I just built a crying time lfo wah and I'm having one small issue. I am getting a ticking sound in about the last quarter of the depth control. I used a 100uf cap for the lfo filter cap instead of the 47uf listed in Jon's layout, so I don't think that's the cause.
The only thing I can think is that the transistor or that the external rate led and/or the vactrol led are causing the problem. But that's just a wild uneducated guess. Anyone know what it could be and how to fix it?
Thanks in advance.
You can file this in the might be related category. I've been finishing up a design for a microcontroller based tremolo that uses a vactrol. Because I set the level of the output voltage to the vactrol with the microcontroller, I've got really tight control on the values. What I've noticed is that if I get the current at just the point where the LED(s) don't ever turn completely off, then I can eliminate all clicks/ticking. Using the depth control when the LED's do turn off, I can mask most of the tick, but then I can't get the complete drop to zero volume that I want. Also, I put a trim pot on the path to ground for the vactrol's LED and this lets me control the current level as well. Getting it set just before the shutoff point for the LED seems to be the key to getting full range and no tick/pop/click.
Maybe you could try socketing the current control resistor to the LEDs and try moving its value up in small increments and see if you can eliminate the tick that way.
Quote from: Dc10 on June 02, 2013, 12:38:56 AM
I just built a crying time lfo wah and I'm having one small issue. I am getting a ticking sound in about the last quarter of the depth control. I used a 100uf cap for the lfo filter cap instead of the 47uf listed in Jon's layout, so I don't think that's the cause.
The only thing I can think is that the transistor or that the external rate led and/or the vactrol led are causing the problem. But that's just a wild uneducated guess. Anyone know what it could be and how to fix it?
Thanks in advance.
Describe the ticking in more detail. Is it a thump, woosh, CLICK, etc.? The reason I ask is because people often use the term 'ticking' (which is an actual LFO issue) when it's really just line noise being affected by the LFO at idle.
In any case, if it really IS a clicking noise, I'll try to think of some things that can be done -- you can also check the original Light Wah thread non DIYSB -- I know early on some people had LFO ticking, but this LFO is usually pretty well behaved.
You could try flipping the transistor, too.
I messed with it a bit more today and here is what I found. I set the rate to the slowest setting and determined that the "tick" is happening at the high side of the sweep when the led is the brightest. It is also present in stuck wah mode when the led doesn't light up so I'm guessing that isn't it.
The "tick" is also present when the effect is bypassed. I found that out by putting a distortion pedal after it. I couldn't here it until then.
Quote from: midwayfair on June 02, 2013, 10:41:57 AM
Quote from: Dc10 on June 02, 2013, 12:38:56 AM
I just built a crying time lfo wah and I'm having one small issue. I am getting a ticking sound in about the last quarter of the depth control. I used a 100uf cap for the lfo filter cap instead of the 47uf listed in Jon's layout, so I don't think that's the cause.
The only thing I can think is that the transistor or that the external rate led and/or the vactrol led are causing the problem. But that's just a wild uneducated guess. Anyone know what it could be and how to fix it?
Thanks in advance.
Describe the ticking in more detail. Is it a thump, woosh, CLICK, etc.? The reason I ask is because people often use the term 'ticking' (which is an actual LFO issue) when it's really just line noise being affected by the LFO at idle.
In any case, if it really IS a clicking noise, I'll try to think of some things that can be done -- you can also check the original Light Wah thread non DIYSB -- I know early on some people had LFO ticking, but this LFO is usually pretty well behaved.
You could try flipping the transistor, too.
The best way I can describe the noise is a click or tick, definitely not a thump or whoosh. Do you think it's the transistor switching?
Could a cap from the transistor base to gnd help or would that mess with the way the lfo operates?
The transistor softens the triangle wave. It's probably not causing the issue.
I wish I had a way to help. Unfortunately it sounds like the LFO bleeding into ground. You might try a different power supply (I had not trouble with a one spot), or ask advice over on the DIYSB thread.
Cool ill check it out thanks
Ok, so tried flipping the transistor. That didn't work. Tried some of Mark Hammers ideas I found online, a LM358 in place of the jrc4558 and tried a higher value CLR between the supply and the power pin of the LFO IC. Those didn't work either.
