zapco SLN-4 Owner's Manual

1

Mission Statement

Committed to excellence

ZAPCO is dedicated to the pursuit of audio
fidelity. Our prime objectives are to design
and manufacture audio products of
unsurpassed quality, to provide
unparalleled support and service for these
products and to conduct business in a
manner that will enhance the quality of life
for all involved.

Experience:
Knowledge from doing

There is absolutely no substitute for
experience; that is a simple fact of life.
Another simple fact is that ZAPCO has, for
over twenty years, been the leader in
defining quality standards for the car audio
industry. These years of experience have
led to a thorough understanding of the
challenges that are unique to the world of
car audio. ZAPCO's relentless quest for
sonic purity consistently yields imaginative
designs that utilize the most innovative
technologies. The resulting products set
the criteria by which all others in the
industry are judged.

2

Contents

Mission Statement......................................................................1

What is the SLN-4?.....................................................................3

What Makes the SLN-4 Better?..................................................4

Construction ...............................................................................4

Key Features...............................................................................5

Setup Procedure.........................................................................6

Switch and Control Settings......................................................7

System Example #1 ...................................................................8

System Example #2 ...................................................................9

Specifications...........................................................................10

Manufacturing...........................................................................11

Troubleshooting .......................................................................12

Technical Assistance ...............................................................13

3

What is the SLN-4?

Thank you for purchasing a Zapco product! This product is
Hand-Crafted in the USA with the attention to detail and quality
that has made Zapco a legend in the car audio industry. You can
be sure that you have purchased one of the highest quality car
stereo components available anywhere in the world today.

SLN-4
The SLN-4 is a four channel outboard noise gate for the
SymbiLink Balanced Signal System. Car audio systems
sometimes use poor quality signal processors, such as third
octave equalizers, that generate noticeable amounts of noise.

The SLN-4 can mute or low-pass the audio signal when the signal
level drops below a specified level. The SLN-4 can mute up to
four channels in tandem.

The SLN-4 features an onboard power supply, allowing it to
operate in a stand-alone application or powered by other
SymbiLink products, through the balanced cables. An optional
trigger line is available from the DAII-SL D/A converter that mutes
the audio when it detects a succession of zero bit audio data.

The SLN-4 introduces virtually no noise or distortion into the
system. SNR measures an astonishing 146dB muted and 138dB
un-muted with less than .0005% THD+N!

4

What Makes the SLN-4 Better?

Noise gates have, in the past, been obtrusive to the audio system
due to noticeable muting noises. This problem makes the typical
noise gate unacceptable to many listeners. In addition, prior
noise gates would have a difficult time detecting music buried in
noise. The engineers at ARPA have solved this problem with
additional features in the SLN-4. First, a special band shaping
filter allows the detection circuitry to focus on the music, ignoring
the noise. Second, the SLN-4 has a band limiting switch so that
the SLN-4 only mutes high frequencies when enabled. If this
switch is enabled the gate functions as follows: as the music
level drops to the selected threshold, the gate will only mute
frequencies above 5 kHz. Frequencies below 5kHz are never
muted. In this way the SLN-4 threshold and decay adjustments
become less critical and the gate operation becomes
undetectable. In addition, the SLN-4 muting circuitry is
completely removed from the audio path when the signal is above
the signal threshold.

Construction

The SLN-4 is constructed of the highest quality components. The
finest components and careful layout assure the best possible
sound quality. Housed in an attractive "half din" rack mount
enclosure, the SLN-4 compliments the finest audio system.

5

Key Features

• SymbiLinkTM balanced input and output

• Adjustable Threshold and Decay

• Ultra high signal to noise ratio, greater than 115 dB

• Ultra low distortion and noise, less than .0005% T.H.D.+N

• Band-shaping music detect filters

• Selectable full range or lowpass muting.

• Built-in power regulated power supply.

• Zero bit detect input for triggering from D/A converters.

• Compact design

• Quality Zapco construction

• Designed and built in the USA

6

Setup Procedure

1. Disable the SLN-4 by pushing the “ENABLE” button in.

2. Adjust the music level such that it is barely audible above the
background noise.

3. Put the SLN-4 in the 5kHz mode by putting the range switch
in the out position. (Recommended)

4. Adjust the decay to .1 seconds. This is a temporary setting
so that you get a quick response to the threshold adjustment.

