[sdiy] 5v ADV Bass / AD EG Question.
jays at aracnet.com
jays at aracnet.com
Thu Mar 17 23:22:30 CET 2005
Bill,
I ment that to be the current limiting resistor on the Iabc pin.
What I'd do to get the bias would be take 2 'identical resistors' and put those in series between gnd and +5. By identical I would take 1% resistors, a good DVM and match them. (Some would take 0.1 decoupling caps and parallel the resistors. I don't know how the slew would affect the bias.) Now we have a pretty good V++/2. Add another resistor between the junction of the two resistors and the plus input on the CA3080.
I've attached a crude jpg of where I'd start.
Jay S
Bill Berzinskas <wberzinskas at nc.rr.com> wrote :
> gnd and 5 indeed.. as far as biasing.. u say 5.1k.. so, this would be
> a voltage divider.. does it go on my signal input or the pin5?
>
>
> ----- Original Message -----
> From: <jays at aracnet.com>
> To: "Bill Berzinskas" <wberzinskas at nc.rr.com>;
> <synth-diy at dropmix.xs4all.nl>
> Sent: Thursday, March 17, 2005 4:25 PM
> Subject: Re: [sdiy] 5v ADV Bass / AD EG Question.
>
>
> > If it is between gnd and +5 then you will probably have to bias the input
>
> > to ~+2.5 volts. Basically V+/2. You'll have to be careful since the 3080
>
> > has a fairly low input voltage for low distortion so bias become
> critical.
> >
> > Also be careful. If the Iabc pin gets to much current it can fry the
> > CA3080. So at least in prototyping the circuit add a current limiting
> > resistor.
> >
> > Crude calculation:
> > V=IR, R = V/I, V=5, I=.001 (1ma), R=4.7K or 5.1K should work.
> >
> > Jay S.
> >
> >
> >
> > Bill Berzinskas <wberzinskas at nc.rr.com>
> wrote :
> >
> >> well.. i breadboarded this this morning.. and
> >> most everything seems to work.. except the
> vca.. any
> >> thing
> >> specific i need to do to get this 3080 vca working
> >> on 5v?
> >>
> >>
> >>
> >> ----- Original Message -----
> >> From:
> >> Bill
> >> Berzinskas
> >> To: Jay Schwichtenberg ; synth-diy at dropmix.xs4all.nl
> >>
> >> Sent: Thursday, March 17, 2005 11:16
> >> AM
> >> Subject: Re: [sdiy] 5v ADV Bass / AD EG
> >> Question.
> >>
> >> preciate that jay.. good
> >> article.. it'll prob take me a bit to get through the math
> tho..
> >> lol
> >> .. :-) time to break out my
> math book from last
> >> semester..
> >>
> >>
> >> ----- Original Message -----
> >> From:
> >> Jay
> >> Schwichtenberg
> >> To: Bill Berzinskas ; synth-diy at dropmix.xs4all.nl
> >>
> >> Sent: Thursday, March 17, 2005 11:10
> >> AM
> >> Subject: RE: [sdiy] 5v ADV Bass / AD EG
> >> Question.
> >>
> >> Bill,
> >>
> >> 2)
> >>
> >> Another issue is that the attack, decay and release
> >> pots on envelope generators are typically log pots, a
> non-linear
> >> scale.
> >> So if the digital pots you use are not log they may not give you
> the
> >> timing
> >> resolution that you are use to. One techinque to do that is buffer
>
> >> the pot
> >> and add a resistor. Picking the right resistor and placing it
> between
> >> the
> >> wiper and the other ends of the pot (assuming using pot as
> attenuator
> >> between signal and gnd) can give you log or expo curves. Try
> >> http://www.geofex.com/Article_Folders/potsecrets/potscret.htm for
>
> >> that
> >> info.
> >>
> >> Good luck.
> >> Jay S.
> >>
> >> -----Original Message-----From:
> >> owner-synth-diy at dropmix.xs4all.nl
> >> [mailto:owner-synth-diy at dropmix.xs4all.nl]On
> Behalf Of Bill
> >> BerzinskasSent: Thursday, March 17, 2005 7:36 AMTo:
> >> synth-diy at dropmix.xs4all.nlSubject:
> [sdiy] 5v ADV Bass / AD EG
> >> Question.
> >> Hello everybody.. just woke up to a
> >> crazy little burst of snow here in NC..
> wierd..
> >>
> >>
> >> Anyhow.. As you probably know i'm
> >> modding the bejezzus out of my adv-bass.. In
> my quest
> >> to make
> >> it digitally controlled, i've hit a few snags.. so
> maybe you
> >> can
> >> help me out..
> >>
> >> 1) I am converting it to digital
> >> control.. mostly thru digital
> pots.. a few things
> >> with
> >> DAC.. so.. for the digital pots, i have to use 5v
> input, and
> >> rather
> >> then use way more opamps then i want to deal with, i would like
> to
> >> make it
> >> operate on 5v possibly with a bipolar or just 12v output stage
> if
> >> necessary.. So..
> >>
> >> I've done some crude experiments with the
> >> Trigger section just to see how it reacts to switching from
> +/-12v
> >> to just
> >> +5v.. I've tried with
> tl082s.. and i just
> >> can't
> >> get the trigger ratio right.. and it always triggers.. so.
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