Variable Slope Filter / Phaser

The Bad Producer · Joined: Mar 08, 2009 Posts: 282 Location: The Manhole

I've just pulled my module, and reverse engineered it (still can't believe I have no idea what I did there!)

I've drawn a diagram of the switch connections, hope it makes sense, the labelling for the contacts might be incorrect, but you'll get the idea!

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Actually I wonder if it is right, seems to make sense I think...

sduck · Posted: Sat Apr 13, 2013 6:46 pm Post subject:

Yes, I think that about nails it! Completely bypasses the mix pot when in the filter position. Good work!

The Bad Producer · Joined: Mar 08, 2009 Posts: 282 Location: The Manhole

Actually, after playing around with it last night in more of a 'test' mode - rather than using it for music - I reckon you could do without the switch if you wanted, there doesn't seem to be any difference between pot full wet and switch on...
It IS useful as a performance on/off switch though, and for that reason alone I would include it...

Boerge · Joined: Sep 02, 2009 Posts: 80 Location: Germany

Hi all,

trying to adjust the Varislope Filter I run into problems. I followed the steps on Jurgens website, but the only voltage I could adjust was the -7.5 Volts on R82, the other points never reach this voltage, for example the voltage on R71 doesnt go lower than ca. -3 Volts. I changed the three LM13700 and also the TL072 (U12), but no change. On pin 1 of U12 I measure ~10 Volts, can anybody confirm this? I had the cutoff pot not connected, the LFO depth pot in ccw position and the CV inputs shorted to GND.

regards

Boerge

sduck · Posted: Mon Jun 17, 2013 7:09 pm Post subject:

JoeMorris · Joined: Apr 26, 2009 Posts: 161 Location: Brighton

I love my variable slope filter (that I built way back in 2009) - but I have noticed on the waveforms that the positive parts of the waveform are trunacted compared with the negtaive parts of the waveform, meaning a loss of bandwidth. Anyone with more knowledge than me have any ideas why this might be the case and how i might go about sorting it?