Make Like A Banana - And Keyboard Split

Let's Split

 There are two voice groups on the SS-30 - Cellos and Violins. There are 49 keys with corresponding keying circuits which provide attack and sustain envelopes. However, it's possible for more than 49 notes to be generated in the SS-30. There are a maximum of 25 notes of the Cello voice and a maximum of 49 notes of Violin. Those of you who have studied mathematics at the very highest levels may have started to see that there is a problem with this arrangement. It has crossed my mind that building another two K boards would solve this problem, but the eminent designers of Yamaha Nippon Gakki are not totally wasting notes. So, what is going on?

The keyboard split rotary switch selector on the SS-30 is numbered. Each split point being given an integer corresponding to the markers just above the keyboard. But what do they represent? Well, as the User Manual,explains:

"Switching this section changes the position of tones of Cello and Violin systems.
There are marks on the panel above the keyboard, so that each point of 1, 2, and 3 may be noticeable during playing"

Actually it's got a huge typo in and repeats some of that which makes it hard to read. It 's also says the marks are on "the keyboard (the panel)".  But that's what they meant to say.


Things become clearer with the following description.

 Right. And so...

"The KBD.SPLIT enables you to produce
chords of the Cello and melodies of Violin by your left and right hands respectively."

 Exactly! It does seem a shame that I couldn't just get all 75 notes at one and the same time, but it's not that they actually all exist at once. Why not?

Gating Away With It

This diagram shows how each K and G board is used for each split.

Except it isn't even as simple as that. The G boards have 4 outputs each which are mixed or rearranged depending on the voice selected.


The key to all this is the split gate.

This is the schematic, but it's not terribly helpful.

What's happening is the outputs of the G boards are being switched on or off. Which sounds simple, but there is a lot going on here. There are 6 inputs but 9 outputs. Two of the inputs are from G1 and the others from G2, where most of the switching action occurs.

This, from the  Block Diagram, is a bit easier to follow.

But combining them both with additional information about the way the voices are put together yields this:

As you can see, you never have all the the outputs from both G boards on at the same time.

It's still a bit hard to follow though, so here it is with the voices grouped together.

Now it's clear!

Cello and Viola use the exact same G1 and G2 outputs as each other, but not at the same time.  The split gate sends those outputs to different filters to convert the raw output to become either Cello or Viola. There's nothing fancy about these filters! But that's for another post.
The Violin is ON at the same time as the Viola, obviously, and it uses the other outputs from G1 and G2.
This whole thing could be simplfied if the split was reduced to either Cello on or Cello off, of course. However, it's a versatile solution and I've no desire to change it.

Splitting My Sides

As I thought more about the split control and where to place it on a the SS-30M panel, I came up with this rearranged front-panel for the SS-30. It places the split in-between the two sets of voices.

The main problem with this design is that the Keyboard Split is going the wrong way! All the way to the left means no Cello and all to the right is all the Cello on. Can that be improved?

The switches positions can be marked up in any way you like, as long as they are in the same rotational order. This version inverts the control so it balances the other way.

This fails in two ways though, because having the knob upside down is unnatural - our hands not naturally designed for this kind of 'twiddling'. The leverage is also naturally top-side. Mostly though, it makes less sense in aligning with the keyboard.

This is the current alignment

 And this is inverted

OK. But that is a nonsense because I simply rotated the drawing! What needs to happen is that the switch is rotated but the markers are kept at the top and reordered. Except that comes to exactly the. same thing as before but the switches action is upside down! Oh.

I have another solution for this though. There is a long tailed knob from the B-75 donor that is like a one-sided chicken-head knob, but with a very long tail. These were designed so that you could easily move them without changing your hand from a fingering position to a grip. Using this control serves two purposes. It makes the rather stiff switch easier to rotate, due to the extra leverage. It also means that the pointer can still be aligned to the split points on the keyboard but the arm points to the balance of Cello and Violin.

