I want to update the ROG SplitterBlend

[niektb]

I found a little schematic that might be something that you could try: (look how the MIX knob is wired). Although I'm not entirely certain if it gives you 100%/100%
https://www.pedalpcb.com/docs/Pythagoras.pdf

[Elijah-Baley]

Ok, it's an alternative. I'm not certain if it gives you 100% - 100%, too.
To me sounds like a kind of volume pot that send the two side to the Vref, so at half setting both the signals go partially to the Vref. I think it depends how the signal is cut.

Anyway, I'm going to do more experiments and more combination of pedals. Beacuse I read that the volume/signal loss could be due to a phase issue. Two signals could "eat" each other, this is the reason of the phase reverse switch.
Indeed, in the confusion of the test because the flying wires, short patchcord, small space, etc... I noticed sometime this volume loss, but just sometime. I uses the phase revers switch, but without hear any difference, maybe sometime it doesn't care, maybe yes. And maybe some pedals have to be placed in that loop?

[Elijah-Baley]

Ok. I did some tests. The half pot settings is not really a problem, even if a balance pot could work differently, maybe better in some case.
I have a problem. I noticed that the phase reverrse switch make a pretty loud pop when I use it the first time or after a while. And when it's open I play a few of minutes the circuit clips (I can hear it when I play the loop, and also when the pedals in the loops are bypassed). The clipping stops if I close the switch, and that's ok even when I open it again, but just for a few of minutes, then the circuit clips again.

I should check the circuit.

Anyway, I wish I have a verified veroboard. I don't like protobard.

[antonis]

Could you post a schematic of your particular phase reverse switch and caps in the neighbourhood..??

[Elijah-Baley]

The schematic is in the first post, it's the stock ROG Splitter Blend.
Anyway, I found a really critical missing link on my board. The two 1M ressitor that should go in the Vref don't acutally go. I'll solder a link tomorrow.

After it, I hope it will be all ok and I'll make other tests.
Then I'll study something more about the Mix Mode, to get a loop at 100% while I mix the other loop. I don't like the thing the fixed loop is not really fixed at 100%.

[Elijah-Baley]

I think I fixed the Vref issue. Now I can use the phase reverse toggle switch without any pop noise, and I played the circuit for a while without getting in the clipping issue.
In general the circuit works fine, volumes are pretty ok. Though I still hear the loss of signals (50% / 50%) when the pot is at half. I can accept it like a characteristic of the circuit.

I still not satisfied by this solution for One Loop Mix Mode:

The general idea would be to have a fixed resistance that can be bypassed on one side of the pot. The value should be close the same as the pot:

Because it seems work, but not exactly like imagine it. It's like I would limit the use of the pot from one side until half, but of course I can do it without this mod.
I tried (actually for the seconda time) to connect the output of one loop directly on the lug 2 or the tip of output jack. In this way I don't have any resistance between the loop and the output. I figurated that this will leave that loop always at 100%. But for some reason this solution doesn't work properly, because I get that loop always at 100%, but I can't hear the other loop until I totally turned the pot to the other extreme, and the first loop signal get low like usually.

Meanwhile, I'm looking for some mixer schematic to understand better the thing.
So I still need heavy help to make the Mix Mode where I can mix one loop to the other loop.

Thanks!

[GGBB]

I tried (actually for the seconda time) to connect the output of one loop directly on the lug 2 or the tip of output jack. In this way I don't have any resistance between the loop and the output. I figurated that this will leave that loop always at 100%. But for some reason this solution doesn't work properly, because I get that loop always at 100%, but I can't hear the other loop until I totally turned the pot to the other extreme, and the first loop signal get low like usually.

This is essentially a "taper" problem. Even a very small resistance compared to absolute zero is theoretically infinitely greater. You are trying to blend the signal "in" by reducing its resistance down to zero, but you always have the other signal with zero resistance. Zero resistance always wins against any resistance. A reverse audio taper pot helps.

My suggestion blends one signal "out" by adding resistance until it reaches the other fixed resistance. It only has zero resistance on one signal when the pot is fully off and that's exactly what you want. As soon as you adjust the pot, you have resistance on both signals, so there is no "zero resistance always wins" situation.

Here's a variation that might "feel" a little better (changes the taper):

[Elijah-Baley]

Thanks for the explanation GGBB.
I don't know if I'll try this, though it's interesting. I really don't want to change the taper of the pot, because I need both the modes, and to make works fine the blend of the two loops the linear pot is necessary for an asimmetric effect.
I'll continue to search other solutions without change the pot.

(Keeping the 25k linear pos is very useful also if I have to use this pedal with an expression pedal. If the noise will be not a problem as we said in previous posts. It seems not for the Wetter Box if it really works more or less like the Splitter Blend. Anyway I can't try this feature because I don't have any expression pedal, now. It was just pure theory.)

[GGBB]

I don't know if I'll try this, though it's interesting. I really don't want to change the taper of the pot, because I need both the modes, and to make works fine the blend of the two loops the linear pot is necessary for an asimmetric effect.

