Building the Meat Sphere

[dc6]

Hi everyone,

Two questions regarding the Meatsphere.

1) What voltage ratings for the capacitors?

2) What is the current draw of the pedal?

Thanks
David

[Vince_b]

It runs on 9v, so to be safe you want your parts to be rated at least for about the double of that. 16v will do fine but 25v will be even better. Everything above that will also be good of course.

For the current draw, I don't know.

[add4]

Starting to populate the pcb right now.. i'm curious at the colour mod you mention... i have scanned the entire thread and couldn't find any colour mod.. can someone give me a pointer on this?
thanks

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
 
   

[add4]

Ok i feel really stupid to ask that, but you seem to have left RLED empty on your pcb. I can't find any value on the taylor's documentation so i assumed i would have to put a standard resistance there and adjust it to my brightness liking, but seeing the pad empty really confuses me ..
What are we supposed to do with this RLED pad ? there should be a resistance in serie with any diode, right? if RLED is empty, there should be no connection to the led.. or am i just completely wrong?
Thanks for your help :p

Which 10k resistor should i leave off from the pcb if i want to do the Moog mod? I seriously cant find any sensible traces coming from pin 8 which could go to a 10k resistor on the pcb, so i have no clue which 10k res can i leave empty.

Referring to the following image: there is a series of resistors left to the TL074. It's the top 10k you need to leave empty.



The wire to pin 8 connects to the left hand resistor pad, the one to pin 2 to the right hand pad.



Peace,

Markus

[Taylor]

Hmm, yes that's an oversight on my part. I can't believe I didn't notice it and nobody has pointed it out to me! This should be in the PDF.

For a blue LED, I use 10k. For red and other low brightness LEDs, use something like 1k.

[WhenBoredomPeaks]

I promised a while ago that i gonna say something about this effect (especially about the Moog mod) when i finished it.

It's done and it is working but i want to put it in an enclosure to be able to try out the loop and the Moog mod before i comment on the sound. Also i want to add some more mods.
Mainly i wanna lower the cutoff frequency (lower than on "LO" setting of that "range" rotary switch) and i want it to be able to oscillate when resonance (the colour pot) is cranked.

I figured out most of the switches and pots but i have some problems with the attack pot. I can't really hear it working, it goes from super fast - to fast during the travel of the pot.
Can you make slow sweeps with it or that is against the role of an envelope follower? (i would need an ADSR/trigger combo i think)

I made an example sound of a slow filter attack speed: http://soundcloud.com/dontpostthepear/filtersweep
(it is a lowpass filter opening up slowly on a signal full of harmonics)
Can you make something like that with the Meat Sphere?

Also is it enough to jumper that 1K5 resistor coming from the 100k Colour pot to make self oscillation possible?

[add4]

So i have the pcb stuffed, everything connected, and it doesn't work so far:
symptoms :
when effect is engaged: no sound, led doesn't blink

The most probable reason why it doesn't work is that i have a MC1458P plugged in in place of the TL1458
Taylor mentioned several times that the TL 1458 is mandatory so it MIGHT be the reason why it doesn't work, i just would like ... an opinion of more experienced people saying something like :'Hey buddy, it seems like the TL1458 is the problem, i'm sure that it will work ok when you'll get the tayda order you just made today'
Anyway, to help you guys giving me an opinion:

Voltages:
TLO74
pins 1-3 : 4.5V
pin 4 : 9
pins 5-10 : 4.5
pin 11 : 0
pin 12 : 1.6
pins 13-14: 4.5
That seems pretty normal to me

MC1458P
pin 1: 6.45
pin 2: 2.9
pins 3:-4 0
pin 5: 5.37
pins 6-7: 6.61
pin 8: 9
This seems strange to me : opamps are supposed to have roughly the same voltages at all pins except power supplies, aren't they?