Then I remembered some thing I read in another thread about someone with a similar issue being told to use a pedal with a buffer in front of the problem pedal. No ticking!
Quote from: Dc10 on June 05, 2013, 11:31:04 AM
Ok, so tried flipping the transistor. That didn't work. Tried some of Mark Hammers ideas I found online, a LM358 in place of the jrc4558 and tried a higher value CLR between the supply and the power pin of the LFO IC. Those didn't work either.
Then I remembered some thing I read in another thread about someone with a similar issue being told to use a pedal with a buffer in front of the problem pedal. No ticking!
I made an EHX Pulsar couple years ago and no matter what I did I couldn't make the ticking go away. The only way to make it silent was to put a highly buffered pedal in front of it. For example, two millenium bypass pedals in front of it made the ticking disappear. But my Ibanez HD1000 rack processor in front of it made it completely noiseless. The more the buffering I guess, the less ticking there is. I'd like to hear an explanation of this if someone cares to chime in...thanks.
Quote from: Cortexturizer on June 05, 2013, 03:30:47 PMI'd like to hear an explanation of this if someone cares to chime in...thanks.
Me too.
Yet another reason I'm thinking of switching to buffered bypass ...
DC10: You might be able to make a source-follower input buffer fit in the 1590A with this. You only need a couple components: the FET, a 10K source to ground, a 470nF input cap, and a 2.2M gate to ground.
Quote from: Cortexturizer on June 05, 2013, 03:30:47 PM
Quote from: Dc10 on June 05, 2013, 11:31:04 AM
Ok, so tried flipping the transistor. That didn't work. Tried some of Mark Hammers ideas I found online, a LM358 in place of the jrc4558 and tried a higher value CLR between the supply and the power pin of the LFO IC. Those didn't work either.
Then I remembered some thing I read in another thread about someone with a similar issue being told to use a pedal with a buffer in front of the problem pedal. No ticking!
I made an EHX Pulsar couple years ago and no matter what I did I couldn't make the ticking go away. The only way to make it silent was to put a highly buffered pedal in front of it. For example, two millenium bypass pedals in front of it made the ticking disappear. But my Ibanez HD1000 rack processor in front of it made it completely noiseless. The more the buffering I guess, the less ticking there is. I'd like to hear an explanation of this if someone cares to chime in...thanks.
Quote from: midwayfair on June 05, 2013, 04:19:45 PM
Quote from: Cortexturizer on June 05, 2013, 03:30:47 PMI'd like to hear an explanation of this if someone cares to chime in...thanks.
Me too.
Yet another reason I'm thinking of switching to buffered bypass ...
DC10: You might be able to make a source-follower input buffer fit in the 1590A with this. You only need a couple components: the FET, a 10K source to ground, a 470nF input cap, and a 2.2M gate to ground.
Me 3! I'd love to understand the reasoning behind this.
Luckily I will have plenty of room for a buffer. I built this in a 4s125.
Anyway, when I get back into town, I'll try that buffer out. It'll be a good opportunity to revisit the amz page on buffers as well. I'll breadboard a few, until I find the one I like best. I wish I didn't have to use a buffer, this peal sounds so much better without it. It really reminds me of a Hendrix / Trower wah tone. (but an lfo wah version of course)
http://i.imgur.com/ySe8i.gif
Here's what people suggested to me when I was trying to work out the ticking issue with the Pulsar. Just insert this buffer they said...well it did not work for although some of them were positive that this is THE solution.
Not for me.
It could be that the tick comes from the movement in the power supply caused by the power draw of the LFO through the LED's. The buffer would mean that you would have a higher impedance input and the output of the buffer would be better able to feed the input of the effect even though the power supply to the op amp is moving/pulsing. I'd think that this would tend to be a bigger issue in effects with BJT or inverting op amp input stages.
If that's the cause of the problem, trying different op amps for the audio op amp might help some. I've noticed that some are more susceptible to ticking/thunking than others. Also, putting a 100nF ceramic cap from the Vcc of the op amp to ground can help. The cap should be as close to pin 8 as you can get it in the layout.
