Casio CZ/ VZ/ FZ - Pro Series

CZ1_LPF.jpg

On Thu, Mar 12, 2015 at 02:00:25PM -0700, forums@... [CZsynth] wrote:
> Opened up my new CZ1 tonight and was somewhat surprise to see two LPFs in this all digital synth.
>  Will these be LPFs for audio or some sort of signal filtering? If they are for audio, Im wondering if they sound good enough to tap into and expose on the facia usings a pair of knobs..
>  

They follow the DAC output and knock off the sharp edges.  They won't act like a subtractive synth VCF, but you might be able to tweak the overall tone of the instrument slightly.

-- 
Gordonjcp MM0YEQ

On Sat, Mar 14, 2015 at 07:21:18AM -0700, smw-mail@... [CZsynth] wrote:
> I would look it up in the service manual before tweaking it. Sometimes those pots are finely tuned.

It's not that fussy.  It's just the 17kHz rolloff on the output of the DAC.

You probably won't hurt anything by fiddling with it, but you won't make a hell of a lot of difference to the sound either.  If you want an actual LPF like on an analogue synth, you'll need to go outboard :-)

-- 
Gordonjcp MM0YEQ

On Sat, Mar 14, 2015 at 02:30:38PM +0000, gordon@... [CZsynth] wrote:
> On Sat, Mar 14, 2015 at 07:21:18AM -0700, smw-mail@... [CZsynth] wrote:
> > I would look it up in the service manual before tweaking it. Sometimes those pots are finely tuned.
> 
> It's not that fussy.  It's just the 17kHz rolloff on the output of the DAC.
> 
> You probably won't hurt anything by fiddling with it, but you won't make a hell of a lot of difference to the sound either.  If you want an actual LPF like on an analogue synth, you'll need to go outboard :-)
> 

And on that note, if you want to build a simple outboard VCF you could do worse than to build a clone of the Steiner Synthacon filter.  Its performance is pretty horrible - it suffers badly from control voltage breakthrough on the output *and* input voltage breakthrough on the control, so its actual cutoff frequency is dependent on the input signal!  However, it has an extremely good performance-to-fiddly-bits ratio.

Here's a prototype clone I made, built "dead bug" style on a bit of scrap PCB
http://gjcp.net/~gordonjcp/filter.jpg

It sounds like this (be careful! My early version had fairly uncontrollable resonance):
http://gjcp.net/~gordonjcp/filtertest.ogg

And it has highpass and lowpass *inputs* - not outputs - so you can use it as a sort of frequency-variable crossfader, like this:
http://gjcp.net/~gordonjcp/mp3s/hilow.ogg

Here's a good writeup:
http://yusynth.net/Modular/EN/STEINERVCF/index-v2.html

-- 
Gordonjcp

Don't touch them, they are calibrated to remove the sampling frequency components


Inviato dagli anelli di saturno

> On 14 Mar 2015, at 15:46, gordon@... [CZsynth] <CZsynth@yahoogroups.com> wrote:
>
> On Sat, Mar 14, 2015 at 02:30:38PM +0000, gordon@... [CZsynth] wrote:
> > On Sat, Mar 14, 2015 at 07:21:18AM -0700, smw-mail@... [CZsynth] wrote:
> > > I would look it up in the service manual before tweaking it. Sometimes those pots are finely tuned.
> >
> > It's not that fussy. It's just the 17kHz rolloff on the output of the DAC.
> >
> > You probably won't hurt anything by fiddling with it, but you won't make a hell of a lot of difference to the sound either. If you want an actual LPF like on an analogue synth, you'll need to go outboard :-)
> >
>
> And on that note, if you want to build a simple outboard VCF you could do worse than to build a clone of the Steiner Synthacon filter. Its performance is pretty horrible - it suffers badly from control voltage breakthrough on the output *and* input voltage breakthrough on the control, so its actual cutoff frequency is dependent on the input signal! However, it has an extremely good performance-to-fiddly-bits ratio.
>
> Here's a prototype clone I made, built "dead bug" style on a bit of scrap PCB
> http://gjcp.net/~gordonjcp/filter.jpg
>
> It sounds like this (be careful! My early version had fairly uncontrollable resonance):
> http://gjcp.net/~gordonjcp/filtertest.ogg
>
> And it has highpass and lowpass *inputs* - not outputs - so you can use it as a sort of frequency-variable crossfader, like this:
> http://gjcp.net/~gordonjcp/mp3s/hilow.ogg
>
> Here's a good writeup:
> http://yusynth.net/Modular/EN/STEINERVCF/index-v2.html
>
> --
> Gordonjcp
>
>

