music machines: exponential.cv
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 09:31:08 1993
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From: ricard@axis.se (Ricard Wolf)
Date: Mon, 26 Jul 93 15:11:13 MET DST
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To: peterc@comm.mot.com (Peter Cassidy), ANALOGUE@magnus.acs.ohio-state.edu
Subject: Re: Exponential CV Convertor
Status: OR
> On Jul 26, 2:00pm, Ricard Wolf wrote:
>
> > True. There are usually two points to worry about - one you can compensate
> > for by using two transistors, and the other, much less noticable, you usually
> > compensate for by using a Q81 somewhere in the circuit.
>
> Yeah. I'm using a transistor compensator at the moment. Q81 ?? Thermistor ??
The Q81 is a 3300ppm temperature coefficient resistor, i.e. a type of thermistor,
but with a well defined, quite low, temperature coefficient. Made by a company
called Tel Labs, but I don't really know how to get hold of them. I've seen
them in Moog synthesisers, and am always worried in case I have to replace
one...
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
-- "Snobbery and Decay" --
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From: peterc@comm.mot.com (Peter Cassidy)
Message-Id: <9307261422.ZM20840@dub-tsw1>
Date: Mon, 26 Jul 1993 14:22:43 +0100
In-Reply-To: ricard@axis.se (Ricard Wolf)
"Re: Exponential CV convertors?" (Jul 26, 2:09pm)
References:
X-Mailer: Z-Mail (2.1.3 26jan93)
To: ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List),
ricard@axis.se (Ricard Wolf)
Subject: Re: Exponential CV convertors?
Status: OR
On Jul 26, 2:09pm, Ricard Wolf wrote:
> Why use BC109's instead of the '3046? I've seen double transistors, i.e.
> just two transistors in the same casing; Maplin in England among others
> have them. I've tried binding descrete transistors together, I don't really
> think it works two well. Some people say uyse epoxy glue and then put some sort
> of styroplastic over to keep the temperatures the same, but since the 3046 isn't
> difficult to get hold of, I don't really see the point.
Well, the main reason was that I only have one of the CA3046 chips, and I was
trying to avoid getting any more as I need six of them. Also (this is silly),
I prefer discrete components, things I can build out of junk bits and pieces.
> Ricard Wolf / | \ / | /- email: ricard@axis.se
> Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
> S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
> SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
--
Pete
--------------------------------------------------------------------------------
| Peter Cassidy - Motorola BV Ireland - Test Systems Engineering |
| peterc@dub-tse.comm.mot.com cassidy-c10404@email.comm.mot.com |
--------------------------------------------------------------------------------
Is measa cara fealltach na/ namhaid follasach.
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 09:14:09 1993
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From: ricard@axis.se (Ricard Wolf)
Date: Mon, 26 Jul 93 15:09:42 MET DST
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To: peterc@comm.mot.com (Peter Cassidy),
ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List)
Subject: Re: Exponential CV convertors?
Status: OR
> On Jul 26, 1:47pm, Ricard Wolf wrote:
> > Subject: Re: Exponential CV convertors?
> > > Nahh. I'm using one of those five-transistors-in-an-IC-package. They maintain
> > > excellent thermal contact. One of the transistors in the cct is solely for
> > > thermal compensation. I have a part number for this package, and I'm cooking
> > > up a schematic for it.
> >
> > Something like a CA3046, eh?
>
> Yup! That's the very one!! I was thinking of substituting in some metal-can
> BC109's if I can get the cct. stable enough. Bind them together with some
> heat-sink compound or something. Any ideas ?
Why use BC109's instead of the '3046? I've seen double transistors, i.e.
just two transistors in the same casing; Maplin in England among others
have them. I've tried binding descrete transistors together, I don't really
think it works two well. Some people say uyse epoxy glue and then put some sort
of styroplastic over to keep the temperatures the same, but since the 3046 isn't
difficult to get hold of, I don't really see the point.
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
-- "Snobbery and Decay" --
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 09:07:09 1993
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From: peterc@comm.mot.com (Peter Cassidy)
Message-Id: <9307261403.ZM20826@dub-tsw1>
Date: Mon, 26 Jul 1993 14:03:04 +0100
In-Reply-To: ricard@axis.se (Ricard Wolf)
"Re: Exponential CV Convertor" (Jul 26, 2:00pm)
References:
X-Mailer: Z-Mail (2.1.3 26jan93)
To: ricard@axis.se (Ricard Wolf), peterc@comm.mot.com (Peter Cassidy),
ANALOGUE@magnus.acs.ohio-state.edu
Subject: Re: Exponential CV Convertor
Status: OR
On Jul 26, 2:00pm, Ricard Wolf wrote:
> True. There are usually two points to worry about - one you can compensate
> for by using two transistors, and the other, much less noticable, you usually
> compensate for by using a Q81 somewhere in the circuit.
Yeah. I'm using a transistor compensator at the moment. Q81 ?? Thermistor ??
> --
> Ricard Wolf / | \ / | /- email: ricard@axis.se
> Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
> S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
> SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
> -- "Snobbery and Decay" --
--
Pete
--------------------------------------------------------------------------------
| Peter Cassidy - Motorola BV Ireland - Test Systems Engineering |
| peterc@dub-tse.comm.mot.com cassidy-c10404@email.comm.mot.com |
--------------------------------------------------------------------------------
Mura dtaga leat tar leo!
