Moog Music Forum

I noticed an issue with my RME several days ago related to Panorama with square LFO. Here's what happens:

I am editing the user defined preset G:68.
I press the Edit button to change the PGM Pedal Dest. on the EDIT Functions 2.4 screen
On the next EDIT Pedal Dest. 1.4 screen, I select Panorama

Now the output from my RME should pan from left to right based on the LFO. The problem is that this only works correctly when the modulation bus source is set to triangle. I see the left and right channels on my mixer evenly shift based on the LFO.

When I set the pedal modulation bus to square, things do not work correctly. The left channel remains louder than the right channel, and it only goes down in level slightly. The right channel is 8 db lower than the left channel and only goes up in level slightly. I always hear a clicking sound from my monitors. I was not sure if this was the way my RME was supposed to work, since triangle seems to work perfectly and is quiet when panning channels.

However, when I hooked up the square LFO output from my CP-251 to the PAN input on my VX-352, the levels alternate perfectly and there is no clicking sound.

Can anyone else reproduce this issue I am experiencing? You do not need the expansion boxes nor the CP-251. Just set your pedal modulation bus to panorama on the edit menu then set the source to square. Do you hear clicking when it attempts to alternate? Is one channel always louder than the other for the output?

I'm trying to find out if I have a bad unit or it's a widespread issue. Also, I would be surprised if this issue only manifested itself with panorama. I would think nothing using square LFO would work correctly.

Thanks.

Edited to correct a couple mispelled words...

I just repeated this test with the CP-251's square LFO patched to PAN input on my VX-352. Note that I do hear a clicking sound, but the levels also alternate from left to right evenly.

My guess is that the clicking sound is normal with square. I cannot imagine why the channel level difference would be seen from the RME's own LFO though.

I double-checked all my settings and experimented with this some more. I am able to get an even right to left channel panorama with square LFO if I change the filter spacing to -50 or so. The pan tracks the keyboard with square. Lower keys have more output to the left channel than right, and higher keys are vice versa. This only happens with square though. Triangle has perfectly matched right to left pan with all keys on the keyboard.

When I press the enter key on my RME to reset the G:68 from the stored preset then patch the square LFO from my CP-251 to PAN on my VX-352, I do not notice what I had described above. The right to left pan is even, and I am not seeing the pan track the keyboard.

Hmm.

The panorama modulation only works with bipolar LFO waveforms that swing from -2.5V to +2.5V

The triangle and S&H are bipolar waveforms. The square is not, it swings from 0V to +5V. That is why the panorama behaves that way with a square wave.

You could get around this problem using a CP-251. The mixer section can provide a negative offset that will translate a unipolar waveform to a bipolar. IE if you feed a unipolar 0-5V square into the mixer and combine it with a -2.5V offset, the square is now bipolar swinging from -2.5V to +2.5V.

Ah...interesting. Thanks for the information.

This must mean that the CP-251 already includes a bipolar square waveform. The Voyager itself does not. This may be why the waveform icons on the two units differ. The RME's square waveform icon is pretty short where the CP-251's square waveform icon is very tall and retangular like.

This is good information to know. I do have an easier work-around by just using the CP-251's square waveform.