Ringdroid - a sample and hold ring modulator

[~arph]

Damn, looks like Im a day late. I'd love one or two boards dude! I'll pay $10.00 each, get more made

Let's see how this run turns out and if the board needs improvements. If there is enough interest or if I need more, we'll do another run.

[moosapotamus]

I'm in for one when you do the next run.

~ Charlie

[tyronethebig]

Me too!

[~arph]

Great guys, I'm flattered by all the interest in this design.

As soon as the boards get here I'll drop everyone a note with the final price.

[pappasmurfsharem]

Is this a typical Oberheim/maestro style S/H circuit?

If so what tranny did you use for the noise source?

I didn't see one in the schematic, but I am also schematically challenged.

[~arph]

In principle the same, it samples a noise source and stores it with a cap, but the circuit is different. For startes it uses a 4066 as a switch and CMOS NAND gates for the oscillator, but the unique thing about this circuit is that it uses the guitar input signal as the noise source. As a result the frequency band of the modulation oscillator narrows as the signal decays.  There are no trannies in this circuit! 

[Ben N]

Count me in for one of the next batch, too, Arnoud. I think that's the most musical ringmod I've ever heard--I can actually see myself using it. I can take shipment in Israel (preferred) or New Jersey.
Ben

[~arph]

FYI,

I'm still waiting for the boards.. shipped from hong kong 12th.
EDIT: I'm having another listen to my video for my enjoyment  
EDIT2: Btw, I have a list of six boards for a possible next run already. Need to verify this run before I put in another order.

Oh and I missed out on Dingus's request so he's getting one too from the current run ( no spare board for me )

[defaced]

Put me down for two on the possible second run. 

[~arph]

Noted.. I consider that *possible* run full too now 

[~arph]

Here is a link to the build documentation:

https://dl.dropbox.com/u/1849818/published_images/ringdroid_v201301.pdf

[Dingus]

...and I missed out on Dingus's request so he's getting one too from the current run ( no spare board for me )

Awww, thanks man!!       This place really shows the love!

[~arph]

Thanks,

I can't wait for the boards to arrive! I just learned that it took seven days for them to depart from hongkong 

[earthtonesaudio]

Might be cool to add an adjustable DC offset at or near IC2A, so that the center frequency would drift either up or down as the note decays.

[~arph]

Should be after IC2A and buffered from it, keeping IC2A biased at 4.5V gives us the maximum range of VCO frequencies. If we meddle with the biasing of that stage we can start to clip the signal, meaning we get a dominant frequency in the VCO and it will appear less random. Can be fun, but it makes the pedal less musical in my opinion . I tried it biased near 0V with more gain too, so the oscillator will go down to tremolo frequencies when the note decays, it's fun, but very limited in use, expect no good ringtone sounds.

The center frequency is determined by two things. One being the bias voltage of IC2A and the other the value of the frequency pot. With the frequency pot you can adjust the center frequency, so basically what you ask for is already provided by the freq. pot.

Unless you mean applying the envelope signal as a DC offset. This would indeed drift the center frequency. You'll get a combination of the ringdroid and this:

 

 

One fun mod is (dis)charging cap on a momentary footswitch. So you can switch between the output of IC2A or the (dis)charging cap. I tried it and this sounds really good. With som extra switches and a pot you can even select between charging or discharging, set the speed at which that happens AND choose between a stepped ramp or a continuous ramp.

One could go as far as replacing the bypass switch with a latched version of the above. So that on switch off the oscillator slows to a stop. (this would require the signal bypass jumper to be installed)

[bluesdevil]

That's great ~arph!! Late to the party and missed out on a PCB this round, but please put down for one if you get another batch done.
I could even etch my own if a layout surfaces before then.... I hope to build it regardless!

[earthtonesaudio]

You could do away with the dual op-amp by:
-Giving IC1A a gain of 7.8 instead of unity (use R8/R7 ratio)
-Increase R9 to about 780k to preserve IC4C output levels
-Replacing IC2A and IC2B with jumpers.
-put a 1/7.8 voltage divider before IC4B to drop the signal level back to unity.

[~arph]

That's great ~arph!! Late to the party and missed out on a PCB this round, but please put down for one if you get another batch done.
I could even etch my own if a layout surfaces before then.... I hope to build it regardless!

I will put you in the list. It's a complicated double sided layout, so home etching will be hard.

[~arph]

You could do away with the dual op-amp
-Replacing IC2A and IC2B with jumpers.

That would only work if the vco in pin on the pll has a very high input impedance, which I don't recall it is. the buffer ic2b is needed to keep the sample cap C4 from discharging.. You could replace it with a fet and a diode plus resistor.. But then you have about the same footprint as a dual opamp

[bluesdevil]

Many thanks Arnoud, looking forward to it.