ADA Depot - A Forum To Support Users of ADA Amplification Gear

ADA Preamps => MP-2 => Topic started by: rnolan on September 07, 2018, 03:10:07 AM

Title: Rockman or MP1 etc in MP2 loop
Post by: rnolan on September 07, 2018, 03:10:07 AM
So here's an idea (maybe not a new one ??).  You can use the MP2 Fx returns as an additional stereo input (obviously with a mixer you can do similar but this idea has a slight advantage)So if you wanted to use a Rockman (X100 is what I have), or a MP1 (or many other things) as an additional tone mixed in to your MP2 signal chain:Split the guitar signal with either a Y lead or an A+B box/switch, so both MP2 and Rockaman or MP1 get the clean guitar output (which is what they are designed for).Return the Rockman or MP1 into the MP2 Fx returns.  Adjust the return vols to taste (balance with the MP2 patch).This way you pick up Tremolo, Cab sims, and more importantly Master vol control (of the whole sound) as they come after the Fx returns.  With MP1 (or any other unit that has it, also Midi control of the additional unit patch (eg MP1).
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: Feki on December 18, 2018, 04:08:45 PM
My final gear rack.
https://feki99.wixsite.com/feki/single-post/2018/12/17/Rack-II-ADA-MP2
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: rnolan on December 19, 2018, 12:19:53 AM
 :thumb-up:
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: astrobushido on September 07, 2019, 05:07:01 PM
Actually, I tried this sometime ago, before I've read this thread (just now).

The problem is, although the tremolo circuit seems to be placed after the return jacks (as per the manual's diagram) and thus should effect the incoming external preamp signal, there is no tremolo effect at all if the external preamp is 100% mixed in the MP2's return loop.

My guess is that the signal from the tremolo effect is itself mixed in parallel with a dry, non-tremolo effected, audio signal from the MP2 preamp section and thus mixing something 100% in the loop fully defeats the tremolo effect (maybe a question of switching sends vs switching returns).

Another consequence is that the only tremolo effect you hear is imposed upon the ADA preamplifier signal exclusively, not on any other external signal (I'm not near my MP2 right now, so can't fully testify this, but I seem to recall this).

Which, if this proves to be generally true (and not some specific bug affecting my two MP2's), is a real shame as you can't use the MP2 as an analog tremolo effects processor, with a very good sounding analog tremolo section that can't be used elsewhere (when apparently it would be easy to be used in such way given its placement in the circuit, post-effects loop).

Does anyone know if my guess is right regarding its behavior or if there is any other thing to it?

Or, am I the only unlucky bastard which MP2's exhibit this behavior? (well, at least other folk would be able to take advantage of the MP2's nice tremolo applied to other preamps)


Title: Re: Rockman or MP1 etc in MP2 loop
Post by: rnolan on September 07, 2019, 09:27:45 PM
Interesting, I actually never tried turning the tremolo on when I plugged an MP1 through the returns.  My interest was partly to use the MP2s CC master vol on the MP1 and also the cab sims for recording.  I'll try it when I get my MP1 back from the tech.  Maybe other with both units can try it and let us know.
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: vansinn on September 09, 2019, 01:44:20 AM
Don't have MP2 schematics available, but from memory, the tremolo is purely done fully after the FX loop, so I don't understand why there'd be any problems using the tremolo with the loop set either mixed-down or at 100%.
At least, I never had this issue when using my loop with an effects device (Digitech TSR-24S or simple reverb pedal).

Would gladly check the schematics, but I'm busy preparing my trailer for the autumn weather..
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: MarshallJMP on September 09, 2019, 09:32:22 AM
There's nothing behind the effect loop, I just checked. I don't even see a tremelo circuit. My guess is (need to verify this) taht they use the master volume vactrol as tremelo.
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: vansinn on September 09, 2019, 11:16:37 PM
I just checked too. No dedicated tremolo circuit to be seen.
I'm busy, no time to check the digital controls circuits, which is where I'd expect finding the control line for the tremolo.
This should then be traceable to whatever analog device does the actual tremolo effect - and I wouldn't be surprised if you're correct about using the Master Volume vactrol for it; that would be typical of how Rand would've done it ;)
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: MarshallJMP on September 10, 2019, 07:53:55 AM
No dedicated tremelo line. I'll check it tonight, have to work on an MP-2 anyway.
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: MarshallJMP on September 10, 2019, 01:46:10 PM
Like I thought, they use the master volume control for the tremolo, so this is just behind the tube section (vactrol) and not behind the effect loop.
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: rnolan on September 11, 2019, 11:39:02 PM
So MJMP do you mean the patch master volume? Does this mean the signal flow schematic in the manual is wrong? as it clearly shows the tremolo, stereo master volume (CC only) and the cab sims after the Fx returns.
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: MarshallJMP on September 12, 2019, 04:00:41 AM
Yes the patch master volume. Like I said before didn't see a dedicated tremolo circuit so the only thing it could be was this. So did some measurements and I could clearly see the CV3 (master volume control voltage) go up and down if I engaged the tremolo. So to be correct the tremolo is actually the master level being modulated. There is no tremolo circuit that can be patched in or out. Maybe they use the dry signal VCA of the effect loop as stereo master volume. I need to check that.
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: vansinn on September 12, 2019, 04:34:51 AM
He, like i said it earlier, this is so typically of how Rand would think..
So, the 8031 cpu will have a loop creating the controlling waveforms for the tremolo, which will then be fed to the master vol vactrol, using this as a dual-function volume control and tremolo gain stage.  Smart!  :bow:
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: MarshallJMP on September 12, 2019, 04:46:06 AM
Yeah why build one if you already have one  ;)
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: MarshallJMP on September 12, 2019, 05:50:48 AM
So, did some testing again and the CC stereo master volume is done by the 4 VCA's in the effect loop. So CV1, 4, 5 and 7 control the output volume with CC.
CV7 dry A and CV5 dry B, CV1 Eff A and CV4 eff B react, this is done when you use the effect loop so everything has to be in sync with each other. What I mean by this is if you lower the dry signal you also have to lower the effect signal.

So anymore questions ? 8)
Title: Re: Rockman or MP1 etc in MP2 loop
Post by: vansinn on September 12, 2019, 08:16:36 AM
Ahh, so, IIUC, what you describe only affects us when using CC commands to change levels.


Yeah why build one if you already have one  ;)

Hehe, and quite the opposite of the Government Spending Rule:
"Why build one when you can have to at twice the price" ;)