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 09:03:55 1993
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From: ricard@axis.se (Ricard Wolf)
Date: Mon, 26 Jul 93 15:00:10 MET DST
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To: peterc@comm.mot.com (Peter Cassidy), ANALOGUE@magnus.acs.ohio-state.edu
Subject: Re: Exponential CV Convertor
Status: OR
> The circuit works on the idea that there is an exponential voltage/
> current relationship in a semiconductor diode. Trouble is, diodes
> are *really* thermally sensitive. If I can get this cheapo cct to work,
> it will be really handy for interfacing log sequencers and MIDI/CV
> stuff to old linear equipment (like the Yamaha CS's and Korg Deltas).
>
True. There are usually two points to worry about - one you can compensate
for by using two transistors, and the other, much less noticable, you usually
compensate for by using a Q81 somewhere in the circuit.
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
-- "Snobbery and Decay" --
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 09:02:38 1993
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From: peterc@comm.mot.com (Peter Cassidy)
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Date: Mon, 26 Jul 1993 13:56:40 +0100
In-Reply-To: ricard@axis.se (Ricard Wolf)
"Re: Exponential CV convertors?" (Jul 26, 1:47pm)
References:
X-Mailer: Z-Mail (2.1.3 26jan93)
To: ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List),
ricard@axis.se (Ricard Wolf)
Subject: Re: Exponential CV convertors?
Status: OR
On Jul 26, 1:47pm, Ricard Wolf wrote:
> Subject: Re: Exponential CV convertors?
> > Nahh. I'm using one of those five-transistors-in-an-IC-package. They maintain
> > excellent thermal contact. One of the transistors in the cct is solely for
> > thermal compensation. I have a part number for this package, and I'm cooking
> > up a schematic for it.
>
> Something like a CA3046, eh?
Yup! That's the very one!! I was thinking of substituting in some metal-can
BC109's if I can get the cct. stable enough. Bind them together with some
heat-sink compound or something. Any ideas ?
> Ricard Wolf / | \ / | /- email: ricard@axis.se
> Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
--
Pete
--------------------------------------------------------------------------------
| Peter Cassidy - Motorola BV Ireland - Test Systems Engineering |
| peterc@dub-tse.comm.mot.com cassidy-c10404@email.comm.mot.com |
--------------------------------------------------------------------------------
Di/ogha gach si/ne sioc ach is measa si/or bha/isteach.
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 08:55:28 1993
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From: ricard@axis.se (Ricard Wolf)
Date: Mon, 26 Jul 93 14:47:36 MET DST
X-Mailer: Mail User's Shell (7.0.1 12/13/89)
To: Peter Cassidy ,
ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List)
Subject: Re: Exponential CV convertors?
Status: OR
> Nahh. I'm using one of those five-transistors-in-an-IC-package. They maintain
> excellent thermal contact. One of the transistors in the cct is solely for
> thermal compensation. I have a part number for this package, and I'm cooking
> up a schematic for it. This is a few weeks away. It's for a MIDI-CV/Gate
> (log) to interface to Yamaha CS5, CS15, CS30 (lin). The interface is working
> at the mo'. When it's finished it will be switchable to log/lin output and
> note on / note on/off. (It's for Steven Collins' new studio).
Something like a CA3046, eh?
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
-- "Snobbery and Decay" --
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 07:48:30 1993
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Date: Mon, 26 Jul 1993 13:25:41 +0000 (N)
From: Rick Jansen
Subject: Re: Exponential CV convertors?
In-Reply-To: Your message of Mon,
26 Jul 93 11:21:43 A. <9307261032.AA23588@comm.mot.com>
To: Peter Cassidy
Cc: sscprick@diamond.sara.nl, ANALOGUE@magnus.acs.ohio-state.edu
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Status: OR
);
Nahh. I'm using one of those five-transistors-in-an-IC-package. They maintain
> excellent thermal contact. One of the transistors in the cct is solely for
> thermal compensation. I have a part number for this package, and I'm cooking
> up a schematic for it.
Hmm... For the Formant I have looked into this too, the VCO's
of course contain a lin/exp converter. If I remember correctly
(off the top off my head, being not a prof electronician) the
lin/log conversion depends on a current in the transistor
which is highly dependent on temperature: the exp dependence
between Ic and Ieb0. A temperature rise of 10 degrees C doubles
this last current. Thats why I had to use the uA726, a double
transistor with a built-in on-chip oven.
National semi ha(d/s) such a device too, the LM119? 199?, with
on-chip temperature control. If you want the part number I can look
it up at home for you.
Rick
--
rick@sara.nl
She's a module and she's looking good
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 07:43:27 1993
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From: peterc@comm.mot.com (Peter Cassidy)
Message-Id: <9307261239.ZM20440@dub-tsw1>
Date: Mon, 26 Jul 1993 12:39:34 +0100
X-Mailer: Z-Mail (2.1.3 26jan93)
To: ANALOGUE@magnus.acs.ohio-state.edu
Subject: Re: Exponential CV Convertor
Status: OR
On Jul 26, 1:25pm, Rick Jansen wrote:
> Hmm... For the Formant I have looked into this too, the VCO's
> of course contain a lin/exp converter. If I remember correctly
> (off the top off my head, being not a prof electronician) the
> lin/log conversion depends on a current in the transistor
> which is highly dependent on temperature: the exp dependence
> between Ic and Ieb0. A temperature rise of 10 degrees C doubles
> this last current. Thats why I had to use the uA726, a double
> transistor with a built-in on-chip oven.
