Meatball/McMeat build report

[markusw]

First of all thanks to Moosapotamus and Joep for making it possible!! It really sounds great. Instead of the VTL5C3 I went with Silonex NSL-32AA. Alternatively, putting standard LDRs (Silonex NSL 19-M51) and green LEDs in some neoprene LED sockets and stuffing them in to a shrinking tube worked the same.

Although the sound possibilities are really huge I am not sure if everything works the way it is supposed to be. The coulour pot, although its wired correctly (I checked at least 10 times) just works in the upper 10%. Below I do not get any sweep although the envelope follower detects the signal. I also measured the resistance across the LDRs (in parallel with the 220k or 120k resistors) and with intensity turned up completely I get roughly 70 k on both LDRs. By the way, why do the two Rs in parallel with the LDRs not have the same value as in the Mutron? Any ideas?  
 
However, its worth to build it.

[Joep]

Hi

I'm pretty sure the Colour control only has a limited useable range, I remember Moosapotamus mentioning something about this (search the forum on "meatball"). My Colour has also a limited range (although I think a bit more that 10%.....I guess 20-30%, so still not much)

When you are changing the LDR/LED combination you are directly influencing the frequency of the filter. You can try to adjust the 100 ohm series resistor.

I updates the PDF last week, did you saw the lastest one? (v1.1) there is a change in the detector part of the circuit.

Bye,

Joep

[markusw]

Hi Joep,

thank you very much for your help. I will try to increase the 100 ohm resistors. Do you think that these resistors do also influence the useful range of the colour pot? Did you ever measure the resistance across the LDRs?

[Paul Perry (Frostwave)]

It won't increase the range in effect, but you can get a pot to work over 100% of its range, when it is only active over a part, by replacing the pot by a resistor and a smaller value pot in series.

[markusw]

Thanks Paul. Great idea, I will try it with a 25k or maybe even 10k pot.

[markusw]

Hi,

an interesting observation: when you connect the wiper and pin 3 (the one going to the 1,5k R and then to Vref) of the colour pot it works nearly over the whole range, and its much easier to adjust. I don´t know why, it was just a gut feeling that it might help. Any explanations would be highly appreciated! Thanks in advance.

[Joep]

Interesting! I'll check it out and let you know!

Joep

[markusw]

Great. I am really interested to see if it works for you.

Markus

[markusw]

Hi,

I did some mathematics to find out why the colour pot of my McMeat works much better if RQ (the 1,5k resistor connected to the colour pot) is fixed at 1,5K.
I have used the formulas in “The Art of Electronics” to calculate G and Q of the filter dependent on the colour pot settings (see below). G and Q are the values you get from the original schematics, GM and QM the values with pin 2 and 3 of the colour pot connected (i.e. fixed RQ).



Interestingly, the respective curves start and end at the same values. Moreover, if you calculate the ratio G/Q you get the same constant value (3,16) over the whole pot range in both cases (original and modified version). The only difference (as you can see) is that if you keep RQ constant, the pot is much easier to adjust due to the linearity of the response. This is actually the same thing I observed while playing (before the mod I had to turn the pot to about 90%, now I am going with about 30-40%).

Any comments are highly appreciated (cause I am not sure if my calculations are OK). :?  :?:

[aaronkessman]

could you post pictures of the inside and outside of the pedal?

Did you include all the jacks for loops and control pedals too?

also, where did you get a schematic?

[markusw]

Search for McMeat. Moosapotamus and Joep did great work in drawing the schematics. And yes, I included all the jacks but I did not test them with expression pedals up to now. So far I have added a TS clone in the FX-loop which gives a quite interesting sound
I will take some pictures (at least from the outside, because the inside is not really tidy). Anyway, its a terrific stompbox.

[markusw]

OK, here are the pics. I admit its a rather huge enclosure but I could not get all the stuff into a smaller one. Good luck for your build.

Markus

[anyuser00]

Looks great , can I ask why the two stomp switches

[aaronkessman]

my god that's massive...

[markusw]

Indeed, it´s massive.
The second stompswitch is to switch the fx-loop solo. I also included an optional inverter for the wet signal of the filter section.

[loki]

it looks awesome... just one question, why 5 rotary switches? aren't them just 4?
and did you use regular jacks or the 8 pin jacks used in the pisotones layouts?
thanks bye

[markusw]

The 5th is for the optional phase inverter of the wet sigal. Then there is an additional active volume control and a variable gain (in addition to the 1,8M fixed resistor). I used standard mono jacks but the two for the fx-loop are isolated from the enclosure (with shrinking tube and rubber seals).

Corr: the two jacks for the pedals are isolated. Sorry.

[markusw]

Finally I had the time to make a picture from the inside. Any comments ? (I know its huge)
Take care,
Markus

[aaronkessman]

yes,

first off, that's awesome. pretty ambitious build. can't believe you used all one color wires. it looks like you used some sort of terminals to mount them to the board...?

with them all going all over the place, do you have any noise issues?

Aaron

PS. i'll say it again. my god that's huge. one of those pedals i never thought anyone would try to build. like a CE-1 or Polychorus.

[markusw]

Thanks! yes I prefer to mount the wires with some kind of pinheads (1mm). Regarding the noise issues: fortunately I don´t have any although it´s hard to believe when you look at all the wires crossing each other. At least if there are any they are not obvoius to me. Maybe it would sound even better if it was a little more tidy, who knows. Anyway, I think there is plenty of room for improving my wiring technique.