API 1608 User manual

A P I M o d e l 1 6 0 8
R e c o r d i n g C o n s o l e
O p e r a t o r ' s M a n u a l
= F E
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Important Safety Instructions
1. Please read these instructions
2. Keep this Manual in a safe place
3. Do not use this console near water
4. Clean only with a dry cloth
5. Do not block any ventilation openings
6. Do not install near any heat sources such as radiators, heat registers, stoves, or other devices
(including the power supply) that produce heat
7. Do not defeat the safety purpose of the polarized or grounding type AC plug
8. Protect both the AC power cord to the power supply and the DC cable between the supply and the
console from being walked on or pinched
9. Use only attachments/accessories specified by the manufacturer
10. Unplug this device during lightning storms or when unused for long periods of time
11. Refer all service to qualified personnel
ATTENTION: Exposure to extremely high noise levels may cause
permanent hearing loss or damage. Individuals vary considerably in
susceptibility to noise-induced hearing loss, but nearly everyone will lose
some hearing if exposed to sufficiently intense noise (or even music) for a
period of time. Be safe.
WARNING – To reduce the risk of
fire or electric shock, do not
expose this apparatus to rain or
moisture.

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Introduction
Thank you for choosing API’s 1608 analog mixing console. Whether you are a
newcomer to API or are already a part of the nearly 40-year tradition of API excellence, we
appreciate your purchase.
The 1608 small format recording console is based on the designs of the original API
1604 built in the 70’s and early 80’s. The success of the 1604 and the continued demand
for a small footprint, high quality console has produced the 1608.
API takes great pride - and great care - in the hand assembly of all our professional
audio products. Above all, we appreciate our loyal users – those who create, track, mix,
engineer, master, and produce - who have made the Company what it is today.
API User’s Manual v1.3 01-09
API part # 910-0500 Written for Automated Processes Incorporated by Dan Pfeifer 2008 – All Rights Reserved

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Table of Contents
1.0 Overview
2.0 548B Channel Module
2.1 440B Fader Module
2.2 Mute/Solo Section
2.3 Preamp Section
2.4 Echo/Auxiliary Sends
2.5 Routing and Output Section
2.6 550A Equalizer
2.7 560 Equalizer
2.8 548B Connections
3.0 E1608 Echo Send/Return Module
3.1 Echo Send Section
3.2 Echo Return Section
3.3 Echo Return 500 Slots
3.4 E1608 Connections
4.0 168B Summing Bus Sub-master Module
4.1 Summing Bus Sub-masters
4.2 168B Connections
5.0 268B Program Bus Output Master and Monitor Output Module
5.1 Program Bus Output Masters
5.2 440B Stereo Master Fader Module
5.3 Monitor Output Controls
5.4 268B Connections
6.0 845B Control Room Monitor Module
6.1 Control Room Monitor Controls
6.2 Control Room Monitor Source Selectors
6.3 845B Connections
7.0 840B Central Facilities Module
7.1 Headphone Amplifier
7.2 Talkback
7.3 Mute Group
7.4 Aux Pre = Mute
7.5 Solo Master
7.6 Channel Meter Control
7.7 Peak Threshold
7.8 Oscillator
7.9 840B Connections
7.10 Headphone Jack
8.0 Meter Bridge
8.1 Channel/Bus Meters
8.2 Left and Right Program Meters
8.3 Echo Send/Return Meters
8.4 Power Supply Voltage Indicators
8.5 Talkback Microphone

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9.0 Rear Panel
9.1 548B Channel Module Connections
9.2 E1608 Echo Send/Return Connections
9.2.1 Echo Sends
9.2.2 Echo Returns
9.2.3 Echo Return 500 Slots
9.3 168B Summing Bus Sub-master (ACA) Connections
9.3.1 Summing Bus Sub-master Outputs
9.3.2 Program Bus Mix Inputs
9.4 268B Program Bus/Master Output Connections
9.5 268B Control Room Monitor Output Connections
9.6 845B 6-Track Playback Input Connections
9.7 840B Ancillary Connections
9.7.1 Talkback Remote Port and Oscillator Output
9.7.2 Stereo Headphone Output
9.8 Expander Port
9.9 PSU Connection
10.0 Application Guide
10.1 Multitrack Recording
10.2 Multichannel Mixing
10.3 DAW Hybrid
10.4 E1608 Echo Send Applications
10.5 E1608 Echo Return Applications
10.6 168B Summing Bus and Sub-master Applications
10.7 Echo Return 500 Slot Applications
10.8 Rear Panel DB25 Connection Diagrams

