McIntosh MC250 hookup help

McIntosh MC250 hookup help

Postby cincinnatiohio » Thu Dec 20, 2012 6:05 am

Ok so I just got my first McIntosh. A MC250. Never tried one at all. I got my fender twin modded for preamp, etc per Waldo's site (thanks Waldo and the community at large!).

Here is what I'm not sure of, even though I do have the MC250 manual:

Could someone or some people PLEASE possibly put up a couple pictures of how their leads are setup for the speaker connections on their Or possibly explain very clearly the hook ups to the leads for both stereo and mono? I am running into a 2x12 JBLK120 cabinet rated at 4 ohms.

I have a 1/4 inch jack wired to speaker wire. It's my understanding one goes to the comone goes to the 4ohm lead on the right side (mono).... But what about bridging to the left 4ohm lead? Is that necessary as well? What if I want to run 50 watts mono through only one side?

PLEASE any help is much appreciated

Thanks from Ohio!
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Re: McIntosh MC250 hookup help

Postby tcsned » Thu Dec 20, 2012 7:20 am

Image

If your back looks like this and you are at 4 ohms you connect the hot line to the 8 ohm terminal (left) and the ground to the bottom ground terminal then jump from the left 8 ohm to the right 8 ohm- that will give you 4 ohms mono. I'm pretty sure this is the right way to do it.
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Re: McIntosh MC250 hookup help

Postby cincinnatiohio » Thu Dec 20, 2012 8:06 am

When you say the "ground to the bottom ground terminal", is the bottom ground terminal the "com" contact and so the hot is on the left 8ohm and the ground is on the left "com" and then I have a small mono speaker wire going from the left 8 ohm to the right 8ohm with the switch on mono?

Am I understanding this correctly?

Thanks for your help!
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Re: McIntosh MC250 hookup help

Postby rugger » Thu Dec 20, 2012 10:47 am

Not a direct answer to your question, but here is what I do: Since I also wasn't entirely clear on how to run it bridged, I just ran it in stereo with each speaker directly connected to it's own channel. Negative to com and positive to the proper ohm rating. Of course when hooking up your JBL's remember the polarity is switched, black being hot and red is ground.

This get's brought up enough it would be nice to see a sticky "how to" thread covering hooking up these Macs.

john in san diego
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Re: McIntosh MC250 hookup help

Postby Pete B. » Thu Dec 20, 2012 10:57 am

I like running the two speakers separately, because I like to mix and match speakers and cabs fairly often. For example, You can mix 8ohm and 4ohm speakers, and set the Mac So the volumes are equal.
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Re: McIntosh MC250 hookup help

Postby DenverEd » Thu Dec 20, 2012 12:04 pm

I had no idea about the reverse polarity on the JBL's.

I have mine wired the "usual" way with my Mac. Is that a problem? They sound fine to me.
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Re: McIntosh MC250 hookup help

Postby cincinnatiohio » Thu Dec 20, 2012 12:11 pm

ok- thanks gents.

so here is my status: i ran home during lunch to check it out and decided to follow your advice. i disconnected my speaker jack and ran each speaker separately into the mac running stereo. now i will first say THANKS, because this is the first time i actually heard anything even coming out of it so this test was semi successful. i say semi successful, because it wasn't clear tone. there was very noticeable breakup. it seemed to increase with volume... and i am not sure why.

the only thing i can think of at this moment is maybe i have the leads to the speakers backwards and what i have in red should be in black and visa versa. could this cause that problem? i am using what i would consider generic speaker cabling so there is a silver side and a copper side... does that matter? obviously i am a little ignorant to this idea. i though theoretically, each side of the speaker cable was the same- it just has to go red to red and black to black... but the backwards JBL thing is throwing me off...

ideas, thoughts, reprimands?

many many thanks again!!
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Re: McIntosh MC250 hookup help

Postby TRG » Thu Dec 20, 2012 12:37 pm

When I first got my MC250 I had distortion at low volumes as well. It ended up needing a recap job. Once it was gone over and recapped it sounded great!

