UK168 Compressor/Dynamic Expander, Amtron 1975

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modman
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Amtron UK168U - Dynamic compander.pdf
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Amtron UK168U - Dynamic compander 1.jpg
Amtron UK168U - Dynamic compressor 2.jpg
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Axldeziak
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Post by Axldeziak »

I spent some time using OCR to get the text from the pics and then used Google to translate the article.
Here is the result:



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

THE FITTINGS ALSO AVAILABLE IN KITS

TECHNICAL FEATURES

Input impedance without signal 200kΩ

Output impedance without signal 100KΩ

Speaker impedance 4÷16 Ω

Led employed CM4-43 or TIL209

Photoresistor employed MKY-7H26

Dimensions 60X30mm

weight 15g




COMPRESSOR - DYNAMICS EXPANDER

-----

One of the problems of the least easy solution presented to the technician interested in audio diffusion systems
(those, to be clear, employed in congress and conference halls, churches. different auditoriums is the regulation of the
gain of the various amplifiers to obtain on one side. comfortable listening when the speaker speaks in a normal voice,
and on the other to avoid distortions, echoes, Larsen reactions when the voice increases following a louder peroration
Vibrate. We have all seen the publication of many circuits that promised an automatic regulation of the
dynamics; but the good ones cost (and do cost) interesting sums and were not a little critical; the others... well, better
forget them altogether. In the description that now follows, we present a C.A.G. for audio that despite being a
discovery and not claiming to be one, nevertheless offers in these cases a very convenient solution: both from the point of view
technical, than from the economic one.

-----

CAG is not a truncated curse word,
and not even the initials of the Geographical Antarctic Center
or the Anti Committee
Gargle: in electronics it means “Control
Automatic Gain” or control
automatic gain and comes from the rearrangement
of the Anglo-American acronym AGC
having the same meaning.

All technicians who are interested in
acoustic and meeting installations
continuously the GAG ​​in televisions ed
also in common radio receivers or complex,
certainly regret that
there is no "something like that" for the
audio amplifiers, and “envying” the performance
of those which are mounted upon
good level recorders and strong price.

Oh yes, because at the level of Ampex or
Sony, there are recorders equipped with
self-control, otherwise, how could one
be interviewing a politician, an artist of
avant-garde or a phone user
who just got the new bills?

These people (there are countless of them)
worthy others) have the dangerous tendency
to whine and hiss menacingly
anatemi (hence the gain control
should be maxed out, for
understand what they mean) and then
suddenly explode in wild cries
to the Sioux on the warpath, or to the
deputy who feels reproached during
Political Tribune certain proclamations of 1944
(then the check should pass
almost zero).

As the interviewer is generally
a normal person, he can not stand
the microphone with one hand, protect yourself
from saliva with the other, check the gain
with a possible third and so on,
for which here is the usefulness of the C.A.G.
make itself manifest.

Unfortunately, there are "VOX" (acoustic relays) sold on the market
as accessories, in large quantities, and even
Anti-trips not to mention pre-amplifiers;
but in relation to the C.A.G.
there is little or nothing. These circuits are, in fact,
inserted only in certain, expensive machines; or nothing.

The following description therefore fills a considerable gap.

It is a compressor circuit that
limits the gain to the necessary level,
so it allows, for example, to maintain
always the volume control rather than
soon “high” without them intervening
distortions at high levels With a simple
switching, however, the same circuit
works as an expander, so, if
you have to pick up a signal that is predictably
“waning” during certain periods, works the way perfectly
contrary.

If the reader hasn't seen the
electric circuit, will believe that a “system-
ma-robot” like that you need who knows
how many ICs, transistors, zeners, diode bridges
and similar; especially if he has analyzed the parallels
automatisms used on recorders. Instead, nothing like that.

THE WIRING DIAGRAM

All the C.A.G. evidently withdraw
the signal at the output of the device
served, they "evaluate" the breadth and of
consequently they act on the entry into
to adjust the sensitivity. Also
this works like this: fig. 1, but differently
from each other, there is a true
and proper coupling between “out” ed
“in , via various loops, so there is no vi
there is a danger that triggers and rotations may occur
phase and distortions.

The signal is taken directly in parallel
to the voice coil of the loudspeaker used
from the audio system you intend to subject
to the automatic control, it crosses the resistor RS and acts
on the LED, protected by the DI diode for the
surges.

Thus the LED diode, which does not
it has no practical inertia at all
audio frequency, it lights up directly
proportional, instant for
instant, to the tension that reaches it.
Now see FI. This item is a
“fast” type photoresistor which has one
tight coupling with the LED and such
optical coupling is the only one employed;
however it follows that, all the greater
is the light emitted by the diode, so much
the lower the internal resistance of the device
sitive.

Thus, we have a resistance that varies
inversely to the power.

This resistance, through the commutator
SW, can be used as is
more appropriate. If you need to "expand" automatically
the audio, via the “ESP” position the variable value will be set
in parallel with R15, so it will decrease
the total resistance value existing between
inlet and outlet port.

