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Random Source NTO: Sync question
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Random Source NTO: Sync question
windchill
I've been experimenting with the sync input on my R*S NTO. I know it's soft-sync and I've also read that it's a little 'weak' but I've been struggling to get anything useful out of it at all. Using squares, of various widths out of my R*S DUSGs I've only been able to get a slightly glitchy, clicky effect.

When I feed my Verbos CO square into it however I get what I expect, a lovely and slightly chaotic sync; very pronounced and very usable.

What's up here? Is it that the peak to peak voltage is higher on the Verbos?
It seems odd that the Serge circuits aren't triggering the sync very well but my other Euro stuff is.

Any comments are welcome.
Navs
Soft sync can be odd in its response and depending on the frequency relationship, it's not always obvious that it is working.

Have you got a way of measuring the output of the Verbos? Also, is it possible that the NTO wants a bipolar signal? Maybe try to amplify and offset the DSG? If it's not that, if you run the DSG at a frequency higher than the NTO do you get a response?
lohacker
I haven't any tools to measure it, but in my experience the DUSG pulse out is slightly lower in volume compared to to SSG cycle out. My NTO syncs better to SSG than DUSG probably because the NTO need at least 5v to properly sync.
windchill
What I found after further investigation is seriously confusing. All my eurorack VCOs, whether bipolar or unipolar, ranging from 5v PP to around 8v PP trigger a similar sync from the NTO.... but both my DUSGs behave differently even when offset and/or amplified to match the euro VCOs and tuned to the exact same frequency.

I found after experiment that I can get almost the same sort of sync sound out of the NTO from a DUSG, but it's better out of the END output than the PULSE (irrespective of the width!) - and for some reason the DUSG needs to be tuned higher than the Euro VCOs to get the same result.

Put simply, and this is what's really confusing, square waves which are identical on my oscilloscope in terms of voltage, width, polarity, and frequency - are getting different sync results out of the NTO.
In addition the NTO syncs on a saw wave from my Verbos CO, but not one from the DUSG, even when it's amplified to match.

Surely this must somehow be my error - but I'm damned if I can find it.

My head hurts and I'm going to have a lay down in a darkened room for a while :-)
Navs
Good info. Does that sound like some sort of impedance problem? (Asking folks who know about such things). E.g. if you buffer the output of the DSG when using it as the sync master, do you get the same result?

Using the DSG as the slave is a different thing (if I understand your description): you're using it to generate subharmonics, right?

https://navsmodularlab.blogspot.com/2010/11/patch-tips-14-sub-harmonic -division.html
luketeaford
I will try tonight-- I think the square + sync thing is just a slightly strange character and not the "classic" sound I associate with sawtooth syncing.

If I am not mistaken, somewhere deep in Rob Hordijk's modular notes, he mentions that the steepness of the syncing waveform matters and it might also matter how long the sync input is high.

Additionally the DUSGs pulse output stays high for longer than you might expect, so I'd probably use the OUT or BP OUT for syncing. (Not pulse or end)
windchill
Buffering doesn't seem to help.
It's really weird. I just set up the DUSG to generate an identical ramp-up saw to the Verbos CO (same voltage, shape, frequency, polarity) and ran it through a buffered mult (plus it was running through the Dave Jones O'tool, which may also buffer) - and the NTO locks onto the Verbos but not the DUSG.
luketeaford
My previous advice is bad-- I am definitely getting more pronounced and interesting sounds (not like I'd call the classic sync sound though) using the DUSGs END or PULSE outputs, and I can't seem to get sync sounds at all using just the regular out.

This is a very different and cool sound and I'm excited to explore it-- thank you for bringing this to my attention!
teezdalien
It is strange behaviour, I've noticed when syncing one NTO to a second NTO, it hasn't been quite what I'd expect. The most pronounced sync sound occurs when using the sawtooth out to the sync input. The pulse output hardly affects the sound of the synced oscillator...
This is almost the opposite of the behaviour when syncing to a DUSG as described by windchill above, and really quite odd considering the sync input is colour coded red to mean it ideally expects gates/pulses/trigs... hmmm hmmm.....
bedhed3000
I don't have a DUSG, but I was able to get a more or less "classic sync" sound from my NTO by patching in a square wave from a Dixie II. I also tried the Hot output from the SSG with it cycling at audio rate, and got pretty similar results.

