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Chip for 0.1 Hz to 20Khz V to F?

F

Funky

Jan 1, 1970
0
The 8038 has a range of 1:1000 which isn't quite good enough for what I
want. Is there a chip as simple and cheap as the 8038 but with this extended
range? It's the sine wave output I'm interested in.

For those interested, I'm building for a musician a module which has 2X
coarse and fine controls to generate two sine waves from 0.1 to 20Khz which
are then added together. The two frequencies will be approximately the same
and so beating against one another. The resulting waveform is converted to a
square wave to get the required timbre.

Thanks for your interest
 
B

Ben Bradley

Jan 1, 1970
0
Funky said:
The 8038 has a range of 1:1000 which isn't quite good enough for what I
want. Is there a chip as simple and cheap as the 8038 but with this extended
range? It's the sine wave output I'm interested in.

For those interested, I'm building for a musician a module which has 2X
coarse and fine controls to generate two sine waves from 0.1 to 20Khz which

I understand the 8038 was never good enough for synthesizers, it
was just a cheap function generator on a chip. There used to be VCO
chips made by SSM and CEM specifically for music synthesizers, but
those are no longer available (except maybe as new-old-stock at high
prices). You can build a good one with opamps and "discrete"
components, though, just the way they did back in the '60's and '70's.
For schematics, here are some likely suspects:
http://hoohahrecords.com/resfreq/index.html
http://www.paia.com

And you surely want exponential exponential voltage-to-frequency
response.
 
R

Robert Baer

Jan 1, 1970
0
Ben said:
I understand the 8038 was never good enough for synthesizers, it
was just a cheap function generator on a chip. There used to be VCO
chips made by SSM and CEM specifically for music synthesizers, but
those are no longer available (except maybe as new-old-stock at high
prices). You can build a good one with opamps and "discrete"
components, though, just the way they did back in the '60's and '70's.
For schematics, here are some likely suspects:
http://hoohahrecords.com/resfreq/index.html
http://www.paia.com

And you surely want exponential exponential voltage-to-frequency
response.

John Bergoun(sp?), an electronics reseller (Solid State Music) in the
Silicon Valley during the good old daze of the Altair, designed the
various SSM chips, and sold the technology to Exar.
Since i was not into music related electronics, i lost track of his
designs after that transfer.
However, if Exar or the second-sourcing makers are still around, the
prices might be reasonable.
Jameco used to carry some of the SSM ICs; i have not checked recently
(leave that up to you).
Hope the history helps.
 
R

Robert Baer

Jan 1, 1970
0
Ben said:
I understand the 8038 was never good enough for synthesizers, it
was just a cheap function generator on a chip. There used to be VCO
chips made by SSM and CEM specifically for music synthesizers, but
those are no longer available (except maybe as new-old-stock at high
prices). You can build a good one with opamps and "discrete"
components, though, just the way they did back in the '60's and '70's.
For schematics, here are some likely suspects:
http://hoohahrecords.com/resfreq/index.html
http://www.paia.com

And you surely want exponential exponential voltage-to-frequency
response.

BTW, anything below 100Hz is useless and inaudible.
Yes, someone will try to dispute that, but just try to hear a 100Hz
sine wave at the same level as a 1Khz wave,where the 1Hhz amplitude is
set to a plesant level.
Goes to show that a 3dB rolloff at 100Hz is very reasonable.

But, on the high end, one might want to be able to generate 100Khz, as
the ear can detect phase differences equivalent to 100KHz.
Houseomever, 20KHz is not unreasonable for the high end.
 
J

John Woodgate

Jan 1, 1970
0
The 8038 has a range of 1:1000 which isn't quite good enough for what I
want. Is there a chip as simple and cheap as the 8038 but with this extended
range? It's the sine wave output I'm interested in.

For those interested, I'm building for a musician a module which has 2X
coarse and fine controls to generate two sine waves from 0.1 to 20Khz which
are then added together. The two frequencies will be approximately the same
and so beating against one another. The resulting waveform is converted to a
square wave to get the required timbre.
You do realise that you are also going to get strong difference-
frequency and sum-frequency tones when you square the waveform? These
are in general not harmonically-related to the original tones and
usually sound very rough indeed.

I suggest you breadboard your project before spending a lot of money on
it.
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Robert Baer
But, on the high end, one might want to be able to generate 100Khz, as
the ear can detect phase differences equivalent to 100KHz.

Or, OTOH, the ear is insensitive to phase at any frequency, except under
very special contrived conditions.

