Tropez Hard Hack
or
Tropez Customization
(Does it sound better ?)


Intro

Ok folks,

My intention here is to try to improve the "usability" of the Tropez in a home studio recording environment. Although it is a multimedia/game card, I believe its sound quality, especially the Wavefront synthesizer's, and its flexibility deserve to be improved (read : I love this card !). Of course, standard disclaimers apply, summerized by "if you fry your card/computer etc ... after reading this note, please don't blame me !"

Also, I worked out this hack relying exclusively on technical documentations available on the Net, on semiconductor manufacturers' pages, or their Faxbacks which # were also indicated on the Net. Based on those documentations, I just followed the "wires" (look Mom, no magnifying glass !) ...

The following still has to be considered as a preliminary note and I encourage (almost beg) anyone to reach me to comment, criticize, share infos and experience etc ... I am not an engeneer in electronics, I can just solder (and follow) wires ...! And if someone thinks I'm doing something illegal by letting public an almost reverse engeneered info, please let me know too !


'Nuff said, let's go !

To start with, I assume a home studio is equipped with at least a decent mixer console. The "hacktomization" I am proposing here is from the musician's point of view and is basically to provide separate outputs for the FM synthesizer, the Wavefront synthesizer and the digital audio signals that is, from the current situation :


            #########              
 MIDI ----->#ONBOARD#              
  AUX -----># CODEC #----> COMMON  
 LINE ----->#   +   #      OUTPUT  
 WAVE -----># MIXER #              
            #########
Fig. 1: Initial status.



obtain something like :


WF SYN -------------------> SEPARATE
FM SYN -------------------> OUTPUTS 
             #########              
  MIDI -/ /->#ONBOARD#              
   AUX -----># CODEC #----> COMMON  
  LINE ----->#   +   #      OUTPUT  
  WAVE -----># MIXER #              
             #########
Fig. 2: Target status.



Once the outputs for WAVE, FM and WF synthesizers are separated, outboard FXs can be applied individually etc, etc ... By the way, forget about connecting a CD audio internally to the card (in which case it replaces the AUX input). There's simply no way to get rid of the interference noise generated by the mouse & the video board. I gave up and sent the cables to the external Mixer Console instead.

If I take the block diagram in Fig. 1 and further expand it, things become horrible :


WF SYN ==> WF DAC --+    OP                                       
                    |--> AMP --+   ###################            
FM SYN ==> FM DAC --+          |   #  AUX2           #            
                               +-->#---------->--+   #            
                                   #  AUX1       |   #            
   AUX --------------------------->#---------->--+   #            
                                   #             |-->#----> COMMON
  LINE --------------------------->#---------->--+   #      OUTPUT
                                   #             |   #            
  WAVE ===========================>#==> DAC -->--+   #            
                                   #                 #            
                                   ###################            
                                   ONBOARD CODEC+MIXER
Fig. 3: More detailed initial status.



Where "==>" represents the digital audio data path, whereas "-->" indicates the analog audio path. "DAC" stands for "Digital to Analog converter" and "OP AMP" for "Operational Amplifier". Note that in the CS4231A (codec/mixer chip) datasheet, AUX and MIDI inputs are referenced as AUX1 and AUX2, respectively. The horror is not the increase in complexity but more the following fact : it seems like the only way to provide both FM and WF sounds was to let the analog audio travel a long way through a hostile noisy environment before it meets the mixer. Even uglier, the FM and WF signals are merely added (almost short-cut !) right before the OP AMP. I hope this schematic explains at least partly why the sound quality between a samplestored file and the original sample file is so different (now I wonder whether muting the FM synth wouldn't help improving the WF synth's sound quality ... but hey, I like FM synthesis for what it is : sound synthesis, not sound mimetics !).

Anyway, the most straightforward way to separate the outputs would consist in bypassing the OP AMP and muting the "MIDI" in the mixer app, i.e :


WF SYN ==> WF DAC --------> SEPARATE
FM SYN ==> FM DAC --------> OUTPUTS 

             #########              
  MIDI -/ /->#ONBOARD#              
   AUX -----># CODEC #----> COMMON  
  LINE ----->#   +   #      OUTPUT  
  WAVE -----># MIXER #              
             #########
Fig. 4: Fast option.



This however doesn't guarantee a noiseless wiring to the outboard mixer console, but it DOES provide separate outs. Suggestions are welcome here to discuss about how to achieve this "FAST" option, the actual wiring, components to add to prevent frying either the DAC or the OP AMP after addition of the wires etc...

If travelling the analog signals inside the computer is a problem, just keep them as digital signals and convert them outside :


##################                               
                 #                               
WF SYN ==========#=====> WF DAC -------->  MIXER 
FM SYN ==========#=====> FM DAC --------> CONSOLE
                 #                               
##################                               

INSIDE THE COMPUTER          OUTSIDE THE COMPUTER
Fig. 5: Analog option.



This option requires to get the respective DACs and pull out three to four wires from the WF and FM chips plus supplying +5V to the DACs. In the case of the YAMAHA YMF262 FM chip, the DAC used on the Tropez is YAMAHA YAC512; for the ICS2115 Wavefront chip, the DAC can be either NEC µDP6376 (actually used on the Tropez), or Phillips TDA1310/1545.

Even more challenging is to keep the digital outs from above as digital outs. The problem is, unlike the SB AWE32, the WF and FM chips' digital outs are not directly compatible with the S/P DIF (or AES/EBU) formats. In order to stay in a usable digital domain, a so-called "Digital Audio Interface Transmitter" is required : 


##################                               
                 #                               
WF SYN ==========#=====> DAIT ========>  DIGITAL 
FM SYN ==========#=====> DAIT ========> EQUIPMENT
                 #                               
##################                               
INSIDE THE COMPUTER          OUTSIDE THE COMPUTER
Fig. 6: Digital option.



Where "DIGITAL EQUIPMENT" can be anything with S/P DIF or AES/EBU ins, including a soundcard with digital I/O (now, you can TRUELY convert MIDI to WAV !). Crystal Semiconductor's CS8402A seems to be a good candidate for performing the digital transmission. FYI, Digital Audio Lab's Digital I/O for the CardD+ is using its cousin, the CS8401A.

Note that the last two options might be a solution for RIO dughterboard owners, if the famous "whine" is really due to its presence inside the computer and the fact that the analog path to the mixer is too long and noisy.


Temporary conclusion

I must reiterate here : I am not an engeneer. Everything written here are logical deductions based on cross references between datasheets and actual "soldering" of the card. For the time being, take it as a concept, not as hard core reality, not yet. If it gave you some nice idea, then I'm more than happy. If it helps you better using the card as it is, same. The best thing you can do is to discuss this with more competent people (more competent than I, that is), and give me feedbacks.

Now, I'd really appreciate if someone could help me with the following:

I still didn't manage to get the tech sheet for NEC D6376 (or µDP6376).

I'll gradually try to sketch out an overall "logical diagram" to further understand how this pretty card works.


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