testing a new QRQ CW Wave Shape - "THE PULLED BOW"

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Comment by Chuck aa0hw on July 2, 2022 at 12:05pm

Here is a LIVE DEMO of this wave form being used to convert a K1EL K40 harsh square wave to the pure sine wave 'pulled bow' wave shape


audio output from K40 CW Keyer is connected to a usb sound card/raspberry pi4 LINE INPUT, by an audio cable(with an internal isolation transformer)

the K40's incoming audio is quite harsh & raspy/square wave, with no edge shaping...

to convert it to a PURE SINE WAVE CW note with shaped edges...it uses two audio plugins

1st is TRIGGER MIDI MONO an audio to midi CW keying data APP

2nd is the KXstudio's FREE Cardinal Synthesizer which creates a software pure sine wave/shaped CPO using the Cardinal Synthesizer's native modules

for more info on 'THE PULLED BOW' cw wave shape see previous video here: https://youtu.be/o6vGBENl2lE

one of the K40's memories was repeated multiple times to provide the 'keying' for this demo

Comment by Chuck aa0hw on July 4, 2022 at 1:10pm

Here is a TWIN-T hardware sine wave oscillator circuit with a 'PULLED BOW' CW wave shape,  being keyed by FLdigi's RTS PIN  - SERIAL PORT KEYING -  feature

TWIN-T circuit has two steering diodes for adjusting the keying RISE/fall time with two of its variable resistor pots

there is a 10k resistor at the TWIN-T OSC's audio output port, where a final PARALLEL LC bandpass filter is placed before going to the laptop's screen recorder's audio input

    about 1 uF in parallel with a 75 mH ferrite rod coil winding

Comment by Chuck aa0hw on July 5, 2022 at 9:46am

Build an adjustable SINE WAVE midi keyed 'shaped' CPO with a tracking bandpass filter using CARDINAL

demo of using the FREE CARDINAL MODULAR SYNTHESIZER to build your own 'midi keyed' code practice sine wave oscillator with sine shaped edges



https://github.com/DISTRHO/Cardinal AUDIO to MIDI app(if direct midi is not being used to key CARDINAL) TRIGGER MIDI MONO https://lsp-plug.in/?page=manuals&section=trigger_midi_mono

in this DEMO, the audio output of FLdigi was sent to the audio input of TRIGGER MIDI MONO and the MIDI NOTEs were varied to change the CW PITCH

NOTE: there is a fine tuning pitch adjustment on the CARDINAL VCO module

NOTE: HOST MIDI's V/oct output wired up to both the VCO and VCF V/oct inputs, enable the audio bandpass filter to track the oscillator pitch and keep it centered in the bandpass width set by the settings on VCF's filter controls(RES/bw & SLOPE

Comment by Chuck aa0hw on August 4, 2022 at 7:38am

another example of the PULLED BOW QRQ CW wave shape that is created by the input FX SONOBUS EQ 

brief demo of the effect of the SONOBUS input FX PARAMETRIC EQ on the original wave shape of a keyed TWIN-T CPO, that has independent RISE/FALL time adjustments where it is adjusted to have 1 to 2 milliseconds of extra fall time to create a PULLED BOW looking waveshape



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