Yeah, this stuff rings a bell! VCO/VCF's are normally linear WRT
frequency. Therefore they normally require a log - lin
convertor before the VCO/VCF. This gives it the 1V/Octave characteristic.
I'll bring in my rough schematic tomorrow. It started off in life as
a log voltage-lin current convertor & I'm hacking it around at the mo'
as a MIDI-CV voltage convertor for linear synths (Yamaha/ Korg).
The chip-oven won't be needed if I get the temperature compensation
right (They're expensive items, those !!)
The circuit works on the idea that there is an exponential voltage/
current relationship in a semiconductor diode. Trouble is, diodes
are *really* thermally sensitive. If I can get this cheapo cct to work,
it will be really handy for interfacing log sequencers and MIDI/CV
stuff to old linear equipment (like the Yamaha CS's and Korg Deltas).
I'll bring in the rough bits-and-pieces tomorrrow.
--
Pete
--------------------------------------------------------------------------------
| Peter Cassidy - Motorola BV Ireland - Test Systems Engineering |
| peterc@dub-tse.comm.mot.com cassidy-c10404@email.comm.mot.com |
--------------------------------------------------------------------------------
Bro/ga sa chliabha/n agus ladhracha sa lathaigh.
--- End of forwarded mail from Mail Delivery Subsystem
--
Pete
--------------------------------------------------------------------------------
| Peter Cassidy - Motorola BV Ireland - Test Systems Engineering |
| peterc@dub-tse.comm.mot.com cassidy-c10404@email.comm.mot.com |
--------------------------------------------------------------------------------
Feileann spallai/ do bhallai/ chomh maith le clocha mo/ra.
From analogue-request@magnus.acs.ohio-state.edu Mon Jul 26 06:43:20 1993
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Date: Mon, 26 Jul 1993 12:16:56 +0000 (N)
From: Rick Jansen
Subject: Re: Exponential CV convertors?
In-Reply-To: Your message of Sat,
24 Jul 93 13:10:06 A. <9307241220.AA00908@comm.mot.com>
To: Peter Cassidy , ANALOGUE@magnus.acs.ohio-state.edu
Cc: sscprick@diamond.sara.nl
Message-Id: <9307261116.AA161321@diamond.sara.nl>
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In message <9307241220.AA00908@comm.mot.com> you write:
> >
> > Did anyone ever come up with (or knows of) a MIDI to
> > Exponential-CV convertor (i.e. Korg MS-20) ?? Or even
> > a linear CV to exp-CV convertor would be a start...
> I'm working on a log - lin (volts/decade) convertor at the moment.
> It's a few weeks off, yet. I can give you more details if you want. It's
> just three or four transistors and a few resistors.
What do you do about temperature effects (drift)?
Do you keep the thing in an oven?
Rick Jansen
--
rick@sara.nl
She's a module and she's looking good
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From: Peter Cassidy
Subject: Re: Exponential CV convertors?
To: ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List)
Date: Mon, 26 Jul 93 11:24:17 BST
Mailer: Elm [revision: 66.25]
Status: OR
>
> In message <9307241220.AA00908@comm.mot.com> you write:
> > >
> > > Did anyone ever come up with (or knows of) a MIDI to
> > > Exponential-CV convertor (i.e. Korg MS-20) ?? Or even
> > > a linear CV to exp-CV convertor would be a start...
>
> > I'm working on a log - lin (volts/decade) convertor at the moment.
> > It's a few weeks off, yet. I can give you more details if you want. It's
> > just three or four transistors and a few resistors.
>
> What do you do about temperature effects (drift)?
> Do you keep the thing in an oven?
>
> Rick Jansen
> --
> rick@sara.nl
>
> She's a module and she's looking good
>
>
Nahh. I'm using one of those five-transistors-in-an-IC-package. They maintain
excellent thermal contact. One of the transistors in the cct is solely for
thermal compensation. I have a part number for this package, and I'm cooking
up a schematic for it. This is a few weeks away. It's for a MIDI-CV/Gate
(log) to interface to Yamaha CS5, CS15, CS30 (lin). The interface is working
at the mo'. When it's finished it will be switchable to log/lin output and
note on / note on/off. (It's for Steven Collins' new studio).
--
Regards,
Peter
-----------------------------------------------------------------------------
| M O T O R O L A B . V . I R E L A N D |
| ----------------------------------------- |
| Peter Cassidy - T.S.E Dublin | Phone : 353-1-840-8866 Ext. 417 |
| MACCVM : C10404 | X400 : peterc@comm.mot.com |
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From: Peter Cassidy
Subject: Re: Exponential CV convertors?
