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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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Posted: Tue Jan 21, 2014 11:19 am Post subject:
Weird Sound Generator - Wacky Osc & Filter Questions |
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Just been finishing up some waaaaay old projects, and dug out this WSG I started long ago (using Andrew Sharp's stripboard layout), with a view to actually finishing it. It never worked right at the time, but I know a bit more these days and have gone through the Troubleshooting section of the MFOS page, and fixed a couple of things, but got a couple of other questions remaining.
Firstly, for each voice, the Wacky Frequency acts like an audio oscillator, and disappears if I turn the knob up full. However, the Troubleshooting page says:
Quote: | 1. Look at on the scope or listen to point: U1-B pin 4. Adjust Wacky Frequency pot R1 until you see and/or hear it oscillating slowly (a few hertz per second). |
So does this mean the Wacky osc should be more like in the LFO ranges? Turning the pot all the way anti-clockwise only goes to something like 100hz, definitely not going to subsonic frequencies!
Secondly, the filter is really muffled. I’ve traced as much as I can but cannot find why. I’ve used a TL071 instead of an LM741, which I didn’t think would affect it. It seems like the pot isn't fully opening the cutoff frequency. The signal going into the filter is as expected.
With both problems, I’ve checked and double checked the wiring, panel wiring and schematics, but haven’t found anything wrong so far.
So yeah... any thoughts? _________________ Circuit Bent Sonic Absurdity:
www.bogus-noise.co.uk
http://www.youtube.com/user/BogusNoise |
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
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Posted: Tue Jan 21, 2014 2:11 pm Post subject:
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I thought Zany was the LFO, what with the 1uF cap rather than .022uF....
Unfortunately my WSG is in an enclosure that is a huge pain to open up, or I would take a frequency range measurement of just that oscillator. |
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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
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Posted: Tue Jan 21, 2014 3:11 pm Post subject:
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It just so happens that my battery is dead, so I will have to open up the thing anyway. I'll take measurements of all 6 oscillators and see what the min/max frequencies are. I'd swear mine went down to lower than 100Hz, but not subaudio. |
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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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Posted: Tue Jan 21, 2014 3:21 pm Post subject:
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Ok cool, thanks for that
100hz was a guess, but it's not in the area I was thinking from the Troubleshooting section, as that implies you have to turn it up to get it to cycle only a few times per second. But yeah, from the schematic the Wacky and Weird oscillators are pretty similar, just there's two 4.7k resistors either side of the pot on the Weird one and one 4.7k on the Wacky one. _________________ Circuit Bent Sonic Absurdity:
www.bogus-noise.co.uk
http://www.youtube.com/user/BogusNoise |
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
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Posted: Tue Jan 21, 2014 4:08 pm Post subject:
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Voice A Osc 1 goes 84 Hz through 8 KHz.
Osc 2, 58 Hz through 14KHz
Osc 3, 1.1 Hz through 264 Hz
Voice B Osc 1, 86 Hz throug 8 KHz
Osc 2, 56 Hz htrough 15 KHz
Osc 3, 1.2 Hz through 271 Hz |
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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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Posted: Wed Jan 22, 2014 3:14 pm Post subject:
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Ok, I'm getting the below results:
Osc 1 - pin 2 98hz - 11khz
Osc 2 - pin 4 100hz - past 15khz, then stops oscillating
Osc 3 - pin 6 <20hz - 350hz
Osc 4 - pin 12 102hz - 11khz
Osc 5 - pin 10 110hz - past 15khz, then stops oscillating
Osc 6 - pin 8 <20hz - 350hz
It probably makes me happier than it should that I guessed it being around 100hz
But yeah, similar results to yours, so I guess it's working right. Could do with 1, 2, 4 and 5 going a bit lower, though might be able to get there with a little tweaking. Also will put a couple of resistors in to limit the top range of 2 and 5.
Regarding the filter... I just found the problem there. The link connecting the two lugs of the Fine cutoff point wasn't soldered properly, so turning the knobs would still have an effect and made it seem like the filter was working but not properly, haha.
Thinking I'll do away with the Coarse tune and change the Fine tune for a 220k pot, and tweak the pot's range a bit to make it closer to an antilog.
Thanks for your help in confirming things! _________________ Circuit Bent Sonic Absurdity:
www.bogus-noise.co.uk
http://www.youtube.com/user/BogusNoise |
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
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Posted: Wed Jan 22, 2014 4:10 pm Post subject:
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Any time |
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Kosmo Mishka
Joined: Apr 18, 2013 Posts: 47 Location: Moscow
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Posted: Tue Mar 18, 2014 6:19 pm Post subject:
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Hi, I just build WSG. And have problem with filter coarse pot. It works, but somewhere at almost full clockwise, the value jumps very significantly. Until this it adjusts smoothly.