It would be interesting to get some measure of the current fluctuation on the power supply into the pedal and see if the tick corresponds to when the current draw hits one of the turn around points.
So, I put this circuit on the breadboard last night. First let me say that it sounds great and is fun to play with.
I've been trying everything I can think of to make it tick or thunk or anything and it just won't do it. I've used a bunch of different op amps in both positions, different LED's, multiple different vactrols and LDR's, different transistors, etc. I've tried putting in the junkiest caps I've got. But, nothing will make it tick. I'm running straight from the guitar into the wah and using a complete garbage cable to get the worst connection reasonable into the input and this still doesn't cause ticking.
So, I was wondering what op amps, LED's, LDR, and transistor you were using. I'd really like to get this to tick so that I can try to understand what is happening.
I'll just say that you are a real ace Rob for doing this, kudos to you man!
Thanks. It's become an interesting puzzle so it's actually kinda fun to try and figure out. Besides that, I'm working on a couple of fairly closely related circuits that do some nutty LFO type things and it will help me to characterize this problem.
I'm kinda stuck for now until I can figure out something else to look at. I've got it sitting on a breadboard though so I can stare at it and see if any enlightenment happens :D. I have noticed that the circuit is sensitive to power supply voltage. I've got one unregulated supply that puts out about 10 to 11 volts instead of 9 and when I use it the wah sweep is reduced a bunch. So, maybe a power supply that is under voltage would contribute to the tick. I'll rig up a sag type circuit to power it with when I get back to it and see what happens.
I'll report back if I figure anything out.
I still haven't been able to get this to tick. I'm building a new variable power supply in the next couple of days though. That should give me a better opportunity to test the voltage theory.
Anyone have info on what op amps were used in designs like this one that do exhibit ticks and thunks?
Quote from: RobA on June 11, 2013, 05:32:07 PM
I still haven't been able to get this to tick. I'm building a new variable power supply in the next couple of days though. That should give me a better opportunity to test the voltage theory.
Anyone have info on what op amps were used in designs like this one that do exhibit ticks and thunks?
Thanks for your time and help. I haven't looked at this thread since your post on the 6th.
Just got back in town or else I would have replied sooner.
Here's a list of what I used. Ne5532 for the audio opamp, a lm358 for the lfo section, vtl5c1 for the vactrol, 2n3904 transistor. High brightness red led for rate indicator.
I did notice that the filter cap for the lfo on my layout is an inch away from the opamp. Maybe that's the problem?
I still had the circuit on my breadboard. I'm keeping it until I have my new power supply finished so I can test it with a continuous voltage range to see if there is a point that'll cause the ticking. So, I put your parts list in there -- no ticking.
I don't have any super-bright red LED's though. I tried with a bright water clear red. This didn't get any ticking.
I'd think the LM358 was a perfect choice for the LFO op amp. The 5532 sounds good, but there is one thing about it that could be related. I've noticed that it draws a pretty large amount of current. This is especially true if an unused op amp isn't terminated. I'd check to make sure that the second side is terminated correctly. Although, I did try on my test board to leave it unterminated and I didn't get ticking.
I doubt if it is the filter cap. I tried moving mine all the way down my breadboard and got no difference. I even tried just taking it out and I got no ticking.
There are two things I've changed that do seem to bring it closer to ticking (closer in that the sweep does seem to bottom out harder); Moving the LED to a brighter variety and moving the cap that goes from pin 3 to ground on the audio op amp to a smaller value.
Two things that might help me get closer to your setup is if you could give me the forward voltage drop of your LED and the voltage at the power input to the board.
Quote from: RobA on June 13, 2013, 03:02:56 PM
I still had the circuit on my breadboard. I'm keeping it until I have my new power supply finished so I can test it with a continuous voltage range to see if there is a point that'll cause the ticking. So, I put your parts list in there -- no ticking.
I don't have any super-bright red LED's though. I tried with a bright water clear red. This didn't get any ticking.
I'd think the LM358 was a perfect choice for the LFO op amp. The 5532 sounds good, but there is one thing about it that could be related. I've noticed that it draws a pretty large amount of current. This is especially true if an unused op amp isn't terminated. I'd check to make sure that the second side is terminated correctly. Although, I did try on my test board to leave it unterminated and I didn't get ticking.