To: svaldez@sdcc13.UCSD.EDU (Steve Valdez) (Steve Valdez)
Date: Sat, 24 Jul 93 13:10:06 BST
Cc: ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List)
In-Reply-To: <9307240427.AA02395@sdcc13.UCSD.EDU>; from "Steve Valdez" at Jul 23, 93 9:27 pm
Mailer: Elm [revision: 66.25]
Status: OR
>
> Did anyone ever come up with (or knows of) a MIDI to
> Exponential-CV convertor (i.e. Korg MS-20) ?? Or even
> a linear CV to exp-CV convertor would be a start...
>
>
>
Hi,
I'm working on a log - lin (volts/decade) convertor at the moment.
It's a few weeks off, yet. I can give you more details if you want. It's
just three or four transistors and a few resistors.
--
Regards,
Peter
-----------------------------------------------------------------------------
| M O T O R O L A B . V . I R E L A N D |
| ----------------------------------------- |
| Peter Cassidy - T.S.E Dublin | Phone : 353-1-840-8866 Ext. 417 |
| MACCVM : C10404 | X400 : peterc@comm.mot.com |
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Date: Mon, 26 Jul 1993 16:17:05 +0000 (N)
From: Rick Jansen
Subject: Re: Exponential CV convertors?
In-Reply-To: Your message of Mon,
26 Jul 93 14:22:43 N. <9307261422.ZM20840@dub-tsw1>
To: peterc@comm.mot.com (Peter Cassidy)
Cc: sscprick@diamond.sara.nl, ANALOGUE@magnus.acs.ohio-state.edu
Message-Id: <9307261517.AA192128@diamond.sara.nl>
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Status: OR
);
In message <9307261422.ZM20840@dub-tsw1> you write:
> On Jul 26, 2:09pm, Ricard Wolf wrote:
>
> > Why use BC109's instead of the '3046? I've seen double transistors, i.e.
> > just two transistors in the same casing; Maplin in England among others
> > have them. I've tried binding descrete transistors together, I don't really
> > think it works two well. Some people say uyse epoxy glue and then put some
> sort
> > of styroplastic over to keep the temperatures the same, but since the 3046
> isn't
> > difficult to get hold of, I don't really see the point.
>
> Well, the main reason was that I only have one of the CA3046 chips, and I was
> trying to avoid getting any more as I need six of them. Also (this is silly),
> I prefer discrete components, things I can build out of junk bits and pieces.
For controlling VCF's and VCA's a simple double transistor will do.
Precision isn't mandatory there, and thus temperature control.
For the control of pitches, in VCO's it is absolutely crucial.
Remember one of the big reasons analog was kicked out was that you can't
rely on the stability of the tuning. Switch on the lighting rig,
or have a steamy audience, and your gear will drift out of tune in half
an hour.
For the Formant 24dB VCF they also proposed two transistors glued together,
but in the extensions book that solution was sort of withdrawn. And thats
only a VCF.
For precision double transistors you may want to look at the MAT02 and MAT03
from PMI (Precision Monolythics). They're not temperature controlled though.
MAT02 is NPN, MAT03 PNP, or vice versa :)
Rick Jansen
--
rick@sara.nl
"Tune in to the temperature"
From analogue-request@magnus.acs.ohio-state.edu Tue Jul 27 05:47:21 1993
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From: Peter Cassidy
Subject: Re: Exponential CV convertors?
To: RICK@sara.nl (Rick Jansen)
Date: Tue, 27 Jul 93 10:39:17 BST
Cc: ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List)
In-Reply-To: <9307261517.AA192128@diamond.sara.nl>; from "Rick Jansen" at Jul 26, 93 4:17 pm
Mailer: Elm [revision: 66.25]
Status: O
>
> For precision double transistors you may want to look at the MAT02 and MAT03
> from PMI (Precision Monolythics). They're not temperature controlled though.
> MAT02 is NPN, MAT03 PNP, or vice versa :)
>
> Rick Jansen
> --
> rick@sara.nl
>
> "Tune in to the temperature"
>
Thanks for the help, Rick.
Here's my ASCIImatic (at the moment) :
0V --------------------*----------*---------*------------*-----------*
| | | | |
# 12| | |8 |
1K# ----------- | ----------- |
# | | |1N | | |
47K 22K/ | 14| | |41 | |6 |
IN >--####------####---*-----| CA3046 | |48 | CA3046 |------*
/ | | | --- | | |
-------* | | A | | |
----------- | ----------- |
13| | |7 |
| | | |
*---------*---------* | |
| | | |
| e +12V| | | |
\ = | /|2 | | |
> = 7|/ |----* | |
BC559 \=_____/ | | |
/=b 6 \741 | | 330K #
/ = 4|\ |-----------------*----####---#47K
/ = | \|3 | #\
| c -12V| # |
Vout <--------* | #10M |
| | # |
# | | |
#10K *---------------------*-----------*-12V
#
|
0V
I know this is messy (it's the best I could do !!). The cct should work OK
but may need some tweaking of resistor values.
--
Regards,
Peter
-----------------------------------------------------------------------------
| M O T O R O L A B . V . I R E L A N D |
| ----------------------------------------- |
| Peter Cassidy - T.S.E Dublin | Phone : 353-1-840-8866 Ext. 417 |
| MACCVM : C10404 | X400 : peterc@comm.mot.com |
-----------------------------------------------------------------------------
From analogue-request@magnus.acs.ohio-state.edu Tue Jul 27 10:12:47 1993
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Date: Tue, 27 Jul 1993 09:33:36 +0000 (N)
From: Rick Jansen
Subject: Re: Exponential CV convertors?
