Voltage controlled pan circuit

I am in the process of doing a voltage controlled Pan circuit to pan between Ramp and Pulse waves on my 6DCO build

I found this circuit


But can’t fathom the comment “To 10K resistor on second channel” surely you don’t want any connection other than the control voltage.

And which 10K the one on the transistor base??? seems odd or the other side of the one on the emitter like this . Neither option makes much sense to me, tempted to leave it out with a link wire footprint…



Why not use a dual VCA chip like the AS3360 or AS3364 if you need multiple, I use half of an AS3364 to pan between white and pink noise. But I made it center 0 but it should be easy enough to cross fade.

I think it takes a single mono channel, and then pans it left or right - so you feed the input into two copies of the variable gain stage. Then, the control voltages seem to be the inverse of each other, so as you pan from left to right you get all the signal out of the left channel, then a mix out of both channels until it’s all out of the right - at least that’s my understanding after looking at it for 20 seconds.

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The circuit you’re linking to is not a combination of panner and crossfader like you’re drawing here. It’s just a panner, mono input to stereo output.

Here’s an example of my panner/crossfader combination, using half a dual VCA. Voltage-controlled panner/crossfader

If what you’re really looking for is a crossfader (2 in, 1 out) as opposed to a panner (1 in, 2 out) or panner/crossfader (2 in, 2 out), there’s also this one by Thomas Henry:


I made this crossfader. Mine works but only if I push it in with my finger, but I think that’s a bad solder somewhere…

@BlackDeath it’s the Voltage control that is important to me, I see yours has a POT copmntrol.

@analogoutput , ahh, well the actual circuit ( yes my bad for missing the full thing ) has a fixed mix to single output after the pan stage to give one output.

I had assumed the original circult was for a stereo in pan to stereo out and just mixing the signal after that would be fine, so was not sure of this extra connectoin I quwstioned, Now if it’s a 1in to 2out then that makes a whole lot more sens.

Kicad seems to have vanished from my laptop after an OS upgrade so I can’t post the full schematic right now.

So yes it’s more of a Crossfade 2-1 … Which I thougt I haad got to , and probably have if I leave that errant wire out of the equation.

Will review the other X-Fade ideas tomorrow.

Cheers All.

The pot on mine is a an attenuator for the CV. It’s based on Xim by Noisereap.

So this is the actual “X-Fade” … I guess I could do it with a bunch of 3360’s but that’s going to get expensive.

Ignore the “Link” and “Link-RV” components, it’s for alternative options.

And yes the cap at the top is Back to front, corrected!



You’d have a hard time, I think, finding a polarized 100 pF cap anyway. In the version in the link you gave up top the input and output AC coupling caps (omitted in your version) are specifically marked “Non Polar” with the same curve-and-straight-line symbol. I don’t think they intended the 100 pF cap to be polarized either. Likewise the 10 nF cap near the transistors, I’d use film for that.

In the original circuit the op amp resistors are 10k rather than 150k. In principle if those resistors change the cap should change too, though stabilization caps are something I’ve seen one too many explanations of — coming to different conclusions about how to choose the value, so I dunno.

your right on the 10K vs150K Resistors, I was working from the original and another variation at the same time, I was intended to stay with the original 10k’s

I rarely see any OPamp designs with stabilisation caps on them, will update anyway and see what effect not having them has during build.

X-Fade Amps

Main Schematic

Control Board

My understanding is the stabilization caps are needed, if at all, only when feeding a capacitive load, like a very long output patch cable for instance. And that even in that case the series 1k resistor (if it’s out of loop) will stabilize the op amp. But I see them often in schematics on op amps in the middle that are definitely not feeding a capacitive load.

Putting in the footprint and then ignoring it unless a stability issue arises certainly is prudent.