Archives for posts with tag: Synth Technology

This week i am going to start an extensive series of mods on an old Korg VC 10 Vocoder.  The Korg VC 10 has a reputation for being flawed in some ways but i think it has a lot of potential despite this.  I always felt that it had an ill defined sound over all.  It lacks a clear robotic synth vibe and also employs it’s noise generator in a not always useful way.

The demo is pretty dorky and kitchy but someone posted the original korg demo for this box and i think it clearly demonstrates the design limitations i’m referring to.  It wants to sound cool but it comes across sounding mushy and muddled to me…

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So, i did some research and found a good amount of info as to possible modifications, this first post will pertain to two major sound quality related modifications:

1,   There’s a quirk in the way the 20 sound generators are treated. Channels 17 to 20 have their carrier input connected NOT to the generator/noise/external mixer, but rather to noise only. The problem here is that this noise signal is attenuated by the generator/noise mixer, resulting in that there will be no carrier to channel 17 to 20 if you turn the generator/noise mixer knob to the generator only position! (which you may often do). Yes, the four highest channels will be quiet! Performing this mod will increase the speech recognition and add the missing edge to the sound.

2,  The bias signal for the sound generator does not affect channels 15 – 20.  By routing the bias signal to all the channels you get a brighter and more well defined vocoder output as all the channels will behave together.  This will also increase the effect of adjusting the bias.  This requires adding a few resistors that are not there for channels 15 and 16 and rerouting the 100k resistors for the remaining channels 17-20.

*** On to the dangerous part! ***

1,  The process:  Locate and release PCB KLM-134 (the filter board).  Locate the wire attached to header H3-1 (noise in).  Cut or unsolder the wire.  Now locate IC1 on the same board.  Find pin 1 and follow the trace to channel 16.  Connect from this point to the (now unconnected) corresponding point of channel 17.  The channel numbers and the traces pretty easy to locate on the PCB.  That one was easy!

2,  The process:  On KLM-134, find IC1 pin 7 (bias).  Follow this trace to R2414 (100k).  Now locate Q115 (channel 15 VCA).  Solder a 100k resistor between bias and the base of Q115 (R2315 is connected to the base).  Then locate Q116 and solder a 100k resistor between bias and the base of Q116 (R2316 is connected to the base).  Channel 17 to 20 already have the 100k resistors you need, but they are connected to ground.  Find R2417, R2418, R2419 and R2420.  Connect them to bias instead of ground.

Both of these mods sound complicated but are very easily seen in the schematic here:

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While i was inside the VC-10 i found a few other curious things that i will be discuss in a future post. I had to order more parts to do these bits!  It was filthy in there too, so i disassembled the bottom plate and did a thorough clean below the key bed.  It’s sounding way better to me with the first round of mods.  I should have done a before / after recording to reference…

To Be Continued!!

PS: These are the main sites i used for reference, technical info, and modification ideas:

Korg VC-10 Flaws & Features

Korg VC-10 Modifications

Vocoder Historical Notes

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It’s a Cat’s Universe, and we are merely playthings…

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Another day another jam.  This one features arpeggiated bleeps and bloops from the highly underrated  Sequential Circuits Multitrack.  I enjoy this synth because it is physically compact, straight forward in it’s layout, and has a very solid versatile sound quality over all.  It’s internal sequencer can hold 4 sequences of 6 parts each and is easy to sync to sequencer clock.  If you plug your sequencer clock into the tape input and put the tempo knob all the way to zero the synth goes into external clock mode.  Pretty slick!  All you need to do now is start it in time with your drum machines and you are off.  If you are slightly tricky you can record your parts to the internal click track and quickly stop recording on a whole measure. this way you can loop your sequence along to your other instruments indefinitely!  The internal arpeggiator is also cool because it will do standard up down or in order played.

PS:  this is what i do with the DSX sequencer as well. If you keep it in loop mode it will just start from the beginning when you punch out of record.  The Oberheim DMX is locked to the same clock and just playing along with the multitrack.

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Side notes:

1, I always hoped to find another dead Multitrack so i could make one of these.

2, I did a quick demo of the Multitrak when i picked it up.  All sounds were generated by and played from the internal sequencer at the same time out of the individual outs on the back.  For instance i made a patch that was a ‘kick’ sound which was track one, a ‘snare’ patch for track two, ‘bass’ for three, ‘pad’ for 4, and lead bloops’ were 5.

3, Note the velocity sensitivity on the snare patch.  There’s not many too MIDI Velocity Sensitive true analog synths from back then!

