Mutron Micro V (+?) build guide

[Gaetano Capuano]

Excellent work!

[Perrow]

You know I thought they had the options before that allowed full res. But they changed things up on their website and I cant find any options for that yet. I uploaded these from my desktop. Because I had issues with the mobile app before. Gonna look into it more. but in the mean time Ill try to use dropbox and google drive with higher res stuff.

I've switched back to the old photobucket layout and the settings link there had the "full resolution but less than 1 Mb" option, don't know about the new layout. I changed because the thumbnails weren't clickable in the new, and the links were harder to get to.

[Ronan]

Really nice layout Pelle! I didn't like the new photobucket thing either, stayed with the old one.

I'd really like to understand how the filter in this schematic works, or just know what it is described as, so I can do some reading on it. I really cannot work it out! Jim, I chose this schematic as it is easier to "read" than the other one at pisotones.com. They are the same, but the component designators are different.

If anyone has any thoughts I'd be interested to read them. It would be much appreciated if RG, PRR, or any other person who has a clue (amptramp? slacker? Merlin? oldschoolanalog? rickholt? sorry-if-I-missed-you? anyone?) could explain this filter, I would appreciate that a lot. The envelope section appears reasonably standard, and seems to work very well (attack and release times, depth).

[midwayfair]

Really nice layout Pelle! I didn't like the new photobucket thing either, stayed with the old one.

I'd really like to understand how the filter in this schematic works, or just know what it is described as, so I can do some reading on it. I really cannot work it out! Jim, I chose this schematic as it is easier to "read" than the other one at pisotones.com. They are the same, but the component designators are different.

If anyone has any thoughts I'd be interested to read them. It would be much appreciated if RG, PRR, or any other person who has a clue (amptramp? slacker? Merlin? oldschoolanalog? rickholt? sorry-if-I-missed-you? anyone?) could explain this filter, I would appreciate that a lot. The envelope section appears reasonably standard, and seems to work very well (attack and release times, depth).

Have you read this? http://www.geofex.com/article_folders/ecftech/ecftech.htm

There are a lot of analogs between the Mutron III and V, and the audio/filter path is very, very similar.

[Ronan]

Thanks Jon, I have read that Geofex article. The Mutron III uses a state-variable filter.

Micro V schematic

The micro v appears to use something else, maybe similar to the voltage controlled low pass filter shown in the LM13700 datasheet fig 17 pg 13, but with some added twists, possibly a peak at resonance through the feedback network of R5 and C4. I am guessing but I think R6 and C5 form the low pass, and the cut-off freq changes with a change in current from the output of the OTA, the gain of the OTA is controlled by the envelope section. I don't understand the purpose of C3 (connects the input signal to the output of the OTA) or C10 on the output of the OTA when hi-range is selected. I keep studying this circuit but not really getting any of those "aaaah I seeee" moments

The C2 and R4/R11 stage have a cut-off freq around 20kHz, so they can't really be an input to the OTA, the input must be via C3, to the output of the OTA, then the feedback network R5/C4 are making the OTA do something...The IC Z1A has no direct feedback from its output to its -ve input and seems to be relying on the OTA to stay in some sort of linear region. If you assume a virtual earth at the inverting input of Z1A you get a 100Hz high pass filter via C3/R6. Maybe there's some hi-pass + lo-pass action going on resulting in band-pass, and the OTA is simply a variable resistor. If I could just link all the bits together and get the big picture...

[GGBB]

I have some questions I hope Jim or someone can answer, but first let me say thanks to all for their input and especially the layouts.

1. What does D3 (CR3) do?  On the schematic, it appears to be some sort of isolation/protection for the battery from the power supply.  But since we now use those switching DC jacks, is D3 even necessary? EDIT: It also appears that D3 is reversed in Jim's layout compared to Pelle's layout and the original schematic.  There is also a different point for +9V power between the tow layouts - Pelle has it where the schematic shows the battery +ve, and Jim has it where the schematic shows the adapter +ve but missing the 470R resistor R19 which I assume is used in conjunction with the zener for reverse polarity protection.  Am I reading the schematic and/or layouts wrong?

2.  In Jim's demo video, when he adjusts the range control, it seems like it is more of a sensitivity thing rather than what I assumed it was - frequency range.  So it's like the Mutron-III's gain control.  And the Micro's low/hi switch is the same as the Mutron-III's range control switch.  Is this right?

