So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

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

So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby Eep386 » 2019-3-15 @ 07:14

...And it works :)

I have a dead CT1740 and a healthy CT2910. I rather like the CT2910 a lot as its YMF289 OPL3 FM chip sounds exactly as I remember the FM synthesis on my first sound card, an Addonics YMF719E-based card, had sounded. But one thing that was off-putting was that notorious bugged v4.13 DSP with its clicks and stutters, so I've been sticking to a CT1770 SB16 SCSI up to this point.

Today I worked up the courage and swapped the DSP chip on my CT2910 with the v4.05 from the dead CT1740, and much to my surprise everything works fine (so far). I haven't tested specifically for the single-cycle DMA clicking problems and the like, but for now I am happy to have a YMF289 OPL3 SB16 with a 'non-bugged' DSP. Earlier on the CT2910 I had changed the MC3403 quad op-amps out for TL074's, and that had cut the hiss roughly in half. I also changed the op-amps on the CT1770, and got a similar (albeit somewhat less pronounced) improvement. The CT2910 already has a good CT1703-A DAC so that does not need to be changed.

Further testing (and pictures) is pending.
Last edited by Eep386 on 2019-3-15 @ 07:25, edited 1 time in total.
My synthesizer hierarchy: Novachord > DX-7 > YM2151 > YM3812 > CT1747/YMF262/YMF289 > CQM > PC Speaker > AudioPCI "FM" (retch)
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Re: So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby Cyrix200+ » 2019-3-15 @ 07:25

Pictures please :)
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Re: So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby Eep386 » 2019-3-15 @ 07:32

Here's the card:
IMG_0879.JPG


The star of the show, the v4.05 DSP:
IMG_0880.JPG


And now a view of the TL074 op-amps:
IMG_0881.JPG


Unfortunately the only way I can think of to get v4.05 DSP chips, is from busted old SB16's. At least the one broken CT1740 I had wasn't going to go to total waste.
My synthesizer hierarchy: Novachord > DX-7 > YM2151 > YM3812 > CT1747/YMF262/YMF289 > CQM > PC Speaker > AudioPCI "FM" (retch)
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Re: So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby kixs » 2019-3-15 @ 07:38

Great to see it working with an older DSP :D More tests please ;)
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Re: So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby appiah4 » 2019-3-15 @ 08:56

The obvious question is - did this completely fix all MIDI interface bugs? Can we once and for all confirm it's DSP related and not a silicon bug in the other ICs?
1989:A500|1M|ACA500+|C1084S
1992:HIPPO-VL+|U5SX-33|8M|GD5428|CT2290|S2
1995:P5I430VX|P133|32M|T64+/MX2|V1|CT3980/32M
1998:S1573S|K6-2/400|64M|RagePro|V2/SLI|CT4500/32M
2001:GA-6OXT|PIII-1200|512M|GF3Ti200|MX300
2004:K8VD|3700+|2G|X1950P|SB0350
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Re: So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby Cyrix200+ » 2019-3-15 @ 09:24

Nice work!
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Re: So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby Eep386 » 2019-3-15 @ 17:17

appiah4 wrote:The obvious question is - did this completely fix all MIDI interface bugs? Can we once and for all confirm it's DSP related and not a silicon bug in the other ICs?


Unfortunately I don't have a single MIDI device to my name to test it with, not even a Wave Blaster-compatible rompler. Guess that will be the next thing on my agenda, next paycheck.

https://www.ebay.com/itm/Dreamblaster-Synth-S2-Daughterboard-WaveBlaster-MIDI-Yamaha-DB50XG-XR385-type/282363679686?epid=2193887349&hash=item41be2fd3c6:g:BvUAAOSw0rdb3cOL
Would this be good? Or is it too expensive?
My synthesizer hierarchy: Novachord > DX-7 > YM2151 > YM3812 > CT1747/YMF262/YMF289 > CQM > PC Speaker > AudioPCI "FM" (retch)
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Re: So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby appiah4 » 2019-3-15 @ 17:54

That auction leads me to a gibberish listing from China I would not trust. Dreamblaster is a fellow Vogoner who makes and sella these MIDI devices, his Dreamblaster S2 wavetable board can be had for around 20 EUR on his wesite http://www.serdashop.com; he also sells other fantastic midi gear.
Last edited by appiah4 on 2019-3-15 @ 20:49, edited 1 time in total.
1989:A500|1M|ACA500+|C1084S
1992:HIPPO-VL+|U5SX-33|8M|GD5428|CT2290|S2
1995:P5I430VX|P133|32M|T64+/MX2|V1|CT3980/32M
1998:S1573S|K6-2/400|64M|RagePro|V2/SLI|CT4500/32M
2001:GA-6OXT|PIII-1200|512M|GF3Ti200|MX300
2004:K8VD|3700+|2G|X1950P|SB0350
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Re: So I replaced the v4.13 DSP on my SB16 CT2910 with a v4.05...

Postby keropi » 2019-3-15 @ 18:05

^ that Chinese seller is legit and he gets his stock from Serdaco in bulk - no issues buying from there if necessary
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