Technical discussion of DSI synths and their DCO pop

Discussions about anything analog, digital, MIDI, synth technology, techniques, theories and more.

Re: Technical discussion of DSI synths and their DCO pop

Postby Jabberwalky » Tue Jul 14, 2009 2:11 am

Well, Tracy from DSI returned my email linking this thread. Might as well bury this one.


As I mentioned in the previous answer that got posted in the thread, this is common to analog synths with free-running oscillators. When the envelopes are gated on, the waveform might be at any point in the cycle. With a fast attack, that results in an almost vertical leading edge and, hence, a click.

It's most noticeable on an unfiltered triangle wave, especially at low frequencies. The click will change from one note-on to another and be less obvious with more complex sounds and/or as the attack time increases. As far as I know, this is the case with all analog synths and is even preferred by some analog purists. If you're used to digital or soft synths that reset the waveforms to a zero-crossing every time a note is gated on, it can be kind of startling and sound "wrong."

So in this case, an OS update would not fix this. I hope this answers your question, and please don't hesitate to contact us with again regarding your Evolver.
Many thanks,


Tracy

Dave Smith Instruments
User avatar
Jabberwalky
Synth Explorer
Synth Explorer
 
Posts: 2120
Joined: Fri Apr 01, 2005 6:03 pm
Location: Pgh, PA
Gear: Eps16 | An1x | Minikorg700s | Monologue | Maxikorg | Bs2 | Ultranova | Dw8k | Poly61 | Paia9700s | Circuit | PreenFM2
Band: VARIAR

Re: Technical discussion of DSI synths and their DCO pop

Postby AstroDan » Tue Jul 14, 2009 2:20 am

It's such a great product by a great company, I don't think anyone wants to believe it...but that last clip was beyond noticeable.
Too futurist to live.
AstroDan
Junior Member
Junior Member
 
Posts: 226
Joined: Sun Jul 24, 2005 12:05 am
Location: Rogers, Ar

Re: Technical discussion of DSI synths and their DCO pop

Postby Joey » Tue Jul 14, 2009 5:46 pm

i still need an evolver...
No one cares, no one sympathizes,
so you just stay home and play synthesizers.

http://wearereplicants.com
User avatar
Joey
Synth Explorer
Synth Explorer
 
Posts: 1885
Joined: Wed Jan 11, 2006 10:13 pm
Location: Berlin
Gear: 18u Eurorack, Octatrack, Pro2
Band: BLUSH_RESPONSE

Re: Technical discussion of DSI synths and their DCO pop

Postby Jabberwalky » Tue Jul 14, 2009 8:02 pm

Now's the time to get one apparently... :)
User avatar
Jabberwalky
Synth Explorer
Synth Explorer
 
Posts: 2120
Joined: Fri Apr 01, 2005 6:03 pm
Location: Pgh, PA
Gear: Eps16 | An1x | Minikorg700s | Monologue | Maxikorg | Bs2 | Ultranova | Dw8k | Poly61 | Paia9700s | Circuit | PreenFM2
Band: VARIAR

Re: Technical discussion of DSI synths and their DCO pop

Postby Jinsai » Tue Jul 14, 2009 9:28 pm

I respectfully differ with Tracy's assessment of the cause.

The glitching is not solely the result of starting the waveform at an arbitrary leading edge or zero crossing - the screenshots I posted make that quite clear.

If it were just a zero-crossing click, even a tiny bit of slow attack would hide the zero-crossing "click", and the problem would disappear after a single complete cycle of the oscillator.

Additionally, a zero-crossing/leading edge problem would result any time you played notes. I can hammer away on a high C note for 15 minutes and not hear any problems, but if I play 4 low Cs first, the first 4 Cs I play will glitch, gar-on-teed.

I believe this is the result of the oscillators "retaining" the pitch of previously played notes. On new note presses, each voice starts to play the last pitch it played and then changes to the new pitch later. In the case of the screenshot I posted, the change is occurring 24 milliseconds after the note is triggered. That's long enough to hear the previous note start - this becomes clear after listening to the MP3, if not from the images.

This is why once the voices "cycle" to higher notes the "clopping" isn't heard.

I don't know whether anything can be done about it even in theory without knowing more about how the synth and chips that power it are designed. I am reluctant to speculate as to possible options.