Kind of like this:

With rack panel layout, it can be more obvious what voice is being pointed at by the long tail.

Except now that there keyboard markers have gone I need to swap the numbers for the actual notes, like so:

Split - The Difference

Much better! But, there is a centrality to this element now, so that anything on the same vertical axis, or group, is inclined to be grouped in common with it. The point of moving it in between Cello and Violin is to control the balance between them. Otherwise the pointers of the longer control become confused. Its location is either between, with the longer pointer, or it's location is almost arbitrary and the knob can be smaller.

That's great, but there could be a problem of space. The control takes up far more room now and the layout demands more separation.

Ideally there would be a control that is common that could also be in the centre. Pitch and vibrato are but that is a lot of controls to fit in. This will take some thought...

 

Pitch CV Input Test

I've got a lot of irons in the fire at the moment and I can hardly keep up with the blog! Today though I got busy with Lightworks and finished another demonstration video.

Anyway, a week or so ago I hooked up a pitch CV input. The pitch control knob is a simple voltage divider between +15 and -15 volts. Therefore it's approximately 0V when it's centred and tuned.

The vibrato input is a smaller voltage though.

This LFO signal and the tune, detune controls are mixed together to provide a pair of control voltages for the two master oscillators. The vibrato is a balanced alternating current so the pitch swings up and down around the centre level set by the main pitch tuning.
The Vibrato depth control is another voltage divider which sets how much of the Vibrato LFO is added to this mix.
For the external control voltage input I simply inserted a signal in place of the Vibrato LFO.
For this test I needed an LFO and the most convenient tool at my disposal was a Roland Bitrazer. The Roland Aira EFX modules can be customised with an application and various virtual modules are available. All I needed was this LFO.

I used my scope to tweak the levels to match those of the Vibrato LFO and tried it out.

I've added captions so you know what waveforms the LFO is outputting at each point. The adjustments on the Bitrazer itself are to set the depth level of the signal. The other tweaks on the iPad are changing the LFO rate. 

In conclusion, this makes far more versatile vibrato effects possible. It could even be used for pitch bend effects. It's limited by the range of plus or minus one semitone, but that's OK. It's a worthwhile addition.

Screen Printing

Joy unconfined! I have found a screen printer in the UK who can give me the front-panel of my dreams.

Screen Dreams

Last week I was on holiday and, with time to think, I once again returned to my desire to have a really great looking front-panel. It was the one thing my mind kept returning to as being unsatisfied by my current plans. Well, that and the fader knobs, but mostly the quality of the printing. As an inveterate Googler I started to scratch away at the itch.

I started by looking around at how screen-printing is done. The process is well documented, but to do it to a high degree of precision is not what you tend to find Instructables for. People do this for DIY synthesizers, but it's not for the faint of heart. Clearly, for a one-off job, I don't want to invest the time or resources in doing this. Let alone doing it perfectly. Once only being a tall order for any kind of skill. Yes, I might do more projects but this isn't a skill I savour the opportunity to learn. The opinion also seems to be that, whilst this is a process which you want to have done for you, it is difficult to find someone and is likely expensive.
However, as I said, I have found someone And quite easily, and for a cost which is reasonable. When I saw the comments about cost I wanted to know how much. Would it really be too much? I Googled 'screen printing one-off metal UK'. and the first result was http://www.21stcenturyscreenprinters.co.uk/.

Clicking on their Metalwork link brought up some (rather grainy) photos of synthesizer panels! There was a link to see more photos and I quickly clicked through to a wonderful sight (and site). Customsynth. https://www.flickr.com/photos/customsynth/

Another Satisfying Custom Synth

The Flickr photostream is rather lovely - lingering over tons of desirable gear is a difficult habit to give up, but lacks a bit of context. Another search led me to this Music Radar interview with the man responsible - Jeff Toman. And also this I Heart Synths interview too. If you need a major renovation or custom look for a world tour, Jeff is your man!