Have you had it looked over yet? I don't think there would be distortion like your describing by just having the neg/pos speaker cable reversed on the JBLs.
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Re: McIntosh MC250 hookup help

Postby cincinnatiohio » Thu Dec 20, 2012 12:47 pm

i have not had it looked over yet. there is a guy here in town that is a McIntosh authorized person but i know it wont be cheap so i am trying all i can before i have to take it there. he did mention caps, etc should be checked out and possibly replaced. he thinks i am a grade-A nutjob though because of how i am using the mac. so i can not be too sure on the feedback i get from him.

but in theory everything should be right since i stopped messing with the jumper (which i would like to figure out) and went stereo. so there has to be something else going on. you may be right TRG.

if i can not figure it out in the next couple days, i will have to suck it up and take it up to this guy's shop. i probably should have it looked through and cleaned up i guess anyway, just i know it'll cost me.
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Re: McIntosh MC250 hookup help

Postby czyfingers » Fri Dec 21, 2012 3:32 am

On the old JBLs the black terminal is the positive and red is negative. I know, goes against normal logic, but its a fact. That being said, connecting them backwards normally would not cause early break up. (I ran mine this way for months before I knew about the reversed polarity JBL phenomenon and it still sounded pretty good) in fact, I could barely tell a difference after correcting it. But you still want it connected correctly for best results. As far as the break up goes, try running some recorded music through it...connect and iPod or some source and see how it sounds cranked up. That would rule out anything in your rig. Keep in mind though, your guitar signal is likely hotter than the music signal you'd be feeding it. If you connect an iPod directly and play a good solid recording of any music, you should pretty much be able to run it wide open with no distortion. If it behaves similarly to when you play guitar though it, it likely needs service to perform top notch.
Hope this helps.
One last thing...this is all said assuming your speakers are in good shape and what you're experiencing is not being cause by a bum speaker. But I'm assuming you had them before the Mac and they were all good.
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Re: McIntosh MC250 hookup help

Postby rugger » Fri Dec 21, 2012 9:38 am

Getting the Mac serviced is a must. It's pure fantasy to hope it will sound "as it should" if it's been sitting around unused and neglected for x number of years. I know, I did the same thing!

Regarding your speaker wire: I use the same stuff, "regular" stranded speaker wire. It doesn't matter which side you hook up to pos. or neg., as long as you are consistent. I would hook up the copper side to the 8ohm screw (+) and run that to the black speaker connection. Hook up the silver to the com screw (-) and run that to the red connection on the speaker. You are in for a treat when you get it all sounding right!

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Re: McIntosh MC250 hookup help

Postby Pete B. » Fri Dec 21, 2012 10:41 am

You might be able to define if one side is working better than the other by running just one speaker to either side and a/b tone vs volume.
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Re: McIntosh MC250 hookup help

Postby cincinnatiohio » Mon Jan 14, 2013 7:51 am

Well... I could kinda get it to work in stereo when I hooked up both speakers separately but I really want to run it mono at 100 watts if possible. I took the Mac in to get serviced, cleaned, etc per recommendations. It does seem the smartest course to make sure it's 100% ready to go.

I should hopefully have it back in another week or so and if I'm real lucky... I'll figure out the jumper thing. I couldn't get the jumper to work when I tried it the first time if my life depended on it. :?

Thanks for all the feedback!
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Re: McIntosh MC250 hookup help

Postby Smolder » Mon Jan 14, 2013 8:31 am

cincinnatiohio wrote:Well... I could kinda get it to work in stereo when I hooked up both speakers separately but I really want to run it mono at 100 watts if possible. I took the Mac in to get serviced, cleaned, etc per recommendations. It does seem the smartest course to make sure it's 100% ready to go.

I should hopefully have it back in another week or so and if I'm real lucky... I'll figure out the jumper thing. I couldn't get the jumper to work when I tried it the first time if my life depended on it. :?

Thanks for all the feedback!



Ask the tech to help with jumping. He certainly ought to know.
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Re: McIntosh MC250 hookup help

Postby mijknahs » Mon Jan 14, 2013 2:11 pm

Running 100W mono is simple.

As tcsned said:

1. Use a jumper wire to jump the 8 ohm (R and L) terminals together. I use a short speaker wire.
2. Have the amp set on MONO
3. Plug in your preamp to the Right side only.
4. hook your speakers up to the 8 ohm and COM on the terminal strip (doesn't matter which side since they are bridged).

You should be playing now with both channels at 4 ohms. You won't hear the difference until you get loud enough (assuming the amp is working correctly). It will just stay cleaner at louder volumes as opposed to running it at 50W.

To use in stereo operation, just hook up the speakers to only one side (R or L) with the corresponding input (R or L). Make sure the switch is on STEREO and you have the ohms matching what the speaker load is. To use both sides in STEREO you need to have dual preamp signals. Either 2 jacks coming out of your amp or a splitter of some sort so you are running signal into both inputs.
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