Tuesday, July 17, 2018

Controls and Connectors

Some notes on the controls and connectors

Rotary Potentiometers

With the exception of the pitch/detune I've decided to use all new rotary potentiometers. For the relatively small price, the peace of mind is worth it.
I need T18 6mm shafts for the knobs to fit onto and there are 11 in total. 1x 50KB for the vibrator delay; 4x  10KB for vibrato depth, sustains and Orchestra speed; and x6 100KA for the rest.

I've decided to go with the vertical mount 9mm Alpha pots from Thonk.



9mm - Approx 9mm body
Vertical - PCB mounted vertically.
T18 - 6mm 18 tooth, split, splined shaft.
RD901F -  Model number

Pins - 1mm hole, 2.5mm spacing.
Hole - 7.1mm

After getting these in my hands I realised that the shafts are far too short to fit to a sub-panel and through the front-panel. I fitted one to my old temporary front-panel.

It actually fits really well. The skirt on the Yamaha knobs covers the nut and washer and is just far enough away from the panel to work. This means I don't need a sub-panel for these rotary controls at all.
However, if I want to use any other knobs, such at this one, which does not have any skirt to hide the washer
 ...then I will need a different pot with a longer shaft.

And the pitch-detune dual-concentric control still need a sub-panel,as I plan to reuse the original part.

Slide Potentiometers

The slide potentiometer is from Bourns.

Bourns 60mm slide potentiometer



45 - stroke length mm (45 = body length 60mm)
4 - no dust cover - 5 = dust cover
3 - single gang
2  - Pins facing down (PCB)
0 - No detent
15  - Lever length
DP  - Lever style
A - Audio Taper
103- 10KOhm

Mounting is difficult. I would like to screw them in place, but the screw has to go into the face of the slider. This means that the height of the lever is critical.
Assuming the knob needs 10mm of the 15mm available and the front panel is 3mm, there is almost no space left for a sub-panel and screw. The sub-panel would have to be 1.5mm (thinnest available from Schaeffer) and the screw would be counter sunk. This sub-panel would then be bolted tight to the front-panel although, in theory, it could be bolted to another sub-panel behind and pushed into the back of the front-panel.

I have ordered some small 2M screws and think this might be the way to do it.

MIDI DIN Connectors

 I'm not a fan of most cheap DIN connectors which have two fixing holes, either side of the socket. I have a bunch of these in a drawer but I wanted something nicer.
Instead, I looked for a part that fits in from the front with a single nut fixing from behind, and found one at Farnell.
Oh, but it was pricey. Eventually I found that CPC, who are part of Farnell had then from half the price. Go figure.

1/4" Jack Sockets

These are Neutrik, so ought to be pretty good.

These were also cheaper at CPC, but I'd already ordered from Farnell.

Cliffcon Miniature ZC Series

I've covered these before in the power supply posts 


I've covered these before in the power supply posts

Rear Panel Ordered

Much to report, but I'm way behind on my posts. The rear panel design is done and, in a couple of weeks I will have it back from Schaeffer. I decided on a black anodized 3mm panel with white printing for the legends. Let's see how it turns out.

The Schaeffer panel is actually a sub-panel that I will bolt onto the panel that came with the case. The original panel is formed perfectly to fit the back of the enclosure and has a lip to hold in the top cover. I will cut a hole in it for the components to fit through and drill holes for machine screws.

The main driver for doing it this way was that I wouldn't have to drill perfect holes for all the components and then worry about how to label them. Also, it will be a lot smarter to have the labels printed and I can add a bit of logo. This will also let me see how good he UV print is with plain white on the anodized black aluminium. If it's really good I could go back to the idea of using that for the front-panel. 

First I laid it out in Front Panel Designer, paying careful attention to the data sheets for all of the connectors. I entered legends for each connector as a placeholder and they were marked as do not produce.

I then created a print layer in Inkscape.
Print layer from Inkscape - orange is the background, not the base colour
Next, this was imported into FPD.

Front Panel Designer view with the print layer added
The design was checked against the layout for the back panel. Most significantly, the stack of G boards is too close to the back panel to allow room for any connectors behind it.

 Hence I have to work around that. 

Full Rear-panel layout with the FDP render imported and nuts etc added - the area reserved for G boards marked in green

Everything fits, so here's a 3D render from FPD.

3D render from FPD
And now the order has been placed.
I will wait for it to arrive before cutting the main panel and wiring things up.

The G boards are already screwed into the baseboard but I will wait till the rear panel is done before fixing the others.

Sunday, July 15, 2018

Power Move

 The unglamourous part of the project is the power supply.

For the past four years the power supply unit (PSU) has been housed in a plastic case, which used to carry car jump leads.

In fact, it's hosted the PSU and the rear-panel connectors through the development and testing phase of the project. But now that time is over and I need to move the PSU to a new home and rewire the rear-panel connections.

Power Struggle

There is no room left in the rack enclosure for the PSU so the plan has always been for a separate case for the PSU.

PSU Requirements

Ventilation  - It gets warm.
Main PCB - 110mm x 110mm
Transformer - 74x66x73mm (WxDxH)
Minimum internal dimensions - 120x200x80mm

Power switch accessible on front panel.

Power On Through

One problem with having a PSU that is tucked away out of reach is that turning the power on and off could be annoying. I thought of several solutions to this, but the one I like best is to have the power switch on the front panel of the SS30-M and loop the live wire through from the PSU for switching.

