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Tandy Sound Compatible PCB

For me personally, it is more interesting to write new software for the card. Develop music tools such as trackers to exploit the capabilities of the SN76489 (you can play samples on it, Rob Hubbard did some nice music for Tandy in One on One and Skate or Die for example), and use the card for better audio in 8088-based games and demos.
Am I the only one here?
 
Can it play sampled sound somehow? I spent a tonne of time with the 1000TL with DeskMate Music and Sound making sampled music, I thought there was a separate DAC for that?
 
pearce_jj said:
Can it play sampled sound somehow? I spent a tonne of time with the 1000TL with DeskMate Music and Sound making sampled music, I thought there was a separate DAC for that?
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Some Tandys have a DAC yes. But afaik the Rob Hubbard games I mentioned don't require it.
Namely, there's a simple trick: You can make any channel play a square wave of '0 Hz'. As a result, the output is always high. By modifying the 4-bit volume, you can change the amplitude, effectively allowing you to play 4-bit PCM samples (very similar to how people do it on C64). There's no buffering or DMA of course, so much like PC speaker or LPT-DAC/Covox, you need to set up a high-frequency timer interrupt and manually bang out the samples. But it doesn't have the PWM carrier wave issue that PC speaker has. Also, you can use one channel to play samples, and still use two other square wave channels and the noise channel to add to the music (that's what Rob Hubbard does).
I've already developed a proof-of-concept of such a routine myself, using DOSBox in PCjr mode, where I play back a VGM file, and instead of one of the square wave channels in the song, I play back a sample on that channel at the same time. By pressing some keys, I can increase or decrease the pitch of that sample, while the music continues playing at the same speed/pitch.
And since this card allows you to mix PC speaker and SN76489, you could theoretically even play samples with both the PC speaker and one or more SN76489 channels in parallel.
 
I'm confused by the BOM. It says we need 4 ceramic 0.1nf capacitors. However it states that C1-C4,C7,C8 are needed. That's 6 capacitors not 4. Does this mean that C2 and C3 are to be left unpopulated or the number 4 in the BOM is an error?
 
Yep updated to 6, sorry. I'm slightly loosing the will to live over the number of errors in this project!
 
Well I'm just sitting here, waiting on the mail so I can populate the last two capacitors to test the amp and start making some videos...
 
Come on James, you did a fantastic job. A couple of errors in this stage is perfectly normal.

Myself i'm just waiting for the damn SN76489's, i built my board today. I also pierced my finger on the 14pin socket... Excitement doesn't come without pain...

IMG_20161210_163806609.jpg
 
CarlosTex said:
Come on James, you did a fantastic job. A couple of errors in this stage is perfectly normal.

Myself i'm just waiting for the damn SN76489's, i built my board today. I also pierced my finger on the 14pin socket... Excitement doesn't come without pain...

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Are you in the U.S.? I ended up with like 30 SN76489's and 15 SN76496's. If yours turn up missing I could mail you one, let me know...
 
Nah i'm from Portugal. Lived in the UK for 2 years but i'm back now. I would actually appreciate a SN76496, just to have something different. Where did you get the 96's? eBay?
 
CarlosTex said:
Nah i'm from Portugal. Lived in the UK for 2 years but i'm back now. I would actually appreciate a SN76496, just to have something different. Where did you get the 96's? eBay?
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I got the 89's off of a private webpage for around $20, and ordered five 96's from Ebay. The 96's never showed up, I didn't hear from the seller for a month, so I ordered another batch from a different seller. The original seller finally replied, sent 5 more, and then the very first 5 showed up...
 
I'm still waiting for both the board and the SN768xx chips (I've ordered from two different vendors on Ebay).
And I guess I need to find two extra 0.1nF caps as well :) I may have them somewhere.
 
C9/C10 are what I'm missing. I think they must be used as noise filters here, I considered replacing with a random value or jumpering completely but I thought it'd be best to actually test out your full design as proposed.
 
C9/C10 are input couplers to the amp.

Lo-tech-Tandy-Sound-Adapter-r01-PCB-1024.jpg
 
I see you left the patch wire loose on the SN76489 side. Couldn't you just fold it back under the PCB and solder it to pin 5 on the underside? At least, as far as I understood, you just need to tap the /IOW signal, so you piggyback off it from that pin because it's already routed there from the ISA bus. You don't pull out the pin on the SN76489, only on the HC688, pin 2 (or you could cut the trace on the PCB itself I guess).
That's how I plan to patch it anyway, so that I don't need to do anything fancy when I insert an SN76489 or compatible in the socket.
 
Scali said:
I see you left the patch wire loose on the SN76489 side. Couldn't you just fold it back under the PCB and solder it to pin 5 on the underside? At least, as far as I understood, you just need to tap the /IOW signal, so you piggyback off it from that pin because it's already routed there from the ISA bus. You don't pull out the pin on the SN76489, only on the HC688, pin 2 (or you could cut the trace on the PCB itself I guess).
That's how I plan to patch it anyway, so that I don't need to do anything fancy when I insert an SN76489 or compatible in the socket.
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I could have done it that way, but i didn't have wire that long. I don't plan to switch stuff around and this is a prototype anyway, so i like the wires on both sides. :cool:
 
CarlosTex said:
I could have done it that way, but i didn't have wire that long. I don't plan to switch stuff around and this is a prototype anyway, so i like the wires on both sides. :cool:
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Got mine fully assembled. PC speaker input and mixer works well.

tandy.jpgtandy back.jpg

I think this needs a volume control on the backplane also, like Sergey's OPL2 card.
 
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I suppose we should start a "compatibility matrix" or list of some sort, maybe on a wiki somewhere.

So far I've tested Champions of Krynn (works perfectly), Conquests of Camelot (works perfectly), and Bubble Bobble (setup can't detect Tandy hardware when selecting audio output, works perfectly after confirming selection.)
 
It's normal that it can't detect. Detection routine most probably involves model byte, Tandy String and machine byte.

This Tandy card can't possible be detected. The SN76489 and variants are write only AFAIK.

Hmmm that level of noise is troubling...
 
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