It only affects the taper of the fader mode. The original blend mode (resistor is jumpered) does not change.

In this SPDT variation, resistance is always 25k on signal A, and variable from 25k to zero on signal B.

In the original SPST version, resistance varies from 25k to 50k on signal A, and 25k to zero on signal B.

Blend mode remains the same as the original circuit for both variations - signal A resistance varies from zero to 25k, and signal B resistance varies from 25k to zero.

[Elijah-Baley]

I'm sorry. I've read wrong.
Well, I'll give it a shot tomorrow and I'll let you know how it works.

[Elijah-Baley]

I tried, but it still don't work like I would. This time I soldered the switch, so I can compare quickly the two modes. The stock Blend mode works fine, but the Mix mode is like before, with the pot at max the signal of the 100% loop is slightly reduced, and the mix of the two loops is exactly like in the Blend mode I set the pot at half.

I really don't have any idea hot to let one loop at real 100%. (I assume that also the other loop don't reach the 100%, probably the Mix mode can set the two loops from 100%-0% to 50%-50%. Just my intuition).

[GGBB]

Ultimately - you probably need another buffer to achieve ideal performance in both blend and fade/mix modes:



You can try this balance/blend pot setup without the buffer (grey section) - might be "good enough".

[Elijah-Baley]

I think there's something we are missing to make the basic stock schematic working well.
With this wiring a balance pot is better than a linear, but I can't use a expression pedal.
Maybe this schematic is not made to work how I'd like, and as you tried, we should modify it a bit.
I'm searching something about parallel signals and panning system. Maybe there's something useful.

[antonis]

Passive panning..

[GGBB]

With this wiring a balance pot is better than a linear, but I can't use a expression pedal.

https://www.ehx.com/products/dual-expression-pedal

[Elijah-Baley]

I was looking right at the Single-Pot Panpot style, indeed. Just I still don't know how it works. I have to find a way to emulate it with my software or looking some video or whatever. Maybe later I can try it on the Splitter Blend. (It's about the same Mix pot in the project linked by niektb. I hope it will be good.)

I didn't know the Dual Expression Pedal. Thanks! I have to look it better and find how it really works. But in this project I prefer to use a regular expression pedal, if it's possible.

[Elijah-Baley]

Hi.
I tried to emulate somehow the first version, the Single Pot Panpot.
I think that could works well enough.

I don't know if that was ok, but I emulated two schematics: a sort of boost with treble cut and another with bass cut. I joint the two input, while I connected A output to R1 and B output to R2. Then the two signals are jointed again after the panpot on the final output.
At one extreme setting of the pot I get the treble cut and at the other extreme I got the bass cut. At half pot setting I get something in the middle, none treble or bass cut, though there's a little treble peak, but I think it depends from the balance of the circuits' gain.
I found it enough linear, checking the emulation at pot setting of 25% and 75%.
I think will be easy even to get the Mix mode, the one with a loop at 100% and the other adjustable. At least in the emulation worked. It's enough diconnect one lug of the panpot, so one loop will go always at 100% while the other one can still be carry on to the ground.

I just noticed an overall volume loss, but changing the pot value from 10k at 25k helps.
Anyway, I'm thinking about the possibility to use a boost for each channel that will give me the two separated gain control, and maybe with the right wiring the two separated output in case I would like to have it.
At this point the board will grow up, and the jack need space, adn those for some features have to be switched. But if all this is ok I'm sure it could be a nice, though peculiar, machine.

[Elijah-Baley]

I'm back. I finally changed the "blend stage" trying the Single-Pot panpot you can see in the schematics above.

Look at this schematic about another topic I found maybe right in this forum:



I just tried the 25k pot of the Splitter Blend.

The blending works ok, I can't say if better or worst, but it's ok.
The I tried to cut off on pot side to get one loop always at 100%, but I get the same issue with the original Splitter Blend: one loop is not always at 100%, but it's attenuated when the other loop is at 0%.
This issue is, I guess, unsolvable. Because, in my opinion, the second loop completely grounded brings a bit even the 100% loop, anything we can do to take it directly at the output.
Probably it won't a problem if the two output are separated, but in this case is a problem.

I thought about this: I will try (I don't know when! ) even to add a gain stages for each loop, to have the gain controls, and I want to do it after the blending. So the two blend outputs will be separated and just the end of the two gain stages will be joint to the final output.

Do you think this will solve the issue?
If it's not clear I can draw a schematic later.

[11-90-an]

^^^ cool. 

There will be a volume drop if you use that ckt (the clean/octave pot mix thingy..) so consider adding recovery gain afterwards if needed...

[Elijah-Baley]

Yes, but the volume drop is noticeable just in the last part of the sweep. A recovery stage to use in this situation is not so fine. impractical in case I will use an external expression pedal.
The only thing I can do to solve this issue is keeping the two signals splitted leaving proceed them into their own gain stages.