Covox sound upgrade

[+Stephen]

I've been messing with Neo Tracker 1.6 (quite an amazing piece of software BTW) for a few weeks now. It supports the Covox sound upgrade (Polish) and gives the machine the ability to playback 8-bit samples. Unfortunately, the only bit of info I can find on the upgrade is this (somewhat mangled) text :

 

*******************************************************************************

		   Easy 4 channels * 8 bits Covox C/A for Atari 8bit
							 by: Gumi/Tight
					mfranczak@ajax.umcs.lublin.pl
		  ---------------------------------------------------

List of needed items:
chips:
1 * 74LS138
4 * 74LS574

resistors:
36 * 1.2 kOhm
28 * 2.4 kOhm

capacitors:
4 * 100-220 nF


To pins of chip 74LS138 you must to attach this signals:
pin 1 - A0
pin 2 - A1
pin 3 - R/W
pin 4,5 - $D6 (page $d6 decoder)
pin 6 - o2 (fi2)
pin 8 - 0V - GND
pin 12 - to clock of #4 C/A
pin 13 - to clock of #3 C/A
pin 14 - to clock of #2 C/A
pin 15 - to clock of #1 C/A
pin 16 - +5V
other pins - not connect

You must to do 4 C/A, like this one:

   ---. .---
   |  | |  |
GND>--|1 '-'20|
   |	   |
  ----|2	19|-->----R1----*		  R1 is 1.2 kOhm resistor
   |	   |			 R2		 R2 is 2.4 kOhm resistor
 D1>--|3	18|-->----R1----*		   C is 100-220 nF capacitor
   |	   |			 R2
 D2>--|4	17|-->----R1----*
   |	   |			 R2
 D3>--|5	16|-->----R1----*
   |	   |			 R2
 D4>--|6	15|-->----R1----*
   |	   |			 R2
 D5>--|7	14|-->----R1----*
   |	   |			 R2
 D6>--|8	13|-->----R1----*
   |	   |			 R2
 D7>--|9	12|-->----R1----*-----C--->out analog signal
   |	   |
GND>--|10   11|-------*
			|
out #4--->-----*---------- LEFT channel


out #2--->-----*---------- RIGHT channel
			|
out #3--->-----*


*******************************************************************************

 

Can anybody here provide me with some more info on this upgrade? NeoTracker will support stereo, so I am assuming this means the dual PoKey upgrade. How would the CoVox interface with that?

 

Stephen Anderson

[krupkaj]

Polish Covox is 4 channel D/A converter. So it is different upgrade than Stereo Pokey.

[fox]

Covox simply consists of two 8-bit D/A converters for the left audio channel and two for the right channel. That's all.

 

Schematics here:

http://atariki.krap.pl/index.php/Covox

[+Stephen]

Covox simply consists of two 8-bit D/A converters for the left audio channel and two for the right channel. That's all.

 

Schematics here:

http://atariki.krap.pl/index.php/Covox

 

Thanks for the quick replies! I"ll try and get this built before the CCAG show I am attending at the end of the month.

 

Stephen Anderson

[Rybags]

One of these with a 256 byte FIFO would be great... just load it up each VBLANK for digitized sound with minimal use of system resources.

[Webzz]

Has anyone found a good schematic for building the COVOX? I've searched and come up empty. Maybe there is one that uses simple da converters instead of all the resistors. Also where does this hook up to GTIA? The instructions above are not clear. Can someone make this any clearer?

[Rybags]

Why would you want it hooked up to GTIA?

 

By the look of it, the circuit would probably has it's own outputs for speakers, seperate to the normal one.

 

The Antic references only seem to be there since it takes Phase 2 clock, R/W and A0-A1 from Antic.

 

 

DM74LS574

Octal D-Type Flip-Flop with 3-STATE Outputs

General Description

The DM74LS574 is a high speed low power octal flip-flop

with a buffered common Clock (CP) and a buffered common

Output Enable (OE). The information presented to the

D inputs is stored in the flip-flops on the LOW-to-HIGH

Clock (CP) transition.

 

They're not A-D convertors, they just latch data and continuously output it on 8 lines, which explains the need for resistor arrays.

 

74LS138 is a decoder/multiplexor - that would be used for chip-select dependant on the state of A0/A1.

Edited December 13, 2007 by Rybags

[Rybags]

You've got me all interested now...

 

could probably build one of these for under $20. Would make a nice little plaything.

[peteym5]

This will probably be a good 3rd sound chip that is additional along with a dual pokey upgrade, maybe build a small board that can contain all 3 chips. That way the circuit would be compatible with dual pokey and whats on this chip. Also depends on how this chip is addressed. Is the a more detailed English description of this chip?

Edited December 13, 2007 by peteym5

[Webzz]

I meant Antic oops... anyhow can we work up a better schematic.

[pepax]

What a nice bees nest and here we have some mating cockroaches for a change.

Datri's schematics...