I doubt if it is the filter cap. I tried moving mine all the way down my breadboard and got no difference. I even tried just taking it out and I got no ticking.
There are two things I've changed that do seem to bring it closer to ticking (closer in that the sweep does seem to bottom out harder); Moving the LED to a brighter variety and moving the cap that goes from pin 3 to ground on the audio op amp to a smaller value.
Two things that might help me get closer to your setup is if you could give me the forward voltage drop of your LED and the voltage at the power input to the board.
Dumb noob question, how do I find the forward voltage drop?
Use your multimeter's diode setting. It's also the continuity tester.
Quote from: midwayfair on June 13, 2013, 05:30:40 PM
Use your multimeter's diode setting. It's also the continuity tester.
I knew it was a dumb noob question. I wasn't thinking. led = diode.
Anyway, I measured the led in the circuit, 1.9v. I have a few LEDs laying around and they measured 1.57 - 1.6v. I measured the voltage at the DC jack at 9.62v. After the 100ohm CLR, it read 9.18v.
Quote from: RobA on June 13, 2013, 03:02:56 PM
I'd think the LM358 was a perfect choice for the LFO op amp. The 5532 sounds good, but there is one thing about it that could be related. I've noticed that it draws a pretty large amount of current. This is especially true if an unused op amp isn't terminated. I'd check to make sure that the second side is terminated correctly. Although, I did try on my test board to leave it unterminated and I didn't get ticking.
I doubt if it is the filter cap. I tried moving mine all the way down my breadboard and got no difference. I even tried just taking it out and I got no ticking.
There are two things I've changed that do seem to bring it closer to ticking (closer in that the sweep does seem to bottom out harder); Moving the LED to a brighter variety and moving the cap that goes from pin 3 to ground on the audio op amp to a smaller value.
Two things that might help me get closer to your setup is if you could give me the forward voltage drop of your LED and the voltage at the power input to the board.
Yeah I went with the lm358 after some reading about lfo ticking. Didn't help but it worked so I left it. I tried a 4558 in place of the ne5532 just to see but it made no difference. I checked the cap you refered to, I have a 1uf tantalum there.
Again, I appreciate both of you helping me with this. It's a very cool pedal and can't wait to get it working right!
Thanks for those numbers. My multimeter actually can't read LED forward voltages for LED's that are higher than about 1.6V. So, I usually just hook them up with a series resistor and measure the voltage across the two leads of the LED.
The tantalum cap is a difference from my circuit. I've got an electrolytic in there. It's not likely to be the cause, but I'll find a tantalum cap to try.
The LED I have in the circuit now is around 1.6V. I'll see if I can find an LED that matches fairly closely to yours.
Your circuit looks to be drawing more current in the LFO than mine, not a lot more but about double. I wonder if that could be part of the problem and I wonder why. So we can get a better idea of where they are at, can you measure the voltage directly across the resistor? Turn the LFO rate to max for the measurement.
I'll let you know what I see when I put the tantalum and different LED in.
The resistor measures .46v.
Quick question on the led, will it give me a false reading since its connected to the circuit?
I think it will be fine. It doesn't have anything in parallel and you are measuring directly across LED.
The voltage across the resistor in mine is 2.8V. So, that could be pointing to something. I'll measure it again when I get a better match for an LED in there.
Any chance we can get a photo of the actual circuit?
I'll have a chance to unbox it Sunday. I'll post it then. Thanks!
Under promise and over deliver. Hopefully that shows you what you need. Let me know if I need to zoom in on anything.
Quote from: Dc10 on June 15, 2013, 01:31:46 AM
Under promise and over deliver. Hopefully that shows you what you need. Let me know if I need to zoom in on anything.
Cool, thanks. I'll compare to mine and see if I can get any clues.
Quote from: RobA on June 15, 2013, 01:39:00 AM
Quote from: Dc10 on June 15, 2013, 01:31:46 AM
Under promise and over deliver. Hopefully that shows you what you need. Let me know if I need to zoom in on anything.
Cool, thanks. I'll compare to mine and see if I can get any clues.