If you think the subjective level of 100 Hz is negligible compared with
that of 1 kHz at the same sound pressure, say 80 dB, consider how far
down 100 kHz is. Can you say 'minus infinity'?
 
B

Bill Sloman

Jan 1, 1970
0
Funky said:
The 8038 has a range of 1:1000 which isn't quite good enough for what I
want. Is there a chip as simple and cheap as the 8038 but with this extended
range? It's the sine wave output I'm interested in.

For those interested, I'm building for a musician a module which has 2X
coarse and fine controls to generate two sine waves from 0.1 to 20Khz which
are then added together. The two frequencies will be approximately the same
and so beating against one another. The resulting waveform is converted to a
square wave to get the required timbre.

Use a pair of DDS chips (Analog Devices AD9833 ?)and a cheap micro
with built in A/D converter (Microchip Technology PIC16F876 ?)to read
the control pots and generate the serial data required to control the
DDS chips.

Much less difficut to design, and many fewer parts.
 
J

Jan Panteltje

Jan 1, 1970
0
The 8038 has a range of 1:1000 which isn't quite good enough for what I
want. Is there a chip as simple and cheap as the 8038 but with this extended
range? It's the sine wave output I'm interested in.

For those interested, I'm building for a musician a module which has 2X
coarse and fine controls to generate two sine waves from 0.1 to 20Khz which
are then added together. The two frequencies will be approximately the same
and so beating against one another. The resulting waveform is converted to a
square wave to get the required timbre.

Thanks for your interest
In the old days, audio signal generator was made by mixing say 100kHz fixed
with a variable 100 kHz to 1020 kHz oscillator, then a low pass.
I used these in the lab.
The 100 kHz tunable is easy to make for a delta of 20 kHz.
A EPROM with lookup sine table driven by a counter from a var osc could
perhaps also work.
For 256 points in the sine wave you would need to sweep from 26 Hz to 25.6 MHz.
FPGA, lookup table in it, r2r ladder as DA on output.
Plenty of inputs for the control.
You could put both channels in it, including the summing.
JP
 
B

Ben Bradley

Jan 1, 1970
0
In sci.electronics.design said:
BTW, anything below 100Hz is useless and inaudible.

I recall Keith Emerson going well below 100Hz on the synth lead in
Lucky Man. Even if your stereo won't reproduce the fundamental, you
can hear the harmonics.
Also, subsonic frequencies are often used to modulate other
oscillators for vibrato (FM. usually around 7 Hz), tremolo (AM in the
same frequency range) and sweep effects.
 
F

Funky

Jan 1, 1970
0
John Woodgate said:
You do realise that you are also going to get strong difference-
frequency and sum-frequency tones when you square the waveform? These
are in general not harmonically-related to the original tones and
usually sound very rough indeed.

I've simulated the effect using Cool Edit and it didn't sound too bad. What
sort of level should the output be at if it's going to a microphone input?
Are the output levels of my PC sound card designed to drive a microphone
input?
Thanks.
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Ben Bradley <ben_nospam_bradley@mi
ndspring.example.com> wrote (in <jglv209k5gc7a59dg11jcjrgli12imek1j@4ax.
com>) about 'Chip for 0.1 Hz to 20Khz V to F?', on Sun, 15 Feb 2004:
Also, subsonic frequencies are often used to modulate other
oscillators for vibrato (FM. usually around 7 Hz), tremolo (AM in the
same frequency range) and sweep effects.

These modulations are not physical signals at those frequencies. Think
about wiggling the volume control of a small radio very fast. You get
tremolo, with absolutely no response at subsonic frequencies.
 
J

John Woodgate

Jan 1, 1970
0
I've simulated the effect using Cool Edit and it didn't sound too bad.
What sort of level should the output be at if it's going to a microphone
input? Are the output levels of my PC sound card designed to drive a
microphone
input?

No: they are 100 to 500 times too big (depending on the sensitivity of
you 'mic input'). You need to attenuate. 10 kohms in series and 1 kohm
to 220 ohms to ground. Mic input goes across the low-value resistor.
 
B

Ben Bradley

Jan 1, 1970
0
In sci.electronics.design said:
John Bergoun(sp?), an electronics reseller (Solid State Music) in the
Silicon Valley during the good old daze of the Altair, designed the
various SSM chips, and sold the technology to Exar.
Since i was not into music related electronics, i lost track of his
designs after that transfer.
However, if Exar or the second-sourcing makers are still around, the
prices might be reasonable.
Jameco used to carry some of the SSM ICs; i have not checked recently
(leave that up to you).
Hope the history helps.

