Hi, i'm in the process of building my first pedal which is the Easyvibe on a breadboard; my idea is to build the circuit in stages so I can test each stage and after it's all working I could play around with the circuit a bit.
I have sketched out (see pic) of what I have built up so far but I can't seem to get my leds pulsating; so i have a couple of questions.
1. Are the opamps shown in my pic (a,b,c) all fed with a supply of +9 and 0v ?
2. if i wanted to build just the basic LFO part so I can check it working / oscillating correctly on my scope, then i'd only have to build the part outlined in red in the circuit?
(http://tinypixels.co.uk/forums/images/9887480f70eca7d4ce941e0ac6a49de3/ev-lfo_v1.jpg)
Thanks in advance. :)
Hi Eastwood, welcome.
1) Yes! You really have 9V, the bias voltage at the 10k resistor and 470u cap, and ground (0V). Opamp power pins are 9V and 0V.
2) Yes! But I'd also include the diode stuff below the opamps, and the depth opamp, drive pot. Everything down that part of the drawing. I have done just that, and it works. Then you will know it is actually driving the LEDs you're using. It is a good LFO for other projects, too.
also welcome. Eastwood is only one suburb away from here.
I agree with everything* Sir Mike says, especially the part about adding pin-numbers to your circuits [helps us check your work], and when he says show us photos of your work, please, even if just the breadboard, and most especially of all when he says what are your voltage measures around the opamp?
* except I don't think you need the stuff below the red line.
ohh, and not VCO, LFO.
Ok. I figured 'the stuff', the diodes, were to make the 4 LEDs operate properly. And of course 'depth' is depth. When I've used this, I've just kept it all as-is and used the LEDs in a project, but as the Duck says, not entirely necessary to do so...
Thanks for all your really helpfully comments! :)
I changed the thread title from "VCO" to "LFO" (my bad!)
Perhaps I'm just missing a wire link or something - i'll take another look now.
I feel so stupid! one of the leds in the power rail wasn't in the breadboard properly because i was trying to straddle too many holes without bending the legs properly; in my defence they were short legged salvaged leds, lol
As soon as that was fixed i saw a nice wave on my scope and the LFO leds are pulsating like a, well like a univibe :)
(http://tinypixels.co.uk/forums/images/9887480f70eca7d4ce941e0ac6a49de3/IMG_20190713_190025_small.jpg)
(http://tinypixels.co.uk/forums/images/9887480f70eca7d4ce941e0ac6a49de3/IMG_20190713_190156_small.jpg)
So, now all i need to do is build up the 4 stage. "phase shift" things ?
Quote from: Mr Eastwood on July 13, 2019, 02:32:25 PM
So, now all i need to do is build up the 4 stage. "phase shift" things ?
I love it when a plan comes together!
(http://thegreatdeep.ryancalder.co.za/wp-content/uploads/2013/01/hannibalateam.jpg)
I finished the final part of the build last night, so i'll come back to it with fresh eyes perhaps later today to see if I missed anything, then I can hook it up and test it, I will report back how that goes :)
(http://tinypixels.co.uk/forums/images/9887480f70eca7d4ce941e0ac6a49de3/IMG_20190714_070002_small.jpg)
Awesome! Hope it works.
So, now all i need to do is build up the 4 stage. "phase shift" things ?
Yup...that's why I suggested leaving the LEDs and that lower stuff in place! :)
(http://tinypixels.co.uk/forums/images/9887480f70eca7d4ce941e0ac6a49de3/IMG_20190714_070002_small.jpg)
looks like it's "gold knobs" week!
nice scope.
Yay - it works! :) I just need to work on the bias / photocells and leds to get a bit more depth to it, I only used tape around the photo / leds so i'm prob loosing some depth there. I'm going to look forward to playing around with this circuit. :)
hah - it turned out the lack of depth was because my wire jumper was in the chorus mode! lol
ok. so I swapped out the red leds for super-bright white leds - which chews a bit more current but that's ok as the final build will be jack powered. and I like the sound, it's pretty nice and clean. I added a fet to drive the leds and then used my function generator to push through different waveforms with different offsets (bypassing the LFO); I liked the sawtooth best - i played with the waveform symmetry but found it was best in the middle. I was thinking of replacing the LFO with a microcontroller, but that will be for version 2 of my circuit; at the moment i've ordered jacks / case etc and i'm just designing the pcb for it.
