Aion Blueshift Biasing

[Timko]

I spent last evening watching some Waza Dimension C videos. Mine definitely isn't that motionless.

[Bio77]

You can download a signal generator on your phone, I use Function Generator PRO.  You need to make a 1/4 inch adaptor.  If you have kids, there's likely a broken pair of headphones around that you can use   

I'm not sure from your post if you have a scope or not.  If you do, you don't need to measure the voltage to bias the BBD, the scope is better.  For multimeter I'd suggest  VC97, it's ~$30 on Amazon, it has a frequency counter.

[Timko]

I have quite a few multimeters and a cheap diy scope. I need to run the 8kHz signal through it and tune it from there. The signal I mentioned using earlier was in the 440Hz range.  I've used that function generator to build my Lab series preamp. I don't know how to make the signal generator output a signal that's 2V peak to peak.

I may check out the VC97, I don't have a frequency counter.

[Bio77]

The app I mentioned above will output a a waveform at any frequency, you can adjust the volume of the waveform in the app.  You will measure the input jack of the pedal with your scope and adjust the volume in the app until you see the 2V p-P you are looking for.  Then you can look at the output pins of the BBD and adjust the bias. 

[Timko]

I passed an 8kHz waveform into the pedal at -20.0dB (2V) and used my super cheap DYI kit to make the signal equal.  However, it's still pulsing way too much.  I'm going over to a friend's house who can let me use their considerably better oscilloscope, and we'll see if there's any difference there once I calibrate it with something more professional.

[Timko]

I was able to run some tests through a Rigol 1054Z at work today. I discovered that the trim pot settings I dialed in with my cheap DYI scope were nearly spot on. The wave shape looks the same on the top and the bottom. I did notice that Aion's wave picture looks more rounded at the bottom; mine looks steeper.

It also may be a function of me not knowing how to dial in the scope correctly, but when I probed both testing points, one wave was still and the other was constantly moving. I had expected to see the waves as inverses of one and other.

The bad news is that I still have way too much motion in the effect. I've moved chips around on the smaller board to rule out any issue there. I'm going to begin looking at the compounder ICs I think next.

Can someone tell me if the output of the 2nd compounder is supposed to be motionless? I think you could audio probe it. I'm trying to find the place where they WO waves are combined back together.  I assume it's there.

[Timko]

I am finally getting around to troubleshooting a few troublesome builds.  I ordered 2 new CoolAudio 3207s and 3102s from Smallbear a few weeks back and decided to change both of the delay parts of the circuit to see if I could find the cause of the issue.  The results were...not helpful. 

Now, when I put my oscilliscope on the testing points, both waves look like this:


I am still noticing IC3 has considerably less impact on the sound, so I may try changing out the Opamp that drives it.

I also noticed what I can best describe as a motorboating sound when I passed the 8000kHz signal through the circuit for testing.  I'm not sure if that's expected.

If anyone has a complete set of voltages for the various ICs and transistors I would be very interested at this point.  This circuit is so complex and difficult to troubleshoot due to the dual board nature that coming up with places to begin investigation has proven to be hard.

[aion]

IC2 (NE570 lower right in Blueshift)
1: 1.03V
2: 1.84V
3: 1.84V
4: 0
5: 1.84V
6: 1.84V
7: 3.11V
8: 1.84V
9: 1.84V
10: 3.03V
11: 3.03V
12: 1.84V
13: 9.86V
14: 1.84V
15: 1.84V
16: 0.52V

IC11 (NE570 top center in Blueshift)
1: 0.95V
2: 1.84V
3: 1.84V
4: 0V
5: 1.84V
6: 3.02V
7: 3.02V
8: 1.84V
9: 1.84V
10: 3.03V
11: 3.03V
12: 1.84V
13: 9.86V
14: 1.84V
15: 1.84V
16: 0.91V

Note: Pin voltages of clock and BBD will vary by bias voltage (MN3207 pin 3) so these aren't necessarily good targets, it just matters that the BBD is properly biased.
"~" denotes oscillating voltage.

