Stage Fright high pitch noise - SOLVED

[MAO]

I have a high pitched noise that I can't pin down. The noise enters at the junction of R3 and R5. Quiet between R3 and C2.

Seems to be everywhere along the audio path after R3, it's the exact noise when audio probing 9V or VB line.  IC1 pin 1 is quiet, all other IC pins with audio signal have the noise.

The trimmer changes the pitch of the noise. And the noise phase shifts. The noise is there with the TL062 and LM13700s pulled. The transistors are not socket-ed, not sure what I was thinking there.

Seems like it should be an easy one to fix, but I'm not sure what to check or try next.

Here are the IC voltages.

TL074
1 4.67
2 4.67
3 4.25
4 9.30
5 4.65
6 4.67
7 4.67
8 7.72
9 4.67
10 4.58
11 0
12 4.65
13 4.67
14 4.67

TL062
1 varies
2 varies
3 varies
4 .05
5 4.67
6 4.67
7 varies
8 9.30

All 3 LM13700
1 1.24
2 0.05
3 4.67
4 4.67
5 5.8
6 0
7 5.8
8 4.67
9 4.67
10 5.8
11 9.3
12 5.8
13 4.67
14 4.67
15 0.05
16 1.25

[jimilee]

Have you checked all your values to make sure they are correct? What are you using to power it?


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[MAO]

Powered with 9v adapter (tried 2 different supplies)

Sorry, was tired last night trying to work out a Harbinger One issue too, forgot some basic troubleshooting.  There is no noise with a battery. 

I'll swap out and or add some filter caps and see what happens.

I have already used a 100uf for C19, rather than 47u

All other components stock and values verified

On another note, with battery powered sounds fairly nice if I bias in a little resonance, but there is a huge tone change with the 5/6 switch. The bass pretty much disappears as if there is a wah filter. Kinda sounds like the tonal change at the very end of Pink Floyd's Have a cigar.

[madbean]

Yeah something is up there. You would naturally have a small tonal change since there is an extra phase stage but it should not be drastic. Please review your parts R31-R35 and C9 to make sure they are correct.

[jimilee]

I was asking about the power supply, phasers seem to pickup when there is too much voltage coming in when every other pedal acts fine. This same think happened to me, I measured the supply itself and found it was pushing 10v


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[MAO]

2 issues for sure, supply noise and now sounds more like a wah filter than a phaser.

1. Noise. I increased C18 to 470uf, C19 to 220u and swapped in a 100n for D1 no change.

There is a hum with my 9.4v adapter and a high pitched whistle with my better regulated 9.3V adapter. No noise when battery powered. The 9.3V adapter has not caused noise in any other to date. The whistle is timed with the LFO speed. It's still there and constant with all the ICs and Transistors removed.

I'll add a daughter-board and try a small value resistor and 9.1 zener between the adapter and 9V board input. See what that does.

2. Wah sound - I cut out the transistors and socketed them. Replaced them with new ones and now it seems like I can't bias out a high resonant wah-type swirl.  Switching from 5 to 6 stages isn't as drastic a change anymore, but both settings now seem more like a filter effect. Sounds kinda cool, but not like a phaser. Reminds me of the Naughty Fish, but in a phaser swirl. 

I had built a Craig Anderton Phase Shifter way back when, and it had a switchable filter mode. Don't recall how that was accomplished, but it sounded similar to what I have now with the Stage Fright, actually this one sounds better, more pronounced.

Could a partly damaged and/or partly not working LM13700 cause a filter effect?

Going to recheck all voltages and will post better lit pictures when I get back to it.   

     

[MAO]

Noise solved, thank you! Added the following daughter board between the 9V adapter and PCB.



Sound clip without daughterboard (make sure your dogs and cats aren't listening)

[cloudset]https://soundcloud.com/maopedals/stage-fright-powwer-supply-noise[/cloudset]

Sound clip with added daughterboard.

Intensity on full, Speed set slower. Sounds to me more like a filter than a phaser.

Starts clean signal, then at 0:13 sec 5 stages, then at 0:31 secs 6 stages, then 1:03 clean again.     

[soundcloud]https://soundcloud.com/maopedals/stage-fright[/soundcloud]


Will post voltages again since I have tamed the 9V and swapped out the transistors.

[MAO]

I believe she is working! Dialed back on the intensity a bit and it sounds pretty good.

Let me know if this sounds right to you...the effect of course, not my playing! :0)

Sound Clips - 1st 5 stages, then 6 stages.

Chords 
[soundcloud]https://soundcloud.com/maopedals/stage-5-6[/soundcloud]


Picking
[soundcloud]https://soundcloud.com/maopedals/rr-1[/soundcloud]


Speed maxed
[soundcloud]https://soundcloud.com/maopedals/fast[/soundcloud]


Here are my updated voltages in case someone else wants a reference:

TL074
1 4.32
2 4.32
3 3.92
4 8.6
5 4.30
6 4.32
7 4.32
8 4.32
9 4.38-4.40
10 4.24
11 0
12 4.30
13 4.32
14 4.32

TL062
1 varies 0-8
2 varies 4.26-4.29
3 varies 3.15-5.3
4 0
5 4.32
6 4.32
7 varies 3.5-5.0
8 8.60

All 3 LM13700
1 1.1-1.18
2 0.01
3 4.32
4 4.32
5 5.29-5.40
6 0
7 5.29-5.4
8 4.32
9 4.32
10 5.3-5.4
11 8.6
12 5.8
13 4.67
14 4.67
15 0.01
16 1.11-1.18

Q1
8.6
0
3.7-3.75

Q2
0
0.45
3.7-3.75

Q3
1.1-1.2
3.7-3.75
8.6

[alanp]

Boy, just as well it was a Stage Fright and not one of the early Low Profile Doppelgangers! Good to hear you got it licked.