What controls Sidekick LFO rate range? *solved*

I have two sidekicks. I used 50k log pots for the 2 LFO rate pots on one and 100k log (described as Audio by mouser) pots for the second. I’ve noticed two things about the 100k pot board. Firstly, the range of LFO seems to be different. I can get the rate very low on the first board, but even at the lowest setting on the second board the LFO rate is high.I would say it’s between 120-140 bpms if that makes any sense.

Secondly, the LEDs that are used for the lfo rates (LED1, LED2) do not blink in the same manner on both boards. On the “100k board” the LED blinking is almost unnoticeable. The LEDs are almost always illuminated fully and only dim slightly in response to the pot. I’m not sure this is related to the pot, but I thought I’d throw it out there.

Any thoughts?

The LFO frequency is 1 / (2 pi R C), where C is the capacitor in the oscillator network (10 uF), and R the resistance set by the pot.

The minimum oscillation frequency is set by the total resistor track value of the pot (50k > 0.3 Hz = 18 BPM ; 100k> 0.15 Hz = 9 BPM), the maximum oscillation frequency is set by the minimum value of the wiper/terminal resistance, which widely depends on the quality of the pot (between 5 ohm and 100 ohm). A conservative value of 50 ohm gives 318 Hz.

You also have to take into account the tolerance of the pots and capacitor (+/- 10%)…

In practice, on the Sidekick I have here:

  • Minimum frequency: 0.2 Hz (12 BPM)
  • Maximum frequency: 400 Hz

Regarding your problem it looks like the oscillator is not working properly. Have you checked the resistor value. Are you using a MCP6002 and not a (non-rail to rail) replacement? TLV272 should work fine, but NOT TL072.

I’m using these caps in the LFO here and these MCP6002’s. I’m using 1% 12K’s, 5% 470’s and some 1% 10k’s I got from a local supply place that looked suspicious, but I checked their resistance before putting them in the circuit. I’ll take some out and see if perhaps I substituted a 10 for a 10K or something to that effect.

Given what you’ve pointed, out I think the “bpm” issue might have more to do with a mistake or cold solder joint than the pot difference.

I figured it out! You were right about the resistor values. The two 10K’s were actually 1K…oops. I had to pull those two out as well as another from the same batch elsewhere on the board. Everything is working fine, now. Thanks!

Here is my new SIDEKICK

Its …ähem… pink?

with glitter…

and rainbow patch points…

i like it :wink:

I was channelling my inner unicorn. I’ve been performing under the name FLCON FCKER lately and I’ve made my latest projects equally obnoxious as the name. I’ve also been using 3mm, 12,000 mcd LEDs….

AAAAAAAAAAAAAAAAAAAAAARGH! Im blind! And Im 10000 miles away… Certainly, you cant bring this thingy to Germany as we are shutting down - due to the infinite Wisdom of our Chancelorette - our Nuclear Power Plants. Sorry - no Gigs in the old World :wink:

DAMMIT! I’m always late to the party! Perhaps I should re-think my stance on the Canada to Houston pipeline people keep proposing these days.

Ok, as its an open secret and rumors have been telling for months i can reveal The Secret™ on what Olivier is working so long … … the Shruthi MK2 will be powered by something like this: The cold Fusion Flux Oscillator…

why is the lower region censored?

obviously there was some obscene insulting necessary to make it work and this forum is mainly used by 3 year old boys…

Those 220uF power supply caps on the filter boards… my girlfriend calls them “blueberry flux capacitors”

they taste like blueberries?

“why is the lower region censored?”

uuuum because the government doesn’t believe in free energy…duh!

“why is the lower region censored?”

The sign says “Designed by Apple in California”