IC3 (MN3207)
1: 0
2: 3.00V ~ 3.10V
3: 3.62V
4: 5.90V ~ 5.95V
5: 6.32V ~ 6.37V
6: 2.94V ~ 3.08V
7: 4.30V ~ 4.34V
8: 4.30V ~ 4.34V

IC4 (MN3102)
1: 6.32V ~ 6.37V
2: 2.94V ~ 3.08V
3: 0V
4: 3V ~ 3.1V
5: 4.62V ~ 5.65V
6: 0.74V ~ 1.74V (no connection to PCB)
7: 3.83V ~ 4.34V
8: 5.90V ~ 5.95V

IC8 (MN3102)
1: 6.31V ~ 6.36V
2: 2.94V ~ 3.10V
3: 0V
4: 2.95V ~ 3.10V
5: 4.19V ~ 5.55V
6: 0.85V ~ 2.09V
7: 3.66V ~ 4.14V
8: 5.88V ~ 5.93V

IC9 (MN3207)
1: 0V
2: 2.95V ~ 3.10V
3: 3.39V
4: 5.88V ~ 5.93V
5: 6.30V ~ 6.36V
6: 2.94V ~ 3.10V
7: 3.97V ~ 4.02V
8: 3.97V ~ 4.02V

The other ICs are just normal op-amps, so they should typically be around 4.8V (1/2 supply voltage) +/- 0.5V for all pins except 4 (0V) and 8 (9.6V).

[Timko]

Thanks Kevin!  The good news is that my IC2 and IC11 look like they're in the ballpark of what you have here. I think I was using a cheaper power supply through my testing rig and had slightly higher values but they are all relative to yours.  However, since I changed out IC2, 3, 8, and 9, I'll need to re-measure those.

I do have a question for you about the optimal wave pattern of the two delays.  When comparing the wave shapes from TP1 and TP2, if I put them on a scope at the same time, should they have some relatable shape to one and other?  When I did my initial testing I saw that they were totally off from one and other but I'm starting to think that I had a bad clock/BBD chip in there.  Now that I am relatively confident they are both good I'll test again.

[aion]

They should look very similar to each other, though not at the same time if you were to take a snapshot (the phase is inverted from each other).

[Timko]

Ok, the inverted phase was what I was hoping to hear.  I'll do some more advanced scope testing once I go through all of my new ICs.

[gordo]

I'll dig out my notes and compare voltages.  I noted EVERYTHING before I boxed it.  I used my crappy little o'scope kit and found that I'd pretty much nailed it by ear.  I seemed to have a decent sized sweet spot right at about the middle of the trimmers.

My PC is also back together so I'll see if I can't record a few snippets.  Haven't tried it stereo yet.

[Timko]

More voltage measurements over the weekend: The ICs Kevin listed above pretty much match what I just measured.  I think if Gordo can post some sound samples I can confirm whether or not what I'm hearing is what I should expect. 

I also just orders a Rigol 1054Z Oscilloscope.  I spent quite a bit of the weekend reading through the topology of BBD and Clock design in circuits and plan to use those 4 channels to ensure all of that is working as designed.  I needed one anyway to do the Lola Phase setup (DeadEndFX's Mutron Biphase project) and this seemed like a good excuse to pull the trigger.

[gordo]

Excuse the lame playing but I wanted to keep it simple so you could hear the effect.  This is a Music Man Silhouette Special on the middle and neck pickups into the the Blueshift into a Scarlett 2i2 (1st gen) into Amplitube (the default American Tube Clean 1) dry.

https://www.gordomusic.com/Madbean/Blueshift.mp3

I paused between switch settings and they are as follows:
Dry
All switches down
Switch 1 up
Switch 2 up
Switch 3 up
Switch 1 and 2 up
Switch 2 and 3 up
Switch 1, 2, and 3 up

I realized now that I didn't get just 1 and 3 up but you get the point.  The differences are subtle, more so in a clean setting like this.

[gordo]

Here's 1&3 a little bit gainier.  I pulled down the top end a bit as the MM tends to be a bunch on the bright side.

https://www.gordomusic.com/Madbean/Blueshift2.mp3