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Make a Yamaha Synth for less than £25.00

Introduction Specifications
First take a look at the specifications listed alongside. Look familiar? Well, to Waveblaster fans probably, as this is the spec. of the Yamaha DB50XG daughterboard, a phenomenally successful product in a long line of excellent audio/MIDI offerings by Yamaha.

For a while now, I’ve come across articles on using a second-hand DB50XG (or clone) as a stand-alone synthesizer, and last week, I took the plunge and ordered a board from Hong Kong via ebay. The supplier sent me an email saying delivery would take up to 20 days, actually it took 2 days. I drew up a schematic in Eagle, and made the whole unit, including a printed circuit board and separate power-supply yesterday. The result is now soak-testing on my bench.

What’s my first impressions? I’m blown away with the sheer quality of the sounds Yamaha have produced, and I’m only sorry I didn’t jump in earlier. In fact I’m thinking of building another, so as to run both in parallel for a really rich sound.
For once, this project contains no PIC and no software, and uses purely conventional components. (no SMD)

Links to the zipped Eagle project, and details of suppliers can be found at the foot of this post.

Tone Generation Method

AWM2 (Advanced Wave Memory 2)

Maximum Simultaneous Polyphony

32-note (last-note priority)

Multitimbral Capacity

16-Part (DVA : Dynamic Voice Allocation)

Internal Voice

Normal Voices

Total …………………………. 676

XG mode ………………….. 480

TG300B mode …………… 579

Drum Voices (Sets)

Total …………………………… 21

XG mode ……………………. 11

TG300B mode …………….. 10

Effects

Reverb (11 Types), Chorus (11 Types),

Variation (42 Types)

Power Consumption

2 W

Shown below is the near-completed synth. This clearly shows the Yamaha daughterboard, with it’s 26 pin header top right, plugged into the breakout-board I made. On the BOB, are mounted everything else except the power-supply, which was kept deliberately separate.

I mounted a small fan, underneath the DB50XG, and provided an exit vent for warm air beside the audio output sockets, thus ensuring that heat is drawn away from the unit, and from the heatsinks on the three regulators.

My almost-completed synthesizer.

My almost-completed synthesizer.

In the following schematic, you will notice that most of it is concerned with powering the daughterboard. I’ve provided on-board, sufficient to support the simple addition of a 12v-0-12v AC supply, and that of 7v-0. The DB50XG requires +12v, -12v at low current (~40ma) and a 5volt supply of at least 300ma. (my board drew 280ma)

You may prefer to use an existing supply, (or supplies) and omit if necessary some of the PSU components. In the spirit of keeping costs low, I re-used 3 unused ‘Wall Wart’ power supplies, by removing the innards from the plastic cases and refitting these carefully in a new box. Most of these units are not regulated and the two supplies I used for the 12v sources were slightly in excess of 16 volts – on load. The other supply was nominally rated at 9 volts and this too, was kicking out nearly 16 volts. Even with a small heatsink, I felt that this was asking a bit much of the 7805, so I fitted a 13 ohm 5 watt resistor (2 X 27 ohm 2.5watt resistors in parallell) in series with the +ve terminal.
Note that if you use a DC input (as I did) you should ensure that the +ve terminal from the negative voltage supply goes to GND, and the -ve terminal of the positive supply goes to GND. The 5 volt supply can be connected any which way how to the bridge rectifier, letting the diodes route the current correctly.

I added 3 LEDs to show that each supply was operative, and a reset switch both on-board and on the front panel.

I used a high-quality opto-isolator as interface to the TTL-level input of the DB50XG, and coupled the left and right-hand audio outputs out to the phono sockets via a couple of 270 ohm resistors. These should protect the output stages of the on-board op-amps in the event of shorting them to GND.

The small 12volt fan plugs onto one of the 12volt supplies – ensuring the the fan is pushing air into the box.

During testing and with the lid off, I used the unit without any heatsinking, the 7805 regulator got quite hot, the others moderately warm. The chips on board the DB50XG get warm also (the board dissipates 3 watts), so I strongly urge heatsinking the regulators and providing the fan, if the unit is to be in a closed box.

The DB50XG BOB Schematic

The DB50XG BOB Schematic

Below, close-up of populated BOB. On version 1.01 I’ve left more room on RH side for panel mounted reset switch. The small outlet vent top-right now has a small piece of steel gauze glued in place.

