adventures in DIY music

Wednesday, 24 May 2017

Roland SH-09 slide pot rehab

When my usual method of cotton-bud-with-De-Oxit didn't fix these crackly slide pots, it was time to open them up and take a closer look.


Note the Resonance pot is inverted with respect to all the others.


Unbending the 6 lugs.







The wiper tines are extremely delicate. I chose to very gently splay them a little so they would be in contact with a fresh area of track, being careful not to deform their angle from the carriage. The contact surfaces were also very gently sanded.



A gentle rub over the conductive track with some 600 gauge superfine sandpaper has taken off the darker layer of oxide. Don't sand the resistive track! The oblique lines across the resistive track are normal, presumably a result of the manufacturing process.


In my case, although the resistive tracks had been cleaned quite well with the De-Oxit/cotton bud, the oxide on the wiper and the conductive track meant the crackles persisted. They are now working like new.... but for how long?

Saturday, 13 May 2017

Akai AX-60/S612 synth/sampler combo




I wasn't initially very excited when an Akai S612 sampler was bundled in with a second-hand deal I was doing. A whole one second of sampling time at 32kHz - woo hoo!! And then I read in the manual about the multi-voice output and it's use with the Akai synths of the day, and got curious.
When I finally found an AX-60 (they were rare even back then in the early 1990's) to partner up with it, I discovered the way these two units work together over midi and the proprietary voice interface was quirky and unique.

As a midi synth of it’s time (1986) the AX-60 had a pretty limited spec - no sys-ex, no velocity or aftertouch, response to CC#s 1 , 7 , and 64 only, and pitch bend. Yes, it had an arpeggiator, but this didn’t clock to midi, it required an old-fashioned voltage trigger for external sync. However, there was a big plus. It was bi-timbral, with a programmable split point, and separate (adjacent) midi channels for each timbre. You could allocate voices either side of the split in several defined ways. You could save the whole set-up - split/voice allocation/patch numbers/midi channels/unison and chorus settings - to one of eight “SPLIT PRESETS” for instant recall.


But it was when you hooked up midi, and the 13 pin DIN cable, to the Akai sampler that things got really interesting.
The multi-way connector allows the 6 voices of the sampler to enter the 6 voice channels of the synth individually. Hitting the “SAMPLER” button on the synth then does two things: it sends a midi mode change message CC# 126 to the sampler, putting it in midi mono mode, and it likewise puts the synth into (a kind of) mono mode. Now, note values generated by the synth CPU will be allocated to one of the six voice channels, and that note will be transmitted on a midi channel 1 to 6, that corresponds to the voice number. Thus, when a synth note is generated on midi ch. 1, Voice 1 on the sampler is triggered and sent to the synth’s voice channel 1 to be affected by the VCF, VCA and chorus circuits. This works for the arpeggiator as well - in fact, this is the only way to get the arpeggiator to transmit its notes from the midi out. (That last fact in itself gives you some interesting options when interfacing other synths with the AX.)


So what happens to this combo when you apply some of the other features?

In Unison mode, it works as expected, pressing a key generates 6 notes on 6 midi channels to the sampler to be processed by the synth. With chorus on, this can be quite a thick sound, but perhaps you wouldn't call it lush.
In Unison + Arpeggio mode, again as you would expect, each arpeggio note is transmitted in 6 note unison.
In Split mode (so says the manual), you can't use the sampler interface. Er... except you can! Although the S612 is not bi-timbral like the AX (it can only hold one sample in memory), the sampler voices each side of the split are treated according to the separate patch settings for the filter, EGs and chorus, so it's kinda bi-timbral in this scenario. The special split voice allocation settings where there are 6 voices one side and zero voices on the other (so the "zero" side of the split can control an external unit) will not work here, because bizarrely there is no midi transmission from that half of the keyboard until you switch the Sampler button off.
In Split+Unison+Arp modes combined, things can get a little hard to keep track of. In the 2/4  voice allocations, you can have Unison on one or both sides, and Arpeggio on just one, and the samples will follow along.

All in all, a powerful and fun combination. So, of course, you would like to control this duo and their interactions from your sequencer, wouldn't you? Well, there is another quirk of the AX-60 that will mess this up if you're not aware. When the Sampler mode is engaged, the AX transmits the mode change to mono mode, but in itself, it only becomes a transmitter in mono mode, not a receiver! It will receive external midi commands, but only on the channels designated while it was in Poly mode. Even more bizarrely, it transmits only notes in mono mode, not pitch bend or mod wheel. Those CCs get transmitted on the Poly channel (or both channels if in Split mode). Phew! 
But hang on, the S612 responds to both pitch bend and mod wheel in mono mode, doesn't it?... in fact, it seems to respond to those CCs on any channel between 1 and 6. 
So, reliable sequencer control of the combo is going to require some thought. I'll grapple with this topic in a future post.



