sinusoidal wavefolder

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hexinverter
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Post by hexinverter » Sun Oct 08, 2017 12:58 pm

guest wrote:great work! ive been digging into the circuit a bunch more lately, as im working on a complete module version. i settled on 47pF in the feedback path, just to keep the frequencies up to 20kHz. i also used a capacitor across R9 in your schematic, to keep the impedances matched.

also, thanks for pointing out the excessively high drive. the 100k to +12V is incorrect, and was meant to go to ground.
Oooh, I hadn't thought of impedance matching those nodes! Thanks. Seems obvious now, I guess it could also likely add some distortion to the overall function. Raising the cutoff seems like a good idea as well. Correct me if I'm mistaken but it could have a pretty noticeable impact when modulating with higher frequency PM or FM as well? :hmm:

Very cool, looking forward to seeing your module! :goo:
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guest
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Post by guest » Sun Oct 08, 2017 1:28 pm

there are definitely harmonics going well above 20kHz with PM, so it depends upon your hearing. i cant hear anything above 18kHz anymore, so i probably couldnt tell the difference. sometimes there are sonic effects if the signal is passed through other modules or mixers. for example, although you cant hear higher frequencies, they can still distort and overload amplifiers and then you hear those effects.

if you put a pot or CV on that 100k (200k in your case) resistor, you can adjust volume into clipping, or just modulate the amplitude.
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wavefold
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Post by wavefold » Mon Oct 09, 2017 8:58 am

loving how this sounds, keeping an eye on this, definitely :eyes:
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Post by daynehacks » Mon Oct 09, 2017 12:37 pm

Anything ever happen with the possibility of a DIY euro module??

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guest
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Post by guest » Mon Oct 09, 2017 1:22 pm

the main difficulty with a DIY is the super small transistors involved. i was talking with synthcube about having that portion of the circuit be put in production, but i havent heard back in a while.
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slow_riot
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Post by slow_riot » Mon Oct 09, 2017 1:45 pm

I've been looking for a reason to use a bunch of OTAs and this is quite a good use for them, getting some matching between diff pairs and simplifying the output.

U can change the current amplifier driving the bias nodes to use single small resistor pushing a larger reference current into an opamp feedback network with all the PNPs in parallel. Personal taste and availability of board space notwithstanding.

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Post by guest » Mon Oct 09, 2017 2:35 pm

quick update: just heard back from synthcube, and boards should be getting in soon.

slow riot: whats your plan with the OTAs? are you using the inidividual diffpair configuration (rather than the one i used with all the emitters tied together)?
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Post by slow_riot » Mon Oct 09, 2017 3:57 pm

Image

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guest
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Post by guest » Mon Oct 09, 2017 11:03 pm

thanks for posting that up.

one thing i thought was a bit nicer about the diffpair versions as compared to the stack of emitter coupled transistors, was that biasing was easier. you didnt need to use current mirrors, and could drive it single-endedly. is there an advantage to the differential drive youve shown? i could imagine that it would improve symmetry, and maybe improve accuracy as the impedance seen by the diffpairs are equal.
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Permette
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Post by Permette » Tue Nov 07, 2017 4:41 am

Looking forward to seeing it available at Synthcube.
Wonderfull work !
Thanks for that.

Cheers

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Rex Coil 7
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Post by Rex Coil 7 » Sat Nov 18, 2017 12:47 am

~wooosh~

the sound of this entire thread going right over my head

neato sounds, pretty pictures on the scopes

neato and pretty is good things
You mean this place has hot chicks, morning drinking, and free vomit? ... I'm all in!
5U PROJECT - (skip pages 4 through 6, boring junk) ... viewtopic.php?t=78836&highlight=
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trip
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Post by trip » Thu Jan 11, 2018 12:46 pm

I made another rev of my 4hp board a while back, the 12v instead of ground going to that node was what was causing my clipping issues as well. I made a pcb panel for it so it can be a permanent fixture in my case as well, it turned out quite nicely. Getting some amazing timbres out of this thing, huge thanks to guest for sharing his work!!

