TC Electronic JUNE 60 chorus box

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#43

That was the thought process behind the extra circuitry especially if you don’t want to start swapping out the SMD resistors in the final mixer circuit. With a basic non inverting op amp circuit you can boost the signal or buffer and attenuate it. It would be fairly easy to mock up with a breadboard and a handful of components. Once you’re settled on the resistor values you could make up the circuit on a bit of veroboard if required.

The true bypass is just that. It can’t attenuate or boost the signal as there are no components in the signal path, the switch just routes the signal from input to output and bypasses the effect so it would sound identical in level and tone. That’s pretty much the true bypass USP.

My guess is the guitar/keys attenuates the P-P voltage level presented to the input to be closer to the P-P voltage level expected of a guitar output (as a guitar output is significantly lower voltage than a line level output), prob just via a voltage divider. The values of the resistors used will also affect the impedance ‘seen’ by the following input stage.

Because the switch is soldered to the PCB if you want to access the effect output before it hits the switch you’re gonna have to either cut a trace or better still remove a component to tap into the circuit and return the output of your mod board back to the Main PCB (and on to the switch and output jack). Unless it sits after the switch I’d suggest there will be a DC blocking electro cap on the output of the effect circuit that you could use to tap into the PCB circuit.

A bit of trial and error on the breadboard would soon have you in the right ball park I’m sure. I guess it depends on how far you want to go but if you’re willing to do a bit if experimentation you should get what you want. I suppose in a pinch you could just feed the effect circuit output to a pot or a couple of resistors to ground to get the 3dB cut you want but you might have output impedance issues then? Using an op amp to buffer the effect output should negate that. Can you find a quoted output impedance of the pedal? That will inform you of what output impedance your modified circuit should have

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#44

Thanks for spending your time and for the detail of your response. I’ll search around specifically to see if there is any information regarding the output impedance of the pedal and move forward from there. I also have some 3pdt footswitches that are a traditional footswitch design and not the faux footswitch which in this case is a latching button on the pcb with a standalone spring and foot actuator suspended above it (that’s what this comes equipped with, I assume to make as much of the pedal electronics assembly automated as possible) so I suppose I could consider replacing the footswitch and wiring a mod between the pcb and the new switch as you suggested would be ideal.

I only generally use pedals with a 9v adapter so power efficiency of the op amp wouldn’t be terribly important but if one or another package is suitable for this purpose and is less likely to generate noise or degrade the effect signal (apart from the expected buffering), I would appreciate if you consider whether you have a specific recommendation and whether it needs to be jfet or if it doesn’t matter.

Thanks again

#45

I’d say something like a TL082 or 072 should do the job. They’re not expensive and will be as good or better than whatever B have used I’d reckon. Not a criticism BTW!

Exchanging the PCB mount switch may well prove the easiest way to tap into the circuit too. Good plan, just as long as you e git clearance without the bottom of the switch fouling on the PCB

#46

You can criticize the big B to your heart’s content, there’s no brand loyalty here, especially when I’m having to modify their design to achieve a useful effects box. Alright, thanks for the recommendation. I’ll move forward at a snails pace but I’ll keep this post informed if there’s any results to speak of.

It looked as though there was clearance, or I wouldn’t have mentioned it. I believe they did this array to save labor and build time, there’s no way that using the separate foot actuator and spring costs any less money in practice than a footswitch, but it does not require a skilled worker to turn a nut but soldering wires may require more skilled laborers.

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#47

Sorry, you misunderstood! I meant I wasn’t criticising their choice of op amp (anything else for that matter!). I’ve git a ton of their stuff and I’m very happy with it! I just meant they’ve prob used a slightly less expensive op amp down to economies of scale

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#48

the only opamp I distinctly recognize on the board is the 4580R.

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#49

I guess that a 4580 would do the job too.

#50

frankly I will buy whatever I can get cheapest on ama-on without overpaying for unnecessary quantity or purchasing that which will not meet my needs now, and then meet my needs again later because I’ll probably be stuck with 100 of them. But I will look at pricing of tl082 tl072 tl074 and 4580 since it seems like they all would work about the same and be relatively inexpensive. if I end up with a quad op amp and don’t use the entire package that’s fine as long as I can make out what pin does what from the datasheet.

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