xr 2206 vco ic

[zipzap]

Here´s a little shematic, in case someone having difficulties with reading the datasheet (like me several weeks ago). I left out the LED driver, we all know that, besides it´s in the vactrol thread.
THe sine/tri adjust pot should be around a few k, i´m not sure right now.
The Distortion pot can be replaced with a 47k resistor, or you want to use it as an overdrive to square things up. If that pin 3 is connected to ground the chip is almost quiet, even more than with the AM Pot connected to ground. But again, this is not voltage but current controll and is not quiet enough to be used with an env. When both pin 1 and 3 are connected to ground it´s total silance, maybe something could be done here, but i´m fed up with it for now. LM13700 is cheap and available. Anyway, if you like you can use pin 3 for an offset by going to some pos or neg voltage with the pot, instead of ground.
The Cab values are just the ones i liked. With the tri/Saw swich closed you get a (sinish) rising ramp at about double freq. The 10k at pin 8 sets a fixed falling time. Smaller values caused some strange distortion. At high freq the saw moves towards tri again, but i don´t care.
Maybe another LDR for that 10k would also work with some circuitry, to have full symmetry controll.
That Am pin 1 should go to neg voltage if not used.
!Max voltage for this ic is +- 13v!
have Fun!

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[Scott Stites]

Edit: oops - posted to the wrong thread

[mosc]

Scott - just edit the post = then cut 'n paste in the right thread - then let me know and I'll delete these posts.

[Scott Stites]

Thanks Howard.

Yep - I cut the reply and pasted it in the "Thomas Henry" XR2206 VCO thread.

[vtl5c3]

English version of the "Cryptophonie" text. I think that this was typed in from the UK version of Elektor.


Talk Funny?
===========

Ring modulator, chopper and frequency modulator
-----------------------------------------------

Deliberate electronic distortion of speech and music signals can give fascinating results.
Professional musicians use extremely expensive equipment to obtain their very own weird and
wonderful 'sound'. For electronics enthusiasts, it is much more fun to get the same sort of
results from very simple circuits. Which is what this article is about: getting effective
effects using a single IC, the 2206.

One of the best known and most impressive distorters for audio signals is the ring modulator.
Normally speaking, a ring modulator circuit has two inputs: one for the audio signal (speech,
for instance) and one for a carrier. The weirdest effects are obtained when the carrier
frequency is within or just above the audio range; using different carrier shapes (sinewave,
squarewave or triangular waveform) can produce different effects.

The circuit can be drastically simplified by using a 2206. This IC contains a suitable
generator for the 'carrier', and a multiplier circuit that is ideally suited for use as a
ring modulator. The internal block diagram is shown in figure 1.

The oscillator (VCO) is already connected internally to the multiplier. This means that,
basically, applying an audio signal to the other multiplier input (pin 1) will produce a
'ring-modulated' output at pin 2. Simplicity itself!

Obviously, a few other components are needed in a practical circuit. Not many, though, as
shown in figure 2. A single capacitor, C4 (C ext. in figure 1), determines the frequency
range of the VCO. With the value given, the 1M potentiometer (P1; R ext. in figure 1) can
be used to set any frequency between approximately 10 Hz and 10 kHz. The wave shape is
selected by means of S1: switch closed for sinewave, switch opened for triangle.

The audio input signal is fed to the modulation input via C1. A voltage divider circuit
(R1, P2, R2) sets two DC bias levels: the voltage across C2 provides the basic internal DC
reference, and P2 is used to adjust the operating point of the multiplier. This adjustment
is important: it determines the 'carrier level' (the output from the oscillator) present
in the final audio output. The easiest way is to short the audio input and then adjust P2
for zero audio output. Only then is the circuit operating as a true ring modulator. If P2
is incorrectly set, the oscillator frequency will appear at the output, amplitude modulated
by the input (speech) signal. This can give interesting effects, but it isn't really the
intention!

