More Schematics


Sorry people, but I am still waiting for infos about some chips. In the meantime some brave souls amongst you may try to build a pre-amp (or have a spare one in a drawer) and attempt what is described below, that is to grab the analog signals, amplify them in order to keep a decent S/N ratio before delivering the audio outs to the external mixer. Consider this to be a guide though, I have no specs to give as far as components go, please tell me if you do.
Keep in mind that althought it is not difficult, maximum care must be taken when performing this kind of customization, in order not to fry your computer or card or whatever. Although it seems unlikely to me, the implementation of components might differ from version to version, so check the connectivities first to make sure you are on the right signal path. For example, make sure the left out from one chip goes to the left in of the following one, after passing through OP AMP, resistors and more condensers...
If you haven't done so yet, read the preliminary notes and get the datasheets to make sure you know what you are doing and more importantly, to check whether I made any mistake. Also, getting help from friends in the electronics sphere would be a really, really good idea. From here on (actually, right from the beginning), the orientation of the card is assumed to be : audio I/Os on the right and ISA connectors at the bottom, electronics facing you.

The Wavefront Sub-Hack

You should know by now that NEC ÁDP6376 is the DAC for the Wavefront synth. The DAC is located to the right of the IDE connector. This is also where the OPL3 and its DAC, as well as the quad OP AMP C084 are clustered. I could work out the ÁDP6376 connections as follows:

       -|         |-       
       -|         |-       
   Lout-|         |-Rout   
       -|         |-       
  LRCLK-|         |-       
       -|         |-       
SERDATA-|         |-       

Fig. 1: ÁDP6376 pins.

You "just" have to draw some wires from the L and R outs to the ins of your pre-amp with as short paths as possible, probably shielded too. If you are luckier and have a DAC in your drawer (from a broken CD player), you may try to pick up the digital data (LRCLK, SERDATA and BCLK), send them out and DAC them outside the computer. It seems easier to me to derive the signals from here because there's more "room" to perform a modification than in the periphery of the WF chip itself. Discussions on how to concretely achieve either transfos much appreciated!

The FM Synth Sub-Hack

I'm aware that it sounds kind of "exotic" to try to improve the FM synth part, but it's nevertheless 24 more voices, isn't it ? And if it is separated, it can be passed through external gears to deepen/thicken uzw..., cook it. The dedicated DAC is called YAC512 and needs two external OP AMPs to trigger sampling/conversion. Here it goes:

    -|         |-    
    -|         |-    
 DIN-|         |-    
    -|         |-    
 CLK-|         |-    
    -|         |-CH2 
SMP1-|         |-CH1 

Fig. 2: YAC512 pins.

The audio signals CH1 and CH2 correspond (on my card) to right and left respectively. The maximum output amplitude is 2.5V according to the datasheet. There again, if you have a handy pre-amp, it should be straight forward. Less obvious might be the external DAC route. As you can see from the YAC's datasheet, it is not a standard format. So the only way to go is the YAC way, i.e. you can not choose your favourite DAC... Unless someone comes up with a brilliant idea !

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