Image

The two big pots are the attenuators for the incoming signals and the small one is the phase offset. Which may seem a bit backwards, but it was difficult to fit 3 full sized pots and all the components on one pcb - I also assumed that the initial phase would be more of a set and forget type parameter, but now I often find myself reaching for it... I'm happy with this though, any of the additions I would have made would have made it an exponentially more complex project, and I figure guest still has a full module coming down the line?

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Post by guest » Thu Jan 11, 2018 4:01 pm

thanks for sharing, your module looks awesome. how much phase angle does your phase knob adjust? this is one of the things i wasnt sure about for the module im doing (all finalized, going into production real soon). i settled on +/-180degrees, with a solder jumper for +/-800 degrees.
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goldenhours
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Post by goldenhours » Thu Jan 11, 2018 4:57 pm

This is all very nice. Following to see where it's going.

trip
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Post by trip » Fri Jan 12, 2018 6:30 am

My pot gives +/- 180 degrees of phase angle, it's really nice to push the phase mod into and out of saturation to give things more edge.

Was so busy putting the thing together I didn't check the features fully and realised I'm not getting folds anymore :doh: Going back over to see what else I might have changed from the last rev that could have caused this.

I'm excited to see what you've come up with for the final version!

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Post by trip » Fri Jan 12, 2018 6:39 am

Ah I caught it, pin 5 J2 - the top of the 51k resistor network is missing a connection to vcc.

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guest
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Post by guest » Sun Mar 24, 2019 6:39 pm

this finally made it into a module by WOMS (west oakland music systems). i put a few quick videos up:

[video][/video]

there are more at the oml channel:

https://www.youtube.com/channel/UCIvT8t ... _3h1PPwNOA
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Bartimaeus
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Post by Bartimaeus » Sun Mar 24, 2019 7:09 pm

Did this ever make it to Synthcube? I'm not finding anything when I search Sinulator.

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diophantine
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Post by diophantine » Sun Mar 24, 2019 7:24 pm

Yes, I just noticed this thread for the first time - has anything been made available DIY? It looks awesome!

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guest
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Post by guest » Sun Mar 24, 2019 10:19 pm

synthcube will be getting it soon, but dont know the exact time frame. right now they have the very-DIY breakout board for the sinecore modulator. the breakout board has approximately half as many folds, but you can stack two of them in parallel to get the same depth as the sinulator module.
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jorg
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Post by jorg » Mon Mar 25, 2019 10:04 am

WOW! Great job!

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cygmu
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Post by cygmu » Mon Mar 25, 2019 11:11 am

I love this circuit so much. Finding out about it here sent me down a huge Barrie Gilbert rabbit hole which has been some of the most enjoyable circuit-studying I've done. Thank you guest for your amazing work here.

A small clarification: on the triangle sine shaping video it is stated that turning up the gain gives the 2nd, 3rd, ... , 6th harmonics, but I think it's actually the 3rd, 5th, ... 11th harmonics, as compared to the fundamental, right? I can't see a way to get even harmonics by shaping a triangle wave with this circuit.

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Post by jorg » Mon Mar 25, 2019 1:05 pm

Barrie Gilbert is the soul of analog electronics. Most of our analog synth technology would not exist without him. And I believe he's still alive and well!

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Post by guest » Mon Mar 25, 2019 2:13 pm

cygmu wrote:A small clarification: on the triangle sine shaping video it is stated that turning up the gain gives the 2nd, 3rd, ... , 6th harmonics, but I think it's actually the 3rd, 5th, ... 11th harmonics, as compared to the fundamental, right?
hey cygmu, thanks so much for catching this. you are right here. i updated the blurb on the video with the correction.
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cygmu
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Post by cygmu » Mon Mar 25, 2019 4:17 pm

Thinking a bit more... can you get even harmonics from a triangle by changing the offset? I guess the gain would then take you through all the evens. Is that right?

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