HOHNER PK250 MIDI SYNTHESIZER (1985) w/ Curtis CEM 3391 Filter

Andro Umeda

"I have got today this ultra rare instrument in perfect working order. It should have analog voices plus sampled drum section. This is a first power-on test. Love the sounds."

Haven't seen one of these before. Some info via legoluft who's done some mods for it:

"I'll describe the modification of a professional arranger keyboard, model Hohner PK-250, in detail. This home keyboard from 1985 offers many possibilities like poly and solo sections, drum machine, portamento and chorus effects, Hohner chords, etc. It produces stunningly high-class sounds with a warm, analog character.

While studying this instrument more specifically, I discovered two Curtis CEM 3391 chips (24 dB low-pass filter with resonance up to selfoscillation) and several SSM 2024 chips (a VCA module which was also built into the legendary "Waldorf Wave"). I got hold of the chips' data sheets and found out that the very flexible CEM 3391 chips in this machine were hardly taken advantage of, and that many important functions were blocked by fixed, unchangeable control voltages.

I built a simple board with 7 adjustable control voltages, using standard CV model 7805. I used the +12 V direct from the device's power supply. Thus, 7 independent CVs were at hand I could now adjust with external potentiometers.

After replacing the device's fixed CVs for the preset sounds with my own, the machine had 7 important synthesizer functions. Despite of the preset sound settings, I can now manually adjust and drastically change the cutoff, resonance and ADSR envelope values.

The result is astonishing and, through the built-in MIDI interface, this device has become a full analog synthesizer with assertive sound."

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Sequential Circuits Prophet 5 Rev 3.2 SN 6363

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via this auction

"Three versions were built between 1978 and 1984. The first, Revision 1, was hand-assembled, and only 182 were made. Revision 2 was mass-produced in quantities over 1,000: this model was more robust, added cassette patch storage, and replaced the koa wood casing with walnut. Revision 3 replaced the Solid State Music (SSM) chipset with Curtis Electromusic Specialties (CEM) chips, necessitating a major redesign. This particular piece is a Revision 3.2. This synth has been well kept and appears very clean..."

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PPG wave 2.2 Wavetable Synthesizer (1982) RetroSound Soundscapes II - sound demo

RetroSound

"(c)2007-20 by RetroSound
supported by UVI: http://bit.ly/retrosound-uvi

PPG wave 2.2 Synthesizer from the year 1982

The PPG Wave 2.2 is the direct successor of the Wave 2 but with 2 oscillators. Only 500 Wave 2.2 were manufactured.

The sound character is different to the later Waldorf Microwave synths and different to the Wave 2.3.

- 8 Voices
- 2 to 16 Oscillators per voice
- 30 Wavetables with 64 waves per table
- analog 24 dB/oct lowpass SSM 2044 VCF
- Curtis CEM 3360 VCAs
- micro processor (6809)
- 8Bit DACs

Used by: Trevor Horn (Propaganda, Art Of Noise, Frankie Goes To Hollywood, Grace Jones), Ultravox, Depeche Mode, Robert Palmer, Talk Talk, Tears For Fears, Thomas Dolby, The Fixx, Thompson Twins, Tangerine Dream, Gary Numan and much more


RetroSound synthesizer demo videos since january 2007.
All is for free. If you like my work, so can you support me with a donation or a purchase of my music albums. Thank you!

Donations: https://www.paypal.com/cgi-bin/webscr..."

1975 Electronic Music Circuit Guidebook

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via this auction

"Scarce title. This fascinating book covers everything you need to know to design and troubleshoot analog synthesizers, including detailed information on SSM and Curtis (CEM) synthesizer chips. A definite must-have for the analog synth enthusiast, filled with schematics and technical information, as well as a few photos of Moog and E-mu Modular systems.

Apart from some moderate cover wear, the book is in very good condition. Softcover, 302 pages. Copyright 1975. This item ships WORLDWIDE."

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OSCar

Published on May 29, 2020 SSM Curtis

Kawai K3 Hybrid Digital Analog Synth w/ SSM Filters

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via this auction

"Its a digital waveform / wavetable synth that then goes thru analog filters and envelopes for that its using the famous sm chips extra lush not curtis.

