tape flange

Algorithm development and general DSP issues

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patb
Posts: 7
Joined: Tue Apr 13, 2010 5:28 am
Location: plymouth uk

tape flange

Post by patb »

Hi,
this is my attempt at the seventies ish phase sound.
I think it works ok, but would be interested in any opinions
or improvements !
It's a bit unusual as the delay / effect signal is in
advance of the original.
Increasing the feedback_level towards 1.0 will create
quite a good ordinary flanger sound too ..... :D

;tape flanger program
;stereo input, mono delay, stereo out
;pot0=mod speed
;pot1=mod depth
;pot2=mix delay / dry
;
mem delay_fx 512 ;16ms delay for effect signal
mem delay_dry_r 256 ;8ms for dry signal
mem delay_dry_l 256
;
equ lp_filter reg1
equ delay_signal reg2
equ feedback_coeff reg3
equ feedback_level reg4
equ input_store reg5
equ crossfade0 reg6
equ crossfade1 reg7
equ faded_dry reg8
equ lp_coeff 0.7
;
; set up ramp lfo, ~0.5Hz:
skp run,loop
wldr 0,12,4096 ;ramp initialization
;
loop:
; crossfade pot
clr
rdax pot2,1 ;crossfade dry and delay
sof 1.2,0
wrax crossfade1,0
sof -1,0.8
sof 1,0.4
wrax crossfade0,0
;
; make variable amplitude triangle wave
cho rdal,rmp0 ;0 - 0.5 ramp
sof 1,-0.25
absa ;0 - 0.25 triangle wave
mulx pot1 ;pot2 for modulation amplitude
sof 0.004,0 ;triangle gain
sof 1,0.00685 ;add delay time
wrax addr_ptr,0 ;store read addr_ptr
;
; reduce feedback slightly with mod depth
rdax pot1,1 ;
sof 0.15,0.7 ;work out feedback coeff 0.7 - 0.85
wrax feedback_coeff,1
;
; set feedback levels
sof 0,0.1 ;feedback gain
wrax feedback_level,0
;
; mod speed pot
rdax pot0,1 ;speed pot
mulx pot0
sof 0.3, 0.02 ;range
wrax rmp0_rate,0 ;store
;
rdax adcr,1 ;mono right channel
wra delay_dry_r,1
wrax input_store,0
rdax adcl,1 ;add mono left
wra delay_dry_l,1
rdax input_store,1 ;mix l and r inputs
sof 0.5,0
wrax input_store,1
wra delay_fx,0 ;store all delays
;
rmpa -1 ;get delayed signal
mulx feedback_level
mulx feedback_coeff
wrax delay_signal,1
rdfx lp_filter,lp_coeff ;feedback filter routine
wrlx lp_filter,-1 ;low pass filter
rdax input_store,1 ;mix in input
wra delay_fx,0 ;store delayed in dram
;
rda delay_dry_r#,1 ;get delayed right dry signal
mulx crossfade0
wrax faded_dry,0
rmpa -1 ;get delayed signal
mulx crossfade1
rdax faded_dry,1 ;mix crossfaded dry and delay
wrax dacr,0 ;write right DAC and invert
;
rda delay_dry_l#,1 ;get delayed left dry signal
mulx crossfade0
wrax faded_dry,0
rmpa -1 ;get delayed signal
mulx crossfade1
rdax faded_dry,1 ;mix crossfaded dry and delay
wrax dacl, 0 ;write left DAC
;
peterv
Posts: 17
Joined: Fri Nov 20, 2009 3:43 am
Location: Netherlands
Contact:

Re: tape flange

Post by peterv »

This is great stuff!!

I recall this to be two reel-to-reel recorder set-up used at the Abbey road studios in that era. Myself I'm more in the guitarsound (Shadows) from that studio and therefore confused towards this flanging beeing only the reel-to-reel combo. Looking at your low freq's in more detail , to my pleasant supprise, are parameters included you would find also in Meazzi tape/disc gear with the emphasis on Wow& Flutter. If this is your intend? Then te 5Hz is possible too high and should be around 2-3.5 Hz pending device covered. In the modeling I did for this the contribution of W&F is < 4% of the delaytime of the echo device (head-head).


Peter
www.echotapper.nl
patb
Posts: 7
Joined: Tue Apr 13, 2010 5:28 am
Location: plymouth uk

tape flange

Post by patb »

Although I think the ROM flanger is probably better :D :D
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