Mutron Micro V (+?) build guide

[deadastronaut]

cheers leo..got it,  

my browser 'opera' is being wierd with trying to save images...i right click and it wants to save as WEBp whatever that is.

anyway sorted. thanks.

[nocentelli]

No prob Rob, hope you can get it working this time: I still haven't done anything with this yet, got distracted with building a Meatball...

[deadastronaut]

yeah me too....i'll take my time breading it, and see how i get on.

cheers

[deadastronaut]

....

[deadastronaut]

got it.....YAY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...

had a dodgy jumper lead...(in the bin now. ..)

excellent, now i can tinker.....

[Mustachio]

That's great news! Can't wait to hear what you come up with.

[deadastronaut]

sounds cool, if a little weak on the envelope..

swapped C6 for a 1nf.....better sweep lo/hi....(in the pf range its mental brightness..but cool too.)


jim what do you have your dial at 12,oclock?...hi setting.?

i listened to your vid again earlier...sounds sweet. great playing too man.

[Mustachio]

Hey thanks man, I think I usually keep it a lil above noon, in the Hi mode. It will depend on the output of your pickups though. The more output the easier the envelope triggers. Single coils are a little weaker on the envelope but they do have a sweet hollow sound to it that is good for bluesy riffs. The humbuckers really whomp around noon maybe a little less then noon on the range pot. My humbuckers are known to be sorta weak (stock duncan design in the schecter) . Ill have to try out that 1nf at C6.

Not sure if you changed the 1m R16 to 500K (2x 1m parallel) but that will make both halfs of the lm13700 work correctly. since its on bread board try removing the output on the second half of the lm13700 and listen to the difference. Its subtle at first until you swap back and forth and you will hear how the whomp is much more pronounced deeper and higher. I think if we cut that resistor down to 120K and put in a second lm13700 and hook up both sides of that as well we can get something that might break a speaker haha, be careful the range these envelope filters and octaves like the pearl seem to have pushed my amp to nearly fail.

Another idea was to use a quad opamp along with the lm13700 buffers to make an fx loop. Let us know if you fine tune it any more or have any new mods!

Thanks,
Jimmy

[deadastronaut]

h jim

re: the 1M R16..

do you mean 1x500k going to pin 1..and another 500k to pin 16 then?....split



still trying to suss out attack/release....length of envelope etc..

[Mustachio]

a single 500K which will lead to pin 1 and pin 16. Normally its 1m but since feeding two bias controls you need it cut in half for 2 sides. I said 2x 1M cause that makes 500K since 500K isnt a common value.

[Perrow]

Just a crazy idea that popped into my head while reading the last few posts; regarding the fx loop, maybe run one of the outputs from the 13700 to the loop?

[Mustachio]

I tinkered when I had the lm13700 on bread board connected to the pcb's IC socket. I think the buffers are expecting a different impedance or signal in some way. Will have to play with it , I was thinking some how get a workable clean signal from the input to a spare channel of a quad opamp and feeding that to the lm13700 buffer to have a buffered fx loop.. I have no idea if any of that can work yet or the science behind it. I'll play with it soon got a few things ahead of it on the choppn' block. But those are some idea's if any one wants to test it out. 

[deadastronaut]

a single 500K which will lead to pin 1 and pin 16. Normally its 1m but since feeding two bias controls you need it cut in half for 2 sides. I said 2x 1M cause that makes 500K since 500K isnt a common value.

ahh gotcha!..

edit: yep much better response now...cheers man, i'll re-evaluate my tinkerings now..

[rutabaga bob]

Well now, fellers...is this put to bed yet?  I am itching to try one.  Larry

[Mustachio]

I haven't tried other peoples pcb layouts but I know the info in this thread is working.

Which layout did you want to build?

I am planing on making another one with smd IC's and removing the high low switch because I never have a use for the low setting. I think that setting might be there to work better with bass or a rhodes piano. And hopefully squeezing it all into a 1590a. I have the IC's and started working on a pcb layout but its got a buncha work ahead still.

If you use my layout you can build it regular and use two 1m resistors parallel for the 500K resistor @ R16 , or if you wanted to use only a single side of the OTA you could cut the traces that connect them over and use a single 1m at R16.

You get a slightly more emphasized sound with both sides working, which the pcb is set up for.

I still need to experiment with the way we change the bias at pin 1 and 16, when I was doing this Ronan was helping me understand it a bit since he was using multipul ota's in his build , I really suggest everyone check out his turkey day entry it was really a heady design and he helped me figure out how to get mine working right.

I think it might be possible to change r10 from 4K7 to something around 2k2 and leave r16 at 1m and get the same results for using 2 sides of the ota. Still just an idea but dropping it down to 500R and using 2 dual OTA chips might be possible. as long as we don't exceed the 2ma the chips can handle at the bias pins. So if any one trys this on bread board or what not make sure you have extra lm13700's on hand in case you fry a few experimenting. But using the build guide here the way it shows should be safe

If you start building this and have any questions let me know ill try to help as best I can.

[rutabaga bob]

Hey, Jim.  Yeah, I was thinking of using yours...just wanted to know if it would be better to wait for any more tweaks. 

[Mustachio]

Hey Larry,

Yup the first one in the pdf I posted will work fine and at this point if you wanted to experiment with what I was talking about it would work on the same layout all you would need to do is change those resistor values I mentioned.

Also if you wanted you could try stacking the lm13700 and cutting the resistor at R16 down even further, I don't how much of a difference it will make it could be huge or small. And the bias pins should not exceed 2ma and the more we cut down this resistor the higher the ma goes. I'm thinking if the OTA was stacked you would put something around 120K resistor at R16 . Ronan explained to me how to figure out the bias. Really smart guy he is! here is what he said.

The bias pin can only take 2mA max, usually I find I get full range from a filter with anything between 0.5mA and 1mA, it depends on the particular circuit. If you measure the voltage drop across the series resistor to the bias pin, you can calculate the current going into the bias pin. For example, say you have a 4k7 series resistor feeding the bias pin, and max voltage drop across it is say 3V with the filter maxed out (max treble, or max sweep), the current into the bias pin is 3/4700 = 0.64mA. That way you can check if you are going close to the 2mA limit (which renders the chip useless).

So the one I made for the contest is good to go and tuned up pretty dang good. If you like the way the mutron micro V sounds , this version with mods is even better! I personally love it.

Not sure when ill be able to finish the 1590a version I'm geussing a few months so if you want to build this now go for it its pretty inexpensive over all. Best part is you don't need to look for a CA3080 and pay out the nose. You can get those LM13700's for cheap anywhere!

Do you etch boards yourself ? If not pm me and I can probably etch one for ya soon.

[rutabaga bob]

I am looking at the one labeled 'MutroMicroVSCRN'...all purty yellow,green, and red.  Thinking my usual perf.

[rutabaga bob]

Regarding "styrene's" popping issues:  he wrote me he switched caps and still got the popping...anyone got any ideas for him?  I reread his post...said he used 5088 and 5457...could this be the problem?  5457 is a jfet.  I'd like to see a successful conclusion...Gord's layout is nice.

@Rob H. - where's your avatar?

[deadastronaut]

@larry:  no idea...been having weird issues with it for ages, my avater was on quacksed for a while too....strange..