Updated SSI2130 VCO Datasheet available...

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DozenCrows
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Re: Updated SSI2130 VCO Datasheet available...

Post by DozenCrows » Sat Feb 13, 2021 1:51 pm

I'm feeding the sync inputs from an LM311 with a 10K pull-up to VREF (2.5V). This is in order to exert some more control over the sync pulse level (the input to the comparator is AC coupled and compared with 2.5V).

This works great for hard sync - I can see 2.5V pulses going into the hard sync pin. But on soft sync, the pulses on the pin peak at around 0.8V. That suggests the 10K pull-up is acting with the 5K internal resistor on soft sync as a voltage divider, so presumably that internal 5K is connected to ground.

Does that sound right?

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Re: Updated SSI2130 VCO Datasheet available...

Post by oldenjon » Sat Feb 13, 2021 2:13 pm

DozenCrows wrote:
Sat Feb 13, 2021 1:51 pm
I'm feeding the sync inputs from an LM311 with a 10K pull-up to VREF (2.5V). This is in order to exert some more control over the sync pulse level (the input to the comparator is AC coupled and compared with 2.5V).

This works great for hard sync - I can see 2.5V pulses going into the hard sync pin. But on soft sync, the pulses on the pin peak at around 0.8V. That suggests the 10K pull-up is acting with the 5K internal resistor on soft sync as a voltage divider, so presumably that internal 5K is connected to ground.

Does that sound right?
Yes, 2.5V*(5k/15k) = 833mV. Easiest thing to do is use a smaller pull-up. I don't understand why you're using AC coupling on the input to the comparator. Why not just have a variable threshold?
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Sat Feb 13, 2021 3:09 pm

DozenCrows wrote:
Sat Feb 13, 2021 1:51 pm
I'm feeding the sync inputs from an LM311 with a 10K pull-up to VREF (2.5V). This is in order to exert some more control over the sync pulse level (the input to the comparator is AC coupled and compared with 2.5V).

This works great for hard sync - I can see 2.5V pulses going into the hard sync pin. But on soft sync, the pulses on the pin peak at around 0.8V. That suggests the 10K pull-up is acting with the 5K internal resistor on soft sync as a voltage divider, so presumably that internal 5K is connected to ground.

Does that sound right?
Figure 11 of the datasheet shows the 5k resistor connected to ground. Your circuit will soft sync WHEN the triangle is falling and below the 833mV that oldenjon calculated and your sync pulse arrives.

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Re: Updated SSI2130 VCO Datasheet available...

Post by J3RK » Fri Feb 19, 2021 12:59 pm

It looks like I'm quite late to the party of people that noticed the SSI2131, but I have to say that is the PERFECT IC!! I can't wait to get my hands on it. I've been thinking about simple cores to add my own wave shapers to, and this looks like just the thing. Plus it's easy to work with. Can't wait to give it a whirl. I think I'm more excited over this one than the 2130.
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Feb 19, 2021 2:57 pm

J3RK wrote:
Fri Feb 19, 2021 12:59 pm
It looks like I'm quite late to the party of people that noticed the SSI2131, but I have to say that is the PERFECT IC!! I can't wait to get my hands on it. I've been thinking about simple cores to add my own wave shapers to, and this looks like just the thing. Plus it's easy to work with. Can't wait to give it a whirl. I think I'm more excited over this one than the 2130.
:tu:

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Re: Updated SSI2130 VCO Datasheet available...

Post by DozenCrows » Sat Feb 20, 2021 7:27 am

Here are some test recordings of the raw outputs I'm getting from my prototype module. This is a 2130 core with a four-way cross-fade between sine, triangle, saw and pulse with additional overtone and sub-octave wave shaping in the same module.

The cross fade needs a bit more tuning - the triangle level is a bit low, and the triangle derived pulse is out of phase with the saw that proceeds it, which causes a dip in amplitude by around 30%.



And here's some on-board wave shaping mixed with the sine wave: an "overtone" a fifth higher or from the octave below, one octave down sub, two octave down sub, then mixing the sub-octaves and finally adding the overtone as well. Note the octave switch I'm using glitches a bit, due to my fumbling fingers.


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Re: Updated SSI2130 VCO Datasheet available...

Post by DozenCrows » Sat Feb 20, 2021 7:57 am

And here's an example of the TZFM with a little arpeggio:

This is using a sine wave as the modulator, first applied to the 2130's sine and gradually increasing the linear FM level, then moving the 2130 up through a few octaves. And then repeating the process with the 2130's triangle wave.

