Building the Meat Sphere

[Hankster]

   I should have read the forum thoroughly. The fake rotary switches have "SET WASHERS" on them! They have numbers on how many positions you want... everything an alpha does. Oops. A washer... I thought it was a little plastic pin.

[markusw]

This weekend I finally found the time to build the Meat Sphere.
It was so much more fun building it than with all the off board switches and pots!   
Thanks a lot to Taylor for the fantastic PCB!
Also thanks a lot to Vince_b for the drilling template!

There are two mods I implemented so far.

First, the previously described colour pot mod, which is mandatory IMHO.

Second, a mod I like to call the "Moog switch".
In contrast to the Meatball (which keeps Q constant with frequency) in  the famous Moog ladder filter Q decreases with frequency, which to my knowledge is an important part of the Moog filters sound.
I like this feature since with bass guitar (didn't check with guitar) the bass may become rather unpredictable at certain settings of the Meatball.
Although it may sound cool the sound engineer hates you for this 
I did a couple of LTSpice simulations to find out that the Moog filters Q frequency dependency can be approximated by adding a 470n cap in series with 10k resistor in the feedback loop of the Meatball.
The "moog switch" is inserted in place of the 10k feedback resistor and has the 10k and the 470n mounted to the switch. It switches between 10k only (meatball mode) and 470n in series with 10k (Moog mode).
For some reason I needed to add a 100k resistor in parallel with the 470n. Without the 100k there was massive distortion. Might be that it was just a cold solder joint on the switch that caused the distortion. Anyway, I didn't care to remove the 100k again since it worked.
Thought I'd share because I really dig the Moog mode. In fact I prefer it with bass guitar.

Still need to add a phase inverter board to make the blend pot work usable when in LP filter mode.

Cheers,

Markus
 
   

[Taylor]

Great mods, Markus, thanks for your post!

[gtown_caps_fan]

This weekend I finally found the time to build the Meat Sphere.
It was so much more fun building it than with all the off board switches and pots!   
Thanks a lot to Taylor for the fantastic PCB!
Also thanks a lot to Vince_b for the drilling template!

There are two mods I implemented so far.

First, the previously described colour pot mod, which is mandatory IMHO.

Second, a mod I like to call the "Moog switch".
In contrast to the Meatball (which keeps Q constant with frequency) in  the famous Moog ladder filter Q decreases with frequency, which to my knowledge is an important part of the Moog filters sound.
I like this feature since with bass guitar (didn't check with guitar) the bass may become rather unpredictable at certain settings of the Meatball.
Although it may sound cool the sound engineer hates you for this 
I did a couple of LTSpice simulations to find out that the Moog filters Q frequency dependency can be approximated by adding a 470n cap in series with 10k resistor in the feedback loop of the Meatball.
The "moog switch" is inserted in place of the 10k feedback resistor and has the 10k and the 470n mounted to the switch. It switches between 10k only (meatball mode) and 470n in series with 10k (Moog mode).
For some reason I needed to add a 100k resistor in parallel with the 470n. Without the 100k there was massive distortion. Might be that it was just a cold solder joint on the switch that caused the distortion. Anyway, I didn't care to remove the 100k again since it worked.
Thought I'd share because I really dig the Moog mode. In fact I prefer it with bass guitar.

Still need to add a phase inverter board to make the blend pot work usable when in LP filter mode.

Cheers,

Markus
 
   

Thanks Markus, but I didn't see the "previously mentioned Colour mod". I looked through the entire thread, and searched it with my browser. Can you please tell more? I just ordered my board yesterday and am sourcing parts now, so if there is a change to the colour pot value or something, it would be great to know in advance.

[markusw]

Hey,

sorry, with "previously" I didn't refer to this thread but to older threads.

The colour pot mod is very simple. No different pot value needed. You just need connect the wiper with the lug connected to the 1k5. Looking at the PCB component side up, pots north it's the left lug you need to connect the wiper to.
The mod doesn't change the available range for resonance or gain. It just makes the pot much more easy to adjust.

Here's an image I did a while ago (in fact it's already seven years   ). Anyway...

Variable RQ (G, Q) is without the mod, fixed RQ is with the mod.



Hope this helps.

Regards,

Markus

[gtown_caps_fan]

Thanks. So just jumper lug 1 to lug 2. I appreciate your assistance.

Bruce

[jefe]

Wow - I haven't been around in a few months - Taylor made a PCB clone of the Meatball, with board mounted rotary switches & pots??!!

*PURCHASED*

Very cool, Taylor, thanks for doing this - I've been wanting to build one of these for a long time, but the offboard wiring looked like a pain. Can't wait!

[soggybag]

Just finished up a build and wrote a report on my site here: http://www.super-freq.com/2011/09/meatsphere/

Thanks Taylor, great PCB makes a really easy project out of what could be a wiring nightmare.

Thanks Vince B, the drilling template worked perfectly!

[Taylor]

Wow, very thorough! Thanks for that report and I'm glad you like the build.

Sorry you don't like the name.   FWIW, the suggestion I heard most but which I vetoed was "Ball Meat". Do I get any points for not using that one?  

Originally I wanted to call it "Computer-generated chrome sphere rolling down a checkered meat hallway" but I couldn't fit that on the silkscreen layer...

[JustinFun]

Since I've started receiving a few build reports and questions about the Meat Sphere PCB, here's a thread for discussion and posting your builds.

Here's the correct way to orient the rotary switches and pots on the board:


I will be posting a drill template and some of my own build photos shortly. The PCB fits comfortably in a 1790NS enclosure. I've been having a lot of fun with the analog octave down, into the Meat Sphere for synth sounds.