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1.0 Overview
Building on API's rich heritage of extremely high quality recording consoles, we are proud to introduce
the new Model 1608, a full featured small format recording console based on the vintage API 1604
console, which has held its demand and value for over three decades.
The 1608 gives all of the advantages of the 1604 Vintage Consoles while adding new, modern features
valuable to today's Engineers, Producers and Musicians.
Features
•16 Input Channels each with Mic Pre and Equalizer
•Accepts up to eight API 500 Series Modules
•8 Main Buses
•8 Auxiliary Buses
•1 Stereo Bus
•8 Echo Returns with main and stereo bus assign
•Full Center Section Control
•Analog Metering
•5.1 Center Section Monitoring
•Comprehensive Rear Patch Connections
The 1608 is built to the same exacting API build standards as our Vision consoles, Legacy consoles, and
modular products.
The standard fit of a 1608 Console is:
16 548B Inputs with Mic/Line and Direct Output
12 550A Equalizers
4 560 Equalizers
8 Echo Returns
1 Complete Central Facilities Section
16 Manual Faders
1 Stereo Fader

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2.0 548B Channel Module
The 548B Channel module provides a single audio path for bringing signals into
the console for mixing and/or routing to external destinations. Together with the
440B Fader, it provides a comprehensive audio path for a variety of applications:
•Microphone/instrument/line preamplifier
•Equalizer
•High-pass filter
•Balanced insert
•Eight (8) Echo/Auxiliary Sends
•Fully featured mute and solo section
•Pan-pot
•Direct Output
•Program and Summing Bus assignments
All eight echo/aux sends can be routed either pre or post-fader. Echo/aux Sends
7/8 can be routed to feed the Summing Buses.
The basic signal flow through the 548B Channel module is as follows:
input preamplifier -> equalizer -> insert -> fader/mute -> output
routing

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2.1 440B Fader Module
2.2 Mute/Solo Section
The 548B Channel module provides a comprehensive set of solo and mute controls including:
•Channel on/off switch
•AFL, PFL, and SIP Solo functions
•Solo Safe
•Mute Group assignment
The controls for the 548B Mute and Solo function as follows:
SAFE: Activates the Solo Safe mode for that channel
•The SAFE button protects that channel from being muted when the Solo-In-Place
function is active and another channel or an Echo Return is soloed.
•Illuminates when engaged
MUTE: Cuts the primary audio output
•The MUTE button is the on/off switch for the primary channel output and is located post-
fader in the signal flow
•The MUTE button is the numbered button located just above each fader
•Illuminates in red when engaged
The 440B Mono Fader is the primary output level control for the channel.
The channel Fader controls the output to the:
•Direct Output
•Summing Buses
•Program Bus
•Post-fader Echo/Auxiliary Sends
•When the Fader is set to 0dB, the level is at unity gain
Each 440B Mono Fader module contains eight mono Alps 100mm faders and
supports the eight channel modules mounted above it
SOLO: Activates the selected solo function
•The following solo functions may be selected via the 845B
Central Facilities Module:
oPre-fader Listen (PFL): Non-destructive, mono
oAfter Fader Listen (AFL): Non-destructive,
mono/stereo
oSolo-In-Place (SIP): Destructive, panned, post-fader
•Illuminates in yellow when engaged
NOTE: PFL is the default solo mode.
NOTE: Channels and Echo Returns must be assigned to the
Program Bus for Solo-In-Place for their mutes to activate when
other channels or Echo Returns are soloed.