I contacted DSI and pointed them at my links. I'll let you know if they respond.
--
"A musician is someone who's heard a lot of music" - Pierre Boulez
User avatar
Jinsai
Junior Member
Junior Member
 
Posts: 131
Joined: Sat Apr 07, 2007 12:07 am
Location: San Francisco, CA
Gear: Alesis Ion
JX-3P w/Kiwitechnics
Nord Lead 2
Poly Evolver Keyboard
Prophet 12
Tempest
Assorted basses, guitars, software
Band: Sid Luscious and The Pants

Re: Technical discussion of DSI synths and their DCO pop

Postby Jabberwalky » Tue Jul 14, 2009 11:20 pm

I don't think dave answers the support emails anymore, which makes sense. I'm really thinking it's a dead issue Jinsai. Perhaps if I'd bought an evolver when they came out this would've been fixed :)
User avatar
Jabberwalky
Synth Explorer
Synth Explorer
 
Posts: 2120
Joined: Fri Apr 01, 2005 6:03 pm
Location: Pgh, PA
Gear: Eps16 | An1x | Minikorg700s | Monologue | Maxikorg | Bs2 | Ultranova | Dw8k | Poly61 | Paia9700s | Circuit | PreenFM2
Band: VARIAR

Re: Technical discussion of DSI synths and their DCO pop

Postby masstronaut » Tue Jul 14, 2009 11:39 pm

Oh he'll definitely know about the discussion though.

I am following with interest even though I don't consider this to be a problem with what is an excellent versatile synthesizer.
masstronaut
Senior Member
Senior Member
 
Posts: 756
Joined: Fri Nov 10, 2006 10:26 pm

Re: Technical discussion of DSI synths and their DCO pop

Postby adamstan » Wed Jul 15, 2009 5:43 am

So it seems, that Evo sends gate signal to EG BEFORE setting oscillators pitch CV. That looks like a software issue.
Man with a tape recorder | Living in the '80s ;-)
User avatar
adamstan
Active Member
Active Member
 
Posts: 511
Joined: Tue Aug 22, 2006 2:56 pm
Location: Poland
Real name: Adam
Gear: Yamaha 2xDX7II|QY-70|PSR-S750|PSR-2000|TYROS|Electone D85|Electone E50
B5 DIY polysynth
KORG Poly61
Vermona DRM
Solton Programmer 24
LEMA EDD-5

Re: Technical discussion of DSI synths and their DCO pop

Postby Stab Frenzy » Wed Jul 15, 2009 6:08 am

adamstan wrote:So it seems, that Evo sends gate signal to EG BEFORE setting oscillators pitch CV. That looks like a software issue.

I concur with your diagnosis of the cause of the issue, but I don't think I could say one way or another whether it can be solved in software. It might be something to do with the order in which the controls from the microprocessor are multiplexed which might be hardware related.

I'd be keen to see what it looks like when you have the amp halfway open before the start of the attack, to make sure the 'clop' is the same frequency as the preceding note and not an artifact of some kind.
User avatar
Stab Frenzy
Moderator
Moderator
 
Posts: 9723
Joined: Tue Jun 06, 2006 5:41 pm
Location: monster island*
Gear: Eurorack, RYTM, Ultranova, many FX

Re: Technical discussion of DSI synths and their DCO pop

Postby Jinsai » Wed Jul 15, 2009 8:07 am

Stab Frenzy, that's an excellent idea - I'll do some testing tomorrow and post some screenshots again.
--
"A musician is someone who's heard a lot of music" - Pierre Boulez
User avatar
Jinsai
Junior Member
Junior Member
 
Posts: 131
Joined: Sat Apr 07, 2007 12:07 am
Location: San Francisco, CA
Gear: Alesis Ion
JX-3P w/Kiwitechnics
Nord Lead 2
Poly Evolver Keyboard
Prophet 12
Tempest
Assorted basses, guitars, software
Band: Sid Luscious and The Pants

Re: Technical discussion of DSI synths and their DCO pop

Postby Jinsai » Thu Jul 16, 2009 7:06 pm

DSI seems to be holding the line about free-running oscillators and "character", at least in the reply I received today.