In-Reply-To: Your message of Mon,
26 Jul 93 13:25:41 GMT. <9307261225.AA171302@diamond.sara.nl>
To: ANALOGUE@magnus.acs.ohio-state.edu, peterc@comm.mot.com
Cc: rick@SARA.NL
Message-Id: <9307270833.AA141703@diamond.sara.nl>
X-Envelope-To: ANALOGUE@magnus.acs.ohio-state.edu
Content-Transfer-Encoding: 7BIT
Status: O
In message <9307261225.AA171302@diamond.sara.nl> you write:
> ...blabla...
> Thats why I had to use the uA726, a double
> transistor with a built-in on-chip oven.
> National semi ha(d/s) such a device too, the LM119? 199?, with
> on-chip temperature control. If you want the part number I can look
> it up at home for you.
I looked it up, the LM199 (or was it 119, argh!) isn't a double
transistor, but a temperature controlled zener. Sorry. You can
build an 'oven' with one though. Or with a more modern sensor
like the LM35, controlling a power transistor as a heater.
My data book lists a 'quick and precise' exp converter though,
using a LM194 double transistor AND a temperature-compensating
resistor, a Q81 with a temp coefficient of +0.3%/C. They're made
by Tel Labs. If you want the circuit I could scan it for you.
But, I still have the feeling that Q81 won't save you entirely.
Rick Jansen
--
rick@sara.nl
"Synthetic electronic parts..."
From analogue-request@magnus.acs.ohio-state.edu Tue Jul 27 13:20:50 1993
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From: ricard@axis.se (Ricard Wolf)
Date: Tue, 27 Jul 93 19:15:12 MET DST
X-Mailer: Mail User's Shell (7.0.1 12/13/89)
To: Peter Cassidy
Subject: Re: Exponential CV convertors?
Cc: ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List)
Status: O
> > Moog use a simple PNP+NPN transistor exponential converter, and they don't even
> > glue them together, in their monophonics. Understandably, they are temperature
> > sensitive, and also go rather flat at high frequencies (just crank the
> > resonance up until you get a sine wave and listen to it). The 3320 used
> > in Sequential stuff (like the Pro-One) is much more stable and accurate.
>
> Sounds like I haven't a hope with my two BC109's !!!
I'd say the fact that the converter goes flat at high frequencies has
little to do with the BC109's, but at high emitter currents, the transistor
emitter resistance causes the converter to deflect from a true exponential.
The 3320 I assume operates internally at lower currents, and they don't
have problems with leaky PC boards etc. I'd say that a couple of BC109's
are about as good as a 3046 in this respect, but of course the
temperature stability of a 3046-based circuit should be better.
Sorry if I caused some confusion here regarding this matter...
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
-- "Ich lieb' dich nicht - du liebst mich nicht" --
From analogue-request@magnus.acs.ohio-state.edu Tue Jul 27 11:27:00 1993
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From: ricard@axis.se (Ricard Wolf)
Date: Tue, 27 Jul 93 17:20:34 MET DST
X-Mailer: Mail User's Shell (7.0.1 12/13/89)
To: Rick Jansen , ANALOGUE@magnus.acs.ohio-state.edu,
peterc@comm.mot.com
Subject: Re: Exponential CV convertors?
Status: O
> My data book lists a 'quick and precise' exp converter though,
> using a LM194 double transistor AND a temperature-compensating
> resistor, a Q81 with a temp coefficient of +0.3%/C. They're made
> by Tel Labs. If you want the circuit I could scan it for you.
> But, I still have the feeling that Q81 won't save you entirely.
Gluing the Q81 and double transistor together might help things...keeping
it all at the same temperature.
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
-- "Six simple synthesisers playing all the sounds" --
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From: ricard@axis.se (Ricard Wolf)
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To: Rick Jansen , peterc@comm.mot.com (Peter Cassidy)
Subject: Re: Exponential CV convertors?
Cc: sscprick@diamond.sara.nl, ANALOGUE@magnus.acs.ohio-state.edu
Status: O
> For controlling VCF's and VCA's a simple double transistor will do.
> Precision isn't mandatory there, and thus temperature control.
> For the control of pitches, in VCO's it is absolutely crucial.
Very true.
> Remember one of the big reasons analog was kicked out was that you can't
> rely on the stability of the tuning. Switch on the lighting rig,
> or have a steamy audience, and your gear will drift out of tune in half
> an hour.
>
> For the Formant 24dB VCF they also proposed two transistors glued together,
> but in the extensions book that solution was sort of withdrawn. And thats
> only a VCF.
Moog use a simple PNP+NPN transistor exponential converter, and they don't even
glue them together, in their monophonics. Understandably, they are temperature
sensitive, and also go rather flat at high frequencies (just crank the
resonance up until you get a sine wave and listen to it). The 3320 used
in Sequential stuff (like the Pro-One) is much more stable and accurate.
>
> For precision double transistors you may want to look at the MAT02 and MAT03
> from PMI (Precision Monolythics). They're not temperature controlled though.
