Joined: Aug 09, 2009 Posts: 2 Location: Los Angeles
Audio files: 1
Posted: Sun Aug 09, 2009 5:38 pm Post subject:
Triple Chorus problem Subject description: Clicking LFOs at output
I've built a triple chorus, but I'm having a problem with it. Delay lines 1 and 3 exhibit a loud cyclical 'clicking' sound. Delay Line 2 exhibits light clicking only at certain setting of the waveform knob. The clicking sound is in sync with the LFO and is more noticeable with higher pitches from an oscillator. It's as if delay lines 1 and 3 are being modulated by Square waves. The clicking is there even with no input. I've checked the values and polarities of the caps and have not found a problem yet. I've attached a recording showing Output 1 (with the clicks), Output 2 (normal), Ouput 3 (with clicks), and Mixed Output where I play with the Waveform pot. Please let me know if you have any ideas. I would GREATLY appreciate the help. Thanks.
triple chorus test.mp3
Description:
I've attached a recording showing Output 1 (with the clicks), Output 2 (normal), Ouput 3 (with clicks), and Mixed Output where I play with the Waveform pot.
Have you checked the Waveforms on the Mod1, Mod2 and Mod3 test points?
Scope shots would be great ...
JH. _________________ "I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
Joined: Jan 31, 2012 Posts: 6 Location: Finland. It's grim up north.
Audio files: 1
Posted: Tue Jan 31, 2012 5:44 pm Post subject:
Re: Triple Chorus problem Subject description: Clicking LFOs at output
Ross wrote:
I've built a triple chorus, but I'm having a problem with it. Delay lines 1 and 3 exhibit a loud cyclical 'clicking' sound. Delay Line 2 exhibits light clicking only at certain setting of the waveform knob. The clicking sound is in sync with the LFO and is more noticeable with higher pitches from an oscillator. It's as if delay lines 1 and 3 are being modulated by Square waves. The clicking is there even with no input. I've checked the values and polarities of the caps and have not found a problem yet. I've attached a recording showing Output 1 (with the clicks), Output 2 (normal), Ouput 3 (with clicks), and Mixed Output where I play with the Waveform pot. Please let me know if you have any ideas. I would GREATLY appreciate the help. Thanks.
Any idea how to sort this out? We have pretty much same problem here.
Joined: Apr 19, 2010 Posts: 346 Location: San Francisco, CA
Audio files: 13
Posted: Sun Jun 24, 2012 11:01 pm Post subject:
pascal25 wrote:
Anyway, unit sounds great, it does that Solina sound, but...
Waveform pot doesn't work at all.
Hmm, so you hear Solina-like chorus but the waveform pot doesn't do anything? That seems surprising. If you check the voltage on the wiper of the waveform pot, you should see the voltage move as you turn the pot, from well below 0v to well above it. If you used IC sockets you could try swapping U9 (MC1458) to see if that has an effect.
Just to be sure, you know that the waveform pot has the effect of varying the amount of modulation? At least in my experience while it is really clear if you compare the sound of CCW (mild or no modulation)and CCW (max chorus), the actual change you hear while turning the pot is pretty gradual.
Another useful thing I did was to compare the 3 individual outputs. Together they make a chorus sound but individually they should effectively sound the same (just phase shifted from one another). So if compare them and one sounds noticeably different than the others it signals a problem (in my case I had one dead TDA1022).
pascal25 wrote:
Fast & Slow trimmers doesn't seem to have any effect either.
Especially in this case, make sure you know what you are listening for. These ones are very very subtle -- if your chorus is working you should hear two frequencies of modulation, one faster and one slower. Once you can focus your attention on them separately, you might hear each one shift as you turn the corresponding trimmer, but again, you really have to be listening carefully.
pascal25 wrote:
Linear & Solina modes are working ok, EQ-mode has no effect.
Offhand the most likely culprit is the wiring. Jürgen's documentation shows this being handled by 2 switches but the Bridechamber / Dragonfly Alley builds use a single rotary switch. Either way you might check continuity between various combinations of the 4 pins on the Mode header that are used. As you change the switch settings you'll expect pins 2+3, then 2+4, and finally 2+5 to connect. (Or is that 1+4, 2+4, 3+4 -- I can never remember which way is up on these.)
