Anybody build their Gristleizer yet, comments on it?

[Taylor]

I’ve got an issue with my gristleizer build and was wondering if you’ve experienced this before. I can hear the tick of the lfo when set to square wave shape on my unit even in bypass mode, the bias also doesn’t lock in the lfo for the square wave so the trem/vibe sound isn’t really there either but you can hear the lfo tick while playing. all other shapes are fine, barely any tick and dead quiet in bypass mode. I was trying to Quiet the tick down so I modded the 100uf caps for 470uf and the optional 10uf for 470uf, also the 10k at the input for 330k to try and bring down the input gain, also changed the bias pot to audio taper. Do you know where in the circuit I should be looking to try and remedy the issue?

Some ticking does seem to be par for the course with the Gristleizer, but it may be down to the offboard wiring - if you can keep your wires as short as possible and keep the switch wires away from your input/output and the bypass switch, it will help.

[Taylor]

The Gristleizer PCB has been out of stock for a few months, but it's now back. 

[telebiker]

Hello!

I'm building the circuit and for now everything looks clear. However, I would like to set up trimpots using a scope. There are the following instructions in the build doc:

viewthe waveform and tweak the trimpot until it most closely resembles a triangle wave

The offset trimpot sets the center of the LFO sweep. Set it so that the waveform iscentered around 0v.

I'm not sure what are injection points for the scope to view the waveform. Could you please advise, what are they?

Also, I think that the following information might be useful if someone is using Alpha SR2612F-0304-18K0B-D8-N rotary switch (http://smallbear-electronics.mybigcommerce.com/26mm-enclosed-3p2-4t/), there is a mapping of PCB contacts and rotary switch pins:

Code: [Select]

PCB             rotary switch
1 A
2 1
3 2
4 3
5 4
6 B
7 5
8 6
9 7
10 8
Remember that you would need to configure rotary switch to select 4 positions by putting a washer accordingly.

[Taylor]

Try putting your scope probe at the center lug of the Depth pot, and turn up the depth.

[eeliyx]

Hello, this is my first post here.
I built the kit from Musikding and I'm looking for some troubleshooting help.
The bypass works, the LED is blinking according to the speed control pot and the level works as expected, although quite delicate control and loud.
However I'm not getting any tremolo-like effect on my audio. A clean sine just turns into a square wave, both in VCA and VCF mode (one is a bit of a sharper wave).
The speed, bias, depth and waveform control seem to have no effect on the audio.
Anyone have any pointers on what to examine first?
Thanks!

[tangerine]

Hello, this is my first post here.
I built the kit from Musikding and I'm looking for some troubleshooting help.
The bypass works, the LED is blinking according to the speed control pot and the level works as expected, although quite delicate control and loud.
However I'm not getting any tremolo-like effect on my audio. A clean sine just turns into a square wave, both in VCA and VCF mode (one is a bit of a sharper wave).
The speed, bias, depth and waveform control seem to have no effect on the audio.
Anyone have any pointers on what to examine first?
Thanks!

This sounds exactly like the problem I have. The speed pot only has a narrow useful sweet zone of about 10º above which it is too fast and below, too slow to be practical..

After three months of frustration, I ended up dismantling everything but the board with the intention of trying again when I have regained my patience.

[eeliyx]

This sounds exactly like the problem I have. The speed pot only has a narrow useful sweet zone of about 10º above which it is too fast and below, too slow to be practical..

After three months of frustration, I ended up dismantling everything but the board with the intention of trying again when I have regained my patience.

No, I actually think my speed pot is doing exactly what is should, since the LED is blinking as expected.
It just seems to have no effect on the audio for some reason.
The speed is supposed to go very fast into audio rate.

[tangerine]

My LED is also blinking. The rate changes with rotation but the control is delicate and has no effect on the audio.

I think I just described things differently.

[Taylor]

Hello, this is my first post here.
I built the kit from Musikding and I'm looking for some troubleshooting help.
The bypass works, the LED is blinking according to the speed control pot and the level works as expected, although quite delicate control and loud.
However I'm not getting any tremolo-like effect on my audio. A clean sine just turns into a square wave, both in VCA and VCF mode (one is a bit of a sharper wave).
The speed, bias, depth and waveform control seem to have no effect on the audio.
Anyone have any pointers on what to examine first?
Thanks!

Are you able to look at the output of the LFO on a scope?

What JFET are you using, and have you verified that the pinout is the same as on the PCB?

[eeliyx]

Are you able to look at the output of the LFO on a scope?

What JFET are you using, and have you verified that the pinout is the same as on the PCB?

