[sdiy] Analog envelope generator offset
Harald
sdiy at haraldswerk.de
Sat Nov 1 17:23:05 CET 2014
Thanks Harald
Am 01.11.2014 um 17:17 schrieb Jason Proctor:
> mirrored here --
>
> http://www.redfish.net/adar0708part_957.png
>
> needless to say if i'm breaking any rules by doing this, i'll take it
> down :-)
>
>
> On Sat, Nov 1, 2014 at 9:08 AM, Matthias Herrmann
> <matthias.herrmann at fonik.de <mailto:matthias.herrmann at fonik.de>> wrote:
>
> i think you have to be logged into muffwiggler :(
>
> matthias
>
>
> > -----Ursprüngliche Nachricht-----
> > Von: Harald [mailto:sdiy at haraldswerk.de <mailto:sdiy at haraldswerk.de>]
> > Gesendet: Samstag, 1. November 2014 17:05
> > An: Matthias Herrmann; synth-diy at dropmix.xs4all.nl
> <mailto:synth-diy at dropmix.xs4all.nl>
> > Betreff: Re: [sdiy] Analog envelope generator offset
> >
> > ...and i can not see or find it.
> >
> > Am 01.11.2014 um 15:51 schrieb Matthias Herrmann:
> > > no problem here. it is a png file...
> > >
> > > matthias
> > >
> > >> -----Ursprüngliche Nachricht-----
> > >> Von: synth-diy-bounces at dropmix.xs4all.nl
> <mailto:synth-diy-bounces at dropmix.xs4all.nl> [mailto:synth-diy-
> <mailto:synth-diy->
> > >> bounces at dropmix.xs4all.nl <mailto:bounces at dropmix.xs4all.nl>]
> Im Auftrag von Harald
> > >> Gesendet: Samstag, 1. November 2014 15:04
> > >> An: synth-diy at dropmix.xs4all.nl
> <mailto:synth-diy at dropmix.xs4all.nl>
> > >> Betreff: Re: [sdiy] Analog envelope generator offset
> > >>
> > >> I am sorry but i can't find or see the schematic. Not on
> Muff's and not
> > >> on Ian's site.
> > >>
> > >> Harald
> > >>
> > >> Am 01.11.2014 um 14:08 schrieb Tom Wiltshire:
> > >>> That's very neat, at least for a simple AD/AR case. And it works
> > >> beautifully. I've tried it in LTspice.
> > >>>
> > >>> Can you explain a bit more how it works please? I sort-of get
> it in
> > >> general (I think) but I'd like to properly understand it, if
> I'm to
> > adapt
> > >> it for my ADSR situation.
> > >>>
> > >>> What I think is going on is something like this:
> > >>> Imagine a gate signal going into the non-inv input of U1B.
> U1B provides
> > a
> > >> Gate-signal-with-gain at its output. The cap then charges
> towards this
> > >> boosted voltage level. Once the cap voltage gets within one
> diode drop
> > of
> > >> the charging level, the diodes around U1B start to conduct,
> and the gain
> > on
> > >> the Gate drops towards unity.
> > >>>
> > >>> I don't really get how the gain around U1B is limited to
> the-gate-plus-
> > >> one-diode-drop, although I can see that it's clearly because
> of the
> > back-
> > >> to-back diodes in the feedback loop. I just don't see how.
> This is where
> > a
> > >> lack of formal training in any of this stuff starts to be a
> pain in the
> > >> neck - again!. Still, I'm always learning.
> > >>>
> > >>> Thanks,
> > >>> Tom
> > >>>
> > >>>
> > >>> On 31 Oct 2014, at 18:36, Ian Fritz <ijfritz at comcast.net
> <mailto:ijfritz at comcast.net>> wrote:
> > >>>
> > >>>> I just posted a typical scheme at Muff's:
> > >>>> http://www.muffwiggler.com/forum/viewtopic.php?p=1708948#1708948
> > >>>> No idea why other designs don't worry about this ... used to
> drive me
> > >> crazy. This solution was published in EN many years ago ... can't
> > remember
> > >> offhand who first came up with it.
> > >>>>
> > >>>> Clipping the envelope to zero when it gets to a small value
> also makes
> > >> sense.
> > >>>>
> > >>>> Ian
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>> At 10:38 AM 10/31/2014, Tom Wiltshire wrote:
> > >>>>> Ian, Harald,
> > >>>>>
> > >>>>> Ok, thanks. That sounds exactly like what I'm looking at. The
> > relevant
> > >> part of my circuit is very similar to this one, though I've
> done the
> > >> control logic very differently. The offset compensation is
> pretty much
> > the
> > >> same too.
