AY 3-8910 vs YMZ284 from ebay
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- Опубліковано 3 жов 2024
- I bought YMZ284 sound generator chip on ebay. It is an equivalent of AY-3-891x series chips which were used in many of the 8-bit computers and some arcade machines. Let's see how it compares to real, original Microchip AY chip I bought years ago from Mouser.
The yamaha chips offer logarithmic volume scaling. That's normal and an improvement. Think of pots... GI chips have linear taper and Yamaha chips have audio taper. The spikes are also normal for any chip with TDM output mixing. The DX7 synthesizer does that too. Lowpass filtering eliminates the spikes. The shrunk package means the three outs are TDM mixed here, where as on the larger YM2149 and the GI chips there are three DAC pins and the outputs are mixed with resistors. The biased output level allows for using single ended opamps in the output filter and driver stages without requiring rail to rail input response. If you want a better comparison, pick up a YM2149F. Common price on Ali is
They may seem worse than they actually sound) Shall we listen? 🙂
yes there are plenty of variations of ay-3-8910 in terms of audio generation, but measuring right at the output of chip does not make big sense because there is still analog part of schematic goes after chip out. usually there in series capacitor that make DC part =0 then opamp and then low pass filter... after all of this output should be more or less same
Even so, the envelope should be the same and it's not, so the sounds on the ymz sounds shorter compared to how they should be. No amount of low pass filtering will correct that.
And the pulsed output will give a much lower output signal when run through a low pass filter, giving a worse signal to noise ratio. It's as though the dc offset indicates the chip needs a dual power supply like -5 and +5V to prevent clipping.
Man, the reason why Yamaha goes down faster is probably because it has lower output level and the lower part is hidden in the noises at the bottom. Choose different scale on the oscilloscope, use proper grounding and I bet you will see this signal.