further, so I know how bad it is! I only used it for 6 shows (4 hours each) and 20-30? practices.....

Ouch!
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Unread 05-18-2011, 10:37 PM   #2 (permalink)
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Re: JCM 2000 DSL 100 watt

there should be a switch on the connector on the cabinet to define your cabinet mode to 16 or 4 ohms... and you should only use ONE speaker cabinet cable ( not a guitar cable ) and connect to the ohms selection you made on the cabinet...

The 8 ohms is setup for two heads on the same cabinet... stereo mode... if you connect two heads on one cabinet it automaticaly goes to 8 ohms per side...

This is only valid if your cab is stock ( unmodified )
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Unread 05-18-2011, 10:38 PM   #3 (permalink)
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Re: JCM 2000 DSL 100 watt

Dude if u want 2x12 configuration just plug in one side to 8 ohm, if you want 4x12 put it in 16 ohm. You dont hook it up twice!
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Unread 05-18-2011, 10:48 PM   #4 (permalink)
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Re: JCM 2000 DSL 100 watt

It is not a Marshall Cabinet. It is a Stereo 8 ohms x 8 ohms or 1 x 4 ohms configuration.


Cabinet:





8 Ohms --------------- STEREO --------------- 8 Ohms

Right............................................. .............. Left <------------------ 4 ohms use this side








It needs to be treated like 2 cabinets.
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Unread 05-18-2011, 11:18 PM   #5 (permalink)
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Re: JCM 2000 DSL 100 watt

What kind of cab is it? Does it say anything about mono on the backplate?
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Unread 05-18-2011, 11:25 PM   #6 (permalink)
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Re: JCM 2000 DSL 100 watt

OK, let me see if I can get you sorted.

Your head should be set at 4 ohms.

Your cab should be set at the 8 ohms each side.

Run your TWO speaker cables out of the amp to each side of your cab.

OR

Just set the cab to 4 ohms mono, the head to 4 ohms and plug ONE speaker cable from the head to the amp. THIS IS WHAT I WOULD DO.

Hopefully you have not damaged your head by running a 4ohm load on the 8ohm lead of the OT.
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My friend, deep down - every guitar longs to play the blues. Even the BC Rich Bitches...
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Unread 05-18-2011, 11:32 PM   #7 (permalink)
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Re: JCM 2000 DSL 100 watt

To help you out:

If you are running ONE 16ohm cab, set the amp to 16ohm

If you are running TWO 16ohm cabs, set the amp to 8ohm (parallel)

If you are running ONE 8ohm cab, set the amp to 8ohm

TWO 8ohm cabs (or TWO 8ohm sides), set the amp to 4ohm (parallel)

ONE 4ohm cab, set the amp to 4ohm.

I hope this helps.



*Speakers in series is a whole other subject but it will be VERY rare to find it in hooking guitar cabs to amps.
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Quote:
Originally Posted by StootMonster View Post
My friend, deep down - every guitar longs to play the blues. Even the BC Rich Bitches...
Heck, I even was doing a little blues on my 2 year old's Ukulele the other day.
Quote:
Originally Posted by Lespaulnmarshall View Post
...LESS BITCHIN' MORE PLAYIN'!
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Unread 05-18-2011, 11:46 PM   #8 (permalink)
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Re: JCM 2000 DSL 100 watt

It is a Line 6 cab spider 412 ( it was all i have)

It does say 4 ohm mono, use left jack.

It has 4 - 16 ohms speakers in it.


What would i have toasted in the head? Tubes? Or MORE?
It still works, is that a good sign, or it gonna shit on saturday at my next gig?

PS. Mono is better than Stereo?
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Unread 05-19-2011, 12:15 AM   #9 (permalink)
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Re: JCM 2000 DSL 100 watt

Quote:
Originally Posted by Torque View Post
It is a Line 6 cab spider 412 ( it was all i have)

It does say 4 ohm mono, use left jack.

It has 4 - 16 ohms speakers in it.


What would i have toasted in the head? Tubes? Or MORE?
It still works, is that a good sign, or it gonna shit on saturday at my next gig?

PS. Mono is better than Stereo?
The Output Transformer (OT) would be your most likely issue. If you are able to run it by a tech for a quick once over that is NEVER a bad thing. I would like to say that now that you are running the amp at 4ohms with the cab at 4ohms (I assume that is what you setup now) that things should be ok but keep in mind that I am not a tech. Solid state amps and speakers are more of where my experience lies. IMHO: Mono is the ONLY way to go on 4x12 cabs. There is a lot more going on with stereo and running a stereo signal in to a split cab doesn't really give the desired effect. Also, running two outputs from one amp is NOT stereo. There is a bit of confusion with stereo vs. dual mono.

As for the speakers, it is all in how they are wired. Marshall uses 16ohm speakers as well in their 4x12 cabs. The key is if they are in parallel or series or series/parallel... There is a lot that goes on with the cabs.
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Quote:
Originally Posted by StootMonster View Post
My friend, deep down - every guitar longs to play the blues. Even the BC Rich Bitches...
Heck, I even was doing a little blues on my 2 year old's Ukulele the other day.
Quote:
Originally Posted by Lespaulnmarshall View Post
...LESS BITCHIN' MORE PLAYIN'!
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Unread 05-19-2011, 02:24 AM   #10 (permalink)
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Re: JCM 2000 DSL 100 watt

Quote:
Originally Posted by Torque View Post
It is a Line 6 cab spider 412 ( it was all i have)

It does say 4 ohm mono, use left jack.

It has 4 - 16 ohms speakers in it.


What would i have toasted in the head? Tubes? Or MORE?
It still works, is that a good sign, or it gonna shit on saturday at my next gig?

PS. Mono is better than Stereo?
You're not getting stereo with one head unit man. That's for two heads run into one cabinet. Or to use one side. Match your impedance or you'll blow your OT (output transformer) which will run you roughly $200 without service.
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Unread 05-19-2011, 09:48 AM   #11 (permalink)
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Re: JCM 2000 DSL 100 watt

Ok, this is what I got outa this:

1. I need to bring my amp to my tech to have him look at it. Tell him what I did, and have him look at the OT. (I would skip this step, but I have a gig this Saturday)

2. I need to use just one cable to either of the jacks on the back of the amp, plugged to the "mono" jack on the cab. It need to be a speaker cable, not a guitar cable, it is.

3. I need to have the ohm switch on 4 ohm.


4. Pray that I didnt wreck a good amp.


Thank you everyone for your input!!

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Unread 05-23-2011, 05:45 PM   #12 (permalink)
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Re: JCM 2000 DSL 100 watt

dsl dude was close but consider this 2 speakers with the same impedence in parellel
present one half of the load that is presented by one.
two 8s in parellel equal 4 ohms two 8s in series equal 16 if in doubt take a dvm and briefly look at speaker line when ready to connect to cabinet.
lets say you have a driver or a network with no markings. let the
meter tell you how to set the impedance selector
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Unread 05-23-2011, 05:49 PM   #13 (permalink)
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Re: JCM 2000 DSL 100 watt

remember LEFT is from the FRONT of your cab, looking at the speakers and Marshall logo.

That can be confusing too.
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