|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.
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)
16-Part (DVA : Dynamic Voice Allocation)
Total …………………………. 676
XG mode ………………….. 480
TG300B mode …………… 579
Drum Voices (Sets)
Total …………………………… 21
XG mode ……………………. 11
TG300B mode …………….. 10
Reverb (11 Types), Chorus (11 Types),
Variation (42 Types)
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.
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.
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.
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
And for more offerings from the Far East, as well as nearer home, try looking here.