Has anyone tried the easyvibe with a bulb? does that give it that "deep vibe" sound? I read a load of forum posts but I'm not sure if it was tried? I'd like to have a switch to toggle between "clean" vibe and "deep" vibe; any pointers? I really like the simplicity of the easyvibe circuit so i'd like to bend that into the "deep" vibe rather than have 2nd complete circuit on the same pcb. Does the bulb give a more linear resistance in the LDR, thus a deeper vibe?
I just tried a couple of 6v wheat bulbs, works much better for me :)
(https://i.postimg.cc/LhgS05b1/2019-08-02-22-55-08.jpg) (https://postimg.cc/LhgS05b1)
Quote from: Mr Eastwood on August 02, 2019, 05:57:31 PM
I just tried a couple of 6v wheat bulbs, works much better for me
Time for a sound clip, perhaps? ;)
Quotedoes that give it that "deep vibe" sound?
There's two variables to play with: the width of the LFO sweep and the offset (ie. shifting the waveform up and down).
You might be able to get the deeper sweep by putting a Schottky diode in series with the opto LEDs. You could try a silicon diode but it might be too much. On the real univibe the lamp drive adjusts both the offset and the sweep at the same time and that deep sweep was set-up using that single adjustment. JC Maillet's viva analog site is one of the few places I've actually seen that drawn up. He also adds an offset adjustment so the offset can be adjusted independently of the sweep width. The EasyVibe edges on the deep sweep by matching up the Diode + 2xLEDs on the bias circuit with the 2xLED on the LED drive circuit. Adding a Schottky will push the LEDs closer to cut-off.
For the lamps you will have to experiment with how many series diodes to add. The opamp in the EasyVibe is probably pushing it to drive lamps.
(https://i.postimg.cc/BLXVPvfW/2019-08-05-00-13-33.jpg) (https://postimg.cc/BLXVPvfW)
(https://i.postimg.cc/9RKNdjcD/2019-08-05-00-14-43.jpg) (https://postimg.cc/9RKNdjcD)
This is my idea for my LFO stage, this little circuit I made uses a microcontroller and 12bit DAC, so potentially I can code it to spit out any custom waveform/s i need. I created a simple triangle waveform to start with. The reason why i've done it like this is I can tweak the offset based on a rate setting. well that's the plan anyway. ;)
[edit: I also need to try some bigger light bulbs and see what they sound like. ]
Aah, the wonders of the uP-controlled LFO! Nice to see other people coming to the party! :)
T.
Hi, I just wanted to share an update on my project; well I got back to this project a few weeks back and decided to put it into a PCB; i've made the first one up and I'm happy with the sound, although I need to re-spin the board as i made a couple of mistakes on it.
(https://i.postimg.cc/zbdhZyZH/2020-06-16-17-37-47.png) (https://postimg.cc/zbdhZyZH)
(https://i.postimg.cc/rDY7mJ1f/2020-06-16-17-39-47.png) (https://postimg.cc/rDY7mJ1f)
ok so here's a phone sound-clip of my "Junivibe" which is basically the Easyvibe but with bulbs and sry for the bad playing! lol
unusually good work Jules ...
from your clip I'm not hearing a "lacking" Vibe sound, which would indicate basic cell range adequacy
you obviously understand the role of OFFSET here, so try getting wider-range cells if you're looking for more phasing
tell us more about your LFO structure if you can ... (some of us are still stuck in the 60's)
I'm curious what a SPEED dependent offset would do for you on a PIC derived waveform ...
good chops btw
Hi Eb7+9 thanks :) well initially i tried the bright white leds then i wanted to try some bulbs, so rather than try and build a circuit to manage the offset i just output a signal from my function gen straight into the base of a mosfet and powered the bulb straight from there; what i found with the function gen was there is a sweet spot of bias where it sounded nice; I recall when i was playing around with the rate I seemed to have to tweak the depth - hence the pic approach where i could adjust the offset based on the rate; shortly afterwards I put the pic LFO on hold until version 2 and I kept the original LFO and switched the mosfet out for a npn; this weekend I need to verify the depth is working correctly as it's seems like I have less control than i recall from my breadboard version, maybe I fried the cheap pots soldering them. the only mistakes on the PCB were the +caps footprints were all backwards, the ldr routing was messed up and the bypass switch holes were about 2mm off along the x axis; luckily it didn't need any trace cuts or bodge wires to resolve. But once I resolve the depth mystery i'll post a final update.