> MAT02 is NPN, MAT03 PNP, or vice versa :)
I think these are available from Maplin in the UK if anyone in Europe
is interested.
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
-- "Six simple synthesisers playing all the sounds" --
From analogue-request@magnus.acs.ohio-state.edu Tue Jul 27 11:03:07 1993
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Message-Id: <9307271457.AA10596@quark.magnus.acs.ohio-state.edu>
From: mlloyd@ihlpm.att.com
Date: Tue, 27 Jul 93 09:51 CDT
Original-From: ihlpm!mlloyd (Michael Lloyd +1 708 713 5497)
To: Rick Jansen ,
peterc@comm.mot.com (Peter Cassidy)
Cc: ANALOGUE@magnus.acs.ohio-state.edu, sscprick@diamond.sara.nl
Subject: Re: Exponential CV convertors?
Status: O
Another transistor array that I've seen in use as a log CV converter
is the CA3096. It contains 2 pnp and 3 npn transistors. I haven't
made any converters with it yet, but I've seen a couple of circuits
in the latest Linear Technology data book that use it as a temperature
compensated converter in an oscillator circuit design for use in
synthesizers. One of the transistors in the CA3096 is used as a heater
for the whole package. The circuit is on page 2-227 of the 1990 Databook;
the datasheet for the LT1055/LT1056 BiFET Op Amp. Has anyone ever built
this oscillator? I'm thinking about using it as one of the oscillators
in my homebrew unit.
Michael Lloyd
From mlloyd@ihlpm.att.com Tue Jul 27 10:57:41 1993
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From: mlloyd@ihlpm.att.com
Date: Tue, 27 Jul 93 09:51 CDT
Original-From: ihlpm!mlloyd (Michael Lloyd +1 708 713 5497)
To: Rick Jansen ,
peterc@comm.mot.com (Peter Cassidy)
Cc: ANALOGUE@magnus.acs.ohio-state.edu, sscprick@diamond.sara.nl
Subject: Re: Exponential CV convertors?
Status: O
Another transistor array that I've seen in use as a log CV converter
is the CA3096. It contains 2 pnp and 3 npn transistors. I haven't
made any converters with it yet, but I've seen a couple of circuits
in the latest Linear Technology data book that use it as a temperature
compensated converter in an oscillator circuit design for use in
synthesizers. One of the transistors in the CA3096 is used as a heater
for the whole package. The circuit is on page 2-227 of the 1990 Databook;
the datasheet for the LT1055/LT1056 BiFET Op Amp. Has anyone ever built
this oscillator? I'm thinking about using it as one of the oscillators
in my homebrew unit.
Michael Lloyd
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From: jna@bronze.lcs.mit.edu (give your body it's freedom)
Message-Id: <9307271815.AA01975@bronze.lcs.mit.edu>
To: peterc@comm.mot.com, ricard@axis.se
Subject: Re: Exponential CV convertors?
Cc: ANALOGUE@magnus.acs.ohio-state.edu
Status: O
Maybe what all of you people are looking for are identical temperature
matched / laser trimmed transistors.
i've seen these made by Linear Electronics and other companies. take a walk
through a couple databooks. they're extremely stable, and work in pairs.
-john
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From: ricard@axis.se (Ricard Wolf)
Date: Wed, 28 Jul 93 09:20:33 MET DST
X-Mailer: Mail User's Shell (7.0.1 12/13/89)
To: till@lucid.com (Don Tillman), ANALOGUE@magnus.acs.ohio-state.edu
Subject: Re: Exponential CV Convertor
Status: O
> The all-time cheapest, simplist circuit I know of is on the ARP Odyssey.
> I don't even mind doing an ASCIImatic for it:
>
> | +15v
> |
> <150k
> < i out
> < |
> | |
> | |/
> +------|
> | |\i
> | |
> | |
> |/i |
> -----| |
> |\ |
> | |
> +-------+--- Gnd
>
>
> The input is from the VCO summing junction and should be near zero. The
> first transistor is a PNP (emitter up) and the second transistor is an NPN
> (emitter down), both in the same package. It don't get much simpler than
> this.
This is the same circuit used for the Moog filter exponential converter, at
least in the Mini, Prodigy and Rogue. Interesting ARP use it for the
oscillators - is it stable/accurate enough.
> Right. I believe the two effects are the base frequency drifting with
> temperature and the scale drifting with temperature. The base frequency
> drift is almost always taken care of with thermally connected transistors
> (or transitors on the same chip). The scale drift is typically ignored.
The Q81 is supposed to take care of this. Curtis recommend using a
Q81 with their 3320 filter (which doesn't have internal compensation for
scale drift, like the oscillator (3340) does).
> The Moog Modular seems to compensate for the scale drift with a temperature
> sensitive resistor. But check this out: some of the other Moogs like the
> MicroMoog and Prodigy use a CA3046 transistor array with one of the
> transistors sensing temperature and another used soley to heat up the chip.
> This compensates for both effects nicely. Pretty damn clever.
I've seen this too. However, upon examining my MG-1 (based on the Rogue
design I believe), the 3046 has a resistor under it (Q81?) which is
difficult to read, since it is bathed in silicon grease for thermal
contact. This leads me to beleive that they abandoned heated chip technology
for some reason, and went back to just using a pair of transistors at
room temperature. Could be there were problems getting the chip temperature
stable enough when the chip was heated. But I don't have the schematic so I
can't be sure.