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MUTE GRP (Mute Group): Assigns the channel to the master Mute Group
•All channels assigned to the master Mute Group will mute when the MUTE GROUP
button on the 845B Central Facilities Module is pressed
•Illuminates when engaged
NOTE: If the channel MUTE GRP button and the AUX PRE=MTE button on the 845B
Central Facilities Module are engaged, all pre-fader Echo/Auxiliary Sends will be muted
when the master MUTE GROUP button is engaged.
2.3 Preamp Section
Line Input: Accepts balanced, low-impedance, line-level signals from the LINE INPUT connector.
The Line Input has the following features:
•-6 dB Pad
•Peak Indicator
•Polarity Inverter (phase reverse)
Note: Line Input is the default channel input.
Microphone Input: Accepts balanced, low-impedance, microphone-level signals from the MIC
INPUT connector. It’s the classic API 212L microphone preamplifier with the following features:
•+65dB of gain
•-20 dB Pad
•Peak Indicator
•Polarity Inverter (phase reverse)
•48v Phantom Power
Note: The MIC button must be engaged to use this input.
Note: The signal from the Microphone Input is replaced with the signal from the
Instrument Input when a 1/4” plug is inserted in the Instrument Input jack.
Instrument Input: Accepts unbalanced, high-impedance, instrument-level signals from the 1/4"
INSTRUMENT INPUT connector. The Instrument Input reduces the need for separate Direct
Injection (DI) boxes and has the following features:
•+45dB of gain
•Peak Indicator
Note: The MIC button must be engaged to use this input.
Note: The Instrument Input jack is a switching jack. The signal from the Microphone
Input is replaced with the signal from the Instrument Input whenever a 1/4” plug is
inserted in the Instrument Input jack.
Note: The Pad and Polarity Inverter (Phase Reverse) do not apply to the Instrument
Input. If these functions are needed, the use of an external Direct Injection (DI)
box connected to the Microphone Input is suggested.
The Preamp section of the 548B provides three audio input options:
•Line Input
•Microphone Input
•Instrument Input
A Peak Indicator is located at the output of the Preamp. The MIC
button serves as the Peak Indicator and turns red when peaks cross
the threshold set on the 840B Central Facilities Module.
Note: The Peak Indication LED functions in MIC, LINE or
INSTRUMENT mode.

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The controls for the 548B Preamp section function as follows:
GAIN: Provides up to +65dB of gain for the Microphone and +45dB for the Instrument Inputs
Line Input: The gain control does not affect the Line input
48V: Provides 48 Volt Phantom Power to the MIC INPUT XLR connector on the rear panel
•Illuminates in red when engaged
PAD: Inserts a -20 Pad for the Microphone or a -6dB pad for Line inputs
•Illuminates when engage
Ǿ: Inserts a Polarity Inverter (Phase Reverse) for the Microphone and Line inputs
•Illuminates when engaged
No Buttons Engaged: Line Input selected
MIC: Selects the Microphone Preamp as the input for the channel
•The MIC button must be engaged for the Instrument Input to
be used
•Illuminates in blue when engaged
•The MIC button provides a peak Indicator by turning red
whenever the peak threshold is crossed
Note:The signal from the Microphone Input is replaced when a
1/4” plug is inserted in the Instrument Input jack.

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2.4 Echo/Auxiliary Sends
The controls for the 548B mono Echo/Auxiliary Sends 1-4 function as follows:
The controls for the 548B stereo Echo/Auxiliary Sends 5/6 and 7/8 function as follows:
The 548B Channel module provides eight fully functional echo/auxiliary sends,
four mono (Sends 1-4) and two stereo (Sends 5/6 and 7/8). Accordingly, the
1608 is equipped with eight balanced Auxiliary Buses and outputs.
•Each mono Echo/Auxiliary Send has an individual level control and an
on/off switch
•Each stereo Echo/Auxiliary Send has a stereo level control, a pan-pot,
and an on/off switch
•Sends 7 and 8 can be routed to feed the 1-4 Summing Buses only in
addition to their Auxiliary Buses
1 and 2 Level: Individual level controls for Sends 1 and 2
1/2 PRE: Routes the pre-fader signal to Sends 1 and 2
•Sends 1 and 2 are fed post-fader when the PRE button is
not engaged
•Illuminates when engaged
1 and 2 (buttons): Individual on/off switches for Sends 1 and 2
•Illuminates when engaged
3/4 Level: Individual level controls for Sends 3 and 4
3/4 PRE: Routes the pre-fader signal to Sends 3 and 4
•Sends 3 and 4 are fed post-fader when the PRE button
is not engaged
•Illuminates when engaged
3 and 4 (buttons): Individual on/off switches for Sends 3 and 4
•Illuminates when engaged
5/6 LVL: Stereo level control for Sends 5 and 6
5/6 PAN: Pan-pot for Sends 5 and 6
5/6 PRE: Routes the pre-fader signal to Sends 5 and 6
•Sends 5 and 6 are fed post-fader when the PRE button is
not engaged
•Illuminates when engaged
5/6 (button): On/off switch for Sends 5 and 6
•Illuminates when engaged
7/8 LVL: Stereo level control for Sends 7 and 8
7/8 PAN: Pan-pot for Sends 7 and 8
7/8 PRE: Routes the pre-fader signal to Sends 7 and 8
•Sends 7 and 8 are fed post-fader when the PRE button is
not engaged
•Illuminates when engaged
7/8 (button): On/off switch for Sends 7 and 8
•
Illuminates when en
g
a
g
ed

