Tonepad Corrral Chorus: op-amp subsituitions?

[theman]

Has anybody tried a different op-amp for IC1 (4558)?  This is used after the initial Q1 buffer -- looks like some gain/filtering then into a filter network into the BBD. The 2nd op-amp is used for mixing the original and delayed signal. It seems like if you wanted a slightly less noisy, more pristine signal, an NE5532 might be good here, though with higher current draw.  Seems like the TL022 (IC2) is not in the audio path at all, as it controls the rate/depth for the clock driver. So you can use a TL072 here.

Any suggestions?

[Morocotopo]

 As far as I know (and it´s not much), TL062, RC4558, TL072, TL022 are all dual opamps, same pinout, but some of them are JFET input ones. When I built my chorus, I researched for TL022 replacements because those cost 10 u$ here!!!! I settled on a TL062. I - THINK- TL022 were used because they have low power consumption, and since they are not in the audio path, that is an important characteristic. I - THINK- you could experiment without worries, as long as the pinout is the same...
Take with a grain of salt, I´m NOT an expert.

Morocotopo

[QSQCaito]

Mm... someone answered to me once.. the differences between the most common op-amps... i remember that the TL072 was less-noisy, gotta check out and i'll bring you back news soon.


Bye bye

DAC

[Mark Hammer]

The TL022 is used in LFO circuits across a surprisingly large range of commercial modulation pedals of various types: flangers, choruses, phasers, tremolos, etc.  My sense is that it accomplishes the task with lower current drain than many other dual op-amps. 

I gather the LFO is often one of the big current hogs in modulation pedals.  This is not just a matter of battery life and I'm-using-an-external-supply-so-what's-the-big-deal.  It is precisely the sudden need for current in the typical LFO that produces the ticking problem which shows up in the audio path.  I'm ust guessing here, but I would assume that using an op-amp with much lower current requirements mean that less current is momentarily "borrowed" from the remainder of the circuit, result in a more tick-free product without having to go to extra lengths to decouple everything and stick more parts on the board.

The upshot is that circuits will likely "work" when an op-amp other than the indicated TL022 is used, but there *might* be some battery and tick issues resulting.

[Fret Wire]

A lot of fx companies used TL022's, TL062's (both duals), and TL061's to keep power consumption down. Texas Instruments still makes the TL022, but recommends it only for replacement, not new designs. Like Mark says, they were used a lot in modulation pedals, and others that had a higher current draw.

[theman]

The TL022 is used in LFO circuits across a surprisingly large range of commercial modulation pedals of various types: flangers, choruses, phasers, tremolos, etc.  My sense is that it accomplishes the task with lower current drain than many other dual op-amps. 

I gather the LFO is often one of the big current hogs in modulation pedals.  This is not just a matter of battery life and I'm-using-an-external-supply-so-what's-the-big-deal.  It is precisely the sudden need for current in the typical LFO that produces the ticking problem which shows up in the audio path.  I'm ust guessing here, but I would assume that using an op-amp with much lower current requirements mean that less current is momentarily "borrowed" from the remainder of the circuit, result in a more tick-free product without having to go to extra lengths to decouple everything and stick more parts on the board.

The upshot is that circuits will likely "work" when an op-amp other than the indicated TL022 is used, but there *might* be some battery and tick issues resulting.

Thanks Mark! I'm gonna try a TL072 first, and if there's LFO noise, I'll probably try the TL062, which is something like 250 uA/channel as opposed to the TL022 which is 125 uA.

[theman]

Finally got around to finishing this, and it works, but you hear the swoosh and ticking of the LFO, as I used a TL072CP as a quick test of things. Used a TL072CP also where the 4558 would go. Looks like I'll have to find a lower power equivalent. The TL022 is hard to find ... maybe a TL062 will work. Thanks for the info Mark.

[Mark Hammer]

I forget what I used, but my Corrral is pretty quiet with no audible ticking, and I have not modded it in any way to deliberately address ticking.  So, maybe the trick IS to use a lower current op-amp for the LFO section.

[Morocotopo]

Theman, my Corrral ticked like hell, you could hear it acoustically from a  few meters away... (just kidding  ), really, ticks got into everywhere there was signal, I solved it by using shielded cable with the shield attached to ground on only one end on the In jack-Switch, Switch-Board In, Board out-Switch and Switch-Out jack cables. After that, no ticking at all, not even a teeny little faint bitty in the distant background, which I supposse is a testament to the great tonepad PCB design.

Morocotopo

[Fret Wire]

My money would go with wiring and/or trimpot adjustment. I haven't built tonepad's layout, but I've done op amp swaps on one of my CE-2's without any ticking problems.

[theman]

Theman, my Corrral ticked like hell, you could hear it acoustically from a  few meters away... (just kidding  ), really, ticks got into everywhere there was signal, I solved it by using shielded cable with the shield attached to ground on only one end on the In jack-Switch, Switch-Board In, Board out-Switch and Switch-Out jack cables. After that, no ticking at all, not even a teeny little faint bitty in the distant background, which I supposse is a testament to the great tonepad PCB design.

Morocotopo

Thanks for the info ... yes, I replaced the TL072 with a low-power TL062, and I could not hear the ticking until I turned up the volume on the guitar. This meant that it was noise induced in the IN signal wire. Sure enough, the IN wire was too close to the LFO section. Just moving it away did the trick. No need for shielding since the wire is very far away now. I turned up my amp almost to max (this is on a 100W solid-state amp) and could only hear the slight swooshing noise of the LFO -- no ticking.

Thanks everybody for their comments and suggestions!

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