Art and Electronics

B

Ban

Guest
After having been to the class-meeting I told you about, I came again in
contact with my former arts teacher.
http://www.florianlechner.de/start.htm
38yrs. ago we had been doing a kybernetic sculpture together, consisting of
a wave-shaped long mirror with 7 flash tubes in the focus points of it.
A small cutout of a piano keyboard(1 octave) was used to trigger those tubes
by the spectators. Now he asked me to restore the original condition again.

I had the idea to make another interface working with a mike array. The
sound of people standing in front is picked up, processed and triggers the
respective bulbs. Bandpass filters with moderate Q(5) resonate between 200
and 800Hz (adjustable). The idea is to get the people humming/singing and if
they hit the right pitch the bulb starts flashing faster up to 5/s. If there
are several people in harmony more bulbs will start flashing, you get it.

To avoid people screaming too loud I want to make a AGC circuit, that keeps
the level constant over a range of 60dB.
Here is my AGC being the most critical block:

60dB AUTOMATIC GAIN CONTROL

1/4 SSM2164 /|----.
o / | \/ | ___ -5V
| .---< | /\ o--o-|___|-o
threshold.-. | \ | | | 15k
.--->| | .-. \|-o--' .-.
| | | | | | | |
| '-' 15k| | | | |510
| | '-' || | '-'
| GND o-----||-o |
| | 1n|| | ---
|0.003..3V___ | |\ | ---560p
| .----|___|--o--|-\ | |
| | 10k | >--o ===
.-o---o------. .--|+/ | GND
| fullwave | | |/ |
| Rectifier| === | ___
| Averager | GND | .-|___|-.
'-----o------' .-o-|\ | 15k |
| ___ | \/| \ | |\ |
o----o---------|___|-o--o /\| >-o-|-\ | ||
Input 15k | | | / | >--o---||---o to
.-. '---|/ .-|+/ || filter bank
| | | |/
510| | |
'-' ===
| GND
---
560p --- 1/4 SSM2164
|
===
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)
--
ciao Ban
Bordighera, Italy
 
Ban wrote:
60dB AUTOMATIC GAIN CONTROL

1/4 SSM2164 /|----.
/ | \/ | ___ -5V
.---< | /\ o--o-|___|-o
| \ | | | 150k
.-. \|-o--' .-.
| | | | |
15k| | | | |510
'-' || | '-'
o-----||-o |
| 1n|| | ---
0.003..3V___ | |\ | ---560p
.----|___|--o--|-\ | |
| 10k | >--o === |\
.-----o------. .--|+/ | GND | \
| Fullwave | | |/ '---------------|-1>-.
| Rectifier| === | / |
| Averager | GND |/ |
'------o-----' .--------------------'
| | ___
| | .-|___|-.
| .-o-|\ | 150k |
| ___ | \/| \ | |\ |
o----o-------|___|--o--o /\| >-o-|-\ | || 300mV
| | | / | >--o---||---o to
.-. '---|/ .-|+/ || filter bank
| | | |/
510| | |
'-' ===
| GND
---
560p --- 1/4 SSM2164
|
===
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

corrected schematic, I forgot the inverter. The circuit works as follows:

3V[3mV] rectifier out, the VCA will have to do +20dB[-40dB] to compensate
for the input current which results in a control voltage
of -33mV*+20[-40]= -660[+1320]mV The inverter makes +660[-1320] +660 =
+1320[-660]mV resulting in -40dB[+20] main gain and 330mV out.
This way there is also a possibility to adjust the threshold with a linear
pot.
--
ciao Ban
Bordighera, Italy
 
Ban wrote...
60dB AUTOMATIC GAIN CONTROL

1/4 SSM2164 /|----.
/ | \/ | ___ -5V
.---< | /\ o--o-|___|-o
| \ | | | 150k
*** .-. \|-o--' .-.
| | | | |
15k| | | | |510
'-' || | '-'
o-----||-o |
| 1n|| | ---
0.003..3V___ | |\ | ---560p
.----|___|--o--|-\ | |
| 10k | >--o === |\
.-----o------. .--|+/ | GND | \
| Fullwave | | |/ '---------------|-1>-.
| Rectifier| === | / |
| Averager | GND |/ |
'------o-----' .--------------------'
| | ___
| | .-|___|-.
| .-o-|\ | 150k |
| ___ | \/| \ | |\ |
o----o-------|___|--o--o /\| >-o-|-\ | || 300mV
| | | / | >--o---||---o to
.-. '---|/ .-|+/ || filter bank
| | | |/
510| | |
'-' ===
| GND
---
560p --- 1/4 SSM2164
|
===
GND

3V[3mV] rectifier out, the VCA will have to do +20dB[-40dB] to
compensate for the input current which results in a control voltage
of -33mV*+20[-40]= -660[+1320]mV The inverter makes +660[-1320] +660
= +1320[-660]mV resulting in -40dB[+20] main gain and 330mV out.
This way there is also a possibility to adjust the threshold with a
linear pot.
Click to expand...
The resistor I marked *** isn't doing anything to earn its keep, is it?
Also, you could use multiplier ICs instead of the ssm2164, saving a few
opamps, right? OK, the ssm2164 is pretty cheap. Speaking of critical
circuits, what's your take on the "Fullwave Rectifier Averager" circuit?
You have two ssm2164 sections left.


