ES_SMPREG_VOL_ADC
snd_es1371_src_write(ensoniq, ES_SMPREG_VOL_ADC, 1 << 12);
snd_es1371_src_write(ensoniq, ES_SMPREG_VOL_ADC + 1, 1 << 12);
snd_es1371_src_write(ensoniq, ES_SMPREG_VOL_ADC, n << 8);
snd_es1371_src_write(ensoniq, ES_SMPREG_VOL_ADC + 1, n << 8);