Cgs synth

Hi there

I'm a bit confused about this LFO

If I set the LFO for a perfect triangle at a certain frequency when I drop the frequency it changes shape.

When its really slow you can't really see the shape on a scope and you have to adjust by ear. And I am finding it very difficult to get a perfect triangle shape at very low speeds.

Also is is that the triangle is positive only does not go below zero?

On Wednesday, 4 October 2017, Mike Burnham mikejburnham@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Hi there

I'm a bit confused about this LFO

If I set the LFO for a perfect triangle at a certain frequency when I drop the frequency it changes shape.

When its really slow you can't really see the shape on a scope and you have to adjust by ear. And I am finding it very difficult to get a perfect triangle shape at very low speeds.

Also is is that the triangle is positive only does not go below zero?

On 4 Oct 2017, at 12:36, Ove Ridé nitro2k01@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

On Wednesday, October 4, 2017, 7:51 AM, Mike Burnham mikejburnham@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Yes thanks that makes sense

Any easy way to match diodes?

I do have some 1n4153 which are supposed to be high tolerance 1n4148

. Maybe these would be better?

Sent from my iPhone

On 4 Oct 2017, at 12:36, Ove Ridé nitro2k01@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

I think this is an inherent flaw in the design, deemed to be of sufficient performance for LFO use. The culprit is probably the matching of the diode pair. One diode in the pair conducts on the positive cycle, and the other on the negative. You may match up the shape for one setting, but then the different I-V characteristics makes the negative and positive cycles differ in length for a different pitch, and so the shape diverges. Getting a matched diode pair seems likethe way to fix it.

From the schematic, the LFO seems to swing both positive and negative of ground as far as I can tell.