> Moog use a simple PNP+NPN transistor exponential converter, and they
> don't even glue them together, in their monophonics. Understandably,
> they are temperature sensitive, and also go rather flat at high
> frequencies (just crank the resonance up until you get a sine wave and
> listen to it).
>
> Um, which Moog model is this? (I've never seen Moog do this.)
Sorry, missed something out, as I said above, many filters use this
circuit, but not the oscillators.
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
-- "You better watch out, you better beware, Albert said that E=mc square" --
From analogue-request@magnus.acs.ohio-state.edu Wed Jul 28 00:31:28 1993
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Date: Wed, 28 Jul 93 13:27:36 JST
From: steve@crl.hitachi.co.jp (Steven Collins)
Return-Path:
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To: ANALOGUE@magnus.acs.ohio-state.edu
Subject: Re: Exponential CV convertors?
Status: O
Pete Cassidy writes:
>When it's finished it will be switchable to log/lin output and
>note on / note on/off. (It's for Steven Collins' new studio).
Ar. He's a good lad is Pete. Oh yes. Fine Calibre of a chap indeed... :-)
Steve
---
+-------------------------------------+----------------------------------------+
| Steven Collins, Visiting Researcher | email: steve@crl.hitachi.co.jp |
| Hitachi Central Research Lab. Tokyo | ph: (0423)-23-1111 fax: (0423) 27-7742 |
+-------------------------------------+----------------------------------------+
From analogue-request@magnus.acs.ohio-state.edu Wed Jul 28 02:21:16 1993
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Date: Tue, 27 Jul 93 23:20:39 PDT
From: till@lucid.com (Don Tillman)
Message-Id: <9307280620.AA06093@acid-rain.lucid.com>
To: ANALOGUE@magnus.acs.ohio-state.edu
In-Reply-To: Ricard Wolf's message of Mon, 26 Jul 93 15:00:10 MET DST
Subject: Exponential CV Convertor
Status: OR
From: ricard@axis.se (Ricard Wolf)
Date: Mon, 26 Jul 93 15:00:10 MET DST
> The circuit works on the idea that there is an exponential voltage/
> current relationship in a semiconductor diode. Trouble is, diodes
> are *really* thermally sensitive. If I can get this cheapo cct to work,
> it will be really handy for interfacing log sequencers and MIDI/CV
> stuff to old linear equipment (like the Yamaha CS's and Korg Deltas).
The all-time cheapest, simplist circuit I know of is on the ARP Odyssey.
I don't even mind doing an ASCIImatic for it:
| +15v
|
<150k
< i out
< |
| |
| |/
+------|
| |\i
| |
| |
|/i |
-----| |
|\ |
| |
+-------+--- Gnd
The input is from the VCO summing junction and should be near zero. The
first transistor is a PNP (emitter up) and the second transistor is an NPN
(emitter down), both in the same package. It don't get much simpler than
this.
True. There are usually two points to worry about - one you can compensate
for by using two transistors, and the other, much less noticable, you
usually compensate for by using a Q81 somewhere in the circuit.
Right. I believe the two effects are the base frequency drifting with
temperature and the scale drifting with temperature. The base frequency
drift is almost always taken care of with thermally connected transistors
(or transitors on the same chip). The scale drift is typically ignored.
The Moog Modular seems to compensate for the scale drift with a temperature
sensitive resistor. But check this out: some of the other Moogs like the
MicroMoog and Prodigy use a CA3046 transistor array with one of the
transistors sensing temperature and another used soley to heat up the chip.
This compensates for both effects nicely. Pretty damn clever.
From: ricard@axis.se (Ricard Wolf)
Date: Tue, 27 Jul 93 17:13:37 MET DST
Moog use a simple PNP+NPN transistor exponential converter, and they
don't even glue them together, in their monophonics. Understandably,
they are temperature sensitive, and also go rather flat at high
frequencies (just crank the resonance up until you get a sine wave and
listen to it).
Um, which Moog model is this? (I've never seen Moog do this.)
-- Don
From analogue-request@magnus.acs.ohio-state.edu Thu Jul 29 04:36:21 1993
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Date: Thu, 29 Jul 1993 10:33:30 +0000 (N)
From: Rick Jansen
Subject: Exponential CV convertors
To: analogue@magnus.acs.ohio-state.edu, peterc@comm.mot.com
Message-Id: <9307290933.AA120992@diamond.sara.nl>
Content-Transfer-Encoding: 7BIT
Status: O
);
In message <9307281151.AA101462@diamond.sara.nl> I write:
> Vout= -log10(Vin/Vref)
> Vin = 10V to 0.1mV or Iin = 1mA to 10nA
Oops, note this is a lin-log conversion, you probably need the
reverse. This can be achieved with almost the same circuit,
but with some things reversed.
A book that has several log and vice versa converters,
also with Q81 temperature compensation, is 'IC Opamp Cookbook'
by Walter Jung. If you'd like his circuits I could scan em.
Just in case you can't find Q81's: Tel Labs is located in Londonderry
in New Hampshire.