I don't know what path they took, but apparently what's left of the
SSM series is made by Analog Devices, and somewhere along the way the
chips that had applications almost exclusively to synthesizers (VCO's
and VCF's) were dropped (leaving mainly mic preamps and VCA's, which
have substantial non-synth applications). The market for such chips
apparently disappeared about the time the Yamaha DX-7 (which used
all-digital circuitry for FM synthesis, and was very popular) appeared
on the market.
 
L

Lasse Langwadt Christensen

Jan 1, 1970
0
Bill said:
Use a pair of DDS chips (Analog Devices AD9833 ?)and a cheap micro
with built in A/D converter (Microchip Technology PIC16F876 ?)to read
the control pots and generate the serial data required to control the
DDS chips.

Much less difficut to design, and many fewer parts.

Why even bother with the DDS-chips? if it's only <20KHz it should be
straight forward to do DDS in the micro, especially if he wants
squarewaves ..

-Lasse
 
F

Funky

Jan 1, 1970
0
John Woodgate said:
No: they are 100 to 500 times too big (depending on the sensitivity of
you 'mic input'). You need to attenuate. 10 kohms in series and 1 kohm
to 220 ohms to ground. Mic input goes across the low-value resistor.

OK, to be more specific, what should I take the input impedance and the max
input level for a microphone input to be?
Is there some sort of standard that defines the signal levels required for
guitar amplifier, microphone input etc?
I think I'm right in saying that there is no need for impedance matching
since I have complete control over the output voltage level?
Regards,
Jmc
 
R

Robert Baer

Jan 1, 1970
0
Ben said:
I don't know what path they took, but apparently what's left of the
SSM series is made by Analog Devices, and somewhere along the way the
chips that had applications almost exclusively to synthesizers (VCO's
and VCF's) were dropped (leaving mainly mic preamps and VCA's, which
have substantial non-synth applications). The market for such chips
apparently disappeared about the time the Yamaha DX-7 (which used
all-digital circuitry for FM synthesis, and was very popular) appeared
on the market.

Makes a sort of sense..the market got "side-tracked".
 
R

Robert Baer

Jan 1, 1970
0
Ben said:
I recall Keith Emerson going well below 100Hz on the synth lead in
Lucky Man. Even if your stereo won't reproduce the fundamental, you
can hear the harmonics.
Also, subsonic frequencies are often used to modulate other
oscillators for vibrato (FM. usually around 7 Hz), tremolo (AM in the
same frequency range) and sweep effects.

"harmonics", "modulation" are all terms that do *not* correspond to
"sine wave".
In either case cited, is the 100Hz heard, just the "distortion"
harmonics.
In essence, you have proven my point.
 
R

Robert Baer

Jan 1, 1970
0
Funky said:
I've simulated the effect using Cool Edit and it didn't sound too bad. What
sort of level should the output be at if it's going to a microphone input?
Are the output levels of my PC sound card designed to drive a microphone
input?
Thanks.

Hell, NO!
Line level outputs is in the VOLT region, and microphone inputs are in
the (roughly) MICROVOLT region.
 
R

Robert Baer

Jan 1, 1970
0
Funky said:
OK, to be more specific, what should I take the input impedance and the max
input level for a microphone input to be?
Is there some sort of standard that defines the signal levels required for
guitar amplifier, microphone input etc?
I think I'm right in saying that there is no need for impedance matching
since I have complete control over the output voltage level?
Regards,
Jmc

Impedance matching is not an issue.
Typically, microphone inputs have a high impedance so as to not load
the input signal (and historically, it was the grid of a tube that was
the input; a rather high impedance).
 
J

John Woodgate

Jan 1, 1970
0
OK, to be more specific, what should I take the input impedance and the
max input level for a microphone input to be?

The input impedance is usually between 1 kohm and 3 kohm. The maximum
input voltage varies widely; some sound cards have AGC. But assume that
it's about 10 mV.
Is there some sort of
standard that defines the signal levels required for guitar amplifier,
microphone input etc?

Yes, IEC 61938. But many manufacturers don't follow it, and the sound
card manufacturers seem to deliberately ignore it.
I think I'm right in saying that there is no need
for impedance matching since I have complete control over the output
voltage level?

Impedance matching in the sense of maximum power transfer has virtually
no place in modern audio interfacing.
 
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