5. Enable the SLN-4 by putting the “ENABLE” button in the out
position.

6. Adjust the Threshold so that the “GATE ON” LED flickers on
and off.

7. Adjust the decay to about 2 seconds.

Preliminary adjustments are now complete. Due to its smart
band limiting circuitry, these should be the only adjustments that
you need to make. If you have system noise that is in the lower
frequency range (you shouldn’t), you may have to put the range
switch in the full range position.

Note: Use the front channels of the SLN-4 if you are using only
two. While the SLN-4 gates all four channels, it only senses
music on the front channels.

7

Switch and Control Settings

8

System Example #1

9

System Example #2

10

Specifications

Maximum balanced output level 16 Volts, R.M.S.
Indicators Two, mute and power

Outputs Balanced SymbiLink
Minimum output impedance 600 Ohms
Decay adjustment .1 to 3 seconds
Frequency response, DC – 20kHz

±.1dB

S/N ratio “A” weighted > 145dB / 138dB
Separation @ 1KHz, “A” weighted > 100 dB
Current requirements 300 mA
Harmonic distortion + Noise < .0005%
Dimensions 5.375”D x 3.5”W x 1.18”H

11

Manufacturing

This Zapco product was completely designed and manufactured
in the USA. The following operations are ENTIRELY performed*
in our own Modesto, California factory.

PC Board insertion

The components are inserted into American made printed circuit
boards. All insertion work is performed in our Modesto, CA
factory.

PC soldering

The printed circuit board assembly is wave soldered.

Pre Testing

The finished assembly product is 100% tested to design specs.

Extrusion machining

American made aluminum extrusion is cut and machined to
precise tolerances.

Assembly

The various sub-assemblies of the product are hand assembled
into a completed unit.

Final test

Every product is tested with the highest quality audio test
equipment to meet or exceed the published specifications.

Inspection and final packaging.

* Many companies claim that their products are built in the USA,
but only a few of the above steps, if any, are actually performed in
America. Many of these companies only do the final assembly,
with steps 1 - 4 being performed outside the USA

12

Troubleshooting

Symptom Possible cause / cure

The muting effect is
audible.

1. Set the range switch to lowpass.

2. Reduce the threshold level.

3. Lengthen the decay time.
The power LED does
not come on.

1. Connect the mute to the source

unit’s remote turn-on lead.

2. Check the power and grouind

connections.
The unit never seems
to gate, the gate LED is
always off.

Check the ENABLE switch setting.

The unit never seems
to un-gate, the gate
LED is always on.

Make sure that you are using the front
channel inputs in a two channel
system.

If are experiencing a problem that is not listed here or you have a
situation that requires special attention, please see the technical
assistance section of this manual.

13

Technical Assistance

Should you experience a problem with your SLN-4, please
contact the dealer that sold you this product. If your dealer is
unable to solve your problem, you may contact the factory
service department directly.

Phone:[phone] Monday - Friday, 8AM - 5PM

Pacific time

FAX: [phone]
Also, check our web page, www.zapco.com, for tips. You can

also e-mail technical help directly from our web page or
[e-mail].

If you need to return this product for repair, please call the factory
for a Return Materials Authorization (RMA) number. We will ask
you for information that will include your name, return shipping
address, daytime phone number, model and serial number, and a
detailed description of your problem. A photocopy of your
original purchase receipt is necessary to determine warranty
status and should also be included. Once we issue you an RMA,
please write it in a highly visible area on the package. Zapco will
not accept any packages that do not have a valid RMA number
clearly marked on the outside of the package.

Once you have a valid RMA number, send all repairs to:
A.R.P.A. of America Corp.

Attn.: Service Department
413 S. Riverside Drive
Suite D
Modesto, California, 95354

14

A.R.P.A. of America Corp.

413 S. Riverside Drive, Suite D

Modesto, CA 95354

[phone]

FAX [phone]

www.zapco.com

SLN-4

Rev. A

3/97 RZ