[Perrow]

As for question one, I tried to arrange those diodes the way the schematic showed them. I'm not sure if Mustachio made an error in his layout or purposely changed it, the schematics way made more sense to me so I tried to mimic that.

[Mustachio]

Sorry I had a real long busy sore bones type of a day haha. I'll have to look and see but I believe what your looking at is reverse polarity protection. I'd imagine they could be omitted. Ill have to look at where the missing 470r is. I'll take a look later tonight.

Thanks for the look the more we refine this the better it will be!

[GGBB]

Not trying to compete, but I've put together another layout (needs verification) from the original schematic.  Not as curvy as Pelle's nor quite as compact, and more jumpers than I like, but I incorporated some changes just to suit my own preferences.  Plus I just love to do layouts.  

I grouped the off-board connections together as much as possible and placed them at the edges of the PCB with room to use Molex connectors.  I've also made it possible to use a PCB mounted pot for the range control but this was largely just because it turned out I could do that.  Not sure if the position is all that great though.

Also, I replaced the 500K resistor with two 1M in parallel just for part sourcing ease.  And I redid the reverse polarity protection to a Zener and a 100R 1W. EDIT: I also added a 100nF cap to the power supply filter section.



EDIT 2: Spotted a missing trace!    Now fixed - and I also tweaked a couple of minor things.  The image has been reloaded.

If somebody could verify this I would really appreciate it.

[Jdansti]

@Gord >Plus I just love to do layouts. 

You're a sick, sick man...   

[GGBB]

You're a sick, sick man...   

[Perrow]

@Gord >Plus I just love to do layouts. 

You're a sick, sick man...  

Doing layouts is almost my favorite part

But perhaps you already knew that.

[Jdansti]

@Gord >Plus I just love to do layouts. 

You're a sick, sick man...  

Doing layouts is almost my favorite part

But perhaps you already knew that.

You're sick too.   

[oldschoolanalog]

You're a sick, sick man...   

You're sick too.   

...said the father/creator of "Odius Max"...

[Jdansti]

You're a sick, sick man...   

You're sick too.   

...said the father/creator of "Odius Max"...

No comment...

[deadastronaut]

any thoughts on reverse sweep?...attack/decay adjust?..

still haven't got my 13700's...so no experimenting at the mo!!!..

[Ronan]

any thoughts on reverse sweep?...attack/decay adjust?..

still haven't got my 13700's...so no experimenting at the mo!!!..

Possibly R14 attack, R15 decay, on the ARP schematic. Or try different values of C11. No idea for reverse sweep.

Jim, did you get around to trying an A/B comparison between the micro V and the Mutron III?

[Mustachio]

I've been so busy working on the house I haven't had a chance to A/B em. Ill try to tonight.

The other night I was messing with a fuzz face before and after the mutron V to see if I could get it to react like Rob's envelope tests. I had built a fuzz face with an external bias for the splatty sounds and it has a mid hump control as well. And it basically does the same thing as robs. When its set up for high bias splatty sound the note actually dies when it first hits the fuzz face and then comes back. I think it has to do with the impedance the fuzz face is expecting. Overdrives seem to work best for dirtying up an envelope filter. Possibly adding an fx loop into the filter might help.

But after playing with these a little I tend to treat them like a regular wah in the sense that I run it first in the signal chain. Before a compressor. And usually turn the comp off. I think these filters sound best when their the only pedal on in the chain. I think Mark Hammer wrote a bunch of stuff about compressors clamping the vol and hindering the dynamics . And running the Mutron III into a dynacompcan cause it to recover very slow almost like it was stressed from the signal coming into it and clamped down on all the tone and volume.

http://www.geofex.com/article_folders/ecftech/ecftech.htm

Its towards the bottom.

I'm gonna do some work on the superfly tonight but ill try to test out the 2 mutrons together and maybe make a video demo to compare them.

[deadastronaut]

@jim:  cool, glad you tried that bias test out, bummer eh!..i'll try and mess around with the input on the fuzz and see if that allows the EF in when in splat mode..

nice one.

(busy today, fitting a floyd onto a crapocaster )

[GGBB]

I've updated my layout a bit (just tweaks, no fixes), so here's the link the the gallery page for it:

http://www.aronnelson.com/gallery/main.php/v/diyuser/GGBB/MutronMicroV_MolexLayout.png.html?g2_imageViewsIndex=1