I am not particularly wise about a lot of these things, but I did go over this thing for days myself, so hope this is helpful. _________________ -Jim
Joined: Jan 31, 2012 Posts: 6 Location: Finland. It's grim up north.
Audio files: 1
Posted: Tue Jun 26, 2012 8:32 am Post subject:
jumunius wrote:
pascal25 wrote:
Anyway, unit sounds great, it does that Solina sound, but...
Waveform pot doesn't work at all.
Hmm, so you hear Solina-like chorus but the waveform pot doesn't do anything? That seems surprising. If you check the voltage on the wiper of the waveform pot, you should see the voltage move as you turn the pot, from well below 0v to well above it. If you used IC sockets you could try swapping U9 (MC1458) to see if that has an effect.
Just to be sure, you know that the waveform pot has the effect of varying the amount of modulation? At least in my experience while it is really clear if you compare the sound of CCW (mild or no modulation)and CCW (max chorus), the actual change you hear while turning the pot is pretty gradual.
Another useful thing I did was to compare the 3 individual outputs. Together they make a chorus sound but individually they should effectively sound the same (just phase shifted from one another). So if compare them and one sounds noticeably different than the others it signals a problem (in my case I had one dead TDA1022).
pascal25 wrote:
Fast & Slow trimmers doesn't seem to have any effect either.
Especially in this case, make sure you know what you are listening for. These ones are very very subtle -- if your chorus is working you should hear two frequencies of modulation, one faster and one slower. Once you can focus your attention on them separately, you might hear each one shift as you turn the corresponding trimmer, but again, you really have to be listening carefully.
pascal25 wrote:
Linear & Solina modes are working ok, EQ-mode has no effect.
Offhand the most likely culprit is the wiring. Jürgen's documentation shows this being handled by 2 switches but the Bridechamber / Dragonfly Alley builds use a single rotary switch. Either way you might check continuity between various combinations of the 4 pins on the Mode header that are used. As you change the switch settings you'll expect pins 2+3, then 2+4, and finally 2+5 to connect. (Or is that 1+4, 2+4, 3+4 -- I can never remember which way is up on these.)
I am not particularly wise about a lot of these things, but I did go over this thing for days myself, so hope this is helpful.
I've been tweaking synths for 20 years and I guess I know what listen to.
Done so far:
I checked voltages on the wiper, and it seems to be ok. From 0 to -9,7v. Replaced U9 and had no different results. Readings from pin 4: -15,04v, and pin 1: between 0v and -9,7v when twiddling the pot.
I've been tweaking synths for 20 years and I guess I know what listen to.
Excellent, just checking. I sometimes come up with my own ideas about what features should do, and it messes with me when I'm testing things.
Quote:
I checked voltages on the wiper, and it seems to be ok. From 0 to -9,7v. Replaced U9 and had no different results. Readings from pin 4: -15,04v, and pin 1: between 0v and -9,7v when twiddling the pot.
Those sound like what I remember getting (and stupidly in my previous post I forgot that the Triple Chorus only uses the negative rail -- you wisely ignored where I said the voltage should swing above zero when the pot goes in one direction!). So the pot and IC works through to the output (pin 1), but somehow nothing gets through to affect the modulators. So the problem would seem to me, in my limited understanding, to happen between U9 pin 1 and D89-91 (where the voltage gets applied to all three modulators). You might check the components between those two places, and you also might check the orientation of D89-91. _________________ -Jim
Joined: Apr 19, 2010 Posts: 346 Location: San Francisco, CA
Audio files: 13
Posted: Mon Jul 02, 2012 2:54 pm Post subject:
pascal25 wrote:
It's working now!
Wrong resistors. Found four 470k, and they should be 470. Replaced them. Very sweet sounding baby this one.
Haha. I almost called that out with regards to R336 since I remember having to look twice at it myself. Anyways, congrats, glad to hear you found it! _________________ -Jim
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