Potentiometers lugs :
(left to right, silkscreen up) i tried to put the pots in the middle each time

blend 4.5 (3 lugs)
intensity 7.38 6.95 6.95
colour 4.45 4.40 4.5
decay 0 0 0 <- ?!?
attack 4.95 4.95 5.90
sensitvity 0 0 0

sensityvity and decay seem dead.. i checked their connections to the PCB, no resistance between the solder and the lug so it seems ok on that side.
I also verified that the 3p4T switches are one the good positions (All left or all right, then put the number of position selector (turned the switches while probing one of the connected lugs of the switch, when there was a voltage showing up, i stopped and left the switch in that position
.
Looking at the schematic, the decay and sensitivity pots are into the part of the circuit which uses the TL1458, that's why i think that could be the reason why it does't work..
Any other ideas? suggestion? confirmation? need for more informations to get further?

Thanks in advance for your help
Peace

[Taylor]

I'm not aware of such a thing as a TL1458. I spec LM1458, but any 1458 should work,so I don't think that's the problem.

Personally, I find audio probing to work much better than trying to debug with voltages.

Probe the key points of the circuit to find out where the signal is dying. If you have no clean signal and no effect signal and no envelope following, then the problem probably lies near the input.

[add4]

Sorry about the LM1458, i meant TL1458

Ok, so i tried the circuit again this morning (couldn't do it loud enough yesterday evening as it was 1am).
I DO get audio out of the effect, i can change the sound with the blend, colour and intensity pots and the hp/bl/lp and range switch.
Bandwith and up/down don't change anything, same for the sensitivity, attach and decay pots.
The LED don't ever turns on.
The sound i get is filtered, but does not change with the envelope.

So i think the problem is really into the LM1458 section, but i don't really know what it is yet.
The voltage difference between the vacrol led pins are around 1V i guess that's not enough to make them work.

I audio probed the parts of the circuits, i get a sound out of every pins of the TL074 so it's not the problem
I don't get any audio if i probe the pins od the LM1458, and the whole row of resistors/diodes left to it, except the lower resistor.
Looking at the schematic it seems that this corresponds exactly to the parts of the LM1458/enveloppe follower section.
i'll try to go further into this.
I get audio from the send pad, but nothing on the center lug of the bandwidth switch, or ,from the schematic,
they are supposed to be connected through a resistor and the sensitivity pot.
I'll check that this section is working correctly

I'm not aware of such a thing as a TL1458. I spec LM1458, but any 1458 should work,so I don't think that's the problem.

Personally, I find audio probing to work much better than trying to debug with voltages.

Probe the key points of the circuit to find out where the signal is dying. If you have no clean signal and no effect signal and no envelope following, then the problem probably lies near the input.

[Taylor]

Do you have a wire from the send pad to the return pad?

[add4]

Yes I do.
If i cut that connection, i don't get any sound at all from the effect.

Do you have a wire from the send pad to the return pad?

[add4]

So i'm still looking at this problem.
I am quite certain the problem is between the pin 14 of the TL074 and the send pad/sensitivity pot.
Looking at the voltages, i get 4.5 volts at pin 14, and 0 at the send pad and sensitivity pot... they are supposed to be connected together.
So i measured the voltages along the via between them.
Starting from pin 14, the via goes from the lower 14914 diode pad to the left of the bandwidth rotary switch.. so far, still 4.5V. then the via goes to a 10uF elec cap and the minus side of this cap goes to sent and sensitivity pot. The problem is: i don't see this cap on the schematic!.
I have 4.5 volts at the plus side of the cap, and 0 at the minus side... that goes to send and sentisitivy...
Is that normal?

[Taylor]

Thanks for pointing out that cap missing from the schematic. It's connected between pin 14 and the sensitivity pot.

Capacitors block DC voltages, so yes it's normal that there would be a DC voltage on what side and not the other side.

Again, IMO (having built probably 500 pedals and done a fair amount of debugging) audio probing gets to the heart of the matter much faster than voltages. If you have sound coming out of pin 14 but no sound at the center pad of the bandwidth switch, then that narrows it down to just a couple of components. Try reflowing all of those pads.

[add4]

500 pedals ! Oo That might explain the uber pcb layout skills!
Well that's exactly what happens : audio sound when i touch pin 14, haven't tested touching the cap pads so far, no sound at the sensitivity pot, no sound at the send and return pads, they are soldered together at the moment.
I'll try reflowing that asap.
Many thanks for your help Taylor!

Thanks for pointing out that cap missing from the schematic. It's connected between pin 14 and the sensitivity pot.