Thursday, 11 May 2017

Funboys "In The Boot" EP


We serious gents, the professor, the doctor and the chocolatier, have our new EP (such a quaint initialism from the vinyl days) out on Club Sweat. And we didn't have to pay these people to say nice things about it here !!

Southworth Music Systems Jambox 4+

Having slowly acquired a bunch of studio equipment over the years, one of my motivations is to ensure that the old stuff maintains some usefulness in the current system. This probably isn't practical for a commercial studio, but for an amateur (in the old sense of the word as well) it contributes to the space having a unique work flow, and therefore hopefully having a unique sound.
So I was delighted recently to discover something incredibly useful that had been lying in storage for the last maybe 20 years or so. I pulled this thing out because I was looking for a way to expand the routing from my midi control area, and it turned out to be just the ticket. It had been left there by someone I had worked with, and I believe they thought it was past its use-by date, because no mac computer had been able to talk to it since the days of System 6 OS.
The Jambox 4+ was a 4 way midi interface  made in 1986 or so. It connected to the Mac via a RS 422 port. It featured 4 midi ins and outs, SMPTE in and out, audio click in and out, and a DIN-sync output that had extra connections that gave you clock speeds other than 24 ppqn. Just straight out of the box, without any configuration, it merged all 4 ins and sent them thru to all 4 outputs, hence its usefulness in a midi master control setup.
However, it turned out that, even though I possessed no computer that could talk to this thing (and no application program for such a computer if I had one), the operators manual gave a bunch of midi sys-ex codes that allowed you to configure the sync options and the ports' midi plumbing. You could do the usual midi filtering, channelising and re-routing. You could set a tempo source: internal, midi clock or audio click, and then generate all those modalities along with 5 volt clocks at the DIN connector at speeds of 24, 48, 96, 192 and 386 ppqn!!  There were also SMPTE and tempo map functions, with which I have no experience, but everything was clearly explained in the excellent manual (a copy of which I will link to, along with the sys-ex codes). The click and 5 volt clock outs could also be handy in a modular set-up.

I opened 'er up on the bench to take a peek inside: very nicely put together as you can see. There are jumpers near the DIN connector to change the clock speeds on a couple of pins. There are also jumpers near the RS422 port whose purpose I don't know. There is a NEC battery (?capacitor) that the manual says will run down after about a week of inactivity, requiring a reset.









My curiosity was piqued. Some clever people had made this. What was the story? 
There wasn't much info about Southworth Music Systems on the web, but recently there had become available online a review by Martin Russ from 1986 of a software sequencing package called Total Music, where he gives it a glowing appraisal, and says 

"To sum up, Total Music is an outstanding sequencer program offering instantly usable and extremely musician-friendly recording, editing and printing facilities, without recourse to superfluous graphics or unwieldy controls. I had no problems in getting it running or in using it - almost everything worked exactly as I expected, and when it didn't, the manual quickly pointed me in the right direction.

In use, it behaved as an idealised 99-track tape recorder, only better. And in the limited time I used it, I feel sure that I only scratched the surface of the creative potential of Total Music's sequencing and editing facilities. Bill Southworth is to be congratulated on such a magnificent achievement. If only all MIDI software were this good!"


Link to the review here:
http://www.muzines.co.uk/articles/totally-musical/1615

High praise indeed. What's more, I got the impression from that review, that the "piano roll" note graphics were quite a new thing at the time. These days, every DAW uses them somewhere. Was that also a Southworth innovation?
Via LinkedIn, I tracked down the founder, Bill Southworth, and he was gracious enough to allow me to quote a fascinating little story he told me:


(Quote) The “invention” of the piano role notation was the result of a brainstorm with Bobby Nathan and Unique Studios in New York.  We were in his studio on 43th street where I was showing off the prototype of Total Music on a 128K first generation Macintosh.  It did realtime standard music notation, which I was quite proud of.  It was written in the Forth language because that was the only native language on the Mac that didn’t require a cross compiler.  As a side benefit, although it was awfully obscure, it was very compact and fast.


So I went through the demo and Bobby and the lady in the room didn’t seem very impressed.  Bobby said after a few minutes, “We can’t use this.”  I was a bit surprised and hurt and asked why.  The lady in the room, Stevie Nicks, said, “Not too many people here read music.”  Bobby added, “and you need more precision like a piano roll.” I said so like a piano roll but with velocity information.  That became the first piano roll notation.



Bobby later used Total Music as a key part to the world’s first midi recording studio, Midi City.



