Abstrakt Instruments Oberheim OB-X User manual

Date: March 4, 2019

Doc: D00282-01

Rev: 1

OB-X Voice Expansion Kits

INTRODUCTION

The Oberheim OB-X was sold in 4-voice, 6-voice and 8-voice variations. Our voice expansion kits were

developed for those wanting to upgrade a 4-voice or 6-voice model, and for those wanting to add multimode

filter support.

Please note: There are also video installation & calibration guides in addition to this pdf document:

OB-X Custom Parts Installation

OB-X Calibration

OB-X Additional notes on filter calibration

CONTENTS

4-Voice Expansion

(4) OB-X Voice Card Assemblies

(1) OB-X Motherboard Assembly (Expansion)

(1) Motherboard Tray

(1) Filter Control Board

(4) 10-Position Connectors

(1) 5-Position Connector

(1) 4-Position Connector

(1) 4-Position Power Connector

(1) 4-Position DF13-style connector (pre-plugged to voice motherboard)

Mounting hardware for mounting motherboard tray, voice cards, and filter control board

8-Voice Kit

(8) OB-X Voice Card Assemblies

(1) OB-X Motherboard Assembly (Primary)

(1) OB-X Motherboard Assembly (Expansion)

(1) Motherboard Trays

(1) Filter Control Board

(7) 10-Position Connectors

(1) 10-Position Connector w/ long wires for gate & CV I/O

(1) 5-Position Connector

(3) 4-Position Connectors

(1) 4-Position Power Connector

(2) 4-Position DF13-style connector (pre-plugged to voice motherboards)

Mounting hardware for mounting motherboard tray, voice cards, and filter control board

INSTALLATION - BOTTOM MOTHERBOARD

The new bottom assembly for voices 1-4 comes partially-assembled & fully calibrated.

If you are only installing a 4-voice expansion please skip to the section Top Motherboard Installation.

1 Remove the top tray assembly to access the bottom motherboard

a) Remove the (6) connectors between the upper voice tray and mainboard. The connectors can be

discarded as new connectors are included in the kit.

b) Remove the 5-position connector on the right side of the voice motherboard.

c) Remove (3) screws from the bottom of the OB-X that are holding the (3) 1 ½” standoffs to the left

side of the upper voice tray. Alternately, remove the (3) 6-32 nuts from the top side of the unit and

leave the standoffs in place for now.

d) Remove the upper tray assembly.

You should now be staring at the bottom tray assembly:

2 Remove the bottom voice assembly

a) Remove the (7) connectors between the upper voice tray and mainboard. The connectors can be

discarded as new connectors are included in the kit. Also remove the connector to the output jacks.

b) In order to remove the voice motherboard voice cards 2-4 must be removed first. To remove the

voice cards remove the (6) 6-32 screws holding down each card and pull out the cards.

c) After voices 2-4 are removed remove the (15) 6-32 screws holding down the voice motherboard:

d) Remove the voice motherboard assembly. With the voice motherboards removed you see the

bottom of the enclosure:

3 Install the new primary Voice Motherboard assembly

a) Place the new primary motherboard in the bottom of the unit and align the outer holes.

b) Note that voices cards 2-4 have been temporarily installed with (3) screws each. This is because

they need to be removed so that the motherboard can be screwed down. Remove the (3) screws

holding each card down and remove them (it is not important to reinstall the voices in the same slot).

c) Install (15) 6-32 x ¼” screws w/ lock washers to hold down the motherboard. All new hardware is

included –old hardware does not need to be re-used.

d) Once the motherboard is installed replace voice cards 2-4. They are hard to install! Make sure to

place even pressure on all connectors (especially “G”) and press until firmly seated.

e) At this time you don’t need to install the screws & lock washers to hold down the voice cards. Do this

later after the install has been tested.

f) Install the (7) new connectors between the voice motherboard and mainboard.

g) Note: The kit includes a new 10-position connector (connector L/M) with long wires to connect to the

CV & Gate I/O jacks. The original connector can be used if it is ok and you don’t want to solder the

new wires.

h) Reinstall the output connector to the output jacks.

i) Dress the small 12”long 4-position cable to the left of the motherboard. It will plug into the Filter

Control Board that will be installed later.

