Omnipressor dynamic audio effects : 50 years  reissue - Page 1
Forum section: electronics / projects

author: jonpaul
author_rank: Super Contributor
timestamp: October 29, 2023, 11:14:23 am
content: Bonjour audio/studio/music people:The digital plugins cannot reproduce it, Eventide has reissued this 19" rackmountanalog dynamic effects processor at the Audio Engineering Society (AES) convention now in New York.My design in 1973. (also many other Eventide boxes like Instant Flanger)Effects are heard in many 1970s, 1980s rock, jazz, albums...Still have the handmade prototype, it still works!https://www.eventideaudio.com/rackmount/omnipressor-reissue/https://vintageking.com/blog/2023/10/eventide-omnipressor-2830auYour feedback appreciated,Jon

author: temperance
author_rank: Super Contributor
timestamp: October 29, 2023, 11:42:16 am
content: Nice, audio effects are big business today. I've seen what they call stomp boxes based on a few chips made by coolaudio being sold €700.The stomp box world is all about appearance. Manufacturers copy schematics from way back and put them in fancy boxes asking €300 for something what is nothing more than a few op amps, some germanium diodes and a 555 based charge pump to generate the negative rail (and the noise at the output you get for free). The remainder is a collection of bad quality parts like very low cost pot's.Long ago I wanted an audio compressor. But those made by DBX and BSS where pretty expensive for a student so I build one myself with a VCA based on junction FET's (BF256). You learn a lot as a teenager from doing this kind of things.8 years later I started working for a pro audio distributor where I got to repair those BSS compressors. I was very disappointment to see that the inside was just terribly made as if it was some hobby project put together by teenagers.

author: moffy
author_rank: Super Contributor
timestamp: October 29, 2023, 11:47:06 am
content: Congrats JonPaul, still novel today.

author: The Soulman
author_rank: Super Contributor
timestamp: October 29, 2023, 12:25:58 pm
content: Congratulations!The pro audio and music industry could really use some more proper build analog gear.Plug-ins sounds like fun but it has a lot of drawbacks. (additional latency, no proper controls, dependent on computer hardware/os for control with al its updates and stability nonsense)Nothing beats the actual hardware with knobs to fiddle!

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: October 29, 2023, 12:32:20 pm
content: Salut Jonpaul,Quote from: jonpaul on October 29, 2023, 11:14:23 amTeardown please. :-)What gain-control-element did you use (J-FET, OTA, VCA??)?Best regards

author: jonpaul
author_rank: Super Contributor
timestamp: October 29, 2023, 12:48:52 pm
content: Rebonjour a tous: Many thanks for the kind comments!"Introduced in the early 1970s, the Omnipressor was the first dynamics effects processor of any kind, suddenly making possible a new, wide range of dynamics effects unlike anything that had come before it.Originally invented by Eventide’s founder, Richard Factor (and later redesigned for production by Jon Paul), the Omnipressor made a host of effects possible. It featured variable control of all aspects of dynamic modification. It also introduced the notion of the ‘side chain’ and foretold techniques that today we take for granted like ‘look ahead’ processing. One of our first customers was a young Brian May, lead guitarist of Queen. With the Omnipressor in his rig, his sound was never the same."See the Eventide "flashback" page, history back to 1971.https://www.eventideaudio.com/50th-flashback-3-the-omnipressor/Given Richard Factor's early prototype, I researched the VCAs and detectors, and worked with Dave BLACKMER, the founder of DBX.https://en.wikipedia.org/wiki/David_E._BlackmerBlackmer's fine VCA and TRMS audio modules were known for their wide dynamic range and low THD. (like a matchbox, metal can and epoxy potting)I redesigned the unit to employ the DBX 207 TRMS logarithmic detector and DBX 202 VCA.The heart of my design was single control function with variable of slope/polarity of the log VCA voltage control. Also the the metering.The unique meter face and control knob calibrations are still very close to my hand drawn calibration of 1973.Enjoy!JonPS: All my effects of 1970s and many more in the Eventide Anthology Plugin set:https://www.eventideaudio.com/plug-ins/anthology-xii/

author: themadhippy
author_rank: Super Contributor
timestamp: October 29, 2023, 01:37:38 pm
content: QuoteTheres plenty of it sitting in dark corners of warehouses and studios ,unused and unsaleable since the rise of the digital desk and computer.

author: The Soulman
author_rank: Super Contributor
timestamp: October 29, 2023, 02:01:15 pm
content: Quote from: themadhippy on October 29, 2023, 01:37:38 pmYeah I know, sadly most isn't that great build-quality wise, and doesn't age well without a major overhaul (pots, switches, caps, etc..).Spending big-bucks on new (and reliable) equipment isn't really a concern at the place were I work, if it serves the purpose in a reliable and user friendly way for at least a decade.I still own a bunch of DBX Project 1 compressors and gates purchased twenty years ago (and modified with different op-amps, capacitors and higher voltage more stable psu's),surprisingly enough these are much nicer build quality than the much more expensive BSS equivalents from the same era.

author: themadhippy
author_rank: Super Contributor
timestamp: October 29, 2023, 03:19:39 pm
content: QuoteMost of the stuff i know about sitting unloved is certainly well build ,otherwise it wouldn't have survived life with the road crew.

author: CaptDon
author_rank: Super Contributor
timestamp: October 29, 2023, 03:32:32 pm
content: Never ran the omnipressor. We had a bunch of Eventide broadcast equipment however. The traditional 'seven second delay' which built up the delay over time with the big yellow DUMP button for our live SportsTalk show and also some pitch shifting equipment where we could take 40 seconds of audio and smash it to 30 seconds without shifting the original pitch. Cool stuff. For processing limiters, gates and so forth we ran the CBS Laboratories Volumax and Audimax known in the trade as 'Level Devils'. Also lots of Orban, LA3A's and so forth. As a guitarist I used the Stolz designed RockMan stuff. I will say the Eventide broadcast stuff was solid as a rock!!! No failures ever even after studio lightning strikes that wiped out other gear in the same chain.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 29, 2023, 05:30:33 pm
content: You can get the schematics and engineer your own.https://www.studioelectronics.biz/sunshop/index.php?l=product_detail&p=6353

author: jonpaul
author_rank: Super Contributor
timestamp: October 30, 2023, 12:45:05 pm
content: Rebonjour a tous:inspired by the vintage manual link from Terry Bytes, I just unearthed pix and docs:1970s Omni prototype internals (pix #1, #2)revised original schematics (#3).The meter was custom made.The TI Log amps were originally for use in IR heat sensors for fuze use.The TI SC76502 DIP was still made in 2004, as TL-441EP SMD.The 1970s DBX modules are long gone.My old friend Les TYLER at THAT corp has IC equivalents.https://thatcorp.comLast photo #4 is my note of the Omni circuit description, especially details of the TI log detector in the meter ckt.Again, your feedback and thoughts are greatly appreciated.HAVE AN ABSOLUTELY FANTASTIC DAY!Jon