Navs wrote:

Soft sync can be odd in its response and depending on the frequency relationship, it's not always obvious that it is working.


The frequency relationship seemed to matter a lot. Bringing the NTO too far apart from the sync oscillator's frequency completely negated the effect.
windchill
luketeaford wrote:
My previous advice is bad-- I am definitely getting more pronounced and interesting sounds (not like I'd call the classic sync sound though) using the DUSGs END or PULSE outputs, and I can't seem to get sync sounds at all using just the regular out.

This is a very different and cool sound and I'm excited to explore it-- thank you for bringing this to my attention!


That confirms my experience as regards the inability to get sync from the DUSGs triangle/saw. Could you do me a big favour and see if you get sync from one of your other Euro saws, like I do?

I'm mystified as to how saws that look identical on a scope can behave so differently.
luketeaford
windchill wrote:
luketeaford wrote:
My previous advice is bad-- I am definitely getting more pronounced and interesting sounds (not like I'd call the classic sync sound though) using the DUSGs END or PULSE outputs, and I can't seem to get sync sounds at all using just the regular out.

This is a very different and cool sound and I'm excited to explore it-- thank you for bringing this to my attention!


That confirms my experience as regards the inability to get sync from the DUSGs triangle/saw. Could you do me a big favour and see if you get sync from one of your other Euro saws, like I do?

I'm mystified as to how saws that look identical on a scope can behave so differently.


Oh wow, it's even weirder now. So if I use the regular saw output of my other NTO, it behaves like I thought (classic sync sounds for all who want them!) and I must have been confusing this with the same kind of saw you can make with the DUSG. The same saw from the DUSG does nothing and doesn't really act much better with either of the other sawtooth waves I have (DPO and Mother 32).

ALSO the behavior using trig out to sync sounds like subharmonics and is completely different than what I think of as "sync"! Great find! Guinness ftw!
Navs
Without seeing the schematics it's going to be difficult to understand what's going on hmmm.....

One last hunch, based on the fact that you're seeing a difference between saw and pulse masters, is that maybe be the NTO wants a thin pulse, i.e. not a gate-like signal. Can you run your master VCO into the trigger input of your DSG, set the DSG for fast rise and fall times and use the envelope output to sync the NTO? Does that work? Another way of doing this might be to run a pulse through a differentiator/high pass filter.

And you say the amount of voltage does not play a role? I modded one of my Plan B Model 15 VCOs for 'harder' soft sync years ago; it only involved a resistor change. Again, we'd need the schematic to know which one is responsible on the NTO ...
windchill
luketeaford wrote:

The same saw from the DUSG does nothing and doesn't really act much better with either of the other sawtooth waves I have (DPO and Mother 32).


Now this is seriously weird! Your DPO and Mother32 saws don't trigger sync on the NTO but my Verbos CO, Mangrove, and Instruo Cs-l do.

But most of all I'm baffled how the NTO can react so differently to apparently identical waves on a scope (voltage, polarity, shape, frequency), even when buffered. Where are the electronics experts when you need them?
Navs
Had a chance to spend some time with a friend's NTO and got an idea of what we're talking about (thanks Erik). It's not the sort of soft sync I was thinking of, namely reversing sync. The NTO resets, like hard sync, right?

So you get discontinuities on the triangle as seen in the 'reset' examples here:

http://www.doepfer.de/a1434.htm

That's also why you can get sounds described by Luke as 'classic sync sounds'. With reversing soft sync, you can't, or at least it's more subtle.

On the master source, we had no problem using a Doepfer CEM VCO but did run into issues using Maths: the EOR was fine, but the envelope was inconsistent.

Our guess was that if the sync circuit does have a passive differentiator/HP filter on its input but no conditioning of the resulting trigger, then the voltage and frequency of the master signal will play a role, i.e. it needs to make it past that part of the circuit intact in order to reset the VCO.

Be interested to hear what you find!
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