Splitter question

[richon]

After looking at the Splitter of ROG I did some mods and I want to ask you what do you think about it.

the goal is to have a DRY signal mixed with another pedal in parallel.



or should I still left the other OPAMP there (like the original in ROG) , even if I don't need it?

[PRR]

[Gurner]

& personally, I would replace the 1M resistor immediately below the text 'send' with something like a 50K Linear pot - that way you can adjust the level a bit if the unit your 'sending' to is a tad sensitive about its incoming signal. Also, the 1M bias resistor at the input to the second opamp seems excessive bearing in mind that's the return from your effect - I'd have gone with 100k (or even less)....but I'm like that!

[slacker]

If you leave out the upper opamp like in Paul's schematic aren't you potentially making it into a "feedback looper"? Depending on the volume of the output of whatever you put in the loop can't some signal pass through the blend pot back into the input of the pedal in the loop?

[merlinb]

If you leave out the upper opamp like in Paul's schematic aren't you potentially making it into a "feedback looper"?

No, because the output impedance of each opamp is exceedingly small, so it will shunt any single trying to feed back.
However, if the coupling caps are too small then yes, that could happen, since the high reactance of the cap is in series with the opamp output impedance. 10u caps are probably the smallest I would dare use.

[slacker]

That makes sense, cheers.

[richon]

tested here: FIXED WAH and EATREMOLO on the SEND RETURN channel...



and video here: http://www.youtube.com/watch?v=0_PSvGH90zc

[richon]

well

it seems something doesn't quite work fine


the PEDAL works great as a mixer... mixing the clean signal with the LOOP signal (pedal) without loosing a bit of good sound

the problem appears with activating or de-activating


it make a huge POP.   

it's not the OPAMP, electro caps, 3pdt Switch, led....

what could make it sound like a ground or vref or DC is getting through the pedal when turned on¿?

[WangoFett]

Do you have a pull down resistor on the input?  Without one, the input cap will leak Vref across it when the pedal is in bypass.  Then when the pedal is engaged, your guitar or the preceding effect would suddenly pull this potential to ground, causing a pop to flow through your splitter.

[richon]

I've added a 1,8M resistor to ground just when i was building it, so i can say : this ain't the problem.


It's seems it has something to do with the Send-Return part...

but i can isolate the Problematic part.

[richon]

update:

it seems the big 10uF and 0.22uF caps take time to be completly charged or discharged to actually have a noise/pop switch to work silent

like 10 seconds or less after the power (battery) is connected the pop when switching on/off the pedal goes away.

[Gurner]

update:

it seems the big 10uF and 0.22uF caps take time to be completly charged or discharged to actually have a noise/pop switch to work silent

like 10 seconds or less after the power (battery) is connected the pop when switching on/off the pedal goes away.

So why not go with dual rail opamps and then remove all the caps...?

[WangoFett]

I can't see where the activate/deactivate switch is in that photo.  Did you add a true-bypass switch around the circuit?
Can you post a schematic as it is now with bypass switching and pulldown resistors?
What makes you say the problem is in the send/return?  When you turn blend fully dry, does that lessen or remove the popping?
Why is the charging speed of the big caps a concern?  If the pedal power is not switched on/off while the effect is engaged then I don't see the problem.
Using a dual-polarity power supply simply to fix a popping problem seems extreme to me.