From analogue-request@magnus.acs.ohio-state.edu Thu May  6 11:14:21 1993
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From: Andrea TONI <andrea@sihp03.si.estec.esa.nl>
Subject: -- FTV converter -- 
To: analogue@magnus.acs.ohio-state.edu
Date: Thu, 6 May 93 17:17:27 MET
Organization:   ESA-ESTEC (European Space Research and Technology Center)
                Keplerlaan 1	2200 AG  Noordwijk (EUROPA)		
Phone: 	       	Int +31 1719 83606
Fax: 	       	Int +31 1719 84697
Machine: 	HP-UX sihp03 A.B8.05 A 9000/730 941406112	
Mailer: Elm [revision: 66.33]
Status: OR

Hi, 

Basically a FtV looks like .. 


Sig (f)	| \
--->----|  \	   | 		|      |	|		
	|OA >--->--| One Shot  	|--->--|  LPF	|---------> out (CV tension) 
      --|  /	   |		|      |  	|		
      |	| /
      |
      / GND 


the OA is an OP amp that function as comparator that is suppose to 
"square" the signal (sig(f) frequency) in a kind of zero-crossing fashion 
in which the positive front are used to trigger the O.S producing every 
time a pulse of Tm. 
The LPF is used to find the average value generated by the OS. 
Since this pulses are all equal in length and amplitude, the average value 
depends in a unique fashion by their frequency .. (that is indeed the 
freq of SIg(f).   SO the tension going out by the LPF is proportional 
to the pitch of the used note and can then be used to CV and tune the VCO . 

this diagram can help a bit more ... 



Sig (f) 
	|	
	|  ^	       ^	
	| / \         / \
	|/___\______/ ___  \_________________________________  t 
              \    /	    \ 	    /
	       \ /	       \ / 
		v		v


OP comparator
	|
	|---        -----	     ----	
	|  |        |	|	     |  |	
	|__|________|___|____________|__|_________________  t




One Shot 
	|	         	      Tm  
	|--	    ---		     ---				
	| |         | |		     | |	
	|_|_________|_|______________|_|___________________  t 



LPF 
	|	
	|			      ___________________	
	| ___________________________/
	|_____________________________________________   t 


Nice he .. to draw in ascii mode !!!!!!! arghhh 

I just would like to add that the length of Tm has to be smaller then the 
shortest Ts of sig(f) otherwise the OS wouldn't be able to keep track 
of sig(f). 
The drawing is of course an ideal situation .. but in the reality the LPF is 
a bit slow in catching up the quick frequency variation.
The most difficult thing is of course in the accuracy and stability required. 
In the standard Cv/Oct two semitone are equal to a difference  of 83 millivolt 
(!!)  and since ears are able to fetch a de-tune of 1/4 of semitone .. we 
can assume that errors need to be in the range of 10 millivolt .. and 
in the analog domain you know what it means !!! (minimum noise .. thermal 
attentions, hi-level components .. ) 
But the advantage compare to a digital pitch-to-midi is the uniform 
functioning of the circuit .. the converter doesn't have to discriminate 
between a legato, vibrato or glissato .. the output tension (CV) will 
*dummyly* follow the frequency of sig(f). From here the name pitch-follower 
may seems more appropriate since the circuit doesn't detect the sig(f) but 
it barely make a conversion. 
In a pitch-to-midi device instead everything is much more complicated 
since the box has to discriminate semitones closer to the real pitch and 
to approximate to the real freq of the pitch-bend command. 

I have both an analog (Korg MS20) and a digital (Roland VP70) PtV(Midi) 
and even if the Korg looks simpler it is in practice more usable .. 
the digital one required a lot more attention when you feed in voice 
(no bending no rapid detuning etc etc ..) 

The Analog Devices  Databooks (89/90) contain a lot of hi-level IC already 
suited for the purpose .. 
AD537 (VtoF) 
AD650 (FtoV and VtoF)
AD652 (VtoF)
AD654 (VtoF)  Low cost .. 
ADVFC32 (FtoV and VtoF)

.. and of course if you find any old databook (the new ones are as bad as 
digital synth compare to analog ..!!! ) you may find several application 
notes and proper explanations .. 

Enjoy !! 

Ciao, 
------------------------------------------------ENV---ENV---ENV----------------
 Andrea TONI (andrea@sihp03.si.estec.esa.nl)     |     |     |
 Planetary and Space                            VCO-->VCF-->VCA--> DUCATI 900SS
 Science Division (SI)                           |     |     |
------------------------------------------------LFO---LFO---LFO----------------

From analogue-request@magnus.acs.ohio-state.edu Thu May  6 13:07:26 1993
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	(16.7/16.2) id AA01786; Thu, 6 May 93 17:17:27 +0100
From: Andrea TONI <andrea@sihp03.si.estec.esa.nl>
Subject: -- FTV converter -- 
To: analogue@magnus.acs.ohio-state.edu
Date: Thu, 6 May 93 17:17:27 MET
Organization:   ESA-ESTEC (European Space Research and Technology Center)
                Keplerlaan 1	2200 AG  Noordwijk (EUROPA)		
Phone: 	       	Int +31 1719 83606
Fax: 	       	Int +31 1719 84697
Machine: 	HP-UX sihp03 A.B8.05 A 9000/730 941406112	
Mailer: Elm [revision: 66.33]
Status: OR

Hi, 

Basically a FtV looks like .. 