Capacitors block DC voltages, so yes it's normal that there would be a DC voltage on what side and not the other side.

Again, IMO (having built probably 500 pedals and done a fair amount of debugging) audio probing gets to the heart of the matter much faster than voltages. If you have sound coming out of pin 14 but no sound at the center pad of the bandwidth switch, then that narrows it down to just a couple of components. Try reflowing all of those pads.

[digi2t]

I'm wonder that I might try and build this into a wah shell, but what would be the best parameter to control with a treadle?

Any opinions?

[Barcode80]

I'm wonder that I might try and build this into a wah shell, but what would be the best parameter to control with a treadle?

Any opinions?

Well, none of the controls are really "on the fly" kind of controls. It seems fairly useless to adjust them while playing. But if I were to pick one I would pick sensitivity.

[Taylor]

On page 1 of this thread, there's a discussion about what the expression pedals controlled on the original. I would think intensity might be the best.

[WhenBoredomPeaks]

I think if you set the trigger switch to "Off" you can control the cutoff freq with the "Intensity" knob.

[add4]

Hello Taylor,
Here's an update on my debugging of thus build:
I'm playing music from my computer into the effect as i probe is, so i can hear what's happening with AC voltages and not be fooled by the cap thing
summary of symptoms:
I get bypassed sound and processed sound.
I can filter the sound with blend, intensity, colour, range, HP/BL/LP/ and UP/DOWN.
The filter is 'fixed' i can't hear any envelope following effect. it currently acts as a rather cool sounding fixed filter.
The LED does not ever light up (but does when i probe certain components, so it's wired correctly)
things not producing a hearable change in sound when tweaked: decay, attack, sensitivity, bandwidth (pretty much the entire circuit block around the LM1458)
reminder: until my tayda order is not here, i'm using a MC1458p instead of the LM1458.. pinout is the same... can't tell about the rest. changing that will be the first thing i do when i receive the right opamp.

When i touch the pin 14 of the TL074, i hear a POP. this pop is also hearable at the via to the second layer: one of the diodes legs next to the TL074. I still have a sound at the other side of the via, and the same pop when i touch the + leg of the middle 10uF cap under the sensitivity pot. So far it seems to be ok since it follows the schematic (without the 10uF cap). From what i read of the schematic: the minus leg of the 10uF pot should then go to
- send
- left lug of sensitivity (near the center of the pcb)
If i touch these components: i hear the volume of the music lower, i guess i'm sucking voltages out of the effect. they seem connected all react the same way, so far so good.
Following the schematic: sensitivity controls the volume of the sound coming into the envelope section, so i should hear something if i probe the middle lug, and i do.
Signal then goes to the 4.7 k resistor which is i guess right under the 3 10uF caps under sensitivity. the lug on the outer side of the pcb which is connected to sensitivity lower the signal too.
The other leg of the 4.7 resistor doesn't produce anything hearable.. and it goes right to the middle lug of the bandwidth switch.. which doesn't work at all....
I tried reflowing the components, doesn't change anything. multimeter says the resistor is 4.7k so is the resistance between the outer lug of the resistance and the middle lug of bandwidth. With i turn bandwidth, it connect either to the lower pad which is connected to the circuit or to the other connected pad, with 4.7 resistance between it and middle lug of sensitivity. so i guess theres signal coming through the resistor (or through another path around the rest of the circuit??  But the changes of having 4.6k exactly seem very low to me) For this reason id say the soldering is ok. And i guess the problem lies ahead.

I'll continue this later. if anybody have an advice on what i have done so far, i'd be glad to follow any ideas

Thanks for pointing out that cap missing from the schematic. It's connected between pin 14 and the sensitivity pot.

Capacitors block DC voltages, so yes it's normal that there would be a DC voltage on what side and not the other side.

Again, IMO (having built probably 500 pedals and done a fair amount of debugging) audio probing gets to the heart of the matter much faster than voltages. If you have sound coming out of pin 14 but no sound at the center pad of the bandwidth switch, then that narrows it down to just a couple of components. Try reflowing all of those pads.

[Dimitree]

can anyone tell me what should be the max-min resistance of the 2 VTL5C3, but not isolated, instead in the circuit (so in parallel with other resistors and so on)