--
Thanks,
- Win
 
Seems way too complicated to me. If all you are looking
for is the presence and relative levels of frequencies over
the voice range, something more class-C-like would work
since we aren't trying to preserve the audio envelope here
for further use.
 
"Ban" <bansuri@web.de> a écrit dans le message de
news:9NfNe.63006$2U1.3402098@news3.tin.it...
Ban wrote:
60dB AUTOMATIC GAIN CONTROL

1/4 SSM2164 /|----.
/ | \/ | ___ -5V
.---< | /\ o--o-|___|-o
| \ | | | 150k
.-. \|-o--' .-.
| | | | |
15k| | | | |510
'-' || | '-'
o-----||-o |
| 1n|| | ---
0.003..3V___ | |\ | ---560p
.----|___|--o--|-\ | |
| 10k | >--o === |\
.-----o------. .--|+/ | GND | \
| Fullwave | | |/ '---------------|-1>-.
| Rectifier| === | / |
| Averager | GND |/ |
'------o-----' .--------------------'
| | ___
| | .-|___|-.
| .-o-|\ | 150k |
| ___ | \/| \ | |\ |
o----o-------|___|--o--o /\| >-o-|-\ | || 300mV
| | | / | >--o---||---o to
.-. '---|/ .-|+/ || filter bank
| | | |/
510| | |
'-' ===
| GND
---
560p --- 1/4 SSM2164
|
===
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

corrected schematic, I forgot the inverter. The circuit works as follows:

3V[3mV] rectifier out, the VCA will have to do +20dB[-40dB] to compensate
for the input current which results in a control voltage
of -33mV*+20[-40]= -660[+1320]mV The inverter makes +660[-1320] +660 =
+1320[-660]mV resulting in -40dB[+20] main gain and 330mV out.
This way there is also a possibility to adjust the threshold with a linear
pot.
Click to expand...
OK, you just have one channel but do you really need 2 VCAs?

|
.-. level adj. ___
| |<--------. .----+-|___|--.
| | | | | |
'-' .-----. | .--o----------.
| \+ -/ | | |
\ / --- | Full wave |
V --- | |
| | | rectifier |
+-----' | |
.------------. | averager |
| 60dB clamp | '--o----------'
'------------' ___ |
| .-|___|-+
.-o-|\ | 150k |
___ | \/| \ | |\ |
o----|___|--o--o /\| >-o-|-\ | || 300mV
| | | / | >--o---||---o to
.-. '---|/ .-|+/ || filter bank
| | | |/
510| | |
'-' ===
| GND
---
560p --- 1/4 SSM2164
|
===
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

BTW what's your threshold function? Is it clamping gain at 60dB for low
level?


--
Thanks,
Fred.
 
"Ban" <bansuri@web.de> wrote in message
news:9NfNe.63006$2U1.3402098@news3.tin.it...
Ban wrote:
60dB AUTOMATIC GAIN CONTROL
Click to expand...
Or you could look at using something like a THAT4301
(http://www.thatcorp.com/4301desc.html). Available through UK-based
ProfusionPLC (http://www.profusionplc.com) for US$18 with MOQ of 2, or about
$9 each in tubes of 25. A bit pricy, but a well-proven single-chip solution
with excellent audio quality (not that the quality matters in this
application).

But you know, the classic technique for a levelling VCA is to use an
optoisolator, like this: http://www.jlmaudio.com/ureila2alater.htm. Okay,
maybe overkill, especially with the tubes :)
 
Hello Ban,

If you want to build a really nice one that preserves as much of the
spectrum as possible look around in ham radio publications (or on sites
like www.qsl.net). Be patient, some of those sites are slow because they
must run at a budget close to zero. There these limiters are usually
called "clippers".

Anyway, another option and a simpler circuit could probably be built
around the old MC1496 which is still around.

Regards, Joerg

http://www.analogconsultants.com
 
Winfield Hill wrote:
Ban wrote...