My impression is they aren't looking at the screenshots or listening to the problem, or if they are, it's not something they can fix, and their response is simply "that's the way it is".

I'm guessing the Curtis chips are clocked in such a way they simply don't respond immediately to pitch changes, and instead take some number of clock cycles to change; or as Bob from the Yahoo Evolver Group said:

...the waveform photo tells the story. The glitch is from a DC offset being added (or not removed) from the waveform after the pitch shift up the octaves. If it is from an incorrectly summed or calibrated keyboard shift, it is possible the evolver's software can be corrected. However, the more likely case is that it is an artifact of the analog circuit that has not been offset by design [emphasis mine] and does not have a pot to tweak, it may be a permanent design "feature" that we have to live with and work around


I still need to do some more tests to see.

I do find this pretty disappointing - both the problem and DSI's response. This isn't "character" like something going out of tune or distorting or how the filter sounds. This is a serious issue with either the chips or the software that negatively affects the way the synth works.
--
"A musician is someone who's heard a lot of music" - Pierre Boulez
User avatar
Jinsai
Junior Member
Junior Member
 
Posts: 131
Joined: Sat Apr 07, 2007 12:07 am
Location: San Francisco, CA
Gear: Alesis Ion
JX-3P w/Kiwitechnics
Nord Lead 2
Poly Evolver Keyboard
Prophet 12
Tempest
Assorted basses, guitars, software
Band: Sid Luscious and The Pants

Re: Technical discussion of DSI synths and their DCO pop

Postby masstronaut » Thu Jul 16, 2009 7:32 pm

Jinsai wrote:I'm guessing the Curtis chips are clocked in such a way they simply don't respond immediately to pitch changes, and instead take some number of clock cycles to change;

Do they pop when pitch is rapidly modulated using an LFO, for instance? I don't think so.
masstronaut
Senior Member
Senior Member
 
Posts: 756
Joined: Fri Nov 10, 2006 10:26 pm

Re: Technical discussion of DSI synths and their DCO pop

Postby Jinsai » Thu Jul 16, 2009 10:35 pm

Good point. Perhaps it's just pitch changes from the keyboard...
--
"A musician is someone who's heard a lot of music" - Pierre Boulez
User avatar
Jinsai
Junior Member
Junior Member
 
Posts: 131
Joined: Sat Apr 07, 2007 12:07 am
Location: San Francisco, CA
Gear: Alesis Ion
JX-3P w/Kiwitechnics
Nord Lead 2
Poly Evolver Keyboard
Prophet 12
Tempest
Assorted basses, guitars, software
Band: Sid Luscious and The Pants

Re: Technical discussion of DSI synths and their DCO pop

Postby masstronaut » Fri Jul 17, 2009 6:11 pm

Yes there's no way the oscillators are that slow to respond to pitch changes. Clearly they can do it very quickly indeed.

Also if it was to do with fast envelopes where the oscillator is in its cycle I would expect the amount of popping to vary more or less randomly from note to note. As you say, that's not how it happens.

In addition wouldn't the VCAs always have a slight lad* when opening and provide a less than instantaneous ramp up to level even with very fast envelopes that would prevent 'popping'?

Either way this does not account for 24ms of glitch. So what the heck is going on with that?

* that should read 'lag' obviously. lol.
Last edited by masstronaut on Sat Jul 18, 2009 10:53 am, edited 1 time in total.
masstronaut
Senior Member
Senior Member
 
Posts: 756
Joined: Fri Nov 10, 2006 10:26 pm

Re: Technical discussion of DSI synths and their DCO pop

Postby Stab Frenzy » Sat Jul 18, 2009 5:11 am

masstronaut wrote:Either way this does not account for 24ms of glitch. So what the heck is going on with that?

The theory that's been suggested by a few people is that the processor sends out the pitch control information after it sends out the envelope information, so the envelope opens and you hear a brief bit of the oscs at the old pitch, before it clunks up to the new pitch.
User avatar
Stab Frenzy
Moderator
Moderator
 
Posts: 9723
Joined: Tue Jun 06, 2006 5:41 pm
Location: monster island*
Gear: Eurorack, RYTM, Ultranova, many FX

PreviousNext

Return to General Synthesizers

Who is online

Users browsing this forum: No registered users and 23 guests