TL022 vs TL062 against "ticking" LFO

[flo]

Common advice to cure a LFO "tick" in a pedal is to use a low-power opamp for the LFO section.
Both the TL022 and the TL062 are often suggested. The TL022 is supposed to be better in reducing the "tick" and I was wondering why.

So I put some datasheet specs together for both of them for parameters that I think matter in this case.
The TL022 seems to be a clear "winner" because of inferior specs which in this case is good.

                                          TL022         TL062
Gain bandwidth                  0.5               1   MHZ
power                               3.9               6   mW
supply current (1opamp)   130/2=65   200   uA    
Slew rate (Av=1)               0.5               3.5   V/uS         
Rise time                            0.3               0.2   uS

See also:
http://www.diystompboxes.com/smfforum/index.php?topic=72953.msg591281#msg591281

The point of using an 022 over an 072 is that the 022 has lower gain ... A tl062 may help, but it is not as good of a choice as a tl022

http://www.diystompboxes.com/smfforum/index.php?topic=68192.msg544705#msg544705

The TL022 can be replaced with a low power op amp of the same pinout. The TL062 and the LM358 should both work. They have a higher current draw though so the risk of ticking will increase.

[rankot]

I see it's an old thread, but why not to revive it - I had a problem with LFO ticking on my Maestro MP-1 build. I put an original TL072 into LFO circuit, but it had a lots of ticking. So I thought I could try with something else - I recently bought a batch of fake TL072 chips, and my IC tester couldn't even recognize them on automatic. Setting it to LM2904 helped ICs be recognized as working. So they are some kind of dual op amps, but definitely not TL0x2 JFET input family. So I tried to put that fake chip into circuit and, to my surprise, works great and no ticking at all! I have some other original dual opamps and I will certainly try with them, but I've found the use for those fake TL072!

[danfrank]

Here, the info in this thread should help you:

https://www.madbeanpedals.com/forum/index.php?topic=32458.0

It's only a coincidence that I'm tooting my own horn! Lol! I lifted the info from somewhere else but the important thing is that this should solve your problem...

[rankot]

Thanks, I will take a look at that, but I'd rather not change the circuit in that way, already too many wires 

For me it is interesting that changing opamp nails it.

I have also tried that solution with cap and resistor in ltpsice and it doesn't change a thing with a LFO such is in Maestro MP-1. Maybe sim is not set right?

Code: [Select]

Version 4
SHEET 1 2524 680
WIRE -368 -48 -560 -48
WIRE -48 -48 -288 -48
WIRE -16 -48 -48 -48
WIRE 96 -48 64 -48
WIRE 144 -48 96 -48
WIRE 96 0 96 -48
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WIRE -528 16 -560 16
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WIRE -512 256 -560 256
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WIRE -416 256 -448 256
WIRE -624 272 -624 256
FLAG -144 128 V+
FLAG 352 240 0
FLAG 352 16 V+
FLAG 304 128 Vb
FLAG 304 224 V-
FLAG 144 -48 OUT
IOPIN 144 -48 Out
FLAG -496 176 V+
FLAG -496 112 V-
FLAG -208 224 Vb
FLAG 96 96 0
FLAG -144 192 V-
FLAG -624 272 Vb
FLAG -384 16 SQ
IOPIN -384 16 Out
FLAG -352 320 Vb
SYMBOL Opamps\\LT1057 -144 96 R0
SYMATTR InstName U2
SYMBOL res -224 128 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 33k
SYMBOL voltage 352 16 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 4.5
SYMBOL voltage 352 128 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 4.5
SYMBOL Opamps\\LT1057 -496 208 M180
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WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
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SYMATTR Value 300k
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SYMATTR InstName D1
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WINDOW 0 0 32 VBottom 2
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SYMATTR Value 10n
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WINDOW 3 36 40 Left 2
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WINDOW 3 24 8 Left 2
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SYMBOL res -336 336 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R6
SYMATTR Value 68k
TEXT -72 264 Left 2 !.tran 0 .3
TEXT -72 296 Left 2 !;.ac oct 100 10 20k


[rankot]

The LFO I'm talking about actually already has that resistor and capacitor for smoothing square wave edges, but with slightly different values. I tried with the values you proposed, but not much changed. So there is probably a problem with grounding on my PCB, which injects thumping noise if using TL072. I will try to cut some traces and rewire LFO IC ground directly to the main reservoir cap.

[anotherjim]

I don't think it helps if the integrator cap is polarized as the polarity effectively reverses between cycles. If the maximum speed is too fast (10k and 4.7u looks fast to me without working it out) the 10k can go to 100k and the cap to a 470n film. Then you get rid of the polarity issue and the peak charge/discharge current spike is much reduced.  The feedback cap on the Schmitt trigger is also going to make a reversal spike but that will be tiny thanks to the 100k from Vb.

That said, there are still going to be some peak current spike effects when the function generator changes state so a separated power & ground scheme is always going to be a good idea.

[Andrekp]

I have found that isolating any LFO as far as ground and power (and sometimes raising the ground a little bit) works for most LFO ticking problems.

[rankot]

I don't think it helps if the integrator cap is polarized as the polarity effectively reverses between cycles. If the maximum speed is too fast (10k and 4.7u looks fast to me without working it out) the 10k can go to 100k and the cap to a 470n film. Then you get rid of the polarity issue and the peak charge/discharge current spike is much reduced.  The feedback cap on the Schmitt trigger is also going to make a reversal spike but that will be tiny thanks to the 100k from Vb.

That said, there are still going to be some peak current spike effects when the function generator changes state so a separated power & ground scheme is always going to be a good idea.

I'm actually using 4u7 MLCC, not electrolytic, so there could be no polarity issue, and there's no thumping when I replace LFO dual opamp with LM2904. Ground is derived from 9VDC, with a resistor divider, after which I have voltage follower using one spare op amp of TL074. Original schematic use SN72LO22P on both positions, but I have no idea what is that (maybe TL022?).

I even tried to cut ground connection to LFO IC, and put a small resistor there, but it didn't help. Tried with a pot varying from 0 to 1k and it doesn't affect LFO noise. Or I shall try to do it on V+ and V-?

[anotherjim]

SN72LO22P probably is a TL022, a TL062 would be a good dual to replace those.

Is the ticking louder at fast speed?

[rankot]

SN72LO22P probably is a TL022, a TL062 would be a good dual to replace those.

Is the ticking louder at fast speed?

Yes, it follows the speed. With LM2904 it is mostly high frequency and not loud, with TL072 it is really thumping.