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Adjusted volume level and added more documentation

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This commit is contained in:
Couriersud 2009-03-01 12:34:41 +00:00
parent 0a7a58fdde
commit a8a09bd084
1 changed files with 26 additions and 3 deletions
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29
src/mame/drivers/btime.c
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@ -1344,9 +1344,31 @@ static const discrete_mixer_desc btime_sound_mixer_desc =
/* R49 has 4.7k in schematics, but listed as 47k in bill of material
* 47k gives proper low pass filtering
*/
#define BTIME_R49 RES_K(47)
/* The input divider R51 R50 is not independant of R52, which
* also depends on ay internal resistance.
* FIXME: Develop proper model when I am retired.
*
* With R51 being 1K, the gain is way to high (23.5). Therefore R51
* is set to 5k, but this is a hack. With the modification,
* sound levels are in line with observations.
* FIXME: Verify R51,R50,R52 and R49 on real pcb
*
* http://www.coinopvideogames.com/videogames01.php
* There are two recordings from 1982 where the filtered sound is way louder
* than the music. There is a later recording
* http://www.coinopvideogames.com/videogames03.php
* in which the filtered sounds have volumes closer to the music.
*
*/
#define BTIME_R52 RES_K(1)
#define BTIME_R51 RES_K(5) /* schematics 1k */
#define BTIME_R50 RES_K(10)
static const discrete_op_amp_filt_info btime_opamp_desc =
{RES_K(1), 0, RES_K(10), 0, RES_K(47), CAP_U(0.068), CAP_U(0.068), 0, 0, 5.0, -5.0};
{BTIME_R51, 0, BTIME_R50, 0, BTIME_R49, CAP_U(0.068), CAP_U(0.068), 0, 0, 5.0, -5.0};
static DISCRETE_SOUND_START( btime_sound )
@ -1368,6 +1390,7 @@ static DISCRETE_SOUND_START( btime_sound )
DISCRETE_MIXER2(NODE_40, 1, NODE_22, NODE_30, &btime_sound_mixer_desc)
DISCRETE_CRFILTER(NODE_41, 1, NODE_40, RES_K(10), CAP_U(10))
/* Amplifier is upc1181H3
*
* http://www.mydarc.de/dj7oh/fad/ics/upc1181/upc1181.htm
@ -1379,9 +1402,9 @@ static DISCRETE_SOUND_START( btime_sound )
*/
/* Assuming a 4 Ohm impedance speaker */
DISCRETE_CRFILTER(NODE_42, 1, NODE_41, 3.0, CAP_U(100))
DISCRETE_CRFILTER(NODE_43, 1, NODE_41, 3.0, CAP_U(100))
DISCRETE_OUTPUT(NODE_42, 32767.0 / 5. * 20.0)
DISCRETE_OUTPUT(NODE_43, 32767.0 / 5. * 35.0)
DISCRETE_SOUND_END