Can it be caused because pot bodies not grounded? (build it in cardbox for testing) |
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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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Posted: Wed Mar 19, 2014 1:22 am Post subject:
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The cardboard won't be at fault, many people have built theirs on cardboard, myself included! (I'll be mounting it in a case once I've tested out some mods, but that's by the by)
There is naturally a bit of a steep curve at the end of the pot range on this design, presumably that's why the Fine pot was included as well. I switched my Coarse pot to a 470k in the end, as I found there wasn't much change in the lower half of the Coarse range anyway. This definitely made it feel a bit more 'playable' for me. _________________ Circuit Bent Sonic Absurdity:
www.bogus-noise.co.uk
http://www.youtube.com/user/BogusNoise |
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Kosmo Mishka
Joined: Apr 18, 2013 Posts: 47 Location: Moscow
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Posted: Wed Mar 19, 2014 6:21 am Post subject:
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Bogus Noise wrote: | The cardboard won't be at fault, many people have built theirs on cardboard, myself included! (I'll be mounting it in a case once I've tested out some mods, but that's by the by)
There is naturally a bit of a steep curve at the end of the pot range on this design, presumably that's why the Fine pot was included as well. I switched my Coarse pot to a 470k in the end, as I found there wasn't much change in the lower half of the Coarse range anyway. This definitely made it feel a bit more 'playable' for me. |
Just to make clear what I mean, recorded audio. Tweaking only Coarse pot, I am almost not rotating it, and it make a very big jump, and until 0 to 1/2 of pot value, it not make significant changes. https://soundcloud.com/bmlaster/wsgfilter . |
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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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Posted: Wed Mar 19, 2014 7:09 am Post subject:
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Kosmo Mishka wrote: | Bogus Noise wrote: | The cardboard won't be at fault, many people have built theirs on cardboard, myself included! (I'll be mounting it in a case once I've tested out some mods, but that's by the by)
There is naturally a bit of a steep curve at the end of the pot range on this design, presumably that's why the Fine pot was included as well. I switched my Coarse pot to a 470k in the end, as I found there wasn't much change in the lower half of the Coarse range anyway. This definitely made it feel a bit more 'playable' for me. |
Just to make clear what I mean, recorded audio. Tweaking only Coarse pot, I am almost not rotating it, and it make a very big jump, and until 0 to 1/2 of pot value, it not make significant changes. https://soundcloud.com/bmlaster/wsgfilter . |
Yes, that's what I experienced. As I say... I found there wasn't much change in the lower half of the Coarse range. A 470k pot is half a 1M pot, so in this instance you get the 1/2 to 1 range only. _________________ Circuit Bent Sonic Absurdity:
www.bogus-noise.co.uk
http://www.youtube.com/user/BogusNoise |
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Kosmo Mishka
Joined: Apr 18, 2013 Posts: 47 Location: Moscow
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Posted: Wed Mar 19, 2014 7:11 am Post subject:
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Thank you,but Ray just e-mailed that it is not normal, it should be smooth. So I am little bit messed, I will check everything double at evening, if that won`t help, I will try 470K. |
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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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Posted: Wed Mar 19, 2014 7:17 am Post subject:
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Ah ok, I figured it was normal as there was a few other threads around where people had a similar result, and through experimenting that was the way that worked it out for me. Be interesting to know if there's another way around it! _________________ Circuit Bent Sonic Absurdity:
www.bogus-noise.co.uk
http://www.youtube.com/user/BogusNoise |
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Kosmo Mishka
Joined: Apr 18, 2013 Posts: 47 Location: Moscow
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Posted: Thu Mar 20, 2014 4:33 am Post subject:
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Bogus Noise wrote: | Ah ok, I figured it was normal as there was a few other threads around where people had a similar result, and through experimenting that was the way that worked it out for me. Be interesting to know if there's another way around it! |
Checked wiring, pcb, and did not find anything wrong. Also I tried your solution, and placed 500K instead of 1M. It is smoother, but still there is a big difference when knob full CW. I am finding it is pretty weird, as I dig like all electro-forums WSG topics, and many peoples have problem with it, and there is no answer to it. Also on youtube, there are a lot of units with similar filter problems. Could it be that there are different versions of WSG?
Also from demos I think mine resonance not giving much feedback.
I used TL071, what did you use? |
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Bogus Noise
Joined: Jun 03, 2009 Posts: 65 Location: Sheffield
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Kosmo Mishka
Joined: Apr 18, 2013 Posts: 47 Location: Moscow
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Posted: Thu Mar 20, 2014 11:08 am Post subject:
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Maybe tl071 and LM741 sound differently? I ordered like 3 different LM741, and one LF411. I will test them all when recieve (next week). |
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Kosmo Mishka
Joined: Apr 18, 2013 Posts: 47 Location: Moscow
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Posted: Mon Mar 24, 2014 7:42 am Post subject:
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Tried LM741 and no success( Still very touchy on full CW, and no bottom. It is usable only on max coarse, fine and res. Any ideas where to dig? Wiring and pcb checked. |
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