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Oberheim OB1 vs SEM
Old 18th May 2012
Lives for gear
NAWAX's Avatar
Oberheim OB1 vs SEM

I've got the opportunity to trade a bunch of stuff for an OB1. I'm having a hard time to find info on this one.
How would you compare it to the SEM ? They both seems to have the same synth architecture. Is the OB1 nothing more than a keyboard version of the SEM ?
Old 18th May 2012
Lives for gear
Rust Creep's Avatar

The OB 1 is beautiful and rare.. love the look of that synth but I know nothing about it besides being highly regarded.. a lot of collector value but may be nothing more than a beautiful SEM with keyboard

copypasta from vintage synth

The OB-1 is a simple and great monophonic synth from Oberheim based on the same synth architecture as the SEM. Released in 1978, it was the first truly programmable analog synth of it's time with 8 program memories.

Classic and fat sounding bass & lead synth sounds. Similar in sound and synthesis from the Roland SH-101 to the MicroMoog. It has two analog oscillators and a very capable 2 or 4 pole switchable VCF filter that sounds great, and a good LFO that can control the VCA or VCF. This is a very versatile monosynth, especially during its time, and makes an interesting alternative to other more common bass-synths. It has been used by Tangerine Dream, Rush, and The Grid.

so its a SEM with keyboard and 8 memories.. and if its the first of its kind... even higher collector value
Old 18th May 2012
Lives for gear
NAWAX's Avatar
That's what I think too. But I'm not sure.
I've seen this article on VSE but I have little to no confidence in it. How come could they compare it to Micromoog and SH-101...
Do they really sound the same ? I've read somewhere that they were different but it might be complete BS as well.
Can anyone who played both the SEM and the Ob-1 give me some insight ?
Old 18th May 2012
Lives for gear

No it is NOT a SEM.

VSE has so many errors and hasn't been updated for YEARS.

The OB-1 filter is different. SEM is 12dB/oct state variable with lowpass/bandpass/highpass/notch. OB-1 is not state variable, it is a pair of cascaded OTA 12dB/oct lowpass filters, both in series gives 24dB/oct lowpass. OB-1 filter sounds good but it is not a SEM filter nor Moog filter.

Other differences:
  • OB-1 VCOs have variable waveshaping from triangle to ramp to variable pulse, SEM is ramp or variable pulse only.
  • SEM has more options in the modulation department
  • SEM EGs are ADS w/shared D/R, OB-1 is full ADSR
  • OB-1 has noise source, SEM doesn't

OB-1 is programmable but LFO rate and filter fine tune are not.

The only way to MIDI the OB-1 is to use a MIDI to CV converter to the CV/Gate input jacks on the rear panel. There is no cpu or firmware in the OB-1 so no software MIDI retrofit possible.

Good sounding synth though.
Old 19th May 2012
Gear Addict

Vco fine tuning is not stored either.
OB1 also has sub oscillator for each vco plus sync and cross mod.
Vco pitch is set in steps of a semitone, so not a regular pot like on the SEM.
Much more practical.
Vco mix on the ob1 is in just 3 steps, on sem it's a pot.
I just checked sem and ob1 and see no difference in modulation options,
but check for yourself using the attachments to this post.
SEM filter is cool because of the highpass and bandpass modes,
ob1's cool because of the 12\24db modes.
I like the ob1 more than the SEM because the ob1 sounds more electronic to me and I don't like the SEM envelopes.
The programmer in the ob1 is ancient, in my experience there are not many techs who can fix it.
Attached Files
File Type: pdf OB-1 Blank Patch Sheet.pdf (24.1 KB, 248 views) File Type: pdf Oberheim OB-1 Owners Manual.pdf (268.0 KB, 1283 views) File Type: pdf Oberheim OB-1 Welcome.pdf (1.00 MB, 472 views)
Old 19th May 2012
Lives for gear
dougt's Avatar

I've had a few OB-1s but sold them all and kept my SEMs. To me the SEM with its multimode filter is a much better bet. OB-1s are a bit of a nightmare service wise as well. You can probably get 2 brand new SEMs for the price of a OB-1 in good shape.
Old 19th May 2012
Lives for gear
NAWAX's Avatar
Thanks for the info.

I think I'll just skip it.
It seems really overprice for what it has to offer.
That being said, it's probably one of the most beautiful synth ever made imo...
Old 25th November 2015
Lives for gear
Space Station's Avatar
Also the early OB-1 has discrete EG's, later in the production run the entire circuit was were replaced with two CEM3310's ...just had to add that to this old thread
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