Reversing the Disney Sound Source

[Megadisk]

Time to Test it

https://www.youtube.com/watch?v=pnncFNk ... r_embedded

So the guards sounds can indeed be heard?

[matze79]

i finally made it:

Now Step 2.

Build the DAC Module.. next free day is DAC Building Day.

- Please move this Thread to Sound.

[keropi]

nice!!!!!

[Stiletto]

Moved!

[matze79]

Somehow its not detected, damn it.
Arachnophobia works, Wolf3d does not..

Accidently i found out that shorting T1 gets DSS is detected and working but with the NE555 Frequency inside signal..

[matze79]

I don't see any error its same design as before, just with a added diode.

Hm tomorrow i will check it again.

Did not get it.
Except for Diode everything is the same.
its NE555 instead of NE555N.. and CBC 337-16 not BC337... but thats all.

[Megadisk]

I've even seen flux do crazy things. You might want to clean the solder side just to be safe and fill those hollow solder points.

[matze79]

EDIT:

Found the error, damn it, its my fault.
i didnt check everything precise.
DRU Rules for Board Design.. one Hole is near one trace and connecting both -> short circuit.

EDIT#2:

Now it works its bit noisy because of the R2R Ladder.
Some LPT Ports are really quiet, others let you listen to every hdd access

[Megadisk]

I'm glad you figured it out. Please sign me up for a board.

[Jepael]

Now it works its bit noisy because of the R2R Ladder.
Some LPT Ports are really quiet, others let you listen to every hdd access

But you have the FIFO chips between LPT port and DAC, so the noise must come from FIFO chips and how they are powered, but not from the LPT port.
Having said that, where is the power to FIFO chips coming from, and is it filtered? I don't see a single bypass capacitor on the board either to stabilize voltages.
If the diode is in series from power supply then there could be some load dependent voltage drop over that too.

[matze79]

The Noise coming from the NE555.. its exactly the 7,?khz Frequenz i can hear.
And from the PS/2 Port from which i power it.

The bypass capacitor is integrated into the Socket on this Unit
or soldered on the backside of the pcb.

[Jepael]

The Noise coming from the NE555.. its exactly the 7,?khz Frequenz i can hear.
And from the PS/2 Port from which i power it.

Ohh, I get it now -- if you hear the sampling rate then that means you don't have a lowpass filter to properly reconstruct the DAC output.

The bypass capacitor is integrated into the Socket on this Unit
or soldered on the backside of the pcb.

Good

[matze79]

I got some AD7524 DAC's, and already made some tests, it improves audio quality over R2R

Also got some Small Low Power AMP TDA7050.
http://www.b-kainka.de/Daten/Analog/TDA7050_CNV_2.pdf
its a cool ic, it does not need any external parts (only output capacitors)

I'm pretty sure i will have a Chip DAC Covox Device in the next few weeks, maybe 1-2 months.

[shock__]

Can confirm random noise slipping through (static buzz, hdd accesses,etc.) once the DSS gets activated, on the board matze produced and on my own loose wire prototype on my 486 (LPT via VLB multi-interface card).
Also happens on my frankenstein IBM 5170 (generic 12MHz 286 board + original IBM interface card), where the random noise is limited to the static buzz.
Doesn't seem to be random enviroment noise being picked up as using an LPT extension cord didn't change anything.

[matze79]

I build a IC CHIP DAC and it works well, crystal clear

but when i connect it to DSS its giving buzzing noise until the DSS is initialised.
It seems the DAC Pin's are floating until the DSS is active.

Then its also crystal clear.
if you leave the program, again noise..

would it help if i use Bus Driver IC before the DAC ?

[shock__]

Triggering a bus driver in parallel to !SO might have some issues with a propagation delay being added by the requirement to invert the signal. Maybe some pulldowns for the outputs might help? I'll actually add some to my DSS-board later today to see if that helps.

EDIT: Didn't help at all. Fun fact: If I remove the DSS from the "chain" the noise output by the covox is pretty much the same as with the DSS. Might be an issue of the covox design I'm using.

[matze79]

Yeah, i have no noise at all. its really quiet.
Only with DSS

i mean, adding the bus driver beetween DSS and DAC.
So there are no issues with delays.

Hmm need to try it. Simple 74HC244 in DATA Lines.

The Noise is gone when i power everything from PS/2 Port, but then i get nasty Operating Sounds from the Escom Computer..

Covox alone, External Power -> 7805 -> 9V Lab Supply, Clean Sound, no Noise
Covox + DSS, External Power -> 7805 -> 9V Lab Supply, Buzzing Noise
Covox + DSS, PS/2 Port Power -> Operating Noise of PC (HDD Access, Memory Access etc...), some Buzz..
Covox External Power, DSS PS/2 Port Power, Buzzing Noise.

[shock__]

Tried 74HCT245 between the data lines, no improvement.
Disconnected LPT-GND from the rest of the DSS circuit, no improvement either.

Jepael is probably right, that the lack of low frequency filtering is passing through.

[matze79]

but the noise is not permanent, it goes away when DSS gets active and playing sounds.
If the filtering is the problem should i not get always the buzzing noise ?

[Paralel]

If the DSS is active, but completely silent, so set to play a string of nulls or something (What I'm thinking is that its actively processing stuff, but what its told to process produces no sound, not sure if I phrased that correctly) [I don't know if this is possible] is it perfectly quiet?