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funny minimal waves…

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My development is become arrested.  Space Lazr hath shaken my brain.  And the Korg wavz re Soooo Squayrwavy…..

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This track consists of the Roland TR 909 from here and the Korg from here… Also, the Korg bloops in the breaks are triggering from a master clock.  the same clock is driving the TR 909 via R-sync and Simmons SDSV Via 96 Sequencer clock ( With MFB sequencer ) here… it’s awesome when everyone talks synth!

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One dollar record of the day of the day!

So there’s a few actual record stores left here in town that i try to go dig for vinyl in with some frequency.  I love them because they have GIANT piles of records for cheap.  I can often get as many records as i can fit in my bag for 1$ each!  Awesome.

So on my last dig i came across a rare gem from synthesizer history.  It’s a record by SynergyLarry Fast ) called Cords.  Larry Fast worked with Peter Gabriel on his first album ( Peter Gabriel ST ) and up until 1986.  Kate Bush on Never For Ever, and even Carl Sagan‘s Cosmos: A Personal Voyage!

Whats fun about this album is it bridges the gap between the lush visual soundscapes i enjoy from Vangelis and the focused stand alone strength of discreet compositions.  It’s hard to believe while listening to this record that it was done on an 8 track in a side room of a house!

As to the synthesizer list, it’s long and sweet.  There’s a Moog modular, Moog Polymoog ( one of the 6 prototypes built ), Paia kits, Oberheim DS-2 sequencer, Micromoog, etc.  I’ve never used a DS-2 sequencer but it looks like a similar idea to the old Roland MC4/MC8 idea where you step in an composition ( two tracks in this case ) and you can play one or the other back to an external clock…

One last thing, the credit of  “Finally guitars…Sort of” on the back cover is funny.  Apparently the first two Synergy records said something to the effect of ” No guitars were used in the making of this album. ”  It was a response to bands like Boston ( halfway down right above the credits ) and Queen ( halfway into first paragraph ) attacking the use of synthesizers in rock music that was becoming more prevalent in the mid to late 70’s

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Here’s one of my personal stand out tracks from Cords.  Be patient and be psyched when it starts kicking ( It’s not my youtube video ):

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There’s a ton of info on the Synergy site Here.  It’s days worth of digging and i’ve already listened through both sides of this vinyl twice writing this post.  I am also a fan of the JH series tape machines.  They are/were total workhorses.  Tougher sounding than the Otari MTR machines and less cold than the Studer 80 series machines.  A little more rock over all.  At 15 ips they could be pretty noisy but at 30 they performed pretty well on delicate recordings.

So awesome for 1978.

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Hello!

It’s tech time again, Today I’m performing an IEC power receptacle upgrade on a Korg  MS-10.  It’s a similar but easier process than the one I did for the Moog Rogue previously.  The MS series is often equated with the MS-10’s big brother the MS-20.  But the 10 has it’s perks as well.  First off, it shares a similar semi modular design which became popular in the mid 1970’s.  This allowed basic sounds to happen easily without patching but also allowed more complex routing to be patched as well.  This one has been moded slightly as you can see by the green wires that go from the mod wheel to the patch bay.  It came like this and I never felt the need to change it.  The wires connect the mod button to the patch bay in more places than it would have stock.  Secondly, the Korg MS-10 sounds HUGE.  The low frequency extension on this single oscillator synth is Awesome.  I think it’s far ‘warmer’ and ‘deeper’ than the Korg MS-20.  I always assumed this was due to the fact that it only has a LPF and not a HPF/LPF.

There’s actually a pretty extensive article about the old Korg filters here.  It even covers the newer Korg Monotron filters as well.  The MS series started in the 70’s with a proprietary chip usually referred to as the Korg35.  Later they went with a more off the shelf design that people think sounds different but not worse or better.

On to the details:

1, We aren’t adding a transformer as the step down is already inside the unit.  So the IEC will better protect you and the instrument by adding a better ground and a more physically robust power input as the hard wired power cables on instruments like this inevitably get dodgy at one end or the other.

2, We will be making a hole in the shell of the Korg.  This is always scary but it gets easier with time, and having The Nibbler helps too!

3, This Korg also has a dodgy low F# key that i want to replace.  I bought one from Synthparts. Thanks Doug!

As always: Be Careful!  120 volts is enough to hurt you!

On to the pics:

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I am glad that worked out!  I will be doing this with a few more instruments in the coming months…

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