INSTALLATION - TOP MOTHERBOARD

1 Place the Upper Voice Motherboard assembly

a) The upper board ships completely assembled & calibrated.

b) If the unit has original 1 ½” hinged standoffs installed remove them.

c) Install the (3) 1”standoffs onto the brass hinges that are pre-installed on the motherboard tray:

d) Place the upper motherboard assembly above the primary motherboard and align the standoffs with

the holes in the bottom of the enclosure. Install (3) 6-32 screws and lock washers from the bottom of

the unit to attach the standoffs.

e) Do not install the screws on the right side of the tray yet. The tray swings open and it should be left

as-is until the voices are tested & verified.

2 Install Connectors

a) Install the (6) new connectors between the upper voice motherboard and the mainboard.

b) If upgrading from a 4-voice OB-X there may be a dummy load resistor attached to the +/-19V power

connector that goes to the upper voice motherboard. Simply unplug it from the old connector. It can

be removed but there is no problem just leaving it. Note: the wires have been cut off in the pic below:

c) Note: There is no connection to the 4-position header at the bottom of the upper voice motherboard.

d) Install the 5-position voice sum connector from the bottom voice motherboard to the upper board.

These are the connections at the bottom-right of each voice motherboard.

e) Dress the small 12”long 4-position cable to the left of the motherboard. It will plug into the Filter

Control Board that will be installed next.

INSTALLATION –FILTER CONTROL BOARD

1 Remove screw from CPU Board

Note: If the Encore MIDI Kit is installed it should be first removed to access the CPU board.

2 Swing open CPU Board and remove IC31 & screw shown

3 Install the included male-female standoff where shown

4 Install the Filter Control Board into socket IC31. Secure it to the standoff with a 6-32 screws &

lock washer

5 Connect the 4-position connector(s) from the motherboard(s). Either connector can be used

w/ either cable - they are in parallel

FILTER CONTROL BOARD –OPERATION

The two switches on the filter control board determine whether the NOISE FULL & NOISE HALF buttons

control the noise level or the filter mode.

1 When the left (HP) switch is in the up position the NOISE FULL button will select highpass mode and

noise full no longer works.

2 When the right (BP) switch is in the up position the NOISE HALF button will select bandpass mode

and noise half no longer works.

Please note: The 4-Voice expansions were shipped with the filter control board included. If it installed you

can use it to have different filter modes for the top four voices. The bottom four voices will not have filter

control and you will lose the noise half and/or noise full volume features if the bandpass and/or highpass

modes are enabled.

Other Abstrakt Instruments Synthesizer manuals

Abstrakt Instruments

Abstrakt Instruments Avalon User manual

Popular Synthesizer manuals by other brands

Kawai

Kawai MP7 Software update

Joranalogue

Joranalogue Contour 1 user manual

Full Bucket Music

Full Bucket Music Mono/Fury manual

Kawai

Kawai PH50 owner's manual

IK Multimedia

IK Multimedia UNO Synth PRO X user manual

Behringer

Behringer DEEPMIND 12 quick start guide

Roland

Roland Gaia SH-01 Quick guidebook

Roland

Roland GR-30 manual

Gotharman

Gotharman Gotharman's anAmoNo-box user manual

Yamaha

Yamaha DX21 owner's manual

QuStream

QuStream HDFS-550 Technical manual

Modal Electronics

Modal Electronics ARGON8 quick start guide

Roland

Roland GS-500 instructions

Octave

Octave Cat SRM Service manual

Dreadbox

Dreadbox Murmux Initiate manual

neutral labs

neutral labs ELMYRA 2 Build guide

Waldorf

Waldorf KYRA user manual

Tubbutec

Tubbutec Juno-66 user manual