On Sat, Mar 14, 2015 at 10:38:00PM +0000, Daniel Boles db0451@... [CZsynth] wrote:
> all competently designed digital synths, assuming they don't use
> oversampling and digital filtering - have analogue reconstruction lpfs to
> get rid of high-frequency imaging (aliasing is a misnomer here and in most
> other cases). these filters are non-resonant and thoroughly uninteresting
> for anything except protecting tweeters and precluding intermodulation
> distortion. i cannot stress enough how mundane a reconstruction filter is -
> and how a little research in digital audio would reveal it as one of the
> simplest concepts therein.

I'm surprised that they use a little ferrite LC filter, quite honestly.  Surely that had to be more expensive than an RC filter and an opamp?  They were really really common in digital synths and samplers at one time, but you don't see them now.

-- 
Gordonjcp MM0YEQ

Many synth of the same era use LC filters to take away the sampling frequency from the signal, is the most efficient way, no distortion (for those little signals) and no noise added by other opamp or transistor stages and easy to tune


Inviato dagli anelli di saturno

> On 16 Mar 2015, at 09:11, gordon@... [CZsynth] <CZsynth@yahoogroups.com> wrote:
>
> On Sat, Mar 14, 2015 at 10:38:00PM +0000, Daniel Boles db0451@... [CZsynth] wrote:
> > all competently designed digital synths, assuming they don't use
> > oversampling and digital filtering - have analogue reconstruction lpfs to
> > get rid of high-frequency imaging (aliasing is a misnomer here and in most

> > other cases). these filters are non-resonant and thoroughly uninteresting
> > for anything except protecting tweeters and precluding intermodulation
> > distortion. i cannot stress enough how mundane a reconstruction filter is -
> > and how a little research in digital audio would reveal it as one of the
> > simplest concepts therein.
>
> I'm surprised that they use a little ferrite LC filter, quite honestly. Surely that had to be more expensive than an RC filter and an opamp? They were really really common in digital synths and samplers at one time, but you don't see them now.
>
> --
> Gordonjcp MM0YEQ
>
>

On Mon, Mar 16, 2015 at 10:41:25AM +0100, Carlo carlojazz@... [CZsynth] wrote:
> Many synth of the same era use LC filters to take away the sampling frequency from the signal, is the most efficient way, no distortion (for those little signals) and no noise added by other opamp or transistor stages and easy to tune
> 

They can't have been cheap though, compared to a conventional active lowpass filter.  Maybe the lower parts count (ie. less board-stuffing) made up for it.

-- 
Gordonjcp MM0YEQ

This is the situation now where active components are very cheap, probably in 80-90 the most expensive components were the Ics compared to a ferrite inductor the last was the cheaper solution.


Inviato dagli anelli di saturno

> On 16 Mar 2015, at 19:11, gordon@... [CZsynth] <CZsynth@yahoogroups.com> wrote:
>
> On Mon, Mar 16, 2015 at 10:41:25AM +0100, Carlo carlojazz@... [CZsynth] wrote:
> > Many synth of the same era use LC filters to take away the sampling frequency from the signal, is the most efficient way, no distortion (for those little signals) and no noise added by other opamp or transistor stages and easy to tune
> >
>
> They can't have been cheap though, compared to a conventional active lowpass filter. Maybe the lower parts count (ie. less board-stuffing) made up for it.
>
> --
> Gordonjcp MM0YEQ
>
>