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Monday, June 20, 2016

The Fonts Of SS30 And YAMAHA


This is getting way off topic but I get spare time in front of a computer and I like good design so here we are with a post about fonts.

Owners Manual Cover

Here on the front page there are four fonts.


 YAMAHA- Helvetica Black Condensed










Yamaha's simple logotype is famous the world over and Helvetica is the about a as famous as a font gets. Helvetica Black Condensed is the font variation they used here.

Strings - Faktor Condensed Extra Bold







STRINGS is rendered in Faktor Condensed Extra Bold a font popular with Yamaha at the time. Here it is again on the SK30 brochure.




SS30 - DDT Extended Heavy








SS-30 is printed here in DDT Extended Heavy although it seems to have been made heavier and extended even further than normal.

Owners Manual - AG Book Rounded


This is where it starts to get difficult. The previous two fonts have some unique features which make it easier to identify them. and the YAMAHA logotype is so famous you can simply look up the answer (although there are several wrong guesses out there). This one is unremarkable in every way. I was sure that it was Akzidenz-Grotesk Book Rounded , but extended.
AG Book Rounded seems closest though


But that was designed in 1980, which is too late.
There are more fonts that fit the bill almost but not exactly. 

Owners Manual Inside 

The section headings have a friendly rounded font


This has lot in common with Arial Rounded.
Except the bottom of the 't' and the top of the 'r' aren't curly enough and the 'O' isn't round it's oval. So, it's not that.

Dynamo 


Elsewhere Yamaha were very keen on this Dynamo font from 1930 which shares some features with Faktor.


Mystery 70s Yamaha font 

Another font from that era was used for the CP, CS, SK and GS ranges of synths. 




















Often this font was just used on the owners manual or brochures but sometime it was emblazoned on the synth itself. I can't find what it is though.




Monday, May 09, 2016

Voltage Controlled Pitch à la Tomita?

I had this post drafted for a while but with the recent passing of Isao Tomita I finished it off.

Whilst researching the SS30 I noticed that it had been used by Tomita.

Isao Tomita - SS30 not pictured
Specifically our favourite strings machine was credited on his Daphnis et Cloe album (also called Bolero in the US)
As you might expect from someone creating synthesizer arrangements of orchestral pieces the albums credits also list a number of other synths which can perform strings duties, and another dedicated stringer, the Roland RS-202. It's hard to pick out the SS30 in amongst all that, but what struck me was that some of the string sounds seem to have pitch bend and even portamento applied.





The SS30 can't do that, but can I modify it to?

First I looked at the pitch control. Would it be possible to simply add voltage control to the existing pitch/detune control? The answer is yes, but the range of control would be very limited. The pitch and detune controls on the SS30 provide minimal control. You can tune it within a very narrow range but to get the kind of variation that's worthwhile it would need to be much wider. That would mean a completely new master oscillator design.
Also, the way that the square waves, produced the divide-down design, are converted to spiky saw-tooth-like waves depends on the frequency of each tone. If you shift the tone up or down you would not only change the pitch but also the wave shape and associated harmonics. So, pitch control isn't a good fit for this strings ensemble, or indeed any other of a similar design.

Rest in peace Isao. 








 




Monday, April 18, 2016

Rare String Synthesizers: Eko, Godwin, Freeman.



Rare String Synthesizers: Eko Stradivarius, Godwin String Concert 249, and Cordova Freeman String Symphonizer. 

This video popped up on MATRIXSYNTH and I though I'd share it here as it shows some rare string synths.

I've been doing a bit of research on other string machines as part of
another post I'm labouring over currently. It's interesting to see the
subtle and marked differences in design and then hear those in the
machines themselves. 

Friday, April 01, 2016

The worlds cheapest VCA?

This post is just about why the key switches use a negative voltage.

It's not vitally important to the whole project, but I wanted to understand the whole keying circuit and satisfy myself as to why it works that particular way. As I said in an earlier post I was looking for a better understanding of the circuits to help with the key switching problem.