Another key contributor to my ideas was Jan Hammer, who had a lot to do with the evolution of the Jambox.  He was one of the first composers to use all midi synths for a TV soundtrack.  He did all the music for the original Miami Vice TV series at his farm in upstate New York. I remember he called me in a panic one weekend because the producers had to squeeze in an extra commercial and he needed to re-time the entire score.  I asked if a graphic curve that could change the tempo gradually would help.  I put the change in.  The very first use of that feature was on the next Miami Vice episode.



So TM and the Jambox had a lot of parents.  Great artists had great imaginations and big needs.  My fondest memories of those days is the people I got to work with from Herbie Hancock to John Tesh (Tour de France 1988) to Pope John Paul II (for the Vatican midi studio). (End Quote)

Thanks Bill, great story, I wanna hear more!


If you're lucky enough to find a Jambox, you may not be so lucky to find a manual. I couldn't find one online. So I have scanned the operators manual (which also covers the Jambox 2) and separately scanned the midi sys-ex documentation. Even if you don't find one, the manual is worth a look for its very lucid and concise explanations  of timecode, midi clock, and DIN and TTL sync. 

Jambox manual © Southworth Music Systems


The Jambox at the centre of the studio's midi control, with a Midipal on the right.

Tuesday, 9 May 2017

Roland MKS-50 repair

Problem: no lights, no sound.
Suspect the PSU of course!
Inspection: hairline cracks in the joints near where the three power transistors are soldered to the main board - very common problem in old synths due to repeated thermal stresses.
Fix: re-solder all the joints in that area.

Power regulation area top right
 
Heatsink






Saturday, 6 May 2017

Roland Jupiter Eight


In the early nineties, on the look out for second-hand bargains, I would often trawl the music equipment stores of the Gold Coast. Once, I absentmindedly wandered past a big synth sitting unloved in the back of "Musician's Pro Shop" at Mermaid Beach. It was on consignment, with a price on it of around AUD$700 or so, as I recall. It looked a sorry sight, covered in scratches and scars, with rusted screws. Apparently it had belonged to a hard-touring aussie band during the eighties. It looked "heavily gigged".
Yet, as I looked at its rainbow of buttons and bright orange labels, a dim memory was surfacing. "A Jupiter 8.. hmmm, why do I know that name? Wasn't that once a big deal?". I had murky visions of nameless gigs at the Playroom, where some band's keyboard player, with the ubiquitous spikey haircut, stood behind a big synth sporting an orange pilot light, and the word "Roland" in white letters across the back.
Finally I remembered. When I had been falling in love with synth music, this synth had been the queen. Especially in 1982, its sound was everywhere.

"It's got MIDI" the Pro Shop salesman said, kind of optimistically, and he held up one end of a cable that definitely was NOT a MIDI cable. I found out later it was a DCB cable. One end was attached somewhere inside the synth at the back. Unfortunately there was no converter box to accompany the other end.
Anyway, it sounded incredible... and all those controls! It made those string pads I had always lusted after. There weren't too many problems with the electronics as it turned out - in fact, it just needed re-calibrating, and one oscillator was "sour". Darryl Watson, the Brisbane Roland tech, sorted that out for me, and after that she sounded as good as new. Shame about how she looked...

These days, I fix the Jupe and most of my other vintage gear myself, having picked up some synth electronic know-how and wisdom from textbooks and generous people around the internet (many thanks to Kevin Lightner, Doug Terrebonne, Juergen Haible, Steve Jones, and the Synth DIY mailing list folks).

I've noticed a couple of problems keep cropping up from time to time with the JP8. One is the "sour" VCO trouble, where the VCO just won't be tuned, although it is not out by a great margin, but enough to annoy. The other thing I've seen a few times is a problem with the selection of the waveform. A particular waveform will be absent or quiet, or just not sound the way it should.
The first problem is not on the VCOs PCB as you might first think, but further afield, over on the "Interface" board, that contains the DAC and the sample and hold circuits that control each VCOs pitch CV. A dual op-amp (TL082) buffers the hold capacitors for two adjacent channels, and somehow when this chip gets faulty the pitch CV going to one or both VCOs gets unstable. Often, only half the chip is faulty, so only one channel is affected. 


You can tell which op-amps I've replaced, cos they're in sockets. 

The same problem, but on a different PCB (the "module controller" PCB - there are two, controlling four voices each) will cause a fault with the control voltages for modulation and the envelope values. You should suspect this if 4 out of 8 voices have an unusual response to some parameters e.g. sustain level, decay time, etc.

The second problem I've found to lie with the waveform selector chip on the voice PCBs, a 4052 analogue switch. These chips can develop faults, sometimes only on one channel, causing a quiet voice, or wrongly selected waveform.