A stabilised supply must be used, otherwise the DC settings may drift. This would mean
regular re-adjustment of P2 - which is rather a nuisance.


Chopping and frequency modulation
---------------------------------

The circuit can be extended, as shown in figure 3. Only a few additional components are
needed to really use the IC to the full. Apart from adding the 'chopper' and 'frequency
modulator' features, a useful linear frequency scale for the oscillator control is obtained
as an additional bonus.

The basic ring modulator circuit is virtually identical to the circuit given in figure 2.
The main difference is that the multiplier bias adjustment is improved: P3 is used for
initial coarse adjustment, with P2 in the mid position; then P2 is used to tune out the
last traces of the carrier.

The chopper circuit makes use of a square wave output available at pin 11. To be more
precise, this is the collector of an internal switching transistor (see figure 1). With
S5 in position 'chopper', this point is connected to the signal output. When the
transistor is turned on, the output is shorted; since the transistor is turned on and off
periodically by the internal oscillator, the chopper frequency is determined by the setting
of P5 (the VCO frequency control). Switch S2 can be used to select the audio signal before
or after the ring modulator; note, however, that in the latter case the 'carrier' frequency
for the ring modulator and the chopper frequency are identical - they are both derived from
the same VCO.

The main reason for modifying the frequency control circuit for the VCO is to obtain a
linear voltage control point. The frequency of the VCO varies linearly with the voltage
at the base of T1; this voltage is determined by the setting of P5, but a frequency
modulation signal can be superimposed via C7. P1 sets the modulation level; S1 is used to
select either the audio input signal or the output signal.

The frequency control range is set by P4. The procedure is as follows. Turn P5 right up
(lowest frequency) and set P4 to maximum resistance. C5 is switched into circuit via S3
and P2 is offset so that the oscillator signal appears at the output. P4 is now slowly
turned down until the oscillator stops, and then turned back until it starts again reliably.
This is the optimum setting. Once again, it depends on the supply voltage - so the latter
must be stabilised.

A simple supply using a 78L12, say, is adequate. A suitable circuit and P.C. board were
given in Elektor, July/August 1978, p.7-75. A basic printed circuit board layout for the
circuit itself is given in figure 4, and the two sides of the front panel with the controls
are shown in figures 5 and 6. Finally, a suggestion for a combined in-and output connection
is shown in figure 7. All of these drawings are included as suggestions only; the final
design may be modified according to personal taste.


How funny does it sound?
------------------------

Sound effects are always difficult to describe - you've got to hear them. The ring
modulator 'sound' is perhaps the best known: all kinds of additional frequencies are added
to the original signal, without any harmonic relationship. If really sharp dissonances are
what you want, the 2206 ring modulator is just the trick!

The effect can be 'improved' by switching from sinewave to triangle: if you're not careful,
you end up with a completely scrambled signal. On the other hand, using a low-frequency
sinewave produces a more 'pleasant' sound - the ring modulator adds an interesting rhythmic
effect to the original.

The chopper facility can be useful on its own, producing a kind of 'robot' or 'computer'
sound. When used in combination with the ring modulator, the most weird results can be
obtained. In the same way, combining frequency modulation with the ring modulator can be
interesting: low modulation levels produce 'a kind of vibrato effect, and high modulation
levels - well. Try it!

Table

Technical data for the complete circuit (figure 3).

Functions:
Ring modulator
Chopper
Frequency modulator

Frequency range of VCO:
Low range: 1 Hz... 300 Hz
High range: 100Hz... 20kHz

Frequency modulation:
±30% frequency swing for 1v top-top modulation signal.

Impedances:
Input 30k
Output 2 k

Signal levels:
Input, nominal 1 Vtt (350 mV RMS) maximum 8 Vtt (2.8 V RMS)
Output, maximum 10 Vtt (3.5 V RMS)

Supply:
12V, stabilised; 30 mA max.

===============================================================================

Talk funny on board
-------------------

The electronic speech distorter, described last month as 'Talk funny?', is quite a nice
little circuit. On second thoughts, it seemed a pity that the P.C. board was not available
via the EPS service - but that is easily remedied.