Why are we forced to think about switching a negative voltages anyway?
The answer lies in way the simple square-waves are transformed into saw-tooth waves and the switching is woven into that circuit. Understanding this leads to the reasons for all this below 0 volts brow-furrowing.

The worlds cheapest VCA?

“I have to find the edge of the envelope and put my stamp on it.”

(Terry Pratchett, Raising Steam)

 
Your actual schematic of the keying drive

Each note (referred to from here on in as tone) has it's own amplitude envelope and this is what makes the SS30 almost polyphonic.  Each key is a switch to start and end an envelope and the envelope is what drives the amplitude of the tones that you hear. When each key is pressed down it's envelope goes through an attack phase, where it increases in amplitude, then a sustain phase when it's held and finally a release phase where the amplitude decreases. The odd thing about the SS30 circuit is that this envelope goes from -7V up to 0V and back down to -7 V.

Trace of envelope from simulated keying drive circuit

Let's be positive!

If we had an envelope generator that went from ground to positive - which would be more normal - how would we put that together with an amplifier to control the amplitude of the tones? I would probably reach for an op-amp.  I'd use the envelope as the control voltage in a simple VCA (voltage controlled amplifier) circuit. This machine was being designed in the mid-seventies though. Maybe op-amps were more expensive then. In which case I'd go for a transistor based design. But what if my boss is already worried about the costs of this thing and transistors tend to demand biasing and all kinds of ancillary components to get a good result. Can I come up with something better cheaper?

Negativity wins the day

There are lots of solutions to the problem which don't use op-amps or transistors but the one actually used is pretty neat - albeit one that introduces those fiddly negative voltages.

The solution lies in AC coupling, DC level-shifting and half-wave rectification.

The square-wave output of the frequency divider chips is AC coupled through a capacitor, the DC level of the signal is then shifted by the envelope and passed through a diode. The following attempts to explain why that's a good idea. 

Conscious coupling

Any AC signal fed through a capacitor will be output on the other side DC-balanced to whatever reference you choose, no matter what the DC offset it went in with.  This is called AC coupling or capacitive coupling. If the output side of the capacitor is tied to ground, or nothing, the signal will swing equally both positively and negatively. The signal's current simply alternates back and forth and with no other reference than ground will centre on 0V. It's DC balanced with equal positive and negative current alternation.
If you introduce a reference voltage though it will be shifted to centre on whatever voltage it's tied relative to. If you tie the other side of the coupling capacitor to a negative voltage, like -7 V,  you will get a signal which is centred on that voltage. You are adding the AC component to the DC component.

Shift up!

This is exactly what happens in the tone switching on the SS30. The square-wave output from the divider chips is passed through a coupling capacitor. The output of that capacitor output is then tied to the envelope generator output thus adding them together.
When the key is down, the envelope is open, the coupling output is tied to 0V and the sum of the voltages centres the signal around 0V. In the trace below you can see the effect of this.

AC coupling - tied to ground


The lower trace is the source square-wave from the divider chip. It is 9Vpp (peak-to-peak) and -4.5 V offset from ground.
The upper trace is the output on the other side of the coupling capacitor, which is summed with the  0V from the envelope. As you can see it's oscillating around 0V.

You will also have noticed that the wave has lost it's square shape. This trace is from a simulation and I'm not going to get into the whys and wherefores of that shape here.

The next trace shows what you get if the output is tied to -7V


AC coupling tied to -7V

In this figure the lower trace is still the pre-coupling signal, all below the ground rail.
The upper trace is the signal summed with the -7V from the envelope.


The effect of the envelope on the signal is to shift it's DC component either completely below or partially above the 0V. That's all very nice, but the signal is never attenuated or 'off'. The amplitude doesn't change at all in fact. What's the purpose of that shift?


Give us a (half) wave!


