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AlasdairMoons
Joined: Dec 03, 2011 Posts: 105 Location: East-Belgium
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AlasdairMoons
Joined: Dec 03, 2011 Posts: 105 Location: East-Belgium
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
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Posted: Mon Aug 04, 2014 12:03 pm Post subject:
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Are you measuring the resistors while they are soldered into the circuit? This can affect what resistance reading you get checking them. For example if my circuit somehow had two 10k resistors going from a common point to ground, measuring one would show me 5K instead because they would be parallel to each other.
You generally can only be sure you're measuring just the resistor in question if you lift one of the legs out of the circuit.
If you meant you measured those in the batch you selected from, without being in a circuit, disregard all that |
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AlasdairMoons
Joined: Dec 03, 2011 Posts: 105 Location: East-Belgium
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AlasdairMoons
Joined: Dec 03, 2011 Posts: 105 Location: East-Belgium
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
Audio files: 16
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Posted: Tue Aug 05, 2014 6:11 pm Post subject:
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Awesome
Good to hear.... |
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MoonBase 69
Joined: Sep 16, 2014 Posts: 19 Location: Outpost 7, Florida
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Posted: Sun Jul 26, 2015 6:17 pm Post subject:
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Amazing what you can find if you dig a little...
Was my first synth piece and it wouldn't go correctly. A bit disheartening for your first piece, the heart of the synth to come up bust. Mine wouldn't oscillate below ~500Hz just make noise. Ended up setting it aside rethinking my approach and moved on to some other projects. Was going to email my old friend Scott but he seems to have fallen off the radar then ran across this now that I have some time between projects.
Turns out I was also fighting the bunk F0919 XR2206. Between 5 of them the low end would cut off between 300 and 500HZ from there down just noise. Varying the + power supply would correct the problem I had to go all the way down to 10V on some of them. What clued me in was it would run down with a nice tone when I cut the power.
Saved by the forum,
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macumbista
Joined: Sep 12, 2007 Posts: 398 Location: berlin
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Posted: Sat Jun 25, 2016 5:25 am Post subject:
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If this is the "problems" thread, then I've got one of my own. I've seen someone else posting about this someplace here but I can't seem to find it.
Since I [finally!] started using an oscilloscope to tune the waveforms of the XR-VCOs I build, I notice that there is often a small error at the peak of the ascending half of the sine wave. A small notch in the waveform exactly at the point where the skew starts to fold it over. Sometimes it's a big bigger, more noticeable and definitely more audible!
I imagine this could have to do with slightly mismatched (although still 1%) resistors in the skew section, but I'm still at a lack as to which ones. Does anyone have experience with this or suggestions? _________________ Esoteric drones and nonlinear distortion
Custom/handmade experimental instruments
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macumbista
Joined: Sep 12, 2007 Posts: 398 Location: berlin
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Posted: Sat Jun 25, 2016 5:43 am Post subject:
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Actually, even the screenshots on the Birth of a Synth project page have this glitch. Does that mean it falls in the realm of "acceptable" noise?
_________________ Esoteric drones and nonlinear distortion
Custom/handmade experimental instruments
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LFLab
Joined: Dec 17, 2009 Posts: 497 Location: Rosmalen, Netherlands
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Posted: Sat Jun 25, 2016 7:12 am Post subject:
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Because of the way these sines are made, there will always be a little niggle at the tops and bottoms of the sine. So rather than using a scope, can you tune it by ear so it has the least amount of harmonic content? Or does it still not sound like a pure sine? |
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AlasdairMoons
Joined: Dec 03, 2011 Posts: 105 Location: East-Belgium
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macumbista
Joined: Sep 12, 2007 Posts: 398 Location: berlin
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Posted: Sat Jun 25, 2016 7:24 am Post subject:
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Yes I've been tuning them also by ear, however the trimmers only affect the offset, roundness and symmetry. The little glitch remains regardless, making me think it could be trimmed elsewhere if I could just figure out where. _________________ Esoteric drones and nonlinear distortion
Custom/handmade experimental instruments
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elmegil
Joined: Mar 20, 2012 Posts: 2177 Location: Chicago
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Posted: Sat Jun 25, 2016 7:49 am Post subject:
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I'd swear that not only does the screen shot show the little glitch, but Thomas' text on that page talks about it briefly too, as in --yes, this is normal, and when you minimize it inaudible. |
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macumbista
Joined: Sep 12, 2007 Posts: 398 Location: berlin
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Posted: Sat Jun 25, 2016 7:59 am Post subject:
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That's all there is about tuning the waveshape (below). I also seem to recall this, maybe it was on an earlier version of the site (on the other server?). I'll keep futzing around with the trimmers and see if I can get all 7 of the XRs I just finished to similar levels of non-distortion...
Quote: | Next, calibrate the Sine Shape. Set the sine/triangle output switch to 'sine'. Calibrate the sine shape by alternating between the Sine Symmetry Trim (R22 25K single turn trimpot) and the Sine Round trim (R3 500R single turn trimpot). You can do this by observing the waveform on an oscilloscope, or you can use your ears. You will be surprised at how accurately your ears can tune a sinewave - just adjust the pots until you detect as much of an absence of harmonics as possible. |
_________________ Esoteric drones and nonlinear distortion
Custom/handmade experimental instruments
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