Edited December 13, 2007 by pepax

[Webzz]

What language is that? I tried polish>english but it comes up garbage.

[pepax]

Czech.

[Webzz]

smokes... here is the bludgeoned translation I got:

 

Budeme potebovat 4x7 nausea 1k2, 4x8 nausea 2k2, 4x74LS574, 1x74LS138, twain telegram , soldering copper njaké what atari , natty twain rukou plus trplivost plus grow cold head. WITHIN substance COVOX nelze title arrangement , or to within poítai nth wild , solely pidává. What about that there goes mystical COVOX??? Them what zaízení které umí pehrát samplovaný sound within osmibitové quality. Use him npíklad Noble , or modesty as well as FRISH demo. OUT OF elektronického standpoints them what pevodník out of digital waft within waft analogue. As forth as certain well met , now dog Pokey it can be too strike to samplovaný sound , however solely tybitov , spigot conjunction dlaších main scented notion osmitového samplu. Sake however nevytvoit svj respective sonic network??? As forth as jsem yet ekl , them what osmibitový DA pevodník. While main , what pevodník. What standard to stal tykanálový COVOX. Mžete him produce out of original DA pevodník , or suck TTL logic plus pevodník si stand. Použijeme 74LS574 which them octuple lapel network. Has eight admittance , eight ascent plus clock. Samozejm , that him however shall njak naadresovat. Hereto použijeme network 74LS137, which them multiplex. Same network yet within atari najdete. Them nigh Pokey tuším that above ním. His vignette máte underneath. As forth as vidíte , has piny D1, D4, D6 plus nevyužity. WITHIN use what operating aromatically now , hither network ídí piston make for network like them Pokey Pia Gtia plus now. Won't here vysvtlovat , sake piny D1 plus nejsou at someone's disposal holiday. Shall me vit , when you eknu , that holiday piny are D6 plus D7. Herewith are acquired dv nests superscription within scope 256 quarter. Samozejm , that budeme apply solely jednu plus out of ní použijeme solely tyi superscriptions. Sake whoever pevodník jednu. You samozejm shall njak select plus hereto použijeme warrants subsequent která simplification accomplishment what , that upstairs bity A0 plus pevede within dekadickou worth 1-4. Piny oznaené ASSETS relation with pinem pvodního network 74LS138. Tyto piny urují , when bude network active. Transudation W plus nkam up poítae. Mžete avail species vignette , whoa symbolise station potebných consequence within nextdoor network. Pipojte stilly GND plus UCC. Herewith them network pipojen plus poíta by ml walk switch on plus work. Consequence CLOCK1-4 are pipraveny plus appointment. Te pijde not bad oíšek. Nearly within celou authority side network 74LS574 shall water nauseas 2k2 plus amongst their konce stilly 1k2 now as forth as them what within vignette. Herewith attainment jakéhosi passive pevodníku. Waft out of projde dog nejvtší poetics nausea plus bude hold weakliest norma plus waft pjde nearly pímo. Within sooth council withal clock them prospective audio ascent. Within the napájíte condenser within mastermind 100nF. Here by Modification všechny tyi networks self what ešil dog SMD nauseas. Mind your eye thereupon , that within hereafter to shall networks slide water within themselves. When what budete hold ohnte with všech network stem clock plus všechny tyi situation within themselves budou to páit tyi beetle. ). Celá levá ( nether ) side pijde pipájet. Stem tvrtého within stem tetího plus you within stem species plus you within stem prime. OUT OF species sides to pájí solely jedna stem UCC. Te what bude size up aromatically now , that you within jedné side trí consequence through you condenser. Now you vemte plus solder them together ( to whom it may concern solder two plus two plus avail like sinister plus very main two about plus two tam. ). UCC pipojte within +5V plus GND underfoot. Nowadays transudation consequence CLOCK1-4 with pipravenými consequence CLOCK network 74LS574. CLOCK1 within prime , CLOCK2 within second plus now. Under skutenosti nezáleží within poadí. Herewith by arrangement mla subsist ready. Poíta by ml normally work plus skrz noble spryly mli hear sound. Mind , that within novjší version mli welter , seeing pravdpodobn nkdo pipojil covox within pin pvodního network takže about dali within výbr dv superscriptions. Self appearing out of pvodní noble plus the takhle operating. Opt stejn like with stereo to whom it may concern avail njaký amplified zastavný up atárka. M subjectiveness to osvdil obyelný 0.5W out of network LM386. Them single úinný plus pull in as well as reprobedniky. Maybe within nm sinus. Stilly delivery , that ascents out of Covoxu mžete dog condenser pipojit within ascents out of pokey. Condenser to about dává make for odfiltrování stejnosmrných unwished composite. Závrem chci íct , that wrap up arrangement jsem solitary strikeout respektive within skeleton ripnutí noble plus ascertainments zpsobu selecting jsem her zptn suggest. Netvrdím , that them 100% justice , however them appointment , singly plus stilly yet nkolikátý year without hang-up operating.