If you send a DC-balanced square wave through a forward biased diode you still get a square wave on the other side. The difference is that you only get the positive half because current only flows in one direction through a diode. This is called a half-wave rectifier as only half of the wave makes it to the other side of the diode.

By now you may have worked out that when the key switch is off, and the envelope signal is -7V, the tone will not get through the diode at all. And furthermore, when the switch is on and the envelope rises to 0V, a half-wave signal will make it through the diode.

The traces below show this half-wave rectification of our shifted signal.

Square wave coupled and rectified


The lower traces are as shown before and the top trace shows the half-wave rectified signal.

(Again, this is based on the sloping topped wave of my simulation. The shape depends on the value of the capacitor and I'll deal with that another time.) 


Putting this all together, we have a kind a amplifier controlled by the envelope for the price of a capacitor and a diode. Ker-ching! If you don't care about the shape of your signal too much then this is a very cheap way of creating a VCA. The cheapest possible I might suggest. 

Arise Circuitry!

This is a grossly simplified and cut-down diagram of the circuits which are employed for each tone. There's more to follow that diode but this is the essence of the shift and rectifier which makes up the quasi-VCA.

Simplified tone switch example
Vss is -7 volts and the square wave is as described above.


You gotta accentuate the negative(?)

That's nearly it, but there's is one more, unexplained, thing. If the output of the divider chips is passed through the decoupling capacitor then why are they negative going to start with? As I noted above it doesn't matter what DC offset you start with; the coupling capacitor balances the signal to whatever reference you choose on the other side. So, why not start with a positive going square-wave?

Perhaps it's because you need fewer power rails. The amount of wiring in the SS30 is already extreme so limiting the power cables around the place is probably a good idea. The G boards use a single -26V supply with on board regulators to step it down.


Progress update

Eurorack DIY is still dominating my time but I'm learning some relevant and interesting things and it will all help with the SS30-M project.

I'm also enjoying some imperial phase Ultravox on BBC4's Top of The Pops repeats from 1981 at the moment. The SS30 has been on stage for Vienna and All Stood Still so far.







Friday, February 05, 2016

Pink Floyd's SS30 S/N 2167

Back again from another long hiatus.

There's no progress to report on the SS30-M today. I'm currently working on some Eurorack DIY but once that's done the rack mounted SS30- will be back to the top of my to-do list.

There was an interesting auction in the UK in December : ☆RARE Vintage YAMAHA SS30 Analogue String Synthesiser!☆ Ultravox, Visage!☆solina

 Rare to find in the UK! An original vintage euro/uk 1977 Yamaha SS30 Analogue String Synthesiser in great fully working condition! These were famous for being used heavily by Ultravox, Dave Formula from Magazine and Visage, and of course Simple Minds.

This instrument actually came from Pink Floyd's cache when they had a sell off of gear many years ago. I was told it was used on 'Animals'...whether that is true I cannot say..but there you go!

The SS30 is very unique sounding amongst string machines as it has two separate VCOs, one of which that can be detuned against the other one to create further chorus and phasing effects(together with the adjustable ensemble effect) This creates a lushness not found in comparable string synths..it also has a separate VCA on every note giving individual attack and release on each key. Most stringers have just one and are 'paraphonic' not multiphonic as in this case!

They are also very high quality an extremely well built in comparison to many other similar synths of the time.

 This sold for £950. You've got to love that cheeky 'solina' in the description! Also, note my coinage of 'multiphonic' in the description.

There were some lovely photos to go with the auction which I've saved for posterity.



