elianda wrote:Maybe you could comment a bit on the stock configuration.
Did the carrier soundcard already sent the signal to Audio-In of the XR385 and did you have to cut those pins first?
Nope, these were not connected. That's why I made this 😀
Why do you utilize a separate amplifier?
I get the OPL signal from the DAC's sample&hold capacitors. You can't draw any current from them, so I use an op-amp as buffer amplifier. A card with a discrete OPL3 chip would not need this extra circuit.
Is it really so much cleaner, because the signal is probably AD converted / effects added / DA converted on the XR385 again?
No, the OPL3 signal does not improve at all! I meant to say it sounds cleaner with normal MIDI music. I got rid of the low-pass filter and amplifier, both which are unnecessary because the XR's DAC has an integrated buffer amp and anti-aliasing filter. I suppose the purpose of this circuit is to amplify the signal from 1V to 2V, but the filter around it attenuates high frequencies and only amplifies (read distorts) the bass. On the YMF card the signal is attenuated to about 1V again through a resistor, now that doesn't make any sense to me so I just connected it directly, leaving only one coupling cap and some resistors in place to remove the 2.5V DC offset.
So what are the DACs on the YMF card and what kind of ADC/DACs are used on the XR385?
The DACs on the YMF are integrated in the chip, so I have no idea. The XR's DAC/ADC is the AK4510 chip near the corner opposite the wave blaster header. If the YMF card had a discrete DAC I would have used the digital signals of course, if they were compatible.
What are your SYSEX command files for Audio-IN + effects setup for XR385 the OPLs new signal path?
Too many to list here, I wrote my own utility to set it up and configure all the various parameters. I'll post it here shortly.
To just pass the sound through, it's:
F0 43 10 49 01 00 00 01 F7 to enable the input
F0 43 10 4C 11 00 00 01 F7 to enable stereo mode
F0 43 10 4C 10 00 0B 7F F7 turns up the input volume for channel 0
F0 43 10 4C 10 01 0B 7F F7 turns up the input volume for channel 1
F0 43 10 4C 10 00 11 7F F7 turns up the dry level for channel 0
F0 43 10 4C 10 01 11 7F F7 turns up the dry level for channel 1
I found all the sysex messages at: http://www.studio4all.de/htmle/frameset090.html
How does your solution behave if the carrrier soundcard can be switched to route audio signals through the external wavetable board?
You mean adding a switch to bypass the XR385? That's just a matter of turning the XR385 volume down and the OPL volume up in the YMF719 configuration utility. Normally these are on the same mixer channel, I guess no one ever thought anyone would be using both at the same time. I connected the XR card to the CD input, so now both have a their own mixer channel.
Do you have any experience which soundcards can utilize the Audio-In functionality of the wavetable header efficiently? I think we tried to discuss this already somewhere else, but there was only very few information available. On the other hand this topic is quite interesting since it could allow after effects on a regular sound card output.
No, I never had one of these cards. I have never even seen one. Though surely these must exist, why else would the waveblaster header include audio input pins?
