Thank you for the video Keith. I have learned a lot from this video and I think it is also valuable for others too in understanding synths sounds/mechanisms.
wonderful instrument you have there Keith. I have the eminent solina mk4 which is a close relative to the arp omni. they just sound so unique. thanks for sharing your amazing videos. best wishes from Markus.
@ Synthesizer KeithThe reason why the Omni has no pitch/CV output is because the Omni is polyphonic and its polyphonic sound generator consists of a single oscillator and numerous frequency divider chips that produces 2 individual tones (8' and 16') for each key on the keyboard. Even a synth with limited polyphony, such as the Oberheim 4-Voice, has a minimum of 4 CV outputs, or one CV output for each note of polyphony. For the Omni, you would need at least 1 pitch/CV output for every key on the keyboard, which means there would have to be e a total of 49 pitch CV/output jacks since there are 49 keys on an Omni. These 49 jacks would only be for the string section (violin and viola's) and would not apply to the bass section. Thus, Pitch/CV outputs would not be practical for the Omni's string section. On the other hand, since the bass/cello section of the Omni is monophonic, you would only need 1 pitch/CV output for the entire bass/cello section. However, the bass section, which relies on the same polyphonic sound generator to produce the bass and cello tones, lacks a keyboard-controlled VCO. Instead, the sound associated with each of these bass keys is gated in such a way that only the sound produced by the lowest of these keys is sent to the bass audio output. Thus, to add a CV/pitch output jack for the bass section, one would have to make a major modification to the keyboard which requires the addition of a CV buss for the 20 leftmost keys (left of the bass split). It would also require additional circuitry. [Although the string section of the ARP Quadra works very similar to that of the Omni, I might add that that the ARP Quadra's bass synth, unlike the Omni, contains a keyboard-controlled VCO. This is why the Quadra is equipped with a Pitch/CV output for its bass section, while the Omni lacks this CV output.]
Super cool. Famous for being Joy Division's synth. I tried to get the plug in version for Reactor but I still use Logic 8 so it's not compatible anymore. :(
Hi Keith, i have an Arp Omni-2 and there's no sound , only air . I've changed the blue capacitors but there's only the air kind of sound. Can you help or suggest me what to do?
Hey Keith - just wanted to thank you for your great uploads and for giving a point of reference to those of us struggling to work on our Omnis. I have an Omni 2 and have a bit of an odd question - I also have an Odyssey that i'm rebuilding that had it's keyboard removed (not exactly by the method in your odyssey video - but not that far off actually!) - I was wondering about the feasibility of driving the odyssey from the Omni keying circuit directly (routing the pitch voltages to a jack on the rear panel and then driving the odyssey with it) - from what i understand (though can't believe really) is that the odyssey cannot be driven via the omni's cv/pitch outputs... but maybe i'm grossly mistaken. My odyssey is not currently functional (lying in parts) so I can't really check that now... any suggestions? Am I trying to reinvent the wheel here? thanks much.
antigen4 sorry i must have been overtired - i guess the triggering scheme for the omni would be incompatible - but hmmmm... can you think of any other ways of doing such a thing - if not directly - then indirectly?
antigen4 Unfortunately, Arp didn't include an additional buss bar and spring contacts on the keyboard assembly, to generate a pitch CV on the Omni. There is no way to drive both the gate and pitch CV of your Odyssey, from an Omni.
thank you Keith. I'm just starting to wrap my head around the overall architecture of the Omni - it's actually pretty amazing to me - the adventures in synthesizer architecture that designers of the 1970s took... part of what created the magic of the ARPs, KORGs, Yamaha CS series, Roland SHs and others of the era... I love the integration of mechanical assemblies and the way they influence pitch voltage and other signals.
I wonder if I could trouble you for a minute. I wouldn't ask this of you - except that I have a problem that's driving me nuts (!) - I'm nearing completion of the rebuild of the aforementioned Omni 2 and have pretty much everything working tickity-boo - EXCEPT for a residual 'stuck note' drone - I know most people will tell me that it's an envelope filter cap - but I've already replaced and double checked ALL of them - but yet I still have the problem - it only seems to occur when the string section is invoked and it's frequency corresponds to the decay portion of F sharp/G minor. However I can still play the corresponding key without affecting the drone at all. So that makes me wonder if there isn't something weirder/deeper going on - I thought maybe of the ADSR board - but that shouldn't make sense if the synth section is off. I'm perplexed. Can you suggest anything else to try? I hope i'm not imposing. thanks
antigen4 Hi Antigen4. I would suggest replacing the envelope capacitor for that specific F-sharp key, even if it looks good to you. It will give you peace of mind, and confirm that the cap is OK. If that doesn't solve the problem, then you'll have to follow the gate signal all the way from the keyboard, through to the envelope generator, and then probe the output of the envelope generator. Also, you may have to follow the signal from the divide down oscillator, to see if there is some weird bleed-through issue (even though that's probably not it). It could even be something as simple as a shorted contact in the keyboard assembly for that F-sharp. Look at the difference between signals/levels from a working key, and the bad F-sharp key. Eventually you'll see something that is different in the F-sharp circuit, and that will give you a clue on what is wrong. You can find the service manual and schematics for the Omni online, if you don't already have them. Solving problems like this can take a surprisingly long time, but in the end you'll have a working Omni. Don't give up!
Synthesizer Keith sure - yes thank you Keith. Sage advice as always. it's driving me NUTS :) - could be a key contact. It was doing it before my total recap (isn't that a schwarzenegger movie) and AFTER as well - so I figure ti's something else where.. I got everything almost sorted out - this was my LAST problem - then suddenly the WHOLE thing stopped working and suddenly ALL FEEDS from the fixed up power supply suddenly went to +8V at 60 Hz... I think i'm losing my mind... that shouldn't even be POSSIBLE... :) GAH! - i'll keep on it though...
Synthesizer Keith thanks for the advice - the new problems seems to have fixed themselves for whatever reason (must be an intermittency somewhere) - so I've started looking at this again - and the 'persistent tone' occurs ONLY in the violin/viola section. Using the synth section only (violin/viola OFF) the problem doesn't exist. Would you suggest looking elsewhere under these circumstances (and yes it does kind of sound like a bleed through insofar as the timbre is a bit different than the other notes - but could just be the decay component talking) - terribly sorry to bother you - I guess this is a liability of youtube... :(
+Synthesizer Keith after getting (finally) the gumption to go back and really take a hard look at it - I discovered (D'OH!!!) I'd soldered in one of my tantalums BACKWARDS! Well at least I found it!! thank you for everything - a big lesson to me here.