One of the most interesting examples, for me, is this Yamaha CS-30L https://www.flickr.com/photos/customsynth/albums/72157626458930565/with/5742061577/




This is a synth that is normally in black, of course, but it has the same knobs I'm using and you can see the great care that has gone into getting the graphics just right. Just as I intend to!

Print Screen

Back to 21st Century Screen Printers

"21st Century Screen Printers have specially adapted printing machine specifically for printing directly onto metal plates and fascias. We can also print directly onto chassis sections of any height and angle."

Jeff mentions that they used to do the panels for the Joe Meek branded studio gear. So, it's professional grade stuff!

I have been in touch and, as I said, the price is well within budget, so my plan is to get the panel cut and coated by Schaeffer and then printed by 21st Century. I just need a design now...

Knobs, Sliders and Switches

Parting out

As you may remember I bought an organ. And now I have a  collection of parts.

For the front panel I now have a few more original Yamaha parts to use and although can't find exactly what I would like, I think I have what I need now.

The Knob-le Art

Last year I decided to buy some original Yamaha knobs. These probably came from a mixer but they are the same as used on the CS-5, 10, 15, 30.

These fit the same knurled shaft potentiometers as used on the SS-30.

They need a bit of clean-up - see below

As I have 12 of these, they will form the bulk of the rotary controls.



The B-75 organ has, sorry, had, a few knobs too, so I have options to use different knobs for different functions.

There are two of these small knobs

One is from a dual-concentric control which was used for Volume/Balance but could be used for Pitch/Detune.

And there are two larger knobs.

Letting Things Slide

The B-75 also has a bunch of slider controls. 

The slider caps are 14x18mm and 11mm high

They also sliders come with these natty covers.

The dimensions are

External 42x19mm
Internal 39.90x16.8mm - for cut-out

opening 28x2.4mm
Slider travel 25mm

inner dimension 36.6x13.3

The tabs are to hold it through a depth of 13.8mm

A possible slider to use with this is: Bourns - PTA2043-2010DPA103 35x9mm, 20mm travel. The original sliders travel is 25mm though. 

This is the main issue with these panel covers - they are quite a small range of travel and I canlt find anything that fits it exactly. The original potentiometers aren't suitabel either, so I might not use them in the end. 

Washing The Pots 

All these old control knobs were a bit grubby, so I gave them a wash.

The New Switcheroo

As noted back in the Attack Formation post I only need switches for the attack control because everything else can be controlled with variable resistors. When I got the organ I was particularly after these switches.

As you can see though, they seem to have had some sort of incident and needed a clean.

In fact the switches were broken. The springs had completed correded.

Luckily the caps come off easily and other switches on eth organ were in fine condition. The desoldering was particularly easy too.

Dimensions 40x14.5

So, I have my attack switches. I didn't wire these up yet but I buzzed the contacts with my multimeter, just in case.

And I also have a power switch

 

Now with MIDI!

Last September I may have mentioned that the SS-30M is now functional. That's to say, the MIDI interface is fully wired up and it works. Mission accomplished! Err, well, the MIDI part is.

Shortly after that milestone the nights closed in and all work ceased. But I did say there would be a video of it all working. Well, I'm pleased to say that this May Day bank holiday weekend the weather has been as sweet and warm as a the sound of an analogue synthesiser. With my usual trepidation I powered up the old monster and was glad to hear it was all working as before. Well, almost. The highest A sharp was pulsing on and off because a transistor had been pushed over and was shorting. And the Violin section only works if the Orchestra section is on, but that's just a bit of a bother with the switch.

Here then is a short bit of unrehearsed and barely thought through keyboard playing. The Yamaha PSS-580 is the MIDI keyboard.

Wow, eh?

Well, I will think of some more interesting things to play on it, but you get the idea. It works!

I also had time to measure the current on the +15V rail. It seems that I will be able to use the existing supply for the MIDI interface too! Hooray! I have another post in the draft folder all about how to have the power supply in a separate unit. Hang on to your hats!