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TO BUS: Routes the output of stereo Send 7 and 8 directly to the Summing Bus 1-4 assignment
section. When TO BUS is engaged the send functions as follows:
•Auxiliary Buses 7 and 8 are fed in addition to the Summing Bus 1-4 assignment section
•Auxiliary Sends 7 and 8 cannot access the Program Bus from the channel module
•The 7/8 on/off button is bypassed for the feed to the Summing Busses, but is still active for
the feed to Auxiliary Buses 7 and 8
•The 7/8 PRE button may be used
•The 7/8 stereo level control and pan-pot are active
•The channel output pan-pot is bypassed for Summing Bus assignments from Send 7/8
•Illuminates when engaged
2.5 Routing and Output Section
Direct Output: The Direct Output feeds the channel output signal to the DIRECT OUTPUT on the
rear panel. The Direct Output has the following features:
•The Direct Output is fed post-fader
•The Direct Output is always active except when the channel MUTE is engaged
•Balanced, line-level output at the DIRECT OUTPUT XLR connector
Summing Buses: The channel output may be assigned to one or more of the eight Summing
Buses or Active Combining Amplifiers (ACA). Some possible applications of the Summing Buses
include:
•Multitrack channel assignments
•Multitrack summing
•5.1 mixing
•Additional channel outputs
•Additional echo/auxiliary sends
•Sub-grouping
The summing buses (ACA) include the following features:
•Individual Summing Bus assignments from the 548B modules
•Switchable Odd/Even Summing Bus panning on the 548B modules
•Routing from Echo/Auxiliary Sends 7 and 8 on the 548B modules
•Individual on/off, calibration, trim, solo, and Program Bus assignment controls on the
168B module
•Balanced, line-level outputs at the BUS OUTPUT 1-8 (ACA OUTPUT) sub-D connector
Program Bus: The channel output can be routed to the Program Bus (also ACA) for stereo
mixing and for the Left and Right channels of a 5.1 mix. The Program Bus includes the following
features:
•Program Bus assignment from the 548B modules
•Program Bus Insert via the 268B module and rear panel connections
•440B Stereo Master Fader
•Individual Left and Right program channel on/off, calibration, and trim controls
•Balanced, line-level outputs via the LEFT and RIGHT PROGRAM OUTPUT XLR connectors
The routing and output section of the 548B Channel module provides a
comprehensive set of routing and output functions including:
•Insert
•High-pass filter
•Switchable panning
•Bus assignments
•Direct Output
The output section provides three simultaneous audio output options:
•Direct Output: Direct balanced line output
•Summing Buses: Any of eight summing buses (ACA)
•Program Bus: The Left and Right stereo Program Bus (PGM)

