Meatsphere almost there / voltages

[Zoot]

Hi everyone,
Finished a Meatsphere, which I thought was going to work directly, but... not quite there.
Signal goes through the pedal in and out, volume gets lower in the exit, not much seems to happen in terms of effect.
I added Colour and Moog mods, these seem to be alright.
The LED doesn't light up. It only does if I take both Vactrols out of the board, and it lightens up with 2 different intensities in 2 positions of the up/down switch.

These are the voltages I get from some components.

TL074
1. 4.3
2. 3.9
3. 3.9
4. 9.3
5. 4.0
6. 4.2
7. 1.4
8. 8.5
9. 1.5
10. 4.0
11. 0
12. 3.4
13. 4.0
14. 4.0

LM1458
1. 2.0
2. 2.0
3. 0
4. 0
5. 4.6
6. 4.4
7. 4.3
8. 9.3

Vactrol 1
LED 9.32/7.65
LDR 1.42/1.45

Vactrol 2
LED 9.32/7.65
LDR 4.20/4.29

Why the LED doesn't lighten up?
What can be going wrong given this voltages?
What's the best next step for debugging?

Would really appreciate a little help.
Thanks in advance.
Zoot

[Zoot]

Hi everyone!
Anyone can help?!
Thanks a lot,
Zoot

Hi everyone,
Finished a Meatsphere, which I thought was going to work directly, but... not quite there.
Signal goes through the pedal in and out, volume gets lower in the exit, not much seems to happen in terms of effect.
I added Colour and Moog mods, these seem to be alright.
The LED doesn't light up. It only does if I take both Vactrols out of the board, and it lightens up with 2 different intensities in 2 positions of the up/down switch.

These are the voltages I get from some components.

TL074
1. 4.3
2. 3.9
3. 3.9
4. 9.3
5. 4.0
6. 4.2
7. 1.4
8. 8.5
9. 1.5
10. 4.0
11. 0
12. 3.4
13. 4.0
14. 4.0

LM1458
1. 2.0
2. 2.0
3. 0
4. 0
5. 4.6
6. 4.4
7. 4.3
8. 9.3

Vactrol 1
LED 9.32/7.65
LDR 1.42/1.45

Vactrol 2
LED 9.32/7.65
LDR 4.20/4.29

Why the LED doesn't lighten up?
What can be going wrong given this voltages?
What's the best next step for debugging?

Would really appreciate a little help.
Thanks in advance.
Zoot

[Govmnt_Lacky]

If you built the Meatsphere then there is only 1 LED that is showing. This LED is not an on/off indicator. It will only respond with the envelope.

The LED should have opposite effects based on the Up/Down switch position. In one position, the LED will light up when the envelope is activated. In the other position, the LED will be on constantly and will go off when the envelope is active.

A few questions:

1) Where did you source your LM1458 from? Bad ICs in this position will cause the envelope to not function properly.
2) Are you aware that your Attack and Decay knob positions must be set correctly to hear the envelope function. One of them always has to be set higher than the other one (can't remember which is which at the moment) You cannot have Hi settings on Attack and Decay at the same time. You also cannot have low setting on Attack and Decay at the same time.

EDIT: The Attack setting MUST be Lower than the Decay setting.

[PMowdes]

Yeah like ol' Lacky said the settings are critical to getting the meatball running.  if you have the wrong settings then you'll get nowt.  Also if there is a send / return on there make sure that the the jacks are wired correctly because the dry signal passes through them and you wont get anything.

The circuit can be sensitive to the IC and vactrols but if they are duff then normally you get something but the trigger or the filter wont work properly.

[Zoot]

Nice guys, Thank you very much.
I'll check eAch point you mentioned and will work on it for the next days. Get back soon.
BTW the LM1458 is actually a Texas Instruments MC1458P (issue?), I got from SmallBear Electronics as a replacement for the LM1458.
Thanks again!
Zoot

[Zoot]

Thank you Govnmt_Lacky and PMowdes,

I checked the points you both mentioned, and have tried all parameters I found in this forum "to start" this pedal taking care of setting ATTACK always lower than DECAY. No luck.

The LM1458 is actually a Texas Instruments MC1458P, I got from SmallBear Electronics as a replacement for the LM1458.

The RETURN ring is connected to the SEND tip, both are grounded.
Instructions are not very clear on this, as it says SEND is connected to the tip of the RETURN jack. And the drawing shows it connected to the ring, which is what I did.

So, this is what happens with it when on:
1. Works when off, sound passes through
2. Turns on and lowers the input volume. BLEND knob works when on
3. Nothing else seems to do anything
4. If a pedal is introduced in the loop, it has no effect on the signal

It's puzzling. I understand for your non-reaction that my voltages are right. If I take out the Vactrols the LED turns on, otherwise not. The Vactrols are the second pair I put, they are Xvive.

I'm trying to figure out what to do next... and any suggestion is very welcome.
Thanks in advance.
Zoot

[anotherjim]

Anybody got a schematic this was made from? The one I found in the build pdf at musicpcb has so many errors it can't possibly work - can it? Like the +9v labelled as Vref and the 1458 inputs all referenced to ground.

[idy]

The musicpcb schematic has an error in the voltage divider making VB, but "other than that" it is a "meatball." It may be that, in adapting an 18v bipolar mutron to 9v they made some odd or even wrong decisions, but they work. I keep wanting to revisit this on the breadboard and see if this can be improved.

Your indicator LED is not lighting up when you play? have you tried using a booster between guitar and meatsphere? They ones I have made need a hot signal to really do their thing.

I've had more luck using LM358...