> > >>>>>
> > >>>>> http://www.cgs.synth.net/modules/cgs78_env.html
> > >>>>>
> > >>>>> Please correct me if I'm wrong, but what I understand is the
> > following:
> > >>>>> As the cap decays towards zero, the voltage across it drops
> below the
> > >> 0.5V or so forward voltage of the diode, and the diode
> basically stops
> > >> conducting, or conducts only very slightly. This means that
> the final
> > part
> > >> of the RC curve doesn't use R, but rather R+some big diode
> resistance.
> > This
> > >> messes up the curve and makes the final portion take
> > aaaaagggggeeeeessss!
> > >>>>>
> > >>>>> So how can one prevent the diode from shutting off when we
> still need
> > >> it, without making it conduct all the time? And if this is a
> very old
> > and
> > >> well known problem, why do most of the current designs either
> not bother
> > >> with any compensation or only use a voltage offset
> compensation? It must
> > >> have been solved way back, no? But I can't find anything,
> aside from a
> > few
> > >> linear envelopes which use op-amp integrators.
> > >>>>>
> > >>>>> Thanks,
> > >>>>> Tom
> > >>>>>
> > >>>>>
> > >>>>> On 31 Oct 2014, at 15:16, Harald <sdiy at haraldswerk.de
> <mailto:sdiy at haraldswerk.de>> wrote:
> > >>>>>
> > >>>>>> A common problem if it uses diode switching. I tried to
> compensate
> > >> that for the Elektor Formant ADSR here:
> > >> http://www.haraldswerk.de/NGF/NGF_ADSR_F/NGF_ADSR_F_110.html.
> Sorry its
> > in
> > >> German i still have to translate this site, but look at the
> schematic
> > for
> > >> IC2C and IC2D.
> > >>>>>>
> > >>>>>> Am 31.10.2014 um 12:47 schrieb Tom Wiltshire:
> > >>>>>>> Hi All,
> > >>>>>>>
> > >>>>>>> I'm playing with an analog envelope generator at the
> moment. This
> > is
> > >> something new for me since all the envelopes I've done thus
> far have
> > been
> > >> digital.
> > >>>>>>>
> > >>>>>>> I noticed that there seems to be a 400mV offset on the output
> > >> voltage. However, when I started testing it, it seems like it
> is just
> > the
> > >> very last bit of the release curve. The output rapidly falls
> from the
> > >> sustain level to about 300-400mV, but then takes another full
> 20 seconds
> > to
> > >> reach something measurably close to zero.
> > >>>>>>>
> > >>>>>>> I realise that in theory it should *never* reach zero,
> but do all
> > >> analog envelopes behave like this? When you trigger a quick
> series of
> > >> envelopes, it amounts to a considerable offset (it would be
> several
> > >> semitones) in the interval between the envelopes. Are there
> tricks used
> > to
> > >> eliminate this effect? I've checked several available ADSR
> schematics
> > and
> > >> none of them seem to do anything different - a cap feeding a TL08x
> > voltage
> > >> follower seems to be standard, and the cap just gets discharged to
> > ground.
> > >> If what I'm seeing is typical, these designs should all have this
> > "offset."
> > >>>>>>>
> > >>>>>>> I'm just looking for some pointers really, since I don't
> know what
> > to
> > >> expect.
> > >>>>>>>
> > >>>>>>> Thanks,
> > >>>>>>> Tom
> > >>>>>>> _______________________________________________
> > >>>>>>> Synth-diy mailing list
> > >>>>>>> Synth-diy at dropmix.xs4all.nl
> <mailto:Synth-diy at dropmix.xs4all.nl>
> > >>>>>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > >>>>>>>
> > >>>>>> _______________________________________________
> > >>>>>> Synth-diy mailing list
> > >>>>>> Synth-diy at dropmix.xs4all.nl
> <mailto:Synth-diy at dropmix.xs4all.nl>
> > >>>>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > >>>>
> > >>>
> > >>> _______________________________________________
> > >>> Synth-diy mailing list
> > >>> Synth-diy at dropmix.xs4all.nl <mailto:Synth-diy at dropmix.xs4all.nl>
> > >>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > >>>
> > >> _______________________________________________
> > >> Synth-diy mailing list
> > >> Synth-diy at dropmix.xs4all.nl <mailto:Synth-diy at dropmix.xs4all.nl>
> > >> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > >
> > >
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl <mailto:Synth-diy at dropmix.xs4all.nl>
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
>
More information about the Synth-diy
mailing list