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The controls for the 548B Routing and Output section function as follows:
PGM (Program): Assigns the channel output to the Program Bus
•The Program Bus is fed post the channel pan-pot
•Illuminates when engaged
FLTR (Filter): Activates the channel output high-pass Filter
•-3 dB at 50Hz
•6 dB/octave slope
•Illuminates when engaged
•The channel output Filter is located post the Fader wiper and pre the Fader amplifier
Note: An additional band-pass filter is available on channels equipped with 550A Equalizers.
INS (Insert): Activates the channel Insert Return
•The Insert Send is fed pre-fader from the output of the Equalizer
•The Insert Send is always active
•The Insert Send is a balanced, line-level signal routed to the INSERT SEND
(EQUALIZER OUTPUT) 1/4” tip-ring-sleeve jack on the rear panel
•The Insert Return accepts a balanced, line-level signal from the INSERT RETURN
(FADER INPUT) 1/4” tip-ring-sleeve jack on the rear panel
•The Insert Return is located post-EQ and pre-fader
•The Insert Return is active only when the INS button is engaged
•Illuminates when engaged
Trim-pot: The trim-pot below the channel pan-pot calibrates the FADER IN to the DIRECT
OUTPUT stage so the path is exactly at unity gain with the channel fader set to 0dB.
PAN (pan-pot): Provides continuous panning control
•Stereo panning between the Left and Right Program Buses
•Odd and Even panning between Summing Buses (when
engaged)
PAN (button): Activates Odd/Even panning between the assigned
Summing Buses
•The PAN button must be engaged to enable summing bus
panning
•The PAN button only applies to summing bus panning and does
not affect Program Bus Left/Right panning
•Illuminates when engaged
Summing Bus (ACA) Assignment 1-8: Assigns the channel output
to one or more of the eight Summing Buses (Active Combining
Amplifiers).
•Assignments to the Summing Buses can be made on an
individual basis
•Summing Buses are fed post-fader or post the channel pan-
pot when it’s engaged
•Summing Bus assignments are only active when engaged
•Switchable Odd/Even Summing Bus panning
•The Summing Buses 1-4 can be fed pre or post fader from
Echo/Auxiliary Sends 7 and 8

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2.6 550A Discrete 3-Band Equalizer
The legendary API 550A Equalizer is installed on channels 1-12 in the standard 1608
configuration.
The 550A provides reciprocal equalization at 15 points in 5 steps of boost to a maximum of
12dB of gain at each point. The fifteen equalization points are divided into three overlapping
ranges. The high and low frequency ranges are individually selectable as either peaking or
shelving, and a band-pass filter may be inserted independently of all other selected equalization
settings. Frequency ranges and boost/cut are selected by three dual-concentric switches, and a
pushbutton "in" switch allows the EQ to be silently introduced to the signal path. A small toggle
switch is used to insert the band-pass filter into the 550A.
The combination of Walker's incomparable 2520 op amp, and his "Proportional Q" circuitry gives
the 550A user an uncomplicated way to generate acoustically superior equalization.
With the long-awaited reissue of this unit, an EQ that has had such a part in the history of
recording is continuing to make history in today's music.
WARNING – WARNING – WARNING – WARNING – WARNING
The use of NON-VPR Alliance approved 500 series modules in the 1608 is vehemently
discouraged, and may cause operational difficulties with the console. Improper
operation, excessive current draw and poor module fit are all potential issues with
these devices.
For the most recent list of VPR Alliance approved modules, please visit
www.apiaudio.com.
API reserves the right to deny warranty claims when non-VPR Alliance 500 series
modules are used.
Features
•3 bands of classic API equalization
•Each band offers 7 API selected frequency centers
•Reciprocal and repeatable filtering
•maximum 12 dB of boost/cut per band
•EQ Band 1 and 3 offer shelf/peak switching
•"Proportional Q" narrows filter Q at extremes
•Traditional API fully discrete circuit design
•High headroom +30 dB clip level
Few equalizers enjoy the respect and admiration of the coveted API 550A.
Designed by the now legendary Saul Walker in the late 60's, the discrete
550A was first used as a modular OEM equalizer. As the industry rapidly
embraced the sonic quality of the 550A, it quickly found its way into many
custom console designs of the era. Many of these consoles are still in use
today.
Forty years later, the 550A remains the standard against which other EQs
are measured, and it has played a major role in the recording industry for
decades. Still copied but never duplicated, the 550A became API's standard
channel module EQ when the company began manufacturing consoles in
1971. With virtually all existing units spoken for, popular demand for this EQ
resulted in API resuming production in 2004.