[anotherjim]

Exactly, LM358 should be used if the inputs are referenced to 0v. The 1458 is basically a dual 741 and 0v input will be outside its working limits and you will have a dead spot between 0v and around 2v in the envelope. 1458 could be made to work, but not without circuit changes.

[Govmnt_Lacky]

The RETURN ring is connected to the SEND tip, both are grounded.
Instructions are not very clear on this, as it says SEND is connected to the tip of the RETURN jack. And the drawing shows it connected to the ring, which is what I did.

The SEND pad on the PCB should connect to the SEND jack Tip. This should also be jumpered to the RETURN Tip Switch. Then, the RETURN tip should go to the RETURN pad on the PCB.

The part of the jack(s) that need to be grounded are the SLEEVEs. There should be NO connections on the RINGs

Look at this diagram of a stereo switched jack. The far right picture shows you where the connections are. This view is with the jack pins facing up and the jack opening at the top.



You might want to verify all of your resistor values, capacitor orientations, and vactrol orientations (make sure the (+) is going to the proper spots and (-) goes to proper spots.

[idy]

Thank you anotherjim for explaining the difference between 1458 and 358... But "all" the people putting out pcbs for this specify 1458... Dead spot precisely...

[Zoot]

Thank you Govmnt_Lacky,
I have wired the S/R switches as per your post, no changes. AND I have mistaken the 330R resistors for 330K. I guess that was the first main issue. Pedal is kind of alive now, I'm still not getting to trigger the envelope, but there's some change on the output signal. A pedal in the loop continues to have no influence whatsoever.
I'll continue my debugging, will report when done or stuck.
Thanks again!
Zoot

[idy]

So again my experience with the 4 of these I have made is that the LM358 is easier to get working and that I need to use the sensitivity up all the way and some kind of preamp to get a good working range... All the sounds you know and love as seen on TV. But it seems like it should be possible to have the sensitivity half way for preamped guitar, all the way up for straight guitar, down for synth or etc...

Today I tried breadboarding just the detector section but putting a 500k pot to select the bias for the opamp.

Anotherjim got me thinking, "yes the 358 works down to 0v(really?) but the led only turns on around 1.8v. So a dead spot... Sure enough it is easy to dial in a point where the LED triggers from even soft playing and no preamp, (not even the buffer the entire meatball circuit has.)

Am I fixing by brute force some stupid mistake? Is there a better solution?

Now I am thinking what is the simple way to implement this on the boards I have working already. replace 22k...with 500k or 1m trimmer?

[Zoot]

Thanks idy and anotherjim,
I found some mistakes and fixed them. Now... LED turns on in UP position, it's off when in DOWN position. But it doesn't respond to any strumming. I tried a boost before, without result, the loop doesn't do anything yet.

I shall continue debugging until I am comfortable I have no more mistakes and then go change IC (LM358), I don't really get what anotherjim or you explain about it in relation with this circuit. Anyways, I think I'll measure voltages again and try to make sense of all this. And probably order a LM 358 meanwhile.

In any case, thanks for your help.
Cheers,
Zoot

[idy]

Maybe trimmer using place of 22k on board but connected "somehow" to VB; you'd never want to bias it to 9v when "monkeying" with the trimmer, (danger to opamp?) but don't want to dump anything bad on VB node?

1m resistor to 100k pot to VB with its own cap from wiper to ground to give me a safe "VC"?

[idy]

Zoot
the talk is about the bias of the opamp in the part of the circuit detecting the signal and turning it into DC to drive the LEDs. Normally, for audio, we bias an opamp so it idles at the mid voltage, 4.5v with a 9v circuit. The wave goes up and down and is a long way from the "rails," 9v and 0. The Mutron circuit used two batteries, so the opamp took 18v for its +, 0v for its - and 9v for its bias. The Meatball uses only 9v and bias to 0, where an engineer would think to put 4.5... but there may be something(s) I'm missing. I think the LEDs are hooked up differently in the two circuits, the mutron used another opamp to invert the signal for the "up/down" settings and the meatball uses a switch to flip the LEDs around. Neat trick if you have lots of rotary switches lying around.

Some opamps behave better "close to the rails" than others. Sometimes they call this a "rail to rail" opamp. Some my handle a signal very close to 0, others may cut out below some value like 2v. I think Jim is saying 358 is better with these low voltages.

[anotherjim]

The LM358 is built for this kind of job where the opamp doesn't have a negative supply. Look at the meter readings for pins 1,2 & 3 for that 1458. The bias input (pin3) is 0v and the other pins are 2v -  opamp action wants the other pins to also be 0v but it can't output lower than 2v and the bias input will have to exceed 2v to make it go higher. The second stage (pins 5,6,7) is behaving how an opamp should (all voltages similar) but the actual voltage is higher than it should be if pin1 is 2v - this could just be because the second stage has drifted because the input is out of range -  or there is another fault!

To get it working better with the 1458, I'd try a 68k resistor between pins 8 and 3. This will raise the bias up to about 1/4 of the supply voltage.

[Zoot]

Hi Everyone, and thanks for sharing your expertise.

Pedal is working much better, still some things to fix. Adding a boost before really makes it react better. The LED follows the chord picking/strums, but not very consistently. It seems stuck or too slow.

To get there, I had to fix some other little mistakes, but mainly the fact that I have swapped both 330R resistors for 330K. Thanks Govnmnt_Lacky to make me re-check my components.

At the same time I ordered LM358, as anotherJim/idy suggested and explained. I guess what is happening now relates more with the chip, and anotherJim posts (specially the one in the other thread).

I'm still having trouble with the R/S jacks, as nothing changed with the proposed modifications. I guess I need to Audio Probe these paths.

Thanks again to you all.
Zoot