60dB AUTOMATIC GAIN CONTROL

1/4 SSM2164 /|----.
/ | \/ | ___ -5V
.---< | /\ o--o-|___|-o
| \ | | | 150k
*** .-. \|-o--' .-.
| | | | |
15k| | | | |510
'-' || | '-'
o-----||-o |
| 1n|| | ---
0.003..3V___ | |\ | ---560p
.----|___|--o--|-\ | |
| 10k | >--o === |\
.-----o------. .--|+/ | GND | \
| Fullwave | | |/ '---------------|-1>-.
| Rectifier| === | / |
| Averager | GND |/ |
'------o-----' .--------------------'
| | ___
| | .-|___|-.
| .-o-|\ | 150k |
| ___ | \/| \ | |\ |
o----o-------|___|--o--o /\| >-o-|-\ | || 300mV
| | | / | >--o---||---o to
.-. '---|/ .-|+/ || filter bank
| | | |/
510| | |
'-' ===
| GND
---
560p --- 1/4 SSM2164
|
===
GND

3V[3mV] rectifier out, the VCA will have to do +20dB[-40dB] to
compensate for the input current which results in a control voltage
of -33mV*+20[-40]= -660[+1320]mV The inverter makes +660[-1320] +660
= +1320[-660]mV resulting in -40dB[+20] main gain and 330mV out.
This way there is also a possibility to adjust the threshold with a
linear pot.

The resistor I marked *** isn't doing anything to earn its keep, is
it? Also, you could use multiplier ICs instead of the ssm216 to 4, saving
a few opamps, right? OK, the ssm2164 is pretty cheap. Speaking of
critical circuits, what's your take on the "Fullwave Rectifier
Averager" circuit? You have two ssm2164 sections left.
Click to expand...
Sorry the delayed response, but I was visiting a beautiful electronic music
festival near Berlin
http://www.antaris-project.de/

The resistor was misdrawn and is not there at all and the value belongs to
the input resistor below.

Here is another part with an adjustable bandpass of Q=2.5...5; Fullwave
rectifier and an integrator driving a comparator to get a repetition
frequency between 0Hz and 5Hz depending on the input level of 3mV to 3V. The
output drives a relais (20ms on) and also the analog switch(1NO, 1NC) .
Power is +/-5V.
I make all sections dual for increased reliability and will handwire the
different sections together.

||
.-||---------.
| ||56n |
___ | .. ___ | ___ ___ ___
o-|___|-o-||-o-|___|-o-----|___|---------|___|-o-|___|-o
10k | || | 100k | 22k 22k | 1M -5V
.-.56n| |\ | |
| | '-|-\ | ___ ___ ___ | .-----.
| |1k | >--o-|___|-o-|___|--o--|___|-o | |
'-' .-|+/ 10k | 10k | 22k | | .-.
| | |/ | |\ - o /o | |
.-. === AD8625 .--o-|-\ ^ 4148 / | |10k
-->| | GND | | >---+ ADG623 / '-'
| 1k| | | -|+/ - o 1u || |
| '-' | GND|/ ^ 4148 +-----||--o
| | | | | |\ || |
'----o '-----------' '--|-\ |
| | >---o
=== GND-|+/ |
GND |/ |
Bandpass adjustable Fullwave Rectifier Integrator |
.----------------'
| switch
| driver
| |\ AD8625 |
'-|-\ |
___ | >--o------------'
+5Vo-|___|--o--|+/ |
33k | |/ |
___ | ___ |
-5Vo-|___|--o--|___|-'
33k 39k

Comparator
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

--
ciao Ban
Bordighera, Italy
 
3rd part
Mike preamp


Electret
+5V o Microphone Preamp
| 150u 40dB gain
| +[/ __ ___
.---o--[|-|___|-o-|___|-.
| | [\ 10 | 1k |
| .-. | || |
--- | | o----||-o
--- | |4k7 | |\ || |15n
3n3| '-' '-|-\ | ___ out
| | || | >--o-|___|--o
o---o----||---o---|+/ 220
| | || | |/| SE5534A
_ | .-. 47n .-. o
| / \--' | | | | +/-5V
|(Mic) | |10k | |33k
| \_/--. '-' '-'
| | | 140Hz-7kHz
o---o ===
| | GND
| / \--' .-.
|(Mic) | |
| \_/--. | |10k
| '-'
| |
'---o
|
===
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

--
ciao Ban
Bordighera, Italy
 
Hello Ban,

3rd part
Mike preamp


Electret
+5V o Microphone Preamp
| 150u 40dB gain
| +[/ __ ___
.---o--[|-|___|-o-|___|-.
| | [\ 10 | 1k |
| .-. | || |
--- | | o----||-o
--- | |4k7 | |\ || |15n
3n3| '-' '-|-\ | ___ out
| | || | >--o-|___|--o
o---o----||---o---|+/ 220
| | || | |/| SE5534A
_ | .-. 47n .-. o
| / \--' | | | | +/-5V
|(Mic) | |10k | |33k
| \_/--. '-' '-'
| | | 140Hz-7kHz
o---o ===
| | GND
| / \--' .-.
|(Mic) | |
| \_/--. | |10k
| '-'
| |
'---o
|
===
GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)
Click to expand...
The feedback resistors 10/1k seem a bit low. Can't you increase those,
lower the 15nF and then get away with a smaller electrolytic than that
150uF? In my experience the smaller electrolytics last longer, they
don't dry up as fast. Assuming that this kind of stuff might be left out
baking in the sun or in a hot car trunk at times.

Regards, Joerg

http://www.analogconsultants.com
 
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