In­struo Cš-L

Com­plex os­cil­la­tor or os­cil­la­tor com­plex? Philip Wise tries out the new dual volt­age con­trolled os­cil­la­tor from In­struo

Future Music - - CONTENTS -

Af­ter leav­ing Qu-Bit Elec­tronix and set­ting out with his own brand, In­struo, a lit­tle over a year ago, Scot­tish de­signer Ja­son Lim has de­vel­oped an im­pres­sive lineup of Euro­rack mod­ules. In­struo’s range stands out from the crowd with a strik­ing de­sign aes­thetic and some unique twists on clas­sic synth de­sign.

The Cš-L is their take on the com­plex os­cil­la­tor, a de­sign pi­o­neered by Don Buchla with the 259 mod­ule in the ’70s that typ­i­fies the West Coast paradigm of cre­at­ing com­plex tones from sim­ple sine waves by way of ana­logue fre­quency mod­u­la­tion and wave­fold­ing. There are many com­plex os­cil­la­tors avail­able in Euro­rack with per­haps the DPO from Make Noise be­ing the most well known. So what sets the Cš-L apart?

For fre­quency mod­u­la­tion you typ­i­cally have a car­rier os­cil­la­tor that pro­vides the ini­tial tone and a mo­du­la­tor that af­fects the car­ri­ers’ fre­quency. In the Cš-L ei­ther os­cil­la­tor can act as the car­rier or mo­du­la­tor or they can both mod­u­late each other si­mul­ta­ne­ously. The two os­cil­la­tors have fun­da­men­tally dif­fer­ent cores (tri­an­gle at the bot­tom, saw at the top) giv­ing a greater range of sonic po­ten­tial than with two iden­ti­cal cores. The sine wave of each os­cil­la­tor is in­ter­nally routed to the op­po­site os­cil­la­tors FM in­put by way of a VCA. Ei­ther lin­ear or ex­po­nen­tial FM can be used for each os­cil­la­tor but not both at the same time as you can on the DPO. For clas­sic FM sounds, sine waves are al­ways used for mod­u­la­tion, but you can patch any other sig­nal into the FM in­put for more ex­per­i­men­tal re­sults. The Cš-L goes be­yond with a com­pre­hen­sive in­ter­nal rout­ing sys­tem that al­lows cross mod­u­la­tion of the wave­folder am­pli­tude and sym­me­try. Hold­ing the in­dex but­ton the six panel but­tons dou­ble up to se­lect the des­ti­na­tion, with the amount of sig­nal fed to each in­put is con­trolled by the as­so­ci­ated at­tenu­verter with the In­dex knob and as­so­ci­ated VCA as an over­all con­trol.

The place­ment of the rout­ing but­tons is un­for­tu­nately not very in­tu­itive and al­though an il­lus­tra­tion is pro­vided, it took me a while to get my head around what was con­trol­ling what. To be fair, the learn­ing curve was com­pli­cated by how much fun I was hav­ing just get­ting lost in the sounds. I had to re­mind my­self I was try­ing to an­a­lyse how the con­trol sys­tem worked!

In­struo’s pan­els are beau­ti­fully de­signed with a dis­tinc­tive matte black and gold aes­thetic, but there is a bit of a com­pro­mise er­gonom­i­cally. With patch points scat­tered all over the panel, once you have some patch­ing go­ing on it be­comes a bit crowded and I did find my­self tweak­ing os­cil­la­tor B’s fine tune knob a few times rather than the In­dex at­tenu­verter which is just above it and looks ex­actly the same. Per­son­ally I much pre­fer the knobs-at-the-top, jacks-at-the-bot­tom de­sign that many man­u­fac­tur­ers use.

A com­plex os­cil­la­tor gen­er­ally has one fi­nal out­put through a wave­folder but the Cš-L has one for each os­cil­la­tor al­low­ing you to use the two main voices at once. The wave­folder over­drives into a slightly rounded fuzzy square when pushed to its ex­treme and it’s com­pletely muted when turned down so it can also func­tion as a VCA of sorts. In a small

sys­tem this is pretty handy al­though you do lose out a lit­tle on tim­bre con­trol. The FM and wave­fold­ing both sound fan­tas­tic with smooth or­ganic sounds un­der sub­tle mod­u­la­tion, and harsh metal­lic Autechre-like tex­tures, bell tones, horn sounds and much more to be dis­cov­ered. The sound is dis­tinctly dif­fer­ent to the DPO (the only com­plex os­cil­la­tor I have to hand for com­par­i­son) and I found it very dif­fi­cult to du­pli­cate the sound of one with the other. The DPO has a thin­ner, harsher tone over­all.

Sit­ting be­tween the top and bot­tom os­cil­la­tor sec­tions you’ll find the Au­dio Mod­u­la­tion sec­tion and the Mul­ti­ply out­put which takes the com­plex­ity in a dif­fer­ent di­rec­tion, though it’s a shame there’s no CV in­put here. This can be switched be­tween ring mod­u­la­tion, half or full wave rec­ti­fi­ca­tion. By de­fault the two in­puts are again fed from the op­po­site os­cil­la­tor sine wave but you can patch other wave­forms or ex­ter­nal sig­nals in and use it in­de­pen­dently of the rest of the mod­ule. This sec­tion could also be used to rec­tify con­trol volt­ages be­fore us­ing them in other parts.

Mov­ing be­yond the com­plex os­cil­la­tor paradigm, the Cš-L has two vari­able width pulse out­puts, the top be­ing a clas­sic pulse wave that has quite a dirty tone. The bot­tom is called a Dou­ble Pulse; this looks like a stepped tri­an­gle where the width of the top and bot­tom steps shift in op­po­site direc­tions un­der mod­u­la­tion and it sounds like an oc­taved square There’s also a stan­dard square wave out that can be dropped one or two oc­taves be­low the main fre­quency for a sub out.

The Cš-L is a very flex­i­ble os­cil­la­tor, it ticks all the boxes for a clas­sic West Coast voice. The Au­dio Mod­u­la­tion sec­tion of­fers an al­ter­nate take on build­ing com­plex­ity from sim­ple sine waves and the dif­fer­ent PWM op­tions take it into East Coast ter­ri­tory. The in­ter­nal mod­u­la­tion rout­ing pro­vides a lot of sonic po­ten­tial with­out a sin­gle patch cable. Once you start self-patch­ing, the range of tones you can tease out of this mod­ule is huge. When it comes to ana­logue syn­the­sis this mod­ule cov­ers a lot of ground. It’s not quite a full synth voice and you need quite a few mod­u­la­tion sources to get the most out of it but it’d make a great core for a sys­tem.

CON­TACT KEY FEA­TURESWHO: In­struo WEB: in­struo.me­dia Com­plex Dual Os­cil­la­tor with two fi­nal out­puts each with a ded­i­cated wave folder. Au­dio Mod­u­la­tion sec­tion that can be used in­de­pen­dently. Sub Os­cil­la­tor with oc­tave switch. Pow­er­ful in­ter­nal rout­ing sys­tem. 26HP Power +12V: 120mA –12V: 80mA

VCO FRE­QUENCY When the top osc is hard synced to the bot­tom, the sub pulse is used for the sync sig­nal, let­ting you al­ter the fre­quency con­tent of the up­per VCO with this switch even if you’re not us­ing the ac­tual sub out­putDC OFF­SET As an Easter Egg the bot­tom pulse out­put has a slight DC off­set so you can patch it into the top half of the AM bus

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