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Author Topic: MP1 - Signal chain for Stereo Effects?  (Read 1364 times)

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MR THUD

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    • MR THUD

Hi Guys,

Well I have to say that the MP1 must be the easiest rack to maintain.
I had no PCB soldering experience and thanks to some parts sourced via MarshallJMP here, within an hour or two I was able to:
Install new EPROM v2, install Battery kit, replace all Pots, and replace the output jacks. :)
All without issue, thanks to the very modular design of the rack housing, making access to the boards easy.

So next is to tone chase...
I have discovered that using the MP1 Effects loop is noisy (I only tested with an Alesis Quadverb GT in mono in the loop).
Will try a few other effects racks, but it seems to me that to take advantage of Stereo effects you probably need to ignore the Mp1 effects loop and instead used the MP1 main outputs into the effects rack then into the power amp inputs (my power amp unfortunately doesnt have a loop).

I currently have no effects before the MP1, so it seems pointless introducing a noise gate that the point, so I guess that the effects rack I need to use must 1- Have stereo inputs and outputs, 2 - Have a noise gate inbuilt.

Unless im missing something and the MP1 effects return socket is balanced/stereo and can take a TRS jack? (I could then use an Insert or Y cable / dual mono from the Alesis effects rack into a single TRS/Stereo input on the MP1 effects return?)

So far the MP1 tones looking promising, will be interesting to se what adding a little delay and reverb will bring.

cheers,
Gerard.
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rnolan

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Re: MP1 - Signal chain for Stereo Effects?
« Reply #1 on: Time Format »

Hey Gerard,  :whoohoo!: glad it's working out for you :thumb-up: The MP-1 loop is mono and no TRS on the return.  The signal goes (sudo) stereo after the chorus so the signal flow is input -> gain (tubes or SS) -> eq -> loop -> chorus =>> out A/B (and/or =>> caps (to take off top end) headphone out).  The loop is notorious for being fiddly to get right. I never used it, though it's a good place to insert a GCX3 cab sim for recording (or use the HP outs).  You can probably get it less noisy by getting the gain structure right.  The MP-1 loop is serial (breaks/interrupts the signal flow) and is designed to work with inst level or line level fxs.  The loop knob is a dual ganged opposite pot.  So increasing the send decreases the return and vis versa.  For a pedal which wants inst level, you adjust the send to be as little as possible (so you don't overload the pedals input) which will make the return up full (because the pedal is outputting inst level and needs boosting back up to line level for the signal flow), for a rack unit (like your QVgt), it wants line level in and out, so turn up the send (which turns down the return).  You balance this up with the QV input and output levels.  When the loop is "in" the overall level needs to be the same as when the loop is "out", it shouldn't add gain (i.e. unity gain).  BTW you need to set these levels for you loudest patch.  I suggest you try with the loop knob in the centre and use the QV input and out put vols (and leds) to fine tune.  This setup also means that the MP-1 chorus is applied after the fx so you are chorusing the delay/reverb etc rather than delaying and reverbing the chorus.Probably the most common way people set up their MP-1 is whats dubbed the 4 cable method (4CM), basically MP-1 A/B -> Fx L/R in, FX L/R out -> poweramp L/R in.  Again you need to adjust the fx input and output for unity gain.
Do you need a gate? and where to put it?  If you are using really high gain patches (OD1/2 on 9 or 10) and it's too noisy/sensitive then a gate is useful.  You could put one in the loop (with 4CM set up) or if the fx unit has one, use it, but then the gate is later in the signal chain, probably after the fx so the delay and reverb will have the noise.  I never needed a gate when I used a MP-1, my MP-2 has one built in and I use it on very high gain patches.  There's a bunch of posts re different patching setups, from the get go with my MP-1 and now MP-2 I always use a small mixer and run the rig like a PA.  So MP-1/2 into 2 channels, fx send 1/2 to QV (I have one of the original QVs) and QV return down 2 channels, QV mix on full wet.  This makes the gain structure easier.  I have the mixer velcroed to the bottom of the rack so it can all stay plugged in.
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MR THUD

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Re: MP1 - Signal chain for Stereo Effects?
« Reply #2 on: Time Format »

Thank you for a comprehensive response Mr Nolan  :thumb-up:
Will likely use the 4CM with the GForce rack at the end of the day.
But may experiment a little with gain structure and trying the loop some more, using some of my mono in /mono out older racks in the interim.

PS.. you now have me interested/researching the MP2, to see what that may be like too :)
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rnolan

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Re: MP1 - Signal chain for Stereo Effects?
« Reply #3 on: Time Format »

Hey Gerard, no worries  :wave: .  The GForce with 4CM is a good option.  I jumped on the MP-2 when it was released here in Australia and sold my MP-1 rig to pay for it.  They are quite different animals, I particularly liked all the extra features, Tremolo, Whah, gate, stereo parallel loop, CC control, MXC midi pedal pack...
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