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 Post subject: Channel switching on mesaboogie triple rec
PostPosted: Sun May 12, 2013 6:00 pm 
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Hello.

I have followed the instructions on the user manual and searched the forum for others who might have had the same problem I'm having...

I'm trying to get my GCX to switch channels on my Mesa Triple rec. I have had it working before with a slightly different setup but can't seem to get it to work this time. The scary part is that when I connect the jacks from OUT/no (loop6, loop7, loop8) to channel 1, 2, 3 of my mesa, a huge HUM appears and channels still dont switch.

I have also tried changing the jacks from OUT/NO to SEND/NC and even return but still no luck.

I even think I started smelling something burning in one of those combinations so I immediately stopped

The switcher and amp are working as you'd expect with pedals, but just when it come to switching the channels it gets all funny.

Please help!


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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Mon May 13, 2013 4:32 am 
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Posts: 1313
There are two things about your situation that concern me:

1. You've successfully done this before with a "...slightly different set up..." and,
2. Not only are you now getting "...a huge HUM..." you say you also thought you smelled something burning.


To me this is an indication that you may have crossed a connection somewhere, perhaps inadvertently connecting to a speaker jack on the Mesa instead of a switching jack. I know that sounds highly unlikely, but crossing connections is something I've done more than once over the years, so I know it is a distinct possibility. Even though you've probably already done this, I strongly suggest you review your connections again.

I also found 34 threads referencing the Mesa Triple Rectifier when I used the Search feature, and many of them, if not most, are about channel switching issues. To save you some time, though, here's a link to a Mesa Triple Rec thread that might help you out. If not, try searching again and check out some of the other threads.

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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Tue May 14, 2013 6:13 am 
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Joined: Sun May 12, 2013 5:43 pm
Posts: 4
Thanks for your response.

Sorry about the confusion with the forum search field. I did search and did find others with similar cases only I couldn't find the solution.

Going back to the facts...

I have had it working before with the same amp and most of the gear. Only difference is I have removed an effects processor to add a pedal shelf instead... However, right now just for the sake of fixing the problem, I have torned it all down to do a really basic setup. I even have the GCX off the rack to make sure I'm not getting any induced groundloop.

Everything is connected to a furman power conditioner, could that generate the loop?

The three jacks are definitely connected to the amps "channel 1, channel 2, channel 3. For the moment I'm doing a very simple setup to find the problem. This is the signal chain.

Guitar to (loop 1 - IN)
Tube Screamer set up on loop 1
(loop 1 - OUT) to the amp input in the front.

So far everything seems normal, I can toggle loop 1 on and off and all sounds good.

As soon as I connect a cable from one of the loops OUT/NO to one of the channel jacks (not the speaker outputs) I get this huge hum. And yes... the burn smell is not good.. I wonder where the power would come form?

The amp has recently been checked and re valved so I'd be surprised to find out it had any problem...
On the back of the amp, there is a knob to select channel, on what setting should this knob be? 1 2 3 or FW (footswitch)?
I have it setup on FW at the moment.

I'm gonna do some more testing tonight and write down the results.

Hopefully you guys know what it could be.


Cheers!





nyteowl wrote:
There are two things about your situation that concern me:

1. You've successfully done this before with a "...slightly different set up..." and,
2. Not only are you now getting "...a huge HUM..." you say you also thought you smelled something burning.


To me this is an indication that you may have crossed a connection somewhere, perhaps inadvertently connecting to a speaker jack on the Mesa instead of a switching jack. I know that sounds highly unlikely, but crossing connections is something I've done more than once over the years, so I know it is a distinct possibility. Even though you've probably already done this, I strongly suggest you review your connections again.

I also found 34 threads referencing the Mesa Triple Rectifier when I used the Search feature, and many of them, if not most, are about channel switching issues. To save you some time, though, here's a link to a Mesa Triple Rec thread that might help you out. If not, try searching again and check out some of the other threads.


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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Tue May 14, 2013 6:17 am 
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Joined: Sun May 12, 2013 5:43 pm
Posts: 4
PS I forgot to ask.... Is there anything that could have gone back to default that I now need to re-configure from the ground control to specify loop 6, 7, 8 should work as channel switchers?


