Digital Scratch - set-up & Thanks

[Keith Wigmore]

Bonjour Julien Rosener & Cyril Coquilleau,

I would like to personally thank you (and the team/contributions) for the great price of software, and making it free under GNU GPL. It took a couple of weeks to get working – sound card issues, learning Linux (Ubuntu), JACK & making to know Digital Scratch. In the end I got it working with two turntables, where I am switching between vinyl and Digital Scratch (using the splitter set-up). Trying it live at weekend, doing a lockdown mix live on Mixcloud (mainly 80s and 90s house music)

My next lockdown project is getting it working on Raspberry PI ver 4 B (with two external sound cards).

I thought I would share my experiences setting up Digital Scratch, in case you wanted to share on your blog / user-group for others to follow / set up.

Thanks very much again :-)

Au Revoir

Keith Wigmore

---------------------------------------------------------------

a) Use Qjackctl, to run JACK (as suggested)

b) Added below to Qjackctl in Advanced, in Server Prefix. This will cause PulseAudio to suspend itself while JACK runs, and restart when JACK exits (or crashes)

/usr/bin/pasuspender – jackd

c) Also I stop auto spawing of the pulse audio

Autospawning can be disabled by setting "autospawn = no" in ~/.config/pulse/client.conf

d) Additionally, I used below before running Qjackctl

pulseaudio --kill (in terminal)

(maybe a little overkill in commands but I reached a working state so stayed with this setup)

e) Used “alsamixer” – this is great to change volume inputs / outputs on the sound cards, Found some ports were set to zero which caused in and out issues when running Digital Scratch. Also check that left and right channels are balanced

alsamixer (in terminal)

f) I had to use separate sound cards (for left and right turntables), but JACK/ Qjackctl only accepts one soundcard. Therefore I used:

alsa_in -d hw:X

alsa_out -d hw:Y

When Qjackctl/JACK is running, first use:

cat /proc/asound/cards (which lists all the sound cards)

then using alsa_in / alsa_out, and this adds the extra soundcards to the JACK and the connection window. I had three sound cards in my configuration in the end..!!!

(as in https://github.com/jackaudio/jackaudio.github.com/wiki/WalkThrough_User_AlsaInOut)

Additionally:

a) I use Audacity to test the input ports, and check levels. Of course test outputs too. Very good for fault finding.

b) Make sure the left and right are the connect way around, as the MP3 play in reverse in not :-) (this is because the left and right signals are 90 degrees out of phase on the timecoded vinyl)

c) Ensure the levels of the right and left are the same, otherwise Digital Scratch doesn't work

d) Soundblaster cards outputs do not normally work with linux (driver issue), which I found out by the long hard way. I used soundblaster as input from vinyl, but had to route to external USB for output (again Connect in Qjackctl will sort out for you)

e) No pre-amp need from turntable into soundcard.

[Julien Rosener]

Hi Keith,

Many thanks for your great comments !

> I thought I would share my experiences setting up Digital Scratch, in case you wanted to share on your blog / user-group for others to follow / set up.

Of course your experience would be an added value for other users: I will add it as a documentation page in the Wiki (https://github.com/jrosener/digitalscratch/wiki).

But I need to confirm something: is the procedure that you described dedicated for the Raspberry PI or is it for your (regular) computer (with 2 sound cards) ? In any case, to make the documentation page more precise, could you please tell me what is

- the version of the Linux distribution that you use with Digital-Scratch

- the model of your 2 sound cards

- the version of Digital-Scratch that you use (or maybe you build it from Git ?)

- the content of your ".jackdrc"

> e) Used “alsamixer” – this is great to change volume inputs / outputs on the sound cards, Found some ports were set to zero which caused in and out issues when running Digital Scratch. Also check that left and right channels are balance

I don't know if you know that you can automatically execute a shell script when Digital-Scratch is starting (c.f. "Settings" >> "Player" >> "External prog to run at startup"). One of the usage is to setup sound card volumes with "amixer", for example for my "USB Maya 44":

#!/bin/sh
echo "======= Configuring card 'USB' (MAYA44 USB+) for Digital-Scratch..."
amixer -c USB cset iface=MIXER,name='Master Playback Switch' on
amixer -c USB cset iface=MIXER,name='Master Playback Volume' 100%
amixer -c USB cset iface=MIXER,name='Line Playback Switch' off
amixer -c USB cset iface=MIXER,name='Line Playback Switch',index=1 off
amixer -c USB cset iface=MIXER,name='Line Playback Volume' 0%
amixer -c USB cset iface=MIXER,name='Line Playback Volume',index=1 0