I'm a little confused by the switches here. I've got these switches from Musikding:

http://www.musikding.de/product_info.php/info/p2852_Rotary-switch-3P4T-sealed-pcb.html

and I can't match the "a/b/c" poles which are labled on the board with the poles on the switches if I mount them behind the board as shown. They would mount properly from the front, but from the back if you line up 'a' then 'b' and 'c' are reversed.

Does it matter? Am I doing something wrong, or have I got the wrong switches?

[soggybag]

Apparently you can mount these switches in any orientation.

Taylor, I forgot my manners I shouldn't have said anything about the name.

[markusw]

I'm a little confused by the switches here. I've got these switches from Musikding:

http://www.musikding.de/product_info.php/info/p2852_Rotary-switch-3P4T-sealed-pcb.html

and I can't match the "a/b/c" poles which are labled on the board with the poles on the switches if I mount them behind the board as shown. They would mount properly from the front, but from the back if you line up 'a' then 'b' and 'c' are reversed.

Does it matter? Am I doing something wrong, or have I got the wrong switches?

I got the same switches from musikding. Don't worry. Orientation doesn't matter. You just need to set the locking washer ("Rastring") to the appropriate number of positions you need.

Regards,

Markus

[JustinFun]

That's great news, thanks Markus and Soggybag!

Completely confused as to how these switches work, though. Will have to do some reading up...

[Taylor]

Apparently you can mount these switches in any orientation.

Taylor, I forgot my manners I shouldn't have said anything about the name.

I'm not offended, I was just kidding around. Picking a name for a PCB is a necessity for practical reasons, but not something I concern myself too heavily with - I expect people to pick their own name for their pedal anyway.

For my own original circuits like the Uncanny Valley and Brazen Prophet, I put something into it and tried to pick a name with some kind of relation to the effect, but with this one my main goal was just not to step on copyright while getting the idea across.

[monkeyxx]

This weekend I finally found the time to build the Meat Sphere.
It was so much more fun building it than with all the off board switches and pots!   
Thanks a lot to Taylor for the fantastic PCB!
Also thanks a lot to Vince_b for the drilling template!

There are two mods I implemented so far.

First, the previously described colour pot mod, which is mandatory IMHO.

Second, a mod I like to call the "Moog switch".
In contrast to the Meatball (which keeps Q constant with frequency) in  the famous Moog ladder filter Q decreases with frequency, which to my knowledge is an important part of the Moog filters sound.
I like this feature since with bass guitar (didn't check with guitar) the bass may become rather unpredictable at certain settings of the Meatball.
Although it may sound cool the sound engineer hates you for this 
I did a couple of LTSpice simulations to find out that the Moog filters Q frequency dependency can be approximated by adding a 470n cap in series with 10k resistor in the feedback loop of the Meatball.
The "moog switch" is inserted in place of the 10k feedback resistor and has the 10k and the 470n mounted to the switch. It switches between 10k only (meatball mode) and 470n in series with 10k (Moog mode).
For some reason I needed to add a 100k resistor in parallel with the 470n. Without the 100k there was massive distortion. Might be that it was just a cold solder joint on the switch that caused the distortion. Anyway, I didn't care to remove the 100k again since it worked.
Thought I'd share because I really dig the Moog mode. In fact I prefer it with bass guitar.

Still need to add a phase inverter board to make the blend pot work usable when in LP filter mode.

Cheers,

Markus
 
   

Hi,

Is the feedback 10K resistor you're referring to the one that goes from pin 1 to pin 2 of U1A in the meat sphere schematic, or the 10K that goes from pin 8 of U1C back to pin 2 of U1A?

really want to try this moog mod

[monkeyxx]

here's my build.  takes a bit of learning, this one, don't be completely disappointed if you don't get any sounds out of it at first... if your rotary switches are off the useful settings (put the washers to the right amount of turns on the switch, tiny numbers are there on the black plastic), and if attack is higher than decay, you'll get no envelope.  sensitivity has to be turned up a lot sometimes to to hear the effect.  I'm liking it so far, but not sure what to do with it yet... I think it's probably going to be an occasional specific use thing, for me.  It does sound good, and I like the tweakability.  might mod the blend knob to use the "wet" signal from the send/return loop rather than the "dry" input

[monkeyxx]

Thanks. So just jumper lug 1 to lug 2. I appreciate your assistance.

Bruce

no.  lug 2 to lug 3 I believe is the correct "colour pot mod"

[markusw]

Hi,

Is the feedback 10K resistor you're referring to the one that goes from pin 1 to pin 2 of U1A in the meat sphere schematic, or the 10K that goes from pin 8 of U1C back to pin 2 of U1A?

really want to try this moog mod

It's the one that goes from pin 8 U1C back to pin 2 of U1A. Sorry, I wasn't more specific about that.

Peace,

Markus

Edit: the jumper for the colour pot mod is set correct. Don't know if this would be lugs 2 and 3 or 1 and 2. I always mix them up

Edit 2: I just Spice simulated the "moog switch" the way you wired it (i.e. from pin 1 to pin 2 of U1A). At high resonance settings it should perform similar, at lower resonance settings it should perform pretty weird: if the Spice sims are correct it would lower the resonance at high AND low frequencies.
 

[markusw]

This is how I wired the "moog switch":



In fact, it doesn't really change the sound if you reverse the wires to pins 2 and 8.

Peace,

Markus

[markusw]

Where did you get the plastic covers for the pots?

Peace,

Markus