When they came from the factory, all but the earliest JP-8 s used a protocol called DCB to talk to the outside digital world. This was just before MIDI arrived in 1983. After that, Roland made a box that could convert midi to DCB messages (notes and patch change only). There were also several possible retrofits (i.e. an aftermarket modification to the synth itself) that gave the JP-8 midi capability. Either way, this connection gave you access to another feature that is not often mentioned: the Jupe can act as a midi/DCB-to-CV and gate converter, thanks to its CV and gate outputs round the back. This single channel of CV/gate comes from the highest note that is generated by the CPU, whether in response to the keyboard or via midi/DCB. The CV is 1 volt per octave, and the gate is a nominal 15 volts. So you could use this to drive your modular, or any one of a number of analogue monosynths. 




Friday, 8 August 2014

Roland MC-50 midi sequencer

I cut my teeth on this hardware sequencer 22 years ago. There was a long break from it in the noughties when I switched to sequencing on a Mac, using Cubase, then Ableton Live. But my development of a technique to synthesize FSK sync signals in Ableton Live and send this as audio to the MC-50's sync-in jacks, has enabled me to slave this hardware to my software with rock-solid timing, giving me the best of both.

 (For details see this article on my website). 

Why use this old technology today? I've found many reasons, but I suppose they can be generalised as either "speed" or "fun", often both.
Keystroke commands can be so much quicker than using a mouse. They are generated at a lower level of brain architecture, and so have a less disruptive effect on conscious attention, allowing it to focus on the creative effect of the task. Using a mouse engages more parts of the brain, and at a higher level of architecture (e.g. optic cortex needs to track the pointer, and relay this information to the motor cortex controlling the mouse-hand). The result of using keystrokes is a feeling of freedom and flow when creating and editing midi parts. Of course, this assumes you have put the time in to acquire the skills in the first place. The time spent is always repaid well.

Some key commands on the MC-50 make workflow extremely fast:
• [PAUSE] + [RECORD] allows you to start recording (or erasing) from the very tick (one tick is a 96th of a quarter note) that you are stopped at.
• UTILITY 8 (tune) sends an A4 note on all channels when you need to check audio connections or tune your analogue synths.
• [STOP] + [MIDI] sends an All Notes Off message on all channels.
• [PAUSE] + [MIDI] updates all pitchbend and CCs up to that point in the song.
• Hit [LOC] and a number to jump to a Locate point, hit [LOC] + [REC] then a number to set a Locate point right where you are.

For rapid rhythm pattern recording, the MC-50 uses the classic old Roland step-write-while-running style of an 808 or a 909, with eight levels of accent. Its quick and intuitive even just using the 2 line display and the key pad, but it's even better if you are using a midi controller keyboard with a sustain pedal, as this allows instant erase of any particular voice by holding the key down with the pedal depressed, while the pattern loops. I've never seen a faster way of writing/editing rhythms - shame they are only one bar long! But once you write them into the  Rhythm Track, you can quickly copy them into a "Phrase" track (a Phrase track is everything else that is not a Rhythm track) to allow sophisticated editing/quantizing that simple pattern writing doesn't allow, so you start simple, then get busy.



There are creative reasons as well. The MC-50, like some other Roland products such as the MC-202 and the TB-303, allow an interesting type of composing whereby you can at first enter, in step time, the notes or chords you want to use, without worrying about their timing position. Then, once they are entered, you can then write, in real time, the velocity/step/gate time of those previously-written notes or chords independently of the actual note values. (Roland call this MODIFY RECORDING). This can get interesting, say, if you send it the midi notes of a groove or a drum machine pattern that you want your sequence to conform to.
Another instant-gratification creative feature are the mute buttons. There are mute buttons for the Rhythm, Tempo, and the eight Phrase tracks. These allow on-the-fly arranging while you are synced to your DAW... Ableton can only beat this for fun if using a fancy, expensive control surface.

Speaking of syncing, there is a widely reported bug in this series of Roland hardware sequencer such as the MC500/MC500mkII/MC50 etc, whereby the unit, when externally synchronized in "loop" or "cycle" mode (the term Roland uses is "Block Repeat"), gets out of time with the sync signal it is being sent. Analyzing this, I have discovered it is because it "loses" a single tick when the loop rolls around again from the end point to the start, causing the timing lag to increase with every cycle. Therefore the bugfix is to specify the loop points, not by bar number, but by LOC (locate) points. This allows you to set the points down to single tick resolution. Place the first LOC point at the 00 point of the first bar, and the end LOC point one tick less than the end of the last bar i.e. at beat 4, tick 95, of the last bar. And so by holding [SHIFT] while hitting [PLAY], loop play will start when the external clock arrives, and continue to play the loop indefinitely, accurately locked to the DAW.

I've written a one page shortcuts guide that I keep near my machine. You can download it here.