"To match diodes, try connecting them in series with a 10k resistor across 10 to 15 volts, and measuring for identical drops across the diodes themselves. It would be best to use the same supply and resistor for all measurements, and try to do all measurements at the same temperature. Avoid handling the diodes while testing them to prevent body heat changing their temperature. Note: I did not do this for my module, so this is untried. Alternatively, you could use the diode test function present on most digital multimeters."
On Thu, Oct 5, 2017 at 12:18 AM, joshua lawson rnrjosh@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:There’s info about diode matching here:
Ken Stone's Modular Synthesizer
Sent from Yahoo Mail for iPhoneOn Wednesday, October 4, 2017, 7:51 AM, Mike Burnham mikejburnham@... [cgs_synth] <cgs_synth@yahoogroups.com> wrote:
Yes thanks that makes senseAny 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 iPhoneI 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.
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?
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/Ove
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