Sig (f)	| \
--->----|  \	   | 		|      |	|		
	|OA >--->--| One Shot  	|--->--|  LPF	|---------> out (CV tension) 
      --|  /	   |		|      |  	|		
      |	| /
      |
      / GND 


the OA is an OP amp that function as comparator that is suppose to 
"square" the signal (sig(f) frequency) in a kind of zero-crossing fashion 
in which the positive front are used to trigger the O.S producing every 
time a pulse of Tm. 
The LPF is used to find the average value generated by the OS. 
Since this pulses are all equal in length and amplitude, the average value 
depends in a unique fashion by their frequency .. (that is indeed the 
freq of SIg(f).   SO the tension going out by the LPF is proportional 
to the pitch of the used note and can then be used to CV and tune the VCO . 

this diagram can help a bit more ... 



Sig (f) 
	|	
	|  ^	       ^	
	| / \         / \
	|/___\______/ ___  \_________________________________  t 
              \    /	    \ 	    /
	       \ /	       \ / 
		v		v


OP comparator
	|
	|---        -----	     ----	
	|  |        |	|	     |  |	
	|__|________|___|____________|__|_________________  t




One Shot 
	|	         	      Tm  
	|--	    ---		     ---				
	| |         | |		     | |	
	|_|_________|_|______________|_|___________________  t 



LPF 
	|	
	|			      ___________________	
	| ___________________________/
	|_____________________________________________   t 


Nice he .. to draw in ascii mode !!!!!!! arghhh 

I just would like to add that the length of Tm has to be smaller then the 
shortest Ts of sig(f) otherwise the OS wouldn't be able to keep track 
of sig(f). 
The drawing is of course an ideal situation .. but in the reality the LPF is 
a bit slow in catching up the quick frequency variation.
The most difficult thing is of course in the accuracy and stability required. 
In the standard Cv/Oct two semitone are equal to a difference  of 83 millivolt 
(!!)  and since ears are able to fetch a de-tune of 1/4 of semitone .. we 
can assume that errors need to be in the range of 10 millivolt .. and 
in the analog domain you know what it means !!! (minimum noise .. thermal 
attentions, hi-level components .. ) 
But the advantage compare to a digital pitch-to-midi is the uniform 
functioning of the circuit .. the converter doesn't have to discriminate 
between a legato, vibrato or glissato .. the output tension (CV) will 
*dummyly* follow the frequency of sig(f). From here the name pitch-follower 
may seems more appropriate since the circuit doesn't detect the sig(f) but 
it barely make a conversion. 
In a pitch-to-midi device instead everything is much more complicated 
since the box has to discriminate semitones closer to the real pitch and 
to approximate to the real freq of the pitch-bend command. 

I have both an analog (Korg MS20) and a digital (Roland VP70) PtV(Midi) 
and even if the Korg looks simpler it is in practice more usable .. 
the digital one required a lot more attention when you feed in voice 
(no bending no rapid detuning etc etc ..) 

The Analog Devices  Databooks (89/90) contain a lot of hi-level IC already 
suited for the purpose .. 
AD537 (VtoF) 
AD650 (FtoV and VtoF)
AD652 (VtoF)
AD654 (VtoF)  Low cost .. 
ADVFC32 (FtoV and VtoF)

.. and of course if you find any old databook (the new ones are as bad as 
digital synth compare to analog ..!!! ) you may find several application 
notes and proper explanations .. 

Enjoy !! 

Ciao, 
------------------------------------------------ENV---ENV---ENV----------------
 Andrea TONI (andrea@sihp03.si.estec.esa.nl)     |     |     |
 Planetary and Space                            VCO-->VCF-->VCA--> DUCATI 900SS
 Science Division (SI)                           |     |     |
------------------------------------------------LFO---LFO---LFO----------------

From analogue-request@magnus.acs.ohio-state.edu Thu May  6 10:11:41 1993
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	(16.6/16.2) id AA24403; Thu, 6 May 93 15:07:13 +0100
From: Peter Cassidy <peterc@comm.mot.com>
Subject: Re: FTV converter
To: RICK@sara.nl (Rick Jansen)
Date: Thu, 6 May 93 15:07:11 BST
Cc: ANALOGUE@magnus.acs.ohio-state.edu (Analogue Mail List)
In-Reply-To: <9305061216.AA110723@diamond.sara.nl>; from "Rick Jansen" at May 06, 93 1:16 pm
Mailer: Elm [revision: 66.25]
Status: OR

> 
> 
> Hey thanks! I didn't know there were standard ic's for this function.
> I'm looking forward to the device numbers.
> 
> -Rick.
> 
> --
> rick@sara.nl
> 
>   She's a Module and she's looking good
> 

OK. Here's one, straight from the R.S catalog:


----------------------------------

TC9400CPD, TC9401CPD, TC9402CPD    ( Varying accuracies)

Teledyne Components

14-pin IC

Works as Freq-to-voltage and Voltage-to-freq

Linear freq to voltage ratio. Single or dual supply, 8 - 15 V or +-4 to +-7.5V

10Hz - 100KHz operation. Worst linearity 9401 = 0.25%
Best linearity 9401 = 0.004%

                        ************
           Ibias        * 1 ****   *  Vdd
           ZERO ADJUST  *    **    *  N.C.
           Iin          *          *  AMPLIFIER OUT
           Vss          *   9400   *  COMPARATOR IN
           Vrefout      *          *  FREQ/2 OUT
           GND          *          *  OUTPUT COMMON
           Vref         *          *  PULSE FREQ. OUT
                        ************

R.S Part number 264-951

-----------------------------------

This looks like a suitable candidate. Are you trying Voice to CV conversion
or vocoding ?? I would be really interested to hear how you get on !!!

--
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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