I don't have a scope yet, ordered one two days ago. I'm supposed to read at the + of the optional cap right?
Will report back when I have my scope.
Using a 2N3819 JFET with the correct pinout.

[telebiker]

As Taylor mentioned recently:

Try putting your scope probe at the center lug of the Depth pot, and turn up the depth.

I believe that should work for you as well since you're debugging LFO.

[eeliyx]

Ok, so I have a scope now and I've been doing some measurements on the center lug of the depth pot with the second probe attached to the common ground on the input jack.
Using the numbering scheme of the rotary switch positions like on page 3 of the doc.
First weird thing I've noticed is that in the switch position 1-2/5-6 when turning up the depth pot (B10K) over 270°, the LFO speed decreases rapidly to about a third.
LFO speed at medium to high depth:

LFO speed at max depth:

 
I will go into more detail on the different LFO settings in my next post.

[eeliyx]

So here are the readouts of the LFO for the other three waveform settings at max depth:

1-3/6-8:

1-4/6-9 (notice the large offset and way higher voltage, also why are both positions "ramp down"?):

1-5/6-10:

I hope someone can make sense of this.

[Taylor]

It seems like there must be something weird in your rotary switch wiring that's connecting things in the wrong way. What type of switch is it? Can you check with a continuity meter that the lugs are actually connecting the right way? 1 to 2-3-4-5 and 6 to 7-8-9-10?

[eeliyx]

What type of switch is it? Can you check with a continuity meter that the lugs are actually connecting the right way? 1 to 2-3-4-5 and 6 to 7-8-9-10?

It's a 2P6T switch I got from the Musikding kit.
Looks exactly like this one I found on aliexpress:

From the schematic above I shorted out the pins 1-2, 5-6, 7-8 and 11-12 so I don't have any dead positions.
I did test the continuities of the switch before I soldered anything because I was confused as to how it works.
Maybe something slipped by me.
I will test the switch more again more thoroughly and report back tomorrow.
Thanks for the help!

[telebiker]

BTW, is there some other bypass switching scheme for Gristleizer apart from the one provided in the build doc? http://i38.photobucket.com/albums/e101/putzdaddy/offboardwiringfordiy.jpg

What I'm looking for is the bypass scheme which would keep the LED blinking while the effect is on, but which would switch the LED off while the effect is off. I already don't have space for the second LED. Would be grateful for help.

[Taylor]

The flashing LED is turned on by the 3904 transistor. You could use the center pole of the bypass switch to connect/disconnect the 3904's emitter pin to ground, in the same way that the bypass diagram shows disconnecting the LED from ground. Might be a little kludgy to wire, make sure to check the 2n3904 datasheet for pinout.

[eeliyx]

Hi everyone, I made some new measurements. This time I took the rotary switch out and soldered the wires together for each configuration.
1-2 / 6-7:

Medium depth

Max depth

As you can see it's still doing something weird to the speed at max depth.

1-3 / 6-8:


1-4 / 6-9:

This is the only one affected by the OFFSET and SHAPE trimpots. I was able to make a centered triangle.

1-5 / 6-10:

Low depth

Medium depth

Max depth

Seems to look a lot more like a square at low depth.

Thanks for taking the time to help!

[telebiker]

The flashing LED is turned on by the 3904 transistor. You could use the center pole of the bypass switch to connect/disconnect the 3904's emitter pin to ground, in the same way that the bypass diagram shows disconnecting the LED from ground. Might be a little kludgy to wire, make sure to check the 2n3904 datasheet for pinout.

Worked for me! Thanks!

[Taylor]

Hi everyone, I made some new measurements. This time I took the rotary switch out and soldered the wires together for each configuration.
1-2 / 6-7:

Medium depth

Max depth

As you can see it's still doing something weird to the speed at max depth.

1-3 / 6-8:


1-4 / 6-9:

This is the only one affected by the OFFSET and SHAPE trimpots. I was able to make a centered triangle.

1-5 / 6-10:

Low depth

Medium depth

Max depth

Seems to look a lot more like a square at low depth.

Thanks for taking the time to help!

Comparing your previous results and these new ones, I notice that you seem to now have both a rising ramp and falling ramp. That would seem to indicate something was indeed weird with the rotary switch.

The next thing I'd try to solve is that the speed of the LFO is changing with the Depth pot. The Depth is just attenuating the signal coming out of the LFO shaper opamp stage, so for that to be affecting the LFO speed at all makes me look to your depth pot wiring and/or an issue with the ground and power supply. Could you post a picture of your PCB and wiring? Is your MAX1044 outputting negative 9v at pin 5? Can you check with a continuity meter that the negative terminal of your power supply is connected to GND on the PCB, your enclosure, and the sleeves on your 1/4" jacks?