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Tue Feb 23, 2021 12:50 pm

Not sure if we should be posting builds here or not ??? (Happy to delete if inappropriate) - it’s an 8hp eurorack version and I’ve also done an expansion board to add the vc-mixer stuff that plugs in... (this is a bit of a test bed to try out all the options - hence the jumpers). Thanks Neil and SSI - it’s a pretty cool chip....
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Tue Feb 23, 2021 1:16 pm

forestcaver wrote:
Tue Feb 23, 2021 12:50 pm
Not sure if we should be posting builds here or not ??? (Happy to delete if inappropriate) - it’s an 8hp eurorack version and I’ve also done an expansion board to add the vc-mixer stuff that plugs in... (this is a bit of a test bed to try out all the options - hence the jumpers). Thanks Neil and SSI - it’s a pretty cool chip....
Awesome! :bananaguitar: :bacon: :nana:

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Tue Feb 23, 2021 1:23 pm

neil.johnson wrote:
Tue Feb 23, 2021 1:16 pm
forestcaver wrote:
Tue Feb 23, 2021 12:50 pm
Not sure if we should be posting builds here or not ??? (Happy to delete if inappropriate) - it’s an 8hp eurorack version and I’ve also done an expansion board to add the vc-mixer stuff that plugs in... (this is a bit of a test bed to try out all the options - hence the jumpers). Thanks Neil and SSI - it’s a pretty cool chip....
Awesome! :bananaguitar: :bacon: :nana:

Neil
Thanks Neil ! I should have added that all the eagle files will be up on my github once I’ve tested/played with it a bit more and made sure I havent missed anything....

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Re: Updated SSI2130 VCO Datasheet available...

Post by anotherlin » Fri Feb 26, 2021 3:33 pm

It works! At least the preliminary tests I've done.
Hopefully the photo is blurry, so we cannot see how bad is my hand soldering :)
I'll try hot air this week-end as I have a few spare boards along with stencil and ICs.

Project was delayed because of Texas ice storm, my order from Mouser need 2 weeks instead of the 2-3 usual days!
I was able to go up to 76kHz. Sawtooth didn't look pretty at that frequency.

This still needs some thorough testing and validation.
I'll setup the github this weekend.
IMG_2842.jpg
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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Feb 26, 2021 6:08 pm

Nice work anotherlin :tu:

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Sun Feb 28, 2021 2:41 pm

This ssi2130 chip is really impressive !! The tracking and temperature stability is wonderful - I’m getting stable tracking within a cent over 6 octaves.
I’m really happy with it and having loads of fun !

Now that I’ve modelled a lot of the example stuff and the evaluator board in Spice, I’ve got lots of ideas for other modules with it !

There are going to be so many commercial VCOs released in the next few months based off it, I guess !

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Sun Feb 28, 2021 6:15 pm

forestcaver wrote:
Sun Feb 28, 2021 2:41 pm
This ssi2130 chip is really impressive !! The tracking and temperature stability is wonderful - I’m getting stable tracking within a cent over 6 octaves.
I’m really happy with it and having loads of fun !

Now that I’ve modelled a lot of the example stuff and the evaluator board in Spice, I’ve got lots of ideas for other modules with it !

There are going to be so many commercial VCOs released in the next few months based off it, I guess !
It's a game-changer for sure, setting a new price-performance point. I'm all for DIY, but why sweat it when you can get a temperature-compensated expo, triangle oscillator with TZFM, sine shaper, 5-channel VCA mixer, and a couple other things, for a couple of bucks?

In my own testing I have found I can get an SSI2131 (same die) to track to within 1 cent over 11 octaves. At that point you stop worrying about expo performance and focus on different problems.

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Sun Feb 28, 2021 6:22 pm

neil.johnson wrote:
Sun Feb 28, 2021 6:15 pm
It's a game-changer for sure, setting a new price-performance point. I'm all for DIY, but why sweat it when you can get a temperature-compensated expo, triangle oscillator with TZFM, sine shaper, 5-channel VCA mixer, and a couple other things, for a couple of bucks?

In my own testing I have found I can get an SSI2131 (same die) to track to within 1 cent over 11 octaves. At that point you stop worrying about expo performance and focus on different problems.
I stopped at 7 octaves :-) but was shocked at how good the temp compensation is! I was really careful and used a few precision voltage refs to try to keep everything stable.
It’s incredible value for money though.... It’s so compact it opens up some interesting ideas for small eurorack modules! I’m also thinking about some other ways it could be used!

My main complaint is that it feels like cheating :-)

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Sun Feb 28, 2021 6:32 pm

forestcaver wrote:
Sun Feb 28, 2021 6:22 pm
neil.johnson wrote:
Sun Feb 28, 2021 6:15 pm
It's a game-changer for sure, setting a new price-performance point. I'm all for DIY, but why sweat it when you can get a temperature-compensated expo, triangle oscillator with TZFM, sine shaper, 5-channel VCA mixer, and a couple other things, for a couple of bucks?

