![]() |
![]() |
![]() |
![]() |
![]() |
![]() |
Inherent Design Errors |
How to restore an OB-X |
New Voicecards |
"Tom Sawyer" rezz |
Features |
OB-X Revs |
OB Model comparisions |
The
patient on the operating
table (no, the KEYBOARD silly!) |
The
pile of replaced components (!!!) |
![]() |
![]() |
![]() |
Rev # |
Description |
0 |
"OB-X" block typeface on top
middle of panel, no Oberheim name on front panel, voicecard enable
three large slideswitches (like TEST1 and TEST2), only two
slideswitches on LH panel (OSC 2 ONLY and TRANSPOSE), rev A voicecards,
no solder mask on any boards, mounting screws visible on LH panel
slideswitches, no bezzle in hole for mod/pitch levers. Polyphonic
glide circuit used CA3240 which fail with age. |
1 |
"OB-X" block typeface and
Oberheim logo above keyboard, three slideswitches on LH panel (OSC 2
ONLY, BROAD/NARROW, OCTAVE) |
2a |
"OB-X" fancy typeface top left
of panel, "Oberheim" brand above keyboard on right, "HOLD" "RESET"
labels right-aligned, voicecards have solder mask |
2b |
"HOLD" "RESET" labels
center-aligned, voicecard enable mini-DIP switch (common failure
point). Noise filter added to AC power inlet, processor & main
board has solder mask, mounting bolts for LH slideswitches now
integrated into LH panel with only visible screws on mod/bend
levers. CA3240 replaced with TL082 (LF353 is suitable
replacement) in polyphonic glide circuit. |
2c |
Power switch moved to top of
panel, "RESET" renamed "CHORD" and center-aligned, rev B voicecards
(gate LED added) |
3 |
Bezzle added in hole for
mod/pitch levers. Gray outline changed to darker scheme with hint
of blue. OTAs matched in polyphonic glide circuit for better (but
never perfect) tracking of glide rates between voices. |
4 |
LH panel slideswitches has gray
border, rev B processor board (adds "Oberheim interface" DB37 connector
on LH endblock), panel boards have solder mask. |
OB-X |
OB-SX |
OB-Xa |
OB-8 | |
VOICE CARD |
4-8 |
4-6 |
4, 6, 8
(even only) |
8 |
VCOs
|
2x discrete |
2x CEM3340 |
2x CEM3340 |
2x CEM3340 |
Modulation
|
XMOD |
XMOD |
VCO2 FM by
VCF EG |
expanded in
software matrix |
PWM
|
yes |
yes |
yes |
yes |
VCF (lowpass only)
|
Discrete
cascaded OTAs, 12dB |
CEM3320, 12dB |
2x CEM3320,
12dB or 24dB |
1x CEM3320, 12dB or 24dB |
VCA
|
3080 OTA +
TL081 buffer |
3080 OTA + TL081 buffer | 2x 3080 OTA + TL081 buffer | 2x 3080 OTA
+ TL081 buffer or CEM3360 |
Voice volume control
|
no |
no |
yes |
yes |
EG
|
2x CEM3310
VCF & VCA |
2x CEM3310 VCF & VCA | 2x CEM3310 VCF & VCA | 2x CEM3310 VCF & VCA |
LFO
|
one |
one |
two (for
dual timbrality split/layer) |
two
(software) |
Noise Source
|
yes |
no |
yes |
yes |
SYSTEM |
||||
# of patches
|
32 |
24/48/56
depending on version |
32/120
depending on version |
120 |
Editing
|
Full |
Limited |
Full |
Full |
User Storage
|
yes |
no |
yes |
yes |
Polyphonic glide
|
analog |
56-preset
version only, digital |
analog |
digital |
Timbrality
|
mono |
mono |
dual |
dual |
Audio Field
|
stereo |
mono |
stereo |
stereo |
Voicecard Audio Summing
|
3080 OTA + TL081 buffer | 3080 OTA + TL081 buffer | CEM3360 |
CEM3360 |
DAC Resolution
|
10 |
10 |
12 |
14 |
MIDI Retrofit
|
Encore
Electronics |
ElectronGate MKC-1 | Encore Electronics | Encore Electronics |