I replied to this about a month ago [as of this post] on LGR's Covox Speech Thing clone Youtube video.

This is what I said, as it is a bit informative, though not over the top information...

It sounds very reminiscent of Amiga MOD tunes in general. Love it, it's amazing how simple of a device can produce such nice rich sampled sounds.

My guess as to why Wolfenstein 3D is not working with the self made Covox is because the Disney Sound Source required additional [DAC bytes] to be sent to an additional control port in order to operate properly. However i'm pretty sure some self made Covox devices emulate Disney Sound Source to get those games to produce sound properly without the need of a Disney Sound Source, though I could be wrong.

Whats neat, is the Disney Sound Source was only $14 USD back when they were first released, and had rudimentary filtering circuitry, which the original Covox Speech Thing did not have.

Chaniyth wrote:

....i'm pretty sure some self made Covox devices emulate Disney Sound Source to get those games to produce sound properly without the need of a Disney Sound Source, though I could be wrong.

If anyone has any additional info on this, I would be interested. Thanks.

The Disney Sound Source is not a simple DAC with on/off control, it also has a 16-sample FIFO buffer and some internal 7kHz clock it runs with. It is also possible to read if FIFO buffer is full or not full from a status pin. Pin 10 low means FIFO can be written, and high means FIFO is full. In fact this status pin can also trigger interrupts on rising edge, but it is unclear if this is ever used - what would be a point in getting an interrupt when the FIFO cannot accept more bytes, it would be better to get an interrupt when the FIFO can accept a byte, but I may be wrong here how it works.

So a program can utilize the FIFO and can send up to 16 samples at a time into the FIFO, so writes can happen in 16-sample bursts every 437Hz or so. This is of course impossible with a normal Covox, because it reacts to every byte instantly, so it needs one sample at 7kHz rate to be equivalent.

But if a program does not use the FIFO, it only uses the control signals to latch single samples into it at the sampling rate, these programs can work with normal Covox. The Covox will only see the data, and the control signals are irrelevant.

And because Covox does not need the control signals, Covox compatible programs cannot work with Disney Sound Source hardware.

It just might be possible to emulate a Disney Sound Source with a microcontroller, but the difficulty is to react to the control port signals because FIFO write pulses might be only 1 microsecond in length and have those bytes transmitted at 100kHz rate or more.
That would be a cool project.

Can we build them?

retro games 100 wrote:

Chaniyth wrote:

....i'm pretty sure some self made Covox devices emulate Disney Sound Source to get those games to produce sound properly without the need of a Disney Sound Source, though I could be wrong.

If anyone has any additional info on this, I would be interested. Thanks.

I'm currently trying to add DSS support to my QDOS port. Basically, the guy earlier said he was using an ISA I/O card which may be why it is not working? I am unsure exactly.

The card is accessed by scanning the three LPT ports and then stuffing 16-bytes FIFO data on them to see if a buffer overflows. If it is overflowed then that is where it assumes the DSS to be.

The DAC may be necessary as it pulls certain pins high and low to enable or disable the amplifier.

More info is at: http://archive.org/details/dss-programmers-guide

butterfly wrote:

Can we build them?

If you could find the DAC and/or FIFO chips required I don't see why not.

I would open my DSS adapter to find out what the chip is inside but it appears to be made of some sort of plastic that would easily snap. It took me a few years of checking ebay off and on to find one at a price I was willing to pay to experiment with one so if I find another one cheap I will take it apart.

No need to open, just use google.

ICS1453, custom IC with FIFO and DAC. Because custom, can be hard to find.

I still have not done anything to emulate it with microcontrollers, although been thinking about it on and off.

Like Jepael said, there's all info you'd need on the web, there's the scheme as well as basic info on what it does + a description of the parts used on the board.
I've started to built a Covox to DSS adapter plug a while ago using a designated FIFO chip, but that didn't work out for some reason or another and looked like this: http://www.dosforum.de/download/file.php?id=21
Design was based around a 555 timer (for the output frequency - on the original it's done with a RC-Circuit), 2 8Byte FIFOs in series and possibly a 74LS04 for inverting various signals. A microcontroller + ordinary covox might actually work better, considering the increasing complexity of the discrete approach.
There's also a russian piece of software which did what my circuit intended to do which required QEMM to be installed, had a slightly off samplerate and due to requiring QEMM didn't work with every piece of software.
Therefore it's probably easier to just grab a DSS for $10 off ebay, considering they're not exactly rare, just don't pop up very often.

http://ep.yimg.com/ca/I/leeland_2258_37435452
http://imageshack.us/a/img708/5646/dsslayout.jpg
http://img14.imageshack.us/img14/9437/dsspcb.jpg

I must be honest, it took me quite some time to track one down on ebay. Granted, I wasn't checking every day (nor did I get emails if they popped up), but I'd check about once a month or so and it took me like a year to find one that wasn't some disney goof with an over-inflated buy it now price.

I think I got mine 3 years ago for like $10, boxed after checking once per week.

I did get mine for $10 CIB as well. I guess that seems to be the average fair price for one.