In my own testing I have found I can get an SSI2131 (same die) to track to within 1 cent over 11 octaves. At that point you stop worrying about expo performance and focus on different problems.
I stopped at 7 octaves :-) but was shocked at how good the temp compensation is! I was really careful and used a few precision voltage refs to try to keep everything stable.
It’s incredible value for money though.... It’s so compact it opens up some interesting ideas for small eurorack modules! I’m also thinking about some other ways it could be used!

My main complaint is that it feels like cheating :-)
I use an automated setup to scan through 0 to 11V and plot the results (pyVisa plus a rack of HP/Agilent test equipment). If you have a good DMM you don't need that precise a voltage source since you measure it at the SSI2130 pins directly. Then the measurement problem turns into needing a good DMM (34401A) and a good frequency counter (53131A).

It only feels like cheating the first time ;)

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Mon Mar 01, 2021 6:13 am

neil.johnson wrote:
Sun Feb 28, 2021 6:32 pm
I use an automated setup to scan through 0 to 11V and plot the results (pyVisa plus a rack of HP/Agilent test equipment). If you have a good DMM you don't need that precise a voltage source since you measure it at the SSI2130 pins directly. Then the measurement problem turns into needing a good DMM (34401A) and a good frequency counter (53131A).

It only feels like cheating the first time ;)
Wow - I’m very jealous! I’m very very much a hobbyist though!

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Re: Updated SSI2130 VCO Datasheet available...

Post by infinitemachinery » Mon Mar 01, 2021 4:48 pm

Here's my breadboard prototype for a SSI2131 VCO. Output is adjusted to 10V p2p.
20210301_213411472_iOS.jpg
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20210301_213423339_iOS.jpg

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Re: Updated SSI2130 VCO Datasheet available...

Post by anotherlin » Mon Mar 01, 2021 5:54 pm

neil.johnson wrote:
Sun Feb 28, 2021 6:32 pm
Then the measurement problem turns into needing a good DMM (34401A) and a good frequency counter (53131A).
I got an even better DMM :) But would definitely need a counter (with a rubidium reference) for checking the frequency stability along with the tuning :)

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Re: Updated SSI2130 VCO Datasheet available...

Post by thx2112 » Thu Mar 04, 2021 12:09 pm

Anyone have any ideas why I'm getting this glitch in the sawtooth (and only the sawtooth, rising or falling)? It happens at exactly the midpoint.

Image

I'm using the VCO IC for an LFO, so the timing cap is 220n.

The glitch is there even when the frequency is well into audible range (like >2kHz).

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Thu Mar 04, 2021 12:44 pm

It's a triangle oscillator, so the sawtooth is generated internally by a waveshaper. Looks like you have persistence turned on. What does a single waveform look like? Could you capture the same signal at audio frequencies? What does it look like with a smaller capacitor? Say 22n or 2n2?

Also, if you could share your schematic and board layout that would help identify any issues there that might be exacerbating the issue. This is something that I haven't seen when playing with the SSI2130, or at least not to the extent that you are seeing.

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Re: Updated SSI2130 VCO Datasheet available...

Post by neil.johnson » Fri Mar 05, 2021 9:00 am

For comparison, here is an SSI2130 sawtooth on the eval board:
ssi2130-sawtooth.png
ssi2130-sawtooth.png (11.58 KiB) Viewed 92 times
It looks better with the noise filter turned on, but the above saw looks pretty convincing.

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Re: Updated SSI2130 VCO Datasheet available...

Post by forestcaver » Fri Mar 05, 2021 10:58 am

thx2112 wrote:
Thu Mar 04, 2021 12:09 pm
Anyone have any ideas why I'm getting this glitch in the sawtooth (and only the sawtooth, rising or falling)? It happens at exactly the midpoint.

I'm using the VCO IC for an LFO, so the timing cap is 220n.

The glitch is there even when the frequency is well into audible range (like >2kHz).
Mine running at lfo speeds if it helps -
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Re: Updated SSI2130 VCO Datasheet available...

Post by thx2112 » Fri Mar 05, 2021 4:10 pm

It looks fine with a smaller cap, but doesn't go as slow as I'd like for an LFO. Maybe 220n is just too big?

Here's a cleaner capture:

Image

And a close-up of the glitch:

Image

The circuit:

Image

SAW goes straight into an opamp gain stage.

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Re: Updated SSI2130 VCO Datasheet available...

Post by thx2112 » Fri Mar 05, 2021 4:11 pm

forestcaver wrote:
Fri Mar 05, 2021 10:58 am
Mine running at lfo speeds if it helps -
What cap value are you using?

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