Building the Meat Sphere

[idy]

I just opened one of mine and tried different values for the caps selected by the "range" switch. I have labeled one on mine "low, high, higher highest" because to me the second lowest already sounds like an angry mosquito and the other two settings maybe are to drive cats crazy.. or maybe bats.

The circuit adds three values to one tiny cap in parallel. (There are two poles doing this to two sets so that two stages of the SVF get equal caps.)
Stock values
2.2n
3.3n (=5.5)
6.8n (=9)
15n (=17.2)
My new ones
3.9n
4.7n (=8.6)
15n (=18.9)
33n (=36.9)

I think I have moved the range down an octave. I was kind of worried about what might happen with bass... there are warnings about not starting earthquakes with the original. With the guitar the new values sound very normal. I want to try some even larger values. I still feel the lowest is a midrange filter.

I guess the point is those values were maybe not handed down from Mt Sinai or conjured up by a real EE. Does anyone ever use the highest settings on the stock pedal?

[lvckv]

Currently building this. What's the deal with the extremely long switches? Are we supposed to cut them or something?


And also can somebody tell me about the send/return? Haven't built a pedal as complicated as this before (and can't read the schematics)...

[Zoot]

Hi Ivckv,
You have to cut them. Measure and cut neatly, with a metal saw it works very nicely.
The S/R jacks need to be switched stereo jacks. You will use them to add another effect, like a boost, for example, inside the MS circuit, adding flavor and control to the MS. This pedal will work only when the MS is on though.
Hope this helps.
Zoot

[lvckv]

Ah thanks for that.

[lvckv]

Have guitar sound when the pedal is off but nothing when turned on (and no LED). Can anyone see what is going wrong here exactly?

[idy]

You did something funny with the pots? I can't see.

The LED you have will (if wired correctly) only light if the envelope generator is triggered. Turning the "up/down" switch to down means it would be normally on, triggering to turn off.


What voltages on the ICs? Are they getting power? Are they biasing up? What chip did you use for the "1458?" This is a dicey application of that chip, "biased" to 0v.

You may have trouble with the optocouplers...most of us ended up "rolling our own" like Lovetone did, from green diffused LEDs and LDR picked to go between a few K and over 1m.

Have you browsed this thread to see the recurring issues? Do you understand the schematic enough to have a rough idea what the Opamps are supposed to be doing?

[lvckv]

The pots are all just wired in standard fashion. Doesn't look anything wrong there.

Everything I have is just standard parts from MusikDing – MC1458P, TL074ACN. I imagine everything they sound would end up producing a real working pedal, rather than having to sub in our own parts, right? I see that the build instructions pdf says "MUST be LM1458 - standard dual opamps will not work" though..

Optocouplers are just VTL5C3.

When I build I usually follow parts placement/wiring diagrams like this because I haven't learned schematics.


I rewired the footswitch to exactly follow the pdf instructions – now there is no sound at all apart from some intermittent white noise, and still no LED.
Previously I had it wired in the same way as taku0319 did here on page 31.

[Taylor]

All your grounds should connect together, so run a wire from one of your 1/4" jack grounds to the ground tab on your power jack.

After that, I'd check with a multimeter the voltages at the power pins of the two chips to make sure they're powered up.

Then, I'd build a little audio probe like this:

https://aronnelson.com/diywiki/index.php?title=Debugging

and check the output of each opamp in the TL074 - that would be the four corner pins, 1, 7, 8, 14. Play some sound into the effect while probing and you should be able to isolate how far through the circuit your signal is making it before things go wrong.

[lvckv]

Ok, seems like it was just some issue with the wiring because I've reworked it and now it seems to be fully working! lol


The LED still doesn't work though... 

[lvckv]

All done. LED is weak when turned on, then it's full when I switch the Up/Down to Down.

Also Down doesn't seem to actually do anything and I can't say I know why.

Everything else seems to work fine though.

[Taylor]

It looks like you've done your bypass switch wiring differently than in the PDF, which I think is why your LED is not working right. Because the LED is meant to light up with the strength of your dynamics, the LED is not wired directly to ground in this circuit, which is why the PDF shows a different form of bypass wiring.

It also looks like your input jack ground is going to the board's LED negative terminal in addition to your star ground, which again isn't directly connected to ground.

You could either try wiring it up again according to the diagram in the PDF, or you could just wire one LED straight to the board's LED terminals, and use a separate LED with your standard bypass wiring diagram like you've used. Then you'd have one LED that shows bypass and one LED that shows the envelope doing its thing, instead of a single LED doing both.

[lvckv]

Will revisit it tomorrow. I wired according to the PDF at first but there was sound when the pedal was bypassed and no sound when pedal was switched on.

Right now the LED is weird, and then there is just 'white noise' sound when Up/Down is set to Down. When I turn Blend to the left the pedal sounds like velcro fuzz, and Sens/Attack/Decay switches do not seem to change anything in the sound.
There were no problems in buiding the board, though, so it's worrying that so much is wrong.

Maybe I should get a new PCB and start afresh.

