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Re: Netlist: 280-ZZZAP sound problems [Re: Colin Howell] #117342 05/17/20 02:37 AM
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Open MP : https://www.openmp.org

It's an compiler extension. I don't like it. It has the usual cheap win appeal but if e.g. you go GPU it really get's awful. nvcc is a lot nicer, more transparent and in the end better to understand. Well, in the end you abstract different backends by templates, anyhow.

Re: Netlist: 280-ZZZAP sound problems [Re: couriersud] #117343 05/17/20 03:39 AM
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Colin Howell Online Content OP
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Originally Posted by couriersud
Open MP : https://www.openmp.org

It's an compiler extension. I don't like it. It has the usual cheap win appeal but if e.g. you go GPU it really get's awful. nvcc is a lot nicer, more transparent and in the end better to understand. Well, in the end you abstract different backends by templates, anyhow.

Ah, that (OpenMP). Which from checking the makefile I assume isn't built in anyway unless OPENMP is enabled for the build.

Re: Netlist: 280-ZZZAP sound problems [Re: Colin Howell] #117344 05/17/20 05:39 PM
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Originally Posted by Colin Howell

Ah, that (OpenMP). Which from checking the makefile I assume isn't built in anyway unless OPENMP is enabled for the build.


Yes, for certain builds, though can't remember which, it caused issues. Using c++ threads should be sufficient for the purpose as well, just need to find the time.

Re: Netlist: 280-ZZZAP sound problems [Re: Colin Howell] #117386 05/29/20 07:15 PM
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OK, an update. At this point I'm about ready to cut a branch, commit, and submit a pull request. The driver works, though I still have some issues with it.

I'm now using an appropriate Zener with a normally-distributed noise voltage source added as the basis for the noise generator: the ad-hoc random current generator is gone.

I also abandoned the low-gain hack of the op-amp after I discovered that getting the oscillators to run at the right frequency and voltage range with that op-amp hack was no easier than with the standard op-amp model with normal gain: I was only getting increased numerical stability because the lower gain kept the oscillator running in a narrower voltage range. Instead I went back to the method of putting a frontier on the Schmitt trigger op-amp's output, which seems to remove the numerical stability problem. Some slight tweaking of the Schmitt trigger op-amp's resistors corrects any change in frequency and voltage range. I no longer adjust the oscillator capacitors.

I removed one of the op-amps in the final amplification stage, since it was effectively unused. Its only purpose in the real circuit is to invert the other op-amp's output so that the final power amps can get opposing signals in order to drive the speaker "push-pull" style.

I took out the reduced accuracy and tolerance parameters for the solver. They didn't improve speed much and reduced sound quality.

Unthrottled performance with static solvers is still around 170%-220% of full speed on my machine, depending on sound workload.

The sound seems higher in treble and lower in bass than what I hear in the few videos of real 280-ZZZAP machines I can find, and the "skid" sound is less distinct than on those machines. Oh well. That may be a difference in the machine's audio "front end" (is that the correct term?). There also may be some differences in component values between the schematic I used and real PCBs. It would be nice to compare with real PCB photos, but I can't find any.

This driver should also be able to support Laguna Racer and Super Speed Race, but there are some component value differences (and circuit differences for Super Speed Race). I don't know how best to handle that: duplicating the whole netlist with components changed seems clumsy. Is there a way to parameterize or have conditional code in a netlist?

Re: Netlist: 280-ZZZAP sound problems [Re: Colin Howell] #117387 05/30/20 01:32 AM
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Further brief update: commits made and pull request now submitted.

Re: Netlist: 280-ZZZAP sound problems [Re: Colin Howell] #117388 05/30/20 03:32 PM
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BTW, the thump when you crash is actually pretty bassy on decent headphones. I imagine in the cabinet it's amplified a lot more.

Re: Netlist: 280-ZZZAP sound problems [Re: Colin Howell] #117392 05/31/20 02:27 PM
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Just saw this reference video: https://www.youtube.com/watch?v=0RA-42dPnPk

The main thing I hear different is that the skid is a lot louder on the real cabinet than in MAME right now.

Re: Netlist: 280-ZZZAP sound problems [Re: Colin Howell] #117393 05/31/20 02:54 PM
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Yeah, that was one of the things I noted. Tried to make sure the noise effects were as loud as possible without distortion, but there doesn't seem to be any more headroom for that as the circuit is currently set up. One of the reasons I'd like to check against real PCBs.

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