Close-up of populated BOB

Close-up of populated BOB

Another view of the unit.

Another view of the unit.

The completed unit in use.

The completed unit in use.

DB50XG BOB Component and link side.

DB50XG BOB Component and link side.

DB50XG BOB Foil Side

DB50XG BOB Foil Side

The zipped Eagle project files are here: http://joebrown.org.uk/images/DB50XG/DB50XG BOB.zip

ESR, my local friendly component suppliers can supply everything apart from the DB50XG. They offer a reasonable and speedy mail-order service, with no minimum quantity, and will ship anywhere in the world. ESR are here: http://www.esr.co.uk/

I got my DB50XG board on ebay, from double-fish1981 for $19.99 (US dollars – about £12.50) post free.
The following information can be found (at time of writing) on ebay:

This card is NEC XR385 midi card, which is an exact clone of the Yamaha DB60XG. The DB60XG is similar to the DB50XG.

Yamaha DB50XG/DB60XG Sound Daughter Board SW1000XG

FREE SHIPPING

And for more offerings from the Far East, as well as nearer home, try looking here.

Just one example of beautiful China

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6 comments to Make a Yamaha Synth for less than £25.00

  • Hollay

    Hello,

    a great idea! Only one question: how to access settings for sounds, drumkits and effects? Can you reach all kind of settings from a Midi controller (such as a controller keyboard)?

    Thanks a lot!

  • admin

    Hi,

    yes is the short answer to your question. Everything is accessible via the MIDI port. I tested the set-up using a MIDI output from a PC via a MIDISport 4X4 and the free PC XG software controller, and all was well. Subsequently I included software in both my own MIDI keyboard controller and MIDI Merger to put the unit into XG mode and select the various patches and banks. The free PDF XG manual details all of the commands etc., necessary.
    Because my intention was to use the units (I now have two) live, without using a PC, I am slowly extending the Merger into a full-blown XG controller, but I must stress this is ongoing work and will take some time.

    Thanks for your question and interest.

    Regards from Joe.

  • Thank you for your excellent project description Joe!!
    I already had some of the daughter boards on order thinking of using them in a larger project.
    But reading your story i think i first will make your board to test things out.

    Best wishes,
    Bas

  • Mark Lindsell

    Hi,
    Great project. I’ve been trying to accomplish this for a while now off and on. I’m an electronics novice really but I’ve got a couple of project under my belt an aural exciter, noise gates and stuff.

    Would this be possible with just 2 power supplies a 9v-0-9v and a 12v-0-12v. I don’t feel too comfotable with tying the -9v side of the 5v supply to earth. Won’t this make things go bang….?

    From reading on the net my understanding is the 5v supply is the digital side and the + and – 12v the audio preamps?

    So can I supply the center tap of the 9-0-9 as the digital earth and the center tap of the 12-0-12 as the audio ground.

    The other two goes I’ve had at this; one i used the elector diagram with the pins numbered incorrectly and my latest attempt produced sound as long as I don’t ground the digital side but it’s really distorted.

    Regards,

    Mark

    Joe replies:

    Hi Mark,
    thanks for your interest.

    Since building the units (I now have 2), I noticed comments regarding the Elektor article. It isn’t the first time they’ve messed up with connector detail – sloppy and unforgiveable are the two words that spring to mind.

    I hope your initial problems don’t put you off from dabbling in Electronics – it’s a great way to stay sane.
    Now to your questions. Convention makes it difficult for relative beginners, because they find out that the broad generalisations assumed by the many, are in fact not the correct way of viewing the reality.

    The simple answer to your question:

    ‘From reading on the net my understanding is the 5v supply is the digital side and the + and – 12v the audio preamps? So can I supply the center tap of the 9-0-9 as the digital earth and the center tap of the 12-0-12 as the audio ground?’

    is yes.

    You don’t say whether you are building the project using my PCB and the following appertains to that only.

    It will help if you open your web page at the article on the synth at: http://www.joebrown.org.uk/wp/?p=3124

    Almost without exception now, I include a bridge rectifier in my circuits – not only can raw AC then be passed to the unit, but it provides bullet-proof protection against polarity inversion.
    I should have explained this part of the circuit a little better, so here goes.