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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Tue May 14, 2013 9:33 am 
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Joined: Mon Jan 25, 2010 8:53 am
Posts: 1313
This is scary:
mikkinilsen wrote:
"As soon as I connect a cable from one of the loops OUT/NO to one of the channel jacks (not the speaker outputs) I get this huge hum. And yes... the burn smell is not good..."
Are you really still experiencing a burning smell, and if so, have you determined where it's coming from? You're not still sending the Mesa FX Send to the Piranha Input are you?


Getting back to the switching, have you tried what John recommended in the post I referenced earlier?

John Clark wrote:
"On the 3 channel Dual and Triple Rectifiers you can get away with using only two loops to control the three channels. The Out/N.C of one GCX Loop will connect to the Channel 1 External Switching jack, and the Out/N.O. of the other GCX Loop will connect to the Channel 3 External Switching jack. It is important that you do not connect any other cables to any of the other jacks on these two GCX Loops."
If you've not done this, I think it's definitely worth a try. Pay special attention to what John said about one connection running from the Out/N.C. jack of one loop and the Out/N.O. jack of the other.

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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Tue May 14, 2013 9:39 am 
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Joined: Tue May 05, 2009 2:33 pm
Posts: 6661
Location: The Lab
These amps have a unique channel switching circuit where the "ground" in the channel switching circuit is actually a few volts lower than the audio/chassis ground. They must remain isolated or the amp channel switching circuit will be damaged.
As shipped, the GCX loops are completely isolated from eachother. Do you have any other cables connected to the three GCX loops you are using for the channel switching? Have you had the GCX modified to internally "normalize" all the loops in series? Do the sleeves of the plugs you are using come into contact with anything metal?

Can you take a picture of the back of your rig and post it here or PM it to me?


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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Tue May 14, 2013 9:48 am 
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Location: The Lab
Hey! The quote above from me has a typo! Both jacks I reference are in fact labeled "Out/N.O." The important part of that quote is about making sure you are not connecting the channel switching ground to the chassis/audio ground by having another cable connected to either of the GCX loops mentioned.

The "N.O." means Normally Open. This is the correct jack to use for all Mesa Boogie 1/4" switching functions. Using the Send/N.C. wont harm anything, it will just reverse the state of the GCX loop status LED to be On when the channel is off.


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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Tue May 14, 2013 10:32 am 
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Thanks for jumping in and clarifying, John!!

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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Wed May 15, 2013 1:23 am 
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Joined: Sun May 12, 2013 5:43 pm
Posts: 4
Hello again, and thanks so much for the replies.
Using just 2 of the loops for switching the mesa is brilliant and can't wait to test it out as soon as I can get this to work.
I was able to do a much more thorough test yesterday and this is what I was able to figure out.

-I plugged my guitar into the first loop and from there straight out to the amp (no pedal connected, clean set up) all good so far...

-Then I connected just one jack from loop8 OUT/NO to channel 1 on the mesa (no hum so far). Then proceeded to test if I could switch to the clean channel.

When I press the footswitch on the ground control which is supposed to change the channel, it does an attempt to switch but instead it starts flickering the clean channel really fast while the 2nd channel (default) still reamins on and when this occurs I get the hum and probably the smell if I leave it long enough.

The exact same thing happens if I try to change to any other channel. flickering channel which I want to change too while steady light on the channel I want to change from.

I can change channel with the knob in the bacl of the amp, no problem... Just happens trying to switch from the gcx.

I'll get photos and video today

Cheers!


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 Post subject: Re: Channel switching on mesaboogie triple rec
PostPosted: Wed May 15, 2013 4:11 am 
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Joined: Mon Jan 25, 2010 8:53 am
Posts: 1313
Did you check your GCPro to see how it's configured for switching?

I suspect you want to set your IA buttons to Momentary, but maybe they're set to Latching. This is just a guess on my part, but it wouldn't hurt to verify.

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I am not affiliated with Voodoo Lab in any way, just sharing what little MIDI and signal routing knowledge I have. If you found my assistance helpful, please pay it forward.


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