While 'cleaning up' the layout given as a suggestion last month, all wiring between
switches, potentiometers etc. was included on the board. This means that these components
can be wired direct to the board; the drawing given as figure 5 in the original article can
be ignored.

One final point: it is advisable to increase the value of P4 to 47 k (50 k), as shown in the
parts list below.

Parts list

Resistors:
R1 = 3k9
R2 = 47k
R3,R8 = 1k
R4= 56k
R5 = 100k
R6= 2k2
R7 = 220R
R9 = 100k
P1 = 100k log
P2 = 470R (500R) preset
P3 = 4k7 (5k) preset
P4 = 47k (50k) preset
P5 = 10k lin

Capacitors:
C1,C7= l00n
C2,C3 = 2u2/10 V
C4 = 1u (not elco!)
C5 = 15n
C6= 1u/10V

Semiconductors:
IC1 = XR2206CP T1 = BC109C, BC549C, or equ.

D1=DUS

Switches:
S1, S2, S3, S5 = single-pole
changeover
S4 = single-pole, make

[GrimReaper76]

Hey!

Im new here, and Ive checked out some of the content of Lunetta, Modular synthezisers etc. - my electronic skill is limited, so bare with my "this maybe work.. hmm" heh

Got my hands on some XR2206 chip, thought of maybe doing some oscillators, no pro stuff! And I wanted(as everyone else) to make some kind of voltage control of the chip.. after looking at the french article(with pictures) at the start of the thread, at the schematic, Ive edited the picture(schematic) for you guys to see my thought..

excuse my poor english(Im from Sweden)

cheers.

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[synthmonger]

I smell free samples!

http://www.exar.com/Common/Content/ProductDetails.aspx?ID=XR2206


For green SDIYists Make sure to get the PDIP. SOIC is surface mount!

[jean-louise]

[Coriolis]

Hi GrimReaper76 , and welcome!

VC of the 2206 has been done Thomas Henry did a complete (and very nice) vco with it. It's over in the Thomas Henry subforum...

C

[Sine]

I smell free samples!


i tried to order samples a few weeks ago.
has somebody experience with what's good to tell them?

That is why the sampling systems go down the toilet, I only sample extremely hard to get chips, when loads of people go sampling basic ic's the logical response is to make sampling very hard or even impossible. ( some companies have already done this )

So only sample what you REALLY can't get anywhere else.

[jean-louise]

[Coriolis]

http://www.futurlec.com/cgi-bin/search/qty_price.cgi?part_no=XR2206

...for instance...

C

[etaoin]

[jean-louise]

thanx coriolis, i've already found a supplier - i was just a little out of my head then.
hm a sample, as i understand that, is something to try it out before, so one can decide if it's worth buying. or not?
ok but nevermind.. i normally don't try to get samples anyway due to impatience
cheers
j

[etaoin]

[jean-louise]

[synthmonger]

Eh I'm not sure just how bad it affects them but I doubt a small group of SDIY people ordering samples is going to cause their business to crash. I know it's not just us ordering samples but if it does indeed hurt their operations then perhaps they should only allow certain email addresses (.edu and businesses etc) to be used. Some do it.

If you hate the long wait for futurlec then go for Mouser
http://www.mouser.com/Search/Refine.aspx?Keyword=xr2206

[jean-louise]

and conrad has them too, for those located in germany

http://www1.conrad.de/scripts/wgate/zcop_b2c/~flN0YXRlPTk1MzQzMzMxMg==?~template=PCAT_AREA_S_BROWSE&glb_user_js=Y&shop=B2C&p_init_ipc=X&~cookies=1&scrwidth=1280

5,74EUR plus postage .. urrgh

[etaoin]

[synthmonger]

[jean-louise]

so you got those samples?

[jean-louise]

[synthmonger]

[jean-louise]

ok
else i would have been jealous

cheers

[Sine]