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2.7 560 Discrete 10-Band Graphic Equalizer
The classic API 560 Equalizer is installed on channels 13-16 in the standard 1608 configuration.
The API 560 was created to fit all applications for the professional engineer. For most of the 70's
and 80's, every remote recording console that API manufactured used this versatile graphic EQ.
It is also ideal for studio and live sound applications, where a professional result is required. The
current 560 design has been taken from the original blue prints and spec control drawings from
the API archives.
The large number of available EQ bands make the 560 an ideal companion to parametric EQ, as
well as ideal for signal sweetening and room tuning. Not lacking in features, the 560 makes use
of API's unique "Proportional Q" design introduced by API in the 60's, intuitively widening the
filter bandwidth at lower boost/cut levels and narrowing it at higher settings. In addition, boost
and cut characteristics are identical, so previous actions can be undone.
The extraordinary headroom made possible with API's proprietary 2520 op-amp offers
predictable and wonderful "analog" performance under duress. With a wider range of 500
mounting options, the 560 is a valuable asset to your performance-critical applications.
The 560 Graphic Equalizer exhibits the reliability, long life, and uniformity which are
characteristic of API products.
WARNING – WARNING – WARNING – WARNING – WARNING
The use of NON-VPR Alliance approved 500 series modules in the 1608 is vehemently
discouraged, and may cause operational difficulties with the console. Improper
operation, excessive current draw and poor module fit are all potential issues with
these devices.
For the most recent list of VPR Alliance approved modules, please visit
www.apiaudio.com.
API reserves the right to deny warranty claims when non-VPR Alliance 500 series
modules are used.
Features
•10 bands of API proprietary equalization
•Familiar graphics operation on one octave centers
•12 dB of boost/cut per band
•"Proportional Q" narrows filter Q at extremes
•Additional resolution within the ±4 region
•Center detent for reliable reset
•Silent bypass button
•Re-issue of the 1969 API 560 EQ
Originally conceived for use in API Consoles of the 60's and 70's, the API
560 is a unique device designed to accomplish tasks that no other EQ can. It
delivers that "one-of-a-kind" API sound, precision easy set filtering, and high
headroom in a very small package. Extremely fast to set and reset using
accurate zero detents, the curve shaping potential of the 560 is unmatched.
At home both in field recording and the studio environment, this "new-old"
560 is true to the original 560 with improved resolution in the critical area of
±4 dB. Incorporating API's exclusive circuitry and proprietary components
(such as the legendary 2520 op-amp), the 560 artfully blends the past with
present—layout with function.

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2.7 548B Connections
The rear panel connections for the 548B Channel module are as follows:
DIRECT OUTPUT:
•Balanced, Line-level
•Male XLR
INSERT RETURN (FADER INPUT):
•Balanced, Line-level
•1/4” tip-ring-sleeve switching jack
•Replaces the EQ Out signal when a jack is inserted
and the INS button is engaged
INSERT SEND (EQUALIZER OUT):
•Balanced, Line-level
•1/4” tip-ring-sleeve switching jack
•The feed to the Insert Return (Fader Input) is
defeated when a jack is inserted
EQUALIZER INPUT:
•Balanced, Line-level
•1/4” tip-ring-sleeve switching jack
•The Preamp Output signal is replaced with this signal
when a jack is inserted
PREAMP OUTPUT:
•Balanced, Line-level
•1/4” tip-ring-sleeve jack
•Half-normalled to feed the Equalizer Input
INSTRUMENT INPUT:
•Unbalanced, High-impedance
•Instrument-level
•1/4” tip-sleeve switching jack
•The Microphone Input signal is replaced with this
signal when a jack is inserted
MIC INPUT:
•Balanced, Low-impedance
•Microphone-level
•Female XLR connector
LINE INPUT:
•Balanced, Low-impedance
•Line-level
•Female XLR connector

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3.0 E1608 Echo Send/Return Module
The E1608 Echo Send/Return module serves multiple functions and
contributes greatly to the extensive flexibility of the 1608. Some possible
applications of the Echo Send/return module include:
•Echo returns from reverbs and effect units
•Additional line-level inputs during tracking or mixing
•Audio sub-grouping
•Echo send masters
•Cue and foldback send masters
•Mix minus matrixes
•Parallel processing
The E1608 Echo Send/Return module has two primary sections:
•Echo Send
•Echo Return