ADA Preamps > MB-1

MB1 vs. MP1/MP2 Chorus

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astrobushido:
Hi, people
big (silent) fan of this forum for years and now I've finally decided to post (more to follow).

First of all, a great 2019 for everybody, plenty of successes!

Having looked around, couldn't find anywhere the answer to this very simple question: does the chorus circuit in the MB1 differs in any way from the ones in the MP1/MP2?
Does it have any kind of filtering or high pass at its input so that the low frequencies are kept dry, unprocesed, as it seems to be usual with bass chorus pedals?
Also is there any special voicing for the chorus operating frequency center or any other difference at all between the MB1 chorus circuit and the other preamps' chorus circuits?

I.e., considering that those guitar preamps' chorus circuits are the same, which I also would greatly appreciate to be informed if they are not.

Does anyone knows the answer? Uh...MarshallJMP ;) ...?

Thanks a lot for your support beforehand, folks!

MarshallJMP:
Well the chorus circuit is almost identical for all 3 units, but from what I can see the MB-1 chorus does only the more high frequency's.

astrobushido:
Thanks a lot for your answer, MarshallJMP!

How would you rate the existing differences, is the isolated effect section of the chorus circuits themselves any different or do the differences relate only to the way they have to be inserted in their respective different preamps (for instance, different input impedances or signal levels to the chorus circuit etc.)?

MarshallJMP:
The differences are more in the LFO section which is created different in the MP-2 due to the use of different technology , the MB-1 and MP-1 use a CD4094 8 bit shifter as an R/2R D/A converter while the MP-2 uses a NJU8101 with a NJU7304 to make the analog voltage feeding a CD4046 PLL used as a voltage to frequency converter to provide the clock signal to the MN3007 BBD. The rest is almost the same for the 3 preamp except like I said the MB-1 only seems to chorus the mid and high frequency's.
Could be that the clock frequency differs a bit from each other. But this is also in the MP-1. That's why some MP-1's chorus sounds better then other MP-1's.

astrobushido:
Thanks for your support!

How does the MB-1 only chorus the mid and high frequencies of the full signal spectrum?
Is it by way of splitting the signal with a high-pass filter before the chorus section input, feeding the chorus processor with only the high-pass filtered signal and then combining the processed signal with the dry full range (or bass-frequency content only) signal near or at the preamp's outputs?
Is there any other method to it?

And by the way, all ADA's guitar preamps' (not the MB-1) claim that the chorus is stereo.
What sort of stereo are they referring to? From what I recall, it doesn't seem to divide the Left/Right signal into chorused vs dry only signals - L/Wet | R/Dry (as the Roland Jazz Chorus amps' seems to do).

Another possibility is to mix the Left dry signal with a normal phase chorused signal while simultaneously mixing the Right dry signal with an inverted phase chorused signal - L / 50% Dry + 50 % normal phase wet | R / 50% Dry + 50% inverted phase wet.

How do they do it after all?


The MP2 manual also states that the stereo chorus is the point where the signal splits and becomes stereo.

At the same time, the MP1 manual says that if you sum its two outputs on a mixing board (i.e. without fully panning those outputs), it will result in phase cancellation of the chorus.
This seems to support the L / 50% Dry + 50 % normal phase wet | R / 50% Dry + 50% inverted phase wet theory.
 
But how do they achieve a mono chorused signal without any phase cancellation if one only uses the mono output A of the preamp?
Instead of simply being a mix/sum of both outputs, does it only output the original Left signal, i.e., discarding the inverted phase chorus signal altogether and only outputting a mix of the dry and normal phase chorused signal?

I'm curious...

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