Author Topic: Stomp LFO not interacting properly with phaser  (Read 490 times)

patrick398

Stomp LFO not interacting properly with phaser
« on: March 01, 2020, 11:15:00 AM »
Hello all, glad we're back online...i was feeling a bit lost these past couple of days.
I'm breadboarding an OTA based phaser at the moment, sounds great and i'm using one of Tom's stomplfo's which is working nicely. It's shifting Vref via a set up i'm unfamiliar with; a couple of trannies and a fet. Can anyone enlighten me?




I have a second LFO set up (standard triangle wave) which provides nice double phase shifting. I've got this LFO on a switch too so it either goes through the same 2 transistor 1 fet set up as the first stomplfo or goes into the base of a transistor with a 47k across C and E and connects to pin 13 and 14 of the TL074 which creates a very cool tremolo along with the stomplfo phasing.

When i replace this second LFO with another stomplfo it starts interacting strangely with the first. When i turn the depth of the second up it reduces the sweep of the first. Also it does not create tremolo when it's sent to the transistor base, is this something to do with the fact that the stomplfo is a pwm output?

I have a phase90 based phaser which used two stomplfo's without any problems, perhaps it's something to do with the way it moves vref?


Kipper4

Re: Stomp LFO not interacting properly with phaser
« Reply #1 on: March 01, 2020, 11:28:19 AM »
Have you a drawing of the scheme Pat?
I'm a bit confused as to how the stomp lfo is shifting the OTA phaser.
Do you have a series R from Stomplfo to OTA Iabc?
Using something like the Mxr OTA phaser.
"Duck_Arse
otherwise, you might end-up with SOIC or gullwings, for surface mounts."


Smoke me a Kipper. I'll be back for breakfast.

Grey Paper.
http://www.aronnelson.com/DIYFiles/up/

patrick398

Re: Stomp LFO not interacting properly with phaser
« Reply #2 on: March 01, 2020, 11:40:04 AM »
Hey Kip,

It's basically the madbean maestro work-a-like:



There's 100k out of the stomplfo, that connects to the base of Q1 and VR is out of Q3 collector, this connects to pins 1 and 16 of all the 13700 via a 1k.
Like i say, the first stomplfo works well, and connecting the original lfo works well along side the stomplfo, the problems arise when using a second stomplfo. It's weird

patrick398

Re: Stomp LFO not interacting properly with phaser
« Reply #3 on: March 01, 2020, 01:47:35 PM »
Ok so i've got the second stomplfo going through a 330k into base of a transistor, emitter to VBias collector to Vref and that seems to be working pretty well, i think the first LFO's sweep is as strong as it was before but i'll have a look on the scope.

Still can't get the second stomplfo to create the tremolo though, weird, more fiddling required