Was the  SS30 used by the Floyd on Animals? It seems unlikely that it's on the recording. Animals was recorded mostly in 1976 and was released in January of 1977. So, unless they had access to an early model, it's just too soon for an SS30. Whereas the ARP Solina had been around since 1974. Moreover, everyone seems to think it was a Solina. This document lists all the keyboards used by Rick Wright with Pink Floyd.
The Solina String Ensemble model V was probably the first ARP synth to become a part of Wright’s rig, from 1974-75 onwards, and it was unofficially dubbed as ‘The Floyd's String Machine’.
There's never any mention of the SS30 being used by Pink Floyd at all (that I can find) till this auction. What is going on then? I guess that Yamaha were keen for their string machine to take a bite out of Solina's market and we know that they were giving SS30s away to bands, as Billy Curie of Ultravox states in an interview for G-Force Software. Although that was a bit later. I guess that Yamaha gave the band an SS30 hoping they would use it instead of their Solina, and maybe they did. I can't find any definite info on what Rick Wright was playing on the In The Flesh Tour later in 1977. Maybe they took it on the road. Maybe they used it when jamming but it never made it onto the recordings because they preferred the Solina. Or maybe it just wasn't documented. Pink Floyd are a very well documented and thoroughly researched band though, so it seems that whilst they may have owned an SS30 it was never part of their main set-up.

I found that auction through this link: http://www.thevintagemusician.com/vintage-find-of-the-week-yamaha-ss30/

Thursday, August 13, 2015

Service Manual and Parts List

I thought I should finally upload the service manual and parts list. I had wanted to put links into the pdf so you could jump from schematic reference to PCB layout and so on. But life is too short. So here they are.

Wednesday, June 17, 2015

The mock-up front-panel/sub-panel

 Panel pondering

Just before the end of last year I'd started to make a mock-up front-panel and posted a picture. The idea is to have somewhere to put all the controls, wire them up properly and test things. That should clear the way for (at long last) the MIDI interface.

When I went back to it a few months ago I decided it was terrible. Cutting MDF has to be done carefully and mine was not done carefully. The drilled holes were fluffy, the board was too thick and I just wasn't happy.

At about the same time I had been thinking about having a wooden front-panel. This thought was itself prompted by returning to the idea of using the original switches and knobs.

In other words, if I use the original switches and knobs they would look best in a wooden panel. But, how would I do that? I thought about rosewood veneer, but then I started looking at laser cutting wood.

 
Once I started looking at this I realised there was a better way to create a mock-up front-panel.

Frikkin' lasers


A wooden front-panel


Here in the UK I found Razorlab. Their prices are reasonable so I took a design I'd already created in Front Panel Designer saved it as vector file (.svg) and then imported that to Inkscape. The design is placed in a special template provided by Razorlab which matches the size of the material. The way it works is that lines drawn in different colours either cut or line engrave or raster engrave with different strengths.

I quickly did this and sent off my design. A bit too quickly as I'd made a couple of minor mistakes, but nothing too critical. Razorlab state they will deliver in 28-days. Well, mine took over that, by a few days, but a few weekends ago I finally got the panel back.




 The first issue was that one of the holes was not completely cut.


Incomplete cut on the bottom-left


 In fact, that cut wasn't needed. The Cello Volume control should have gone there, but it's also part of the sub-panel on the row of knobs above. I had included a hole for it there and on the next picture you can see the reverse side and where that ended up.

Reverse side

As this is a mock-up it doesn't matter too much about one misplaced control, but it's a good reminder that these things should be checked carefully.

Sub or front panel?

. One thing that makes for a tidy finish is a sub panel. Basically the controls are fixed to the sub-panel and then the front-panel is fixed to sub-panel. The front-panel just has holes and no unsightly bolts and fixings.
In the original SS30 the metal sub-panels are screwed into the wood. The switches have spacers between the switch assembly and the wood to ensure that they sit just proud of the panel surfaces. The knobs' sub-panels are simply screwed into the wood and the thickness of the wood is such that when the knobs are fitted onto the pots they sit just above the surface and don't sick out too far.

In the shot above you can see that I've bolted the pots directly onto the panel. The sub-panel is still there behind but it's just held on buy the bots at the front. You can see on the pots that have knobs on they stand too far out.

But for the switches I had to screw them to something and so I decided I might as well make them sit back and be positioned more or less correctly.








Now that's done its time to wire everything up.