[Rybags]

How is it addressed?

 

Pretty simple, I'd say.

 

Just store the sample "levels" to $D600-$D603, each address corresponding to an individual "voice".

 

I might try and make one - just breadboard it and only use the one chip as a proto.

 

Really, to take advantage of this upgrade, you'd want a large RAM expansion. 8 kHz sample rates probably give the lowest "acceptable" quality for digital playback which in itself equates to 8K per second per voice.

 

But, it would be good for wavetable type output as well, albeit quite demanding on CPU resources. Something like a PIC controller to take the workload away might be more desirable.

[peteym5]

I think putting this on a small board be a good ideal. That photo I see with all the resisters kinda scares me. Does it have any control registers or anything? Actually seems more primitive than pokey.

Edited December 14, 2007 by peteym5

[Rybags]

Effectively, one control register (per chip). The chip select tells the IC to sample the data bus on the low->high transition of the clock input.

 

$D60x as a base is "easy" on the Atari since the logic is already present to give the chip select output needed.

 

I've just gone and bought a 74HC573 and am building one up on a proto-board. That chip should be OK since it effectively does the same thing.

 

Mine's turning into a bit of a confused mass too - but that's expected with the number of resistors involved.

 

I'll probably try it on my XEGS - don't want to risk my other machines.

[Webzz]

I built a 2 MB EPROM 'super-cart' which will give me 255 * 8K banks in cart slot B address range 8000-9FFF so I will have plenty of room for samples. I've designed many projects with AVR's as well, but not sure how I could use one here. I need to understand exactly what this thing is doing and how the software works. I assume it is sending a bit stream to the latches. Why are there 2 latches per channel? What speed do the latches get updated?

[+Stephen]

How is it addressed?

 

Pretty simple, I'd say.

 

Just store the sample "levels" to $D600-$D603, each address corresponding to an individual "voice".

 

I might try and make one - just breadboard it and only use the one chip as a proto.

 

Really, to take advantage of this upgrade, you'd want a large RAM expansion. 8 kHz sample rates probably give the lowest "acceptable" quality for digital playback which in itself equates to 8K per second per voice.

 

But, it would be good for wavetable type output as well, albeit quite demanding on CPU resources. Something like a PIC controller to take the workload away might be more desirable.

 

The reason I am building (I know - I am slow to get this done) is for the Neo Tracker program. It works with single PoKey, stereo PoKey, and CoVox. If you guys have not tried this program, check it out. It is an amazing piece of software for our little 8-bit machines.

 

Stephen Anderson

Edited December 14, 2007 by Stephen

[krupkaj]

I built the version with resistors and it works very well with Neo Tracker. I used SMD resistors, photo of my version is here.

[MEtalGuy66]

Pfft..

Thats easy as hell to build..

 

If you want, I'll cad up a board for it monday...

 

I'd do it now, but I gotta move this weekend and itsd almost 5 oclock..

 

Hint.. To build the output resistor networks, use a single dip-style "straight through" resistor array and then two SIP style reistor arrays.. Piece of cake if you make a PCB for it..

 

make it where it piggybacks on some chip socket that has most of the needed signals..

[Rybags]

"Two latches per channel" gives two voices per channel (stereo, 4 total).

 

The latches are updated by software.

 

According to the datasheet, the ICs are more than fast enough to react well under the cycle time of an Atari (although of course the A8 could only possibly load one latch every second cycle).

 

Most of the inputs needed are present on ANTIC - except the Chip Select for $D7XX - it's pin 9 on the 74LS138 (U2 on 800XL).

[rdhays82604]

I was was wondering if a MAX506 would work? It is a quad DAC.

 

http://www.jameco.com/Jameco/Products/ProdDS/814240.pdf

 

3-input NAND gates could be used to decode the writing to it.

2 to invert the R/~W and ~D6XX lines the output of the third would drive the ~WR line of the MAX506.

 

2 IC's....No resistors or capacitors!

[Rybags]

Before I proceed any further, some questions:

 

1. I'm using 74HC series IC's (that's all they had). Are they OK?

 

2. Is the output from D7XX (pin 9 of U2) active low?

 

3. For the audio output itself: I assume the output from each resistor array then just goes through individual 100nF capacitors? And, the ground for the audio can just be common to that which the ICs use?

[rdhays82604]

Before I proceed any further, some questions:

 

1. I'm using 74HC series IC's (that's all they had). Are they OK?

 

2. Is the output from D7XX (pin 9 of U2) active low?

 

3. For the audio output itself: I assume the output from each resistor array then just goes through individual 100nF capacitors? And, the ground for the audio can just be common to that which the ICs use?

 

 

1. The HC stands for High Speed CMOS. Function for function and pin for pin they are the same.

2. Yes, all DXXX lines are active low.

3. Yes, I assume the same.

Edited December 15, 2007 by rdhays82604