Also, If I get a chance, I'll pick up a different power supply today and see if that makes a difference. I have 2 but they are both Boss psa120.
It couldn't hurt to check with a different power supply. But, I'd think that Boss has plenty of current available.
I went through your photos to see if I could see anything obvious that we have different. I couldn't see anything. But, some spots are hard to trace in the photo. Do you have a link to the schematic you worked from?
You guys tried just using a battery? If there's no tick when using a battery, you're at least narrowing it down to the power supply. just a thought....
Sent from my PG86100 using Tapatalk 2
Quote from: RobA on June 15, 2013, 05:09:41 PM
It couldn't hurt to check with a different power supply. But, I'd think that Boss has plenty of current available.
I went through your photos to see if I could see anything obvious that we have different. I couldn't see anything. But, some spots are hard to trace in the photo. Do you have a link to the schematic you worked from?
This should be it. 2 differences, I didn't use the ramp mod but I did use the stuck wah mod. If I remember correctly its just a diode in parallel with the external rate led.
That looks to be what I have on my breadboard. I haven't got the stuck wah mod though. I'll have to look at that.
Well, I did finally have to pull this off my breadboard with no success in causing it to tick. Before I did though I was able to put my new little oscilloscope to use and look at the LFO with various op amps in it. Based on that, I have one suggestion you might want to try. I think that you said you thought it was ticking at the top of brightness curve. If that's the case, this might help.
I noticed the top of the LFO trace is most distorted with the LM358 in it. The LM358 is good though because its input includes the negative rail. Lot's of other op amps latch up and flip to the positive rail while the input is too low. So, you need an op amp the can handle the negative rail and does better at the top of the curve. I've been looking at lots of LFO's lately and found that the TLC272 does the best job of hitting both those requirements of the op amps that I see commonly used in pedals.
I'm not sure that it'll help at all, but if you have a TLC272 or can put one in your next order, it's worth a try.
Quote from: RobA on June 28, 2013, 12:29:58 PM
Well, I did finally have to pull this off my breadboard with no success in causing it to tick. Before I did though I was able to put my new little oscilloscope to use and look at the LFO with various op amps in it. Based on that, I have one suggestion you might want to try. I think that you said you thought it was ticking at the top of brightness curve. If that's the case, this might help.
I noticed the top of the LFO trace is most distorted with the LM358 in it. The LM358 is good though because its input includes the negative rail. Lot's of other op amps latch up and flip to the positive rail while the input is too low. So, you need an op amp the can handle the negative rail and does better at the top of the curve. I've been looking at lots of LFO's lately and found that the TLC272 does the best job of hitting both those requirements of the op amps that I see commonly used in pedals.
I'm not sure that it'll help at all, but if you have a TLC272 or can put one in your next order, it's worth a try.
I don't have one of those but I'll give it a try.
I tried a few things the other day. I hooked up a 9v battery, still ticked. I tried a voodoo lab 4x4, still ticked. I tried a different 100uf cap for the power supply filter, no luck. Then I breadboarded a buffer using a 2n5088 with a separate power supply. The ticking went away but when I switched the pedal to bypass, I got a loud pop. I switched it off and on a couple of times but the pop didn't go away.
Quote from: Dc10 on July 03, 2013, 04:54:34 PMbut when I switched the pedal to bypass, I got a loud pop. I switched it off and on a couple of times but the pop didn't go away.
Did you use a pull-down resistor before the buffer? It's just like anything else with true bypass; it'll pop if you don't protect it.
Quote from: midwayfair on July 03, 2013, 04:56:35 PM
Quote from: Dc10 on July 03, 2013, 04:54:34 PMbut when I switched the pedal to bypass, I got a loud pop. I switched it off and on a couple of times but the pop didn't go away.
Did you use a pull-down resistor before the buffer? It's just like anything else with true bypass; it'll pop if you don't protect it.
. At first no because I wired the buffer without a footswitch. I just breadboarded it and put an in and an out jack both of which had ground wires attached to them. Then I wondered about needing a pull-down so I put a 1M at the input... No difference, still popped.
Also, I ended up putting the buffer in the pedal and running it with the existing supply and filtering. It ticked as if the buffer wasn't even there. But the popping disappeared.