Rick Jansen
--
rick@sara.nl
"Ohm Sweet Ohm"
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From: ricard@axis.se (Ricard Wolf)
Date: Thu, 29 Jul 93 09:16:00 MET DST
X-Mailer: Mail User's Shell (7.0.1 12/13/89)
To: till@lucid.com (Don Tillman), analogue@magnus.acs.ohio-state.edu
Subject: Re: Exponential CV Convertor
Status: O
> I can't speak for ARPs in general, but my ARP Odyssey is pretty stable and
> accurate (except for the first 15 minutes after power on).
So's mine, as far as I recall, but I don't use it much. Lack of octave
switches on the oscillators is a real pain; some day I might be
getting around to doing som mods...
> I've seen this too. However, upon examining my MG-1 (based on the Rogue
> design I believe), the 3046 has a resistor under it (Q81?) which is
> difficult to read, since it is bathed in silicon grease for thermal
> contact.
>
> [Checking the schematic...] Yeah, the Rogue uses the five transistors in a
> 3046 as follows: VCO1 driver, VCO2 driver, VCF driver, temperature
> compensating diode drop, and unused (shorted). There are two temp comp
> resistors by the chip, one for each VCO driver.
...You have the schematic for the Rogue...!???! Ahrm, (cough), you wouldn't
be able to copy it for me if I send you some $$$ to cover postage and
copying charge..? I haven't been able to find the Rogue schematic in my
searches...
/Ricard
--
Ricard Wolf / | \ / | /- email: ricard@axis.se
Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
From analogue-request@magnus.acs.ohio-state.edu Thu Jul 29 03:07:15 1993
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Date: Thu, 29 Jul 93 00:05:00 PDT
From: till@lucid.com (Don Tillman)
Message-Id: <9307290705.AA07859@acid-rain.lucid.com>
To: analogue@magnus.acs.ohio-state.edu
In-Reply-To: Ricard Wolf's message of Wed, 28 Jul 93 09:20:33 MET DST
Subject: Exponential CV Convertor
Status: O
From: ricard@axis.se (Ricard Wolf)
Date: Wed, 28 Jul 93 09:20:33 MET DST
> The all-time cheapest, simplist circuit I know of is on the ARP Odyssey.
This is the same circuit used for the Moog filter exponential converter, at
least in the Mini, Prodigy and Rogue. Interesting ARP use it for the
oscillators - is it stable/accurate enough.
Really? [...checking...] Well so they do, I hadn't noticed before.
(Hmmm, the MicroMoog/MultiMoog are different; they use the heated 3046
transistor array for both the VCO and VCF drivers.)
I can't speak for ARPs in general, but my ARP Odyssey is pretty stable and
accurate (except for the first 15 minutes after power on).
> The Moog Modular seems to compensate for the scale drift with a
> temperature sensitive resistor. But check this out: some of the other
> Moogs like the MicroMoog and Prodigy use a CA3046 transistor array with
> one of the transistors sensing temperature and another used soley to
> heat up the chip. This compensates for both effects nicely. Pretty
> damn clever.
I've seen this too. However, upon examining my MG-1 (based on the Rogue
design I believe), the 3046 has a resistor under it (Q81?) which is
difficult to read, since it is bathed in silicon grease for thermal
contact.
[Checking the schematic...] Yeah, the Rogue uses the five transistors in a
3046 as follows: VCO1 driver, VCO2 driver, VCF driver, temperature
compensating diode drop, and unused (shorted). There are two temp comp
resistors by the chip, one for each VCO driver.
This leads me to beleive that they abandoned heated chip technology
for some reason, and went back to just using a pair of transistors at
room temperature. Could be there were problems getting the chip temperature
stable enough when the chip was heated. But I don't have the schematic so I
can't be sure.
A mystery to me. I can't think of a reason why the heated chips would not
be best.
-- Don
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From: Peter Cassidy
Subject: Re: Exponential CV convertors?
To: ricard@axis.se (Ricard Wolf) (Ricard Wolf)
Date: Tue, 27 Jul 93 17:23:45 BST
Cc: ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List)
In-Reply-To: ; from "Ricard Wolf" at Jul 27, 93 5:13 pm
Mailer: Elm [revision: 66.25]
Status: OR
> Moog use a simple PNP+NPN transistor exponential converter, and they don't even
> glue them together, in their monophonics. Understandably, they are temperature
> sensitive, and also go rather flat at high frequencies (just crank the
> resonance up until you get a sine wave and listen to it). The 3320 used
> in Sequential stuff (like the Pro-One) is much more stable and accurate.
Sounds like I haven't a hope with my two BC109's !!!
> >
> > For precision double transistors you may want to look at the MAT02 and MAT03
> > from PMI (Precision Monolythics). They're not temperature controlled though.
> > MAT02 is NPN, MAT03 PNP, or vice versa :)
>
> I think these are available from Maplin in the UK if anyone in Europe
> is interested.
I might just try this .
> Ricard Wolf / | \ / | /- email: ricard@axis.se
> Axis Communications AB /__| \/ | \__ uucp: axisab.se!ricard
> S - 223 70 LUND / | /\ | \ Tel: +46 46 19 18 63
> SWEDEN / | / \ | \__/ Fax: +46 46 13 61 30
--
Regards,
Peter
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