[idy]

Blend to left = fuzz means something happening to what should be your buffered clean signal. Possible bias. Again, using a meter to measure voltages on the pins of the ICs would help diagnose.

If you read this thread you will see these things don't always fire up right the first time, there are several things that could be wrong, don't lose hope...yet.

Did you put the little "stop" washers on the rotaries so that they have the correct number of positions?

What settings are the rotary switches on? The bandwidth must be on "full" (or at least "1/2") for the trigger to work. That just switches in a smaller cap to make the trigger less sensitive to low notes. Turning it "off" totally disables the trigger section.

Decay must be higher that attack. Sensitivity and Intensity should be full for testing. My first ones needed a booster before to make the passive pickup signal hot enough to trigger. That issue has since been cleared up...

[lvckv]

Have tested the voltages of both ICs.

LM1458

7.00      0.01
6.63      6.72
8.75      6.53
0.12      7.48

TL074

4.46      4.46
4.46      4.46
4.39      1.58
0.00      8.53
4.41      4.41
4.46      4.46
4.46      4.46



I've also rewired again to follow the PDF. The stop washers have been in the switches in the correct position, yes.
This is how each setting sounds at the moment...

• OFF/FULL/HALF - UP - LO/1/2 - x = filter with a quiet high pitched buzz


• OFF/FULL/HALF - DOWN - LO/1/2 - x = regular guitar tone


• OFF/FULL/HALF - DOWN - HI - x = white noise


• OFF/FULL/HALF - UP - HI - x = jangly regular guitar tone that sounds like a bridge pickup

Only the Colour and Intensity switches affect the sound in any position. The bottom right filter switch doesn't affect the sound either.

[Govmnt_Lacky]

Have tested the voltages of both ICs.

LM1458

7.00      0.01
6.63      6.72
8.75      6.53
0.12      7.48

You sure about these? Make sure you are listing the voltages correctly. Like this:



OR this:


**** PICS ARE FOR REFERENCE OF NOTCHES OR DOTS ON THE CHIP. NOT FOR TYPE OF OP AMP ****

[lvckv]

Ah ok. I laid it out as it is on the IC – top row left to right, next row etc.

So it's like this then.

1: 7.00
2: 6.63
3: 8.75
4: 0.12

5: 7.48
6: 6.53
7: 6.72
8: 0.01

and

1: 4.46
2: 4.46
3: 4.39
4: 0.00
5: 4.41
6: 4.46
7: 4.46

8: 4.46
9: 4.46
10: 4.41
11: 8.53
12: 1.58
13: 4.46
14: 4.46

[Govmnt_Lacky]

Ah ok. I laid it out as it is on the IC – top row left to right, next row etc.

So it's like this then.

1: 7.00
2: 6.63
3: 8.75
4: 0.12

5: 7.48
6: 6.53
7: 6.72
8: 0.01

You should be getting around 9VDC on Pin 8 of this IC. You are getting 0.

EDIT: Are you using an LM1458 for this chip? Is so, where did you get it from? Nevermind... I read it above.

[lvckv]

It's an MC1458P and the other is a TL074ACN.

Everything from Musikding as part of the Meat Sphere kit.

[Govmnt_Lacky]

I would remove the MC1458 chip and check for continuity between Pin 8 of the MC1458 and Pin 11 of the TL074. If you do not have continuity, you need to find out why not.

If you do, then you need to find out what is draining all of the voltage going to Pin 8 of the MC1458.

[idy]

This is kind of repeating other faster responses. I am taking one of mine out and measuring....

I'm still not sure you are counting right, or there is something really odd... Counting counter-clockwise with 1 on the left side upper corner near the notch. With the pots on "top" the 1 pin is upper left on both chips.

With the 1458 you should at least see 0 (or close) on pin 4 and 9v (or close) on pin 8. It is a dual Opamp, like the first diagram Govt Lackey posted, they are all like that. When the up/down is set to "up" you should see less than 1v on the other 6 pins. This opamp is kind of funny; usually we have them biased to mid voltage, but this trigger is referenced with a 22k to ground, and the 1458 doesn't really function close to ground, everything hangs at less than 1v. Even when the up/down is set to down the pins won't go far above 2v.

Pin 12 of the 074 is not good. That is the input of the buffer your guitar goes into first. It should be 4.5v. There is a 1.8m resistor connecting it to Vref. Is that correct? Do you measure 4.5v at the other end? Is it not soldered well? Is pin 12 shorted to something? It seems like vref is working because we see lots of 4.5 on the opamp.

I don't understand your "settings". Not clear which switches you are referring to.
For testing:
*bandwidth should be on full, which is the middle setting.
*up/down you may want to toggle back and forth, as that mimics the action of the trigger section, turning the LED with no signal off or on.
  *the range and lp/bp/hp are not so important yet. Lowest setting of range is easiest to hear though.

The knobs are important. Sensitivity and Intensity max. Attack CCW, decay up a little bit. Blend you will need to go back and forth to hear the buffered guitar at CCW and the filter at CW.