I de-CQMed my AWE32 PnP CT3990...!

Discussion about old sound cards, MIDI devices and sound related accessories.

Re: I de-CQMed my AWE32 PnP CT3990...!

Postby Tiido » 2019-3-14 @ 02:14

I have successfully de-CQM'd a CT3990 and CT3600 :
Image
Image

I also took a look at the CQM chip and it runs off 46.615120MHz, with 20x cycles per BCLK and 960 cycles per sample, giving 48557.416...Hz sample rate. Output format is 16bit i2s with 48x BCLK cycles per sample. Original OPL2/3 sample rate is 3.579545 / 72 = 49715.903...Hz.
YMF289 has 16bit Right-Justified format so no reuse of the TDA1387 DAC is possible, one will have to use the crappy Yamaha's DAC.
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Re: I de-CQMed my AWE32 PnP CT3990...!

Postby suntac » 2019-3-14 @ 03:17

Tiido wrote:YMF289 has 16bit Right-Justified format so no reuse of the TDA1387 DAC is possible, one will have to use the crappy Yamaha's DAC.


Good to know. Thanks!
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Re: I de-CQMed my AWE32 PnP CT3990...!

Postby Thermalwrong » 2019-4-26 @ 22:53

Thanks Eep386 and everyone else for the information :) Going through the list of parts to change and the YAC516 datasheet, I've managed to switch my "Soundblaster 32" CT3620 and Soundblaster 16 CT2950 from CQM to the YMF289's OPL3.
Both of them are working well on my test PC, which is good because the CT2950 wasn't so useful otherwise. I'm really happy with the CT3620 - my AWE64 Gold broke and this fills the gap very nicely with 8MB ram fitted.

My main takeaways from this:
  • The 10 ohm resistor needs to be a bit bigger apparently
  • Cheap 33.8688 Mhz oscillators from China work fine and arrived quickly
  • Removing the CQM chip and TDA chips requires a heatgun
  • Fitting the YMF289 & YAC516 chips was easier to carefully hand solder
  • YMF289 bought on ebay from China (notice it's missing the 'B' ?) mayyyy be a clone, but it's definitely a proper OPL3 clone if it is one
  • YAC516 works well - note it's upside down on the CT2950

I ended up making some graphics to work from:

CT3990:
CT3990-Upgrade-to-OPL3.jpg


CT3620:
CT3620-Upgrade-to-OPL3.jpg

CT3620-Upgrade-to-OPL3-AfterUpgrade.jpeg
CT3620 after upgrade


CT2950:
CT2950-Upgrade-to-OPL3.jpg

CT2950-Upgrade-to-OPL3-AfterUpgrade.jpeg
Soundblaster 16 'Pro' PnP - CT2950 with YMF289 fitted
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Re: I de-CQMed my AWE32 PnP CT3990...!

Postby Eep386 » 2019-4-29 @ 21:24

Fantastic! Maybe now we won't have to be afraid of so many CQM cards that are otherwise quite nice...
My synthesizer hierarchy: Novachord > DX-7 > YM2151 > YM3812 > CT1747/YMF262/YMF289 > CQM > PC Speaker > AudioPCI "FM" (retch)
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