To do this I need a live wire out from the PSU into the SS-30M then onto a switch before returning back to the PSU. Most important here is that the connector out of the PSU is safe. No live pins. Also, I don't want there to be any doubt that this is not a normal mains inlet. It will short out a normal supply so using a domestic main connector is a no-no. After looking around a bit I decided to use Neutrik PowerCon connectors. You get different designs for input and output and they are safe. I found knock-off cheaper copies from China too.
PowerCon connectors from eBay

I got these and made up the cable.

This is the drawing of the panel connector

 Mains Event

The next step was supposed to be a choice of PSU enclosure. Instead, after a bit of research, I decided to make another temporary case. I was heading towards making or designing and having made, a bespoke enclosure and that would have taken too long. Too long in the sense that it would have delayed the making of the SS30-M. I was also keen to re-house the PSU in the final configuration so I could see if there were any issues and prepare the way for a better case later on.
I looked around my garage and found a three-bottle, wooden wine case which was an ideal temporary solution.

Rjoca, if you must know
The nice thing about this box, as well as being wooden and thus easy to work and the right size, is that it has a hinged lid, with a catch. This makes it easy to open and close, but one disadvantage is that the wood is fairly thick, which makes it hard to mount some of the components and connectors. 
 I decided to reuse the original back panel again but this time with only the power connectors. That meant a bit more vandalism of the original SS-30.

Original SS-30 rear-panel marked up for cutting and components unscrewed

Main panel side of temporary PSU no.2 under construction

Finished mans panel with original switch and lamp.
On the other side of the box, I had to create a panel to mount the Cliffcon Miniature ZC connector. Again I looked around the garage and found a nice strip or thin, polished metal (originally something to do with a kitchen unit I think) which was cut down and drilled.

Power Output side of the temp PSU no.2

Power Output with cable connected
Once the connector mounting was done it was onwards to wiring it up. The power regulator PCB has a connector header and obviously i wanted to reuse that, which meant the wires from the actual synth had to be cut at last.

And I had to decide which wires go to which pins.

And I decided to do a good job, with heat-shrink and everything.

When all is ready, I throw this switch

Whilst I'm still working on the rest of the main enclosure I don't want the front-panel mains power switch in there. Hence I've made a temporary switch box and that's the PSU temporary PSU no.2 all done!

Burly Chassis

 The  following is just some notes on a PSU case.

e.g. http://uk.farnell.com/multicomp/mb4/box-abs-black/dp/301279 
but that has no ventilation,

Or in metal
also no vent


1. Standard electronics project case - e.g. Hammond http://www.hammondmfg.com/pdf/1454P.pdf
2. Aluminium amplifier case  - e.g https://diyaudiostore.com/collections/chassis but other options on eBay from China
3. 19" rack case - 3U - Too much
4. laser cut enclosure in wood/perspex

The laser cut option wins because:
  • Exact sizing is a given
  • Can cut in ventilation slots
  • Cheap
  • Can cut in exact holes for connectors etc.
  • Can etch in legends and logo

Here's an online tool to deisgn a case ready for laser cutting.

"MakerCase lets users create cases with flat edges or interlocking edges using finger joints or t-slots for retaining nuts and bolts. "

This is the kind of plan you get.

This site shows how the nuts are held into the t-slot and then it all fits together. http://store.curiousinventor.com/blog/how-to-make-cheap-lasercut-custom-boxes-for-your-diy-electronics/

It seems a bit shonky though. You have nuts protruding as well.
This is another one done with wood and perspex http://www.instructables.com/id/AutoCAD-to-Trotec-Laser-I-Made-It-at-TechShop/

I'm really not sure about having metal nuts all over the sides of the case when there's no way to earth them. There's mains inside and I'd like it to stay there.

For Inkscape this guy has a plug-in


Finger joints will create a basic shape, but I would still need some way of holding it together without, again, ending up with lots of exposed metal on the outside.
Gluing three pieces into a U shape and the other three into another U reduces the need for lots of bolts. All the connectors and switches etc would have to go on either side of one U so the other could be removed without un-wiring anything. Holes can be cut to allow bolts to through to right-angle brackets which are then fitted into nuts.

Friday, July 06, 2018

Connections & Controls

I decided to write down a simple list of all the front-panel, rear-panel and power supply unit controls and connections.

This post will be draft until the SS-30M is complete. I might still chnage my mind about a few things!

All items function as on the original SS-30, unless marked as follows:
* New feature - not found on SS-30
** Modified feature - enhancement to SS-30 functionality (e.g. switch is now variable)
*** Supplemental feature - Not required on SS-30 (e.g. external PSU connections)


  1. Pitch
  2. Detune
  3. Pitch CV Input*
  4. Vibrato Delay
  5. Vibrato Depth
  6. Cello 1 Level**
  7. Cello 2 Level**
  8. Cello Attack
  9. Cello Sustain
  10. Cello Brilliance
  11. Keyboard Split
  12. Viola Level**
  13. Violin 1 Level**
  14. Violin 2 Level**
  15. Violin Attack
  16. Violin Sustain
  17. Violin Brilliance
  18. Orchestra Speed**
  19. Orchestra Feedback*
  20. Cello Orchestra Mix**
  21. Violin Orchestra Mix**
  22. Orchestra External Signal Input*
  23. Volume
  24. Power Switch


  1. Main Output
  2. Cello Output*
  3. Violin Output*
  4. Foot Control. Volume
  5. Foot Switch. Sustain
  6.  MIDI In*
  7. MIDI Thru*
  8. MIDI Expression Output*
  9. Mains Power Switch Loop***
  10. Power Input


  1. Mains Input
  2. Pilot Lamp
  3. Fuse Holder
  4. Main Voltage Selector
  5. Mains Power Switch Loop***

Monday, June 18, 2018

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...


Sunday, June 17, 2018

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.

Monday, June 04, 2018

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