Quote from: Mr Eastwood on June 17, 2020, 03:24:34 PM
... what i found with the function gen was there is a sweet spot of bias where it sounded nice
8)
that's a pretty typical thing to hunt for in any phasor (the so-called bias adjustment) ... and if there's some non-linearity somewhere in the control path that is frequency dependent - could be the driver circuit or devices, could be the bulb's thermal latency preventing from turning off enough and then limiting upper cell range - we can end up missing the fast-action zone near the turn-off point ... and end up having a dull sounding effect // why some phasors have an external color (manual offset) control
well done!
I'm sure the empirical steps would make an interesting study ...
if you don't mind, pls explain to me one thing if you will ...
what is the reason for going thru a DAC ?
have you tried driving the bulb by PWM directly ? ...
I'm just asking out of curiosity,
it's not like there's any risk of inducing zipper noise in the system
maybe there's an advantage I'm not aware of ...
cheers and thx for the detailed reply
Aww late to the party.
I would only use a bulb if the LFO was a replica of the original Uni Vibe - that way you get the same behavior to the original which is what the LED based easy vibe LFO is trying to do with LEDs. Very similar to the Micro Vibe.
What I mean is - a bulb takes longer to dim than it does to light. This is a signature trait of a Uni Vibe. Even though the bulb is getting a steady sine wave, between the photocells and bulb we get slightly different result.
(https://i.postimg.cc/pLjYG8VQ/Wave-Form-Comparison-1.png)
My favorite Easy Vibe is one with six stages. Lush AF :icon_wink:
Ah I'm rambling. Neat project here!!!
-KM
Quote from: Eb7+9 on June 19, 2020, 04:43:23 AM
what is the reason for going thru a DAC ?
have you tried driving the bulb by PWM directly ? ...
I guess I just wanted a really smooth waveform without having to worry about filtering, pwm would be interesting though.
Quote from: Kevin Mitchell on June 19, 2020, 12:08:25 PM
I would only use a bulb if the LFO was a replica of the original Uni Vibe - that way you get the same behavior to the original which is what the LED based easy vibe LFO is trying to do with LEDs. Very similar to the Micro Vibe.
(https://i.postimg.cc/pLjYG8VQ/Wave-Form-Comparison-1.png)
yes sawtooth did sound the best to my ears for the leds - that's a nice explanatory pic ;)
Quote from: Mr Eastwood on June 19, 2020, 06:12:48 PM
pwm would be interesting though.
a couple of things to note when driving analogue parts directly from a digital (pwm) port ... current draw being the first, so a series resistor (trimmer) should be used here - I think 40mA continuous is the limit on an Arduino digital port if I recall correctly ... as far as directly applied voltage goes, the turn-on voltage of, say, an NSL-32 opto-coupler/3mm red LED is around 1.3v and that of a 1.5v/25mA grain of wheat bulb maybe around 1volt ... in a 5-volt system either of these light source choices lead to turn-on voltages (w resistors included) corresponding to duty-cycle values that are far enough away from the beginning zero duty limit, the zipper-noise zone ... in both cases the turn-on threshold forces the system to operate in the more continuous-like part of the digital control range ...
Quote from: Mr Eastwood on June 19, 2020, 06:12:48 PM
Quote from: Eb7+9 on June 19, 2020, 04:43:23 AM
what is the reason for going thru a DAC ?
have you tried driving the bulb by PWM directly ? ...
I guess I just wanted a really smooth waveform without having to worry about filtering, pwm would be interesting though.
If you use PWM, you *don't* have to filter. The LED/bulb/LDR response will do that for you. PWM gives a more linear relationship between signal and brightness when compared to voltage, especially with LEDs - bulbs I'm not so sure, don't use 19th century tech myself ;)
Just make sure the PWM frequency is fast enough that the LDR response is enough to smooth it and off you go.
Hi, just an update to my circuit / pedal; i left it for a while then came back it late last year and re-spun the board with some minor changes and then this year I finally got around to soak testing it for 120 hrs and then making a nice case for it to go in. I was very pleased with the results and look forward to looking at making some other types of pedals. :)
(https://i.postimg.cc/yD7Tc01P/2021-01-10-16-30-53.jpg) (https://postimg.cc/yD7Tc01P)
(https://i.postimg.cc/Xrxk8XX0/20210110-111834.jpg) (https://postimg.cc/Xrxk8XX0)
(https://i.postimg.cc/3yRCb7D0/20210110-114825.jpg) (https://postimg.cc/3yRCb7D0)
Quote from: Mr Eastwood on July 13, 2019, 09:26:50 AM
Hi, i'm in the process of building my first pedal which is the Easyvibe ...
"not bad" for your first pedal ... ;)
congrats!