modulated echo

Algorithm development and general DSP issues

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Joined: Tue Apr 13, 2010 5:28 am
Location: plymouth uk

modulated echo

Post by patb » Sun Feb 05, 2017 3:42 am

I'm sure I heard someone else using this sound somewhere !

It takes a mono right ADC input, stereo out.
Mod speed is preset, and pot1 sets mod depth.
Due to lack of pots the echo output level pot2 has 2 ranges,
one with almost no feedback and one with alot of feedback.

Best sound is 400ms or so delay with full modulation,
or with no mod as a plain echo.

;modulated echo program
;mono right adc input, two channel out
;pot0=delay time
;pot1=modulation depth
;pot2=echo level, with 2 preset feedback levels

mem delay 32767 ;1s delay block
equ feedback reg0
equ delay_time reg1
equ input_store reg2
equ level reg3
equ echo_out_r reg4
equ right_delay reg5
equ echotype reg6
equ mod_depth reg7
equ tri_original reg8
equ tri_amp reg9
equ tri_gain 0.017 ; max triangle amplitude
; now generate ramp LFO
skp run,start
wldr 0,12,4096 ; modulation LFO
; modulation
sof 0,0.004 ; preset modulation speed
wrax rmp0_rate,0 ; store

rdax pot1,1 ; mod depth pot1
wrax mod_depth,0
cho rdal,rmp0 ; 0 - 0.5 ramp
sof 1,-0.25
absa ; 0 - 0.25 triangle wave
mulx mod_depth ; mod amplitude
wrax tri_original,tri_gain ; triangle
wrax tri_amp,0
;delay time pot
rdax pot0,1 ;delay pot
and %01111110_00000000_00000000
sof 1,0.05 ;40ms - 1s delay
wrax delay_time,1 ;
rdax tri_amp,1 ;add mod
wrax addr_ptr,0 ;store read addr_ptr
rmpa 1 ;delay signal
wrax right_delay,0 ;right delay signal

rdax pot2,1 ; pot2, -1 to +1
sof 1,-0.5
wrax echotype,1 ;
;echo level pot, feedback ;
sof 0,0.35
wrax feedback,0 ; preset feedback
rdax echotype,1 ;
skp gez,there
sof 0,0.05 ; less feedback
wrax feedback,0
rdax echotype,1
sof 1,0.5 ;
wrax echotype,0
rdax echotype,1
sof 1.999,0 ;2 level ranges, 0 to max
wrax level,0
rdax adcr,1 ;mono right channel
wrax input_store,0
rdax right_delay,1
wrax echo_out_r,1
mulx feedback ;feedback portion
rdax input_store,1 ;mix in input
wra delay,0 ;store input in dram
rdax echo_out_r,1
mulx level
rdax input_store,1 ;mix in original
wrax dacr,1 ;write right DAC and invert
wrax dacl,0 ;write left DAC

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