If, as is more frequent, you must instead "compress"
the signal, carrying
SW in the "COMP" position the value
resistance variable will be placed in series
in RIO, while the couple will be paralyzed
to R20.

Thus, when the speaker in
will give the LED a wider voltage,
there will be resistance at the output of the device
lower, which will limit the dynamics instantly.

The one and the other effect, will be more
evident if the source of the signals is ad
high impedance (for example, if using
the classic piezoelectric ceramic microphone,
or maybe a “professional” a
condenser, or — why not? They go by
fashion - to electret).

If instead the source of the signals will have
a low impedance, or worse very low,
the effects will be less pronounced
ciati, but still the device will be
useful.

COMPRESSOR ASSEMBLY
DYNAMICS EXPANDER

Comparative to performance, vi
they are certainly few electronic devices
simple like this.

For the wiring, as is usually used,
a printed base is provided which
appears in figure 2. On this they go
mounted the four fixed resistors, signed:
RS, RIO, RIS, R20; the diode DI and the
LEDs.

The latter two obviously have one
polarity that must be respected; sc
one of the two is inverse, with respect to the other,
it won't work, so be careful
to the clear ring stamped on the ID,
because it indicates the heart side and attention
even at the shorter end of the LED
because similarly it belongs to the cathode
of this other.

The light-emitting diodes, while not
being delicate in a particular way, in the
temperature comparisons, they don't have to
never be overheated, so it's convenient
leave 6 or 7 mm distance between the
back of the LED and the welding point.

At this point, inserted and soldered that
are the anchors, the breadboard is almost
complete. To complete it, he will slip on
“head” of the LED the opaque sheath ad
funnel, and in the wider side of this,
the photoresistor FI. The terminals of the
toresistance, after being isolated by
small pieces of plastic tube will go to the points
“3 - 4” of the printout.

Using a thin stick, or the tip
of a pencil, you will push the element
photosensitive as “lower” as it is
possible, i.e. it will be placed next to the LED.

Now, since the complex must be
enclosed in a metal box
which also acts as a protection
and from the screen, you will choose the type that,
for the shape or other characteristics, yes
better suited to the job. we suggest
to employ a small “utility
box” in aluminum, on sale at all
the Headquarters of the Italian GBC, in the package
00/2800-00.

The switch will be fixed on this box.
“COMP-EXP” (Compression/
Expansion) which can be of type a
slide, but also rotary for fixing
thu easier to wrap. The contacts of
these will go to the terminals “5-6-7) of the
base, and the same will be mounted inside
of the casing using the spacers
corners that can be seen in figure 3.

For inputs and outputs, you can
use simple coaxial jacks
GBC “GQ/1796-00” or similar.

This is because being of high impedance
za, the entrance, if not provided for
an accurate shielding, one would incur
evidently in an uptake of
buzz that could not be accepted
in no plant by the qualities not
only "professional" but not even "commercial".

THE TEST

The “1-2” anchors of the PCB
they have to go to the moving coil
of the loudspeaker employed, or of one of the
speakers employed, if so
you use the system in its most “natural” function;
as a plant compressor
of auditoriums, meeting rooms, etc.

This connection doesn't matter what
is shielded, in fact it runs between a "source"
low impedance and a “load”
equally low impedance.

Instead, it must be shielded, and a lot
well, the connection that goes from the generator
(microphone) at the entrance; as well as
from the appliance outlet to the inlet of the amplifier.

You need normal coaxial cables for
low frequency applications.

Since the circuit is very simple, yes
it should work perfectly
already on the first try.

A possible failure cannot depend
that from the incorrect connection of
one of the two diodes.

In conclusion, we will say that this “cor-
rector” is recommended for the e word
not for music; but in the latter
campo has two indications of use, however.

The first is when due to particulars
environmental conditions you have
many echoes, and consequently are born
“indomitable” Larsen effects that intervene
only in the “pienissimo” or “fortissimo”.

The second is when they want to create
very special musical effects; then,
expander function can be
interesting to create some “bursts of
sound” such as are often heard
during pop concerts.

-----

AMTRONCRAFT KIT COMPONENTS LIST UK 168/U

RS : 1 carbon film resistor 56 Q - + 5% - 0.67 W-Q0 6x4

R10 : 1 carbon film resistor 10 KQ - + 5% - 0.33 W-0 2.9 x 8.3

R15-R20 2 carbon film resistors 100 kQ - + 5% - 0.33 W -0 29x83

DI : The PA148 diode

LED : I CM 4-43 (or TIL209)

FI : MKY7H26 photoresistor

1 : black plastic cap

1 : PCB assembly

8+1 PCB anchors
cm 10 : black vipla tube O 1,5

4+1 : MIx4-T.C. screws

2 : hexagonal spacers L = 7 mm

1 : cursor switch

1 : tin pack

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jmpj45
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Post by jmpj45 »

Man that’s is crazy you converted all that. Is the 1 and 2 on the Pcb the power inputs. Hey do you think you could print out the pcb and use it to make your own pcb. I would like to try and build it. Do you have any idea what kind of photo resistor you can use.

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