    Pin 4 on the power connector is intended to be the 0 connection for a balanced supply of 12-0-12 AC, or +15 0 -15 DC for the audio circuitry, as you have mentioned.

    Connectors 1 and 2 are intended for 0-5 AC or 7-12v DC for the 5v logic. The upper bridge rectifier provides steering in the case of connecting a DC supply.

    Now this gives several possibilities for connection, which is deliberate, and here’s where I’m probably confusing people. I will enumerate the ways in which you can supply the 5v logic as follows:

    1. DC of between 7-12v across connector pins 1 & 2.
    2. AC of between 7-9v across connector pins 1 & 2.
    3. DC of between 7-12v across connector pins 1 and 4. (+ve connection goes to pin 1)

    The method of connection MUST take into account as to whether the 2 supplies have an independant 0 (GND) return.

    In the case of your 9-0-9 supply, from your words I’m assuming that this is DC. You could think about the supply differently, and as follows:

    +9 as +18 volts
    0 as +9 volts
    -9 as 0 volts

    Therefore you could connect either limb (0-9) of the 9-0-9 to connectors 1 & 2, or indeed the -9v to pin 4 and the 0v to either pin 1 or 2 on the connector, the latter only if the 0v of your 9v supply is separate from the 0v on your 12v supply.

    If the 0 volts of both your supplies is commoned, then always connect 0v of each supply to pin 4. and for the logic supply, connect the +9v to pin 1.

    Looking back over this I may have confused you further, if so I’m sorry. The reason for the ‘open-ended’ connection system is it is very general and will handle most methods and types of supply.

    The answer to your question: ‘So can I supply the center tap of the 9-0-9 as the digital earth and the center tap of the 12-0-12 as the audio ground.’ is of course yes, and take the +9v to pin 1 on the connector.

    Yamaha deliberately separated the 2 GND returns to stop digital noise entering the audio stream, and this is good practise.

    However at some point these have to be tied to the same potential i.e. 0v or GND. On the PCB I made this point the -ve connection on the 220uF capacitor – which is also where I commoned the incoming 0v from each of the supplies.

    Here’s a tip. Populate the PCB with ONLY the power connector, bridge recifiers and filter capacitors. Connect up your supplies and test. You should have a +v voltage of 7-12v going to IC3, another positive voltage of at least 14 volts going to IC2 and a negative voltage of at least -14 volts going to IC3.

    Next install the regulators and check the voltages again, including the output voltages of the regulators. Using this method of development saves blowing up anything!

    I hope this helps.

    Regards, Joe.

  • admin

    Posted Today, 08:07 on http://midibox.org/forums/topic/8127-put-waveblaster-daughter-board-yamaha-db50xg-in-a-box/page__st__100__gopid__132202#entry132202

    Hi,
    I read with interest the comments above on stand-alone MIDI synth using Yamaha daughterboard. To answer a couple of comments:
    1. Yes, it’s a home-made PCB. These days I can make one in less than 30 minutes, once the schematic/track is laid down in Eagle. Naturally, I don’t reflect the time spent in terms of price in my estimate for the total cost of my project. For those who haven’t had a go yet, I urge you to try – pick a simple project and use one of those ‘boil-in-a-bag’ etch solutions to start with. Once you get hooked, then you can lash out and buy a bubbler tank etc.

    2. The MIDI OUT connection on the Yamaha card pin 8 is not used in my design, but I always tend to take potential future use into account. The last comment mentions that the connection should go via a resistor and the MIDI loop to a resistor tied to +5v and this is quite correct. I tend to sprinkle extra GND and power points on my PCB’s these days, because I found that I tended to forget stuff and ended up having to solder GND connections directly to the foil on the PCB. The juxtaposition of a GND connection to the MIDI OUT pin is just sloppy on my part!

    I urge anyone considering hooking up a Yamaha board in a similar way to go ahead. I was so pleased with the result, I ordered another board and built a second unit. The sound of two units in parallel is absolutely awesome.

    Regards from Joe.
    Ref article: http://www.joebrown.org.uk/wp/?p=3124 Make a Yamaha Synth for less than £25.00

  • C Burton

    I’ve just ordered one of these boards. Is the PCB in the Elektor magazine working or is the schematic wrong?
    I think I might build yours Joe.

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