Sometimes it sounds like roland warm pads next minute like a ppg but always very classy and rich warm"

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PPG Wave 2.2

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via this auction

"This is one of my most prized and cared for possessions. If we weren't in the middle of an unprecedented financial crisis, I would prefer have this beauty buried with me. ;) It's the absolute king of wavetable synthesizers, the first and only of its kind if you ask me (and virtually anyone else who's had the privilege to use one). I've had this particular one for the better part of 20 years, and she's never let me down (unlike multiple new synths where I find myself flustered when firmware corrupts or memory erroneously wipes out); she's just been steadfast and true for her treasured time with me. Always kept in a non-smoking studio, voltage regulated and on battery backup. When I bought this beauty some 20 years ago I was under the impression the previous owner had a good working relationship with PPG when they were still in business and this was one of the first editions in circulation. This beauty was exported to the UK and found a home with one of the curators of the early 2000 (UK) PPG Conferences. With the help and guidance of PPG connoisseur, H. Seib, she was gone through with a fine tooth comb and had been swapped out with new bushings, keys and factory formatted. Since my acquisition of this unit (3rd owner by my understanding) I had created and sculpted custom waves with the Waveterm A (When it still functioned, but sadly that is now a very distant memory) and a wide range of factory sounds which are still in place. I had considered the upgrade to V8.3 to save much of the library I had created but wouldn't attempt it without the expertise and assistance of a few friends in Toronto who had years of experience working on these, but sadly that never did come to fruition. Time is always the greatest enemy, isn't she? ;) I also have the entire factory soundset from the floppy disk of the 2.3, Waveterm A and B as well as many wavetables shared on the old PPG forum so the update would probably be worth it. It's a fairly easy upgrade and still available to purchase if you're considering using the SYSEX features of V8.3. There was discussion some years ago about a virtual waveterm being available at some point (Waveterm C), perhaps a gentle nudge in the PPG discussion forum and it will eventually materialize with those DIY monowaves. ;) Until then, I leave you with one of the worlds finest synthesizers ever imagined. This is the stuff dreams are made of, not kidding. Serious inquiries only, thanks!

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1980s Sequential Circuits Prophet 5 Rev 3.3 Vintage Analog Synthesizer w/ MIDI SN 6275

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via this auction, also on Reverb

"Recently serviced and given a clean bill of health from our techs here at Mike & Mike's Guitar Bar, this Prophet is the final iteration of the synth that shaped the '80s and revolutionized the industry, having been subsequently outfitted with MIDI. Founded by Dave Smith in 1974, Sequential Circuits forever changed music technology with the advent of the Prophet 5, which broke new ground as not only the first polyphonic synthesizer to enable players to store and recall presets, but also as the first musical instrument with an embedded microprocessor.

The Prophet 5 features five voice polyphony, and for its principal sound sources each voice contains two VCO's (voltage controlled oscillators), OSC A and OSC B, in addition to a white noise source which can be mixed into a resonant low-pass VCF (voltage controlled filter). The filter modifies the voice timbre under control of its four-stage envelope generator. The filter may also be resonated and serve as a sound source. Following each filter, a VCA (voltage controlled amplifier), also controlled by a four-stage envelope generator, shapes the voice amplitude. Supplementing the basic voices are polyphonic modulation (POLY-MOD) signal routings within each voice that allow OSC B and the filter envelope generator to function as modulation sources applied to OSC A frequency or pulse width, or the filter frequency. Finally, there is a single LFO (low-frequency oscillator) and a pink noise source which can be mixed to modulate all five voices, as adjusted by the MOD wheel. The analog filters, envelope, and LFO are all extremely rich sounding and notably flexible, and the Prophet 5 boasts patch memory storage as well, which scans and memorizes every knob setting for storing and recalling your sounds.

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Prophet VS Ram Card

Note: Auction links are affiliate links for which the site may be compensated.
Published on Aug 19, 2019 SSM Curtis

"Prophet VS Ram Card - additional 16 x 100 patches on ram Card."

Available on Reverb

"A regular SCI RAM card and internal VS RAM has 100 programs and 32 User waveforms.
Our new SYNTHTASTE VSC-16 Card has 16 banks: thats 1600 Programs and 512 User waveforms in total! Developed and designed in Germany

This card can be used on your PROPHET VS keyboard AND your PROPHET VS rack, it is fully compatible and the display is easy readable on both.

The new VSC-16 SYNTHTASTE card includes:
- a tested and preformatted cardridge
- the original SCI PROPHET VS factory bank
- PLUS 4 extra banks fully loaded with SYNTHTASTE customer programmed sounds (that’s 500 preinstalled sounds in total you can start with
- space for up to 1100 personal sounds
- 2 digit bank display
- 2 bank buttons"

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Vintage Analog Strings

Published on Jun 24, 2019 SSM Curtis

Part I:
Solina String Ensemble
Roland RS 505
Logan String Melody II
Korg Polyphonic Ensemble
Farfisa Syntorchestra
Vermona Piano Strings
Yamaha SK 20

Part II:
Logan String Orchestra (~1977)
Elka ElkaTwin (~1979)
Roland VP 330 (1979)
Siel Orchestra 2 (1983)
Crumar Multiman-S (1977)

Part III:
Roland RS 505 (1978)
Farfisa Syntorchestra (1975)
Yamaha SK 20 (1979)
Roland VP 330 (1979)
Siel Orchestra 2 (1983)
Crumar Multiman-S (1977)

1982 Electronic Music Circuits Book by Barry Klein

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via this auction

"1982 Electronic Music Circuits ~ 302 pages

Scarce title. This fascinating book covers everything you need to know to design and troubleshoot analog synthesizers, including detailed information on SSM and Curtis (CEM) synthesizer chips. A definite must-have for the analog synth enthusiast, filled with schematics and technical information, as well as a few photos of Moog and E-mu Modular systems. Overall, the book is in very good condition. Softcover, 302 pages. Copyright 1982. This item ships WORLDWIDE."

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A simple patch with new Doepfer A-151 Sequential Switch

Published on Mar 23, 2019 zerozero island

"Just a quick video showing my new A-151 and a simple patch i threw together. I'm using it to cycle through all 4 waveforms out of a Doepfer VCO, and create a sort of goofy rhythm pattern in 5/4.

Modules used:
RYO Penta
Dave Smith Curtis Filter
Doepfer A-105 SSM VCF
Doepfer A-151 Seq. Switch
Erica Synths Envelope
4ms Rotating Clock Divider
Makenoise Maths
Makenoise Tempi
Makenoise Rosie
Expert Sleepers Disting Mk. iv w/MIDI breakout
Doepfer A-110 VCO
Befaco Slew Limiter
Penrose Quantizer
BMC 4 channel VCA Mixer
Sound Study Spring Reverb w/ 2spring Accutronics tank

Come to think of it, i guess it's not that simple! Only took a few minutes to patch together, though. That Seq. Switch is a pretty handy gizmo!"

Sequential Circuits Prophet 5 Rev 2 w/ Kenton MIDI

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via this auction

"The rev 2 used the earlier SSM chips that sound to my ears so much better than the later Curtis chips. The problem with the SSM chips (and probably why they went to the Curtis chips) and more generally the rev 2 was the tuning stability. This is why bands quite often used the rev 2 in the studio but the rev 3 on tour (Talking Heads, Japan etc). This problem has been resolved in the rev2 thanks to the masterly work of James at Synth Repair Services...there are now 8 little pixies running around inside making sure the tuning is just tickety-boo (well thats what James told me)

for the more technically minded, the power supply was upgraded (see toroidal photo), all presets replaced, and very high precision resistors used in DAC circuit. There is probably more to this mod but thats all I could work out from James Walker(Synth Repair Services).

I have been told that this was one of the earlier Prophet 5 rev 2's as it has a smooth panel surface, I have not been able to verify this. If anyone out there is more knowledgeable on the different rev2's it would be great if they could let me know if this is true or not."

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Creamware Pro-12

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via this auction

The description at the listing is currently for a Minimax. Pictured is the Pro-12 which was a virtual twelve voice Prophet-5. I forget if it was based on the Rev 2 SSM or Rev 3 Curtis filter model, or both. If anyone knows feel free to comment.

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PPG wave 2.2 Wavetable Synthesizer (1982) Elektroplankton

Published on Nov 29, 2018 RetroSound

"(c) 2018 vintage synthesizer demo by RetroSound

all sounds: PPG wave 2.2 Synthesizer from the year 1982

The PPG Wave 2.2 is the direct successor of the Wave 2 but with 2 oscillators. Only 500 Wave 2.2 were manufactured.

- 8 Voices
- 2 to 16 Oscillators per voice
- 30 Wavetables with 64 waves per table
- analog 24 dB/oct lowpass SSM 2044 VCF
- Curtis CEM 3360 VCAs
- micro processor (6809)
- 8Bit DACs

Used by: Trevor Horn (Propaganda, Art Of Noise, Frankie Goes To Hollywood, Grace Jones), Ultravox, Depeche Mode, Robert Palmer, Talk Talk, Tears For Fears, Thomas Dolby, The Fixx, Thompson Twins, Tangerine Dream, Gary Numan and much more"

Sequential Circuits PROPHET 5 synthesizer - sounds & presets【SYNTH DEMO】

Published on Oct 19, 2018 synth4ever

"Sequential Circuits Prophet 5 analog synth demo. Playing sounds and presets on vintage Prophet 5 analog synth from Sequential Circuits including pads, bells, polymod, filter and resonance tweaks. The Prophet 5 in this sound demo is a Revision 3.3.

The Sequential Circuits Prophet 5 synth was created by Dave Smith (from DSI/Dave Smith Instruments) and John Bowen, and manufactured from 1978-1984. Nearly 6,000 Prophet 5 synths were made in total, and three major revisions: revisions 1 and 2 used SSM chips, while the later revision 3 used Curtis chips.

The Prophet 5 has 5 voices of polyphony and was the first fully programmable polyphonic synth with an embedded microprocessor. It features 2 VCOs (square/pulse/tri/saw), 1 LFO, 4-pole resonant low pass filter, 2 ADSR envelopes, 61 keys, FM (Polymod) and can store between 40-120 patches (depending on model).

The SCI Prophet 5 is a legendary synth and commands high prices on the second hand market. It is known for having a warm, lush and brassy tone and for being very organic. The Prophet 5 has been used by many artists over the years on many hit records.

This Sequential Circuits Prophet 5 synthesizer demo was filmed at the Vintage Synthesizer Museum in Oakland, CA. Visit them at www.vintagesynthmuseum.com or watch the studio tour I did here:" [posted here]

SCI Prophet 5 Rev 2 polyphonic analogue synthesizer

Note: Auction links are affiliate links for which the site may be compensated.

via this auction

"The rev 2 used the earlier SSM chips that sound to my ears so much better than the later Curtis chips. The problem with the SSM chips (and probably why they went to the Curtis chips) and more generally the rev 2 was the tuning stability. This is why bands quite often used the rev 2 in the studio but the rev 3 on tour (Talking Heads, Japan etc). This problem has been resolved in the rev2 thanks to the masterly work of James at Synth Repair Services...there are now 8 little pixies running around inside making sure the tuning is just tickety-boo (well thats what James told me)

for the more technically minded, the power supply was upgraded (see toroidal photo), all presets replaced, and very high precision resistors used in DAC circuit. There is probably more to this mod but thats all I could work out from James Walker(Synth Repair Services).

I have been told that this was one of the earlier Prophet 5 rev 2's as it has a smooth panel surface, I have not been able to verify this. If anyone out there is more knowledgeable on the different rev2's it would be great if they could let me know if this is true or not."

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New CEM and SSM Chip Clones

A few new CEM and SSM chips for the DIYers out there.

First we have Latvian CEM Synth IC clones from ALFA:

AS3310 Voltage Controlled Envelope Generator. CEM3310 pin-to-pin compatible
AS3320 Voltage controlled filter. Improved CEM3320 pin-to-pin compatible
AS3330 Dual Voltage Controled Amplifier (VCA). Improved CEM3330 replacement.
AS3340, AS3345 Voltage Controlled Oscillator (VCO). CEM3340, CEM3345 pin-to-pin compatible
AS3360 Dual Voltage Controled Amplifier (VCA). CEM3360 pin-to-pin compatible
AS16M1 Serial Controlled, 16-Channel SPCO Switch

Next, Coolaudio [Behringer] announced they are working on new SSM chip clones (news via Soviet Space Child):

"Now that we have successfully cloned the famous Curtis 3340 and 3320 synth chips, we are now looking into reviving the great sounding SSM2044 and SSM2033 chips."

Sound Semiconductor recently announced the SSI2164 QUAD VCA.

And last, but definitely not least, considering, Curtis Electro Music announced the CEM3340 VCO re-issue in 2016.

For a list of CEM and SSM chips in synthesizers see Wikipedia here.

For previous posts including some with demos, see the corresponding labels below.

This post, like all posts, is an FYI that this all exists. It's up to makers and DIYers to decide where they get their chips. This post is worth reading.

Sequential Circuits Pro One Sequencer

Published on Feb 8, 2018 SSM Curtis

Kawai SX240 Midi CC Sysex Update

Published on Feb 6, 2018 SSM Curtis