Bridge mode with Matrix GT800FX HOW??

Tremonti

Fractal Fanatic
Special cables??? How do you do this? I see it on the website but not understanding. Also my cab has 4 or 16ohm for mono......so I'd be running 8ohm bridged to a 16ohm cab? Wouldn't this be lessvolume?
 
Hey Tremonti

Thought I'd posted a thread on how to make the "bridged" cable but either dreamt it or cant find it! Doh!

I've made the cable. I used a Planet Waves speaker cable 12AWG thickness I think. Mono cable with two cores separately insulated. Chopped the cable in half, split the cores and then attatched the ends to the +1 positives of two speakon connecters. Both speakons need to be connected as the signal comes from both positive outputs of the back of the amp. If only one cable is used or one connecter then you get an out of phase sound. I've got a video that I did a while back so if I edit the footage I'll get it made available.

Hope that helps
 
I also don't understand this from the Matrix manual. Can you not just use a regular, heavy duty 1/4" speaker cable?
 
Yes you can use a regular heavy duty speaker cable but you have to split it. So long as tip is going to positive on output A and sleeve is going to positive on output B. Way easier to do with speakons. It's also a safety feature in that you dont accidently set it to bridge mode and pump 800w into your V30!!
 
You have to use a special cable because the outputs are combi-jacks. On the XT versions there not, there just speakons. The difference is that the speakons have 4 contacts - a +1, +2, -1, and -2. For normal use you connect to +1 and -1 and for bridged you connect to +1 and +2. with the combi jacks there are only 2 contacts for the speakon part +1 and -1. Thats not Matrix's fault in Neutrics. They dont make a combi that gives 4 connectors. Therefore in the GT version, because we wanted the ability to run 1/4" outputs, we have the combis. To make the bridge mode work you need to connect the +1s from each output. Bit of a pain - but necessary if you want the 1/4" o/ps.

So yeh - basically any speaker cable (that should have 2 individually covered cores). Split the cores and stick one speakon plug on each core, attached to the +1 connector of each plug then connect one plug to the L and the other to the R O/P, with the selector set to bridged.

For your cab you'd need to run in 16 Ohm mode as the 4 Ohm is too little when bridged and the amp will go into protect. So - basically you have the choice, of running a single channel in to your cab configured at 4 Ohms - for 400W output OR bridge the amp into you cab configured at 16 Ohms for 520W (ish) power.

What is the power rating if your cab? if your using V30s and similar rated speakers you cab is 240W - so id stick to the mono channel at 400W anyway. If your running higher rated speakers and have a 400W+ cab then it may be worth bridging for a little headroom.


The safety thing lightningboy refers to isnt so much to protect your speakers though - if you run 800W into a Jack socket your more than likely going to melt it !! - its not built to take that high power - hence speakons on PA equipment as they are. The last thing you want is you jack socket welding itself to your amps output sockets.
 
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Yeah most probably won't need to mess with the bridge anyways. My cab is 325 watts 8 ohm. A single channel certainly seems loud; I just haven't played with the band yet so we'll see.

Of course one option is to use a 4ohm cab to maximize wattage.
 
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My VHT blowed a fuse today... i am really seeing the day for SS amp becoming a reality... I forgot how I hate to open tube amps.... how is your Matrix doing paul?....
 
Yesterday I was mailed from Matt that he would upload a DIY custom cable video tutorial on YouTube in a couple days or so

Paul,when you drive the gt800fx to it's maximum do you see any channel led blinking?I don't see mine...
 
Depends how hot the input signal is.

The LED starts to flicker when the O/P of the Matrix is at -9db (so 50Watts into a 4 Ohm load or 30 Into an 8 Ohms Load). That is a combination of the mastrix volume dial (which is actually attenuates the inlut signal) and the output of the AFX.

If you have tha Matrix at full, and arent seeing anything from the LED then the output from the AFX isnt high enough. If the AFX is at full as well then your patches are very low signal level. Increase the Global output gain - or the level in your amp blocks.

In 90% of my playihg I dont get an LED flicker. when I turn up full I do - but Ive set my gain structure up so it happens at that point (means Im getting 30W at full -and 60W when my vol boost in engaged. My cab is rated at 60W). Im not actually getting close to the Matrix's max output - my cabs wont take it.
 
hi guys !

finally I find the speakon connectors ... here is my job


STEP 1: this is the "original" cable I ever used ...
speakon_1.jpg



STEP 2: these are the Neutrik connectors to make the job
speakon_2.jpg

speakon_3.jpg



STEP 3: I cutted off the orginal jack connectors and put each cable on +1 of the Neutrik connector ... here is the result
speakon_4.jpg




Did I forgot something ?
 
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No. That will work fine.

Personally I would have stripped the outer covering back further, then put heat shrink over the neutric connectors and inner wires back to the split, Then put more heat shring starting an inch or so behind where the inners split up to the point where you need them to seperate to reach the amp outputs. Not really necessary but I think it puts less strain on the single wires - particularly at the split point.

But - your job looks perfetly OK to me.
 
thank you Paul ! ;)


last (stupid) question: is it important to match the colour to the "right" speaker connector ? Can I reverse the brown / blue connector switching from "A" to "B" output ? is there a correct positioning ?


P.S.: during the night I thought about the heat shrink ... I'll do this "upgrade" very soon ! :D
 
Doesnt matter which way round really. The cone movement will be reversed when you switch the cables round, but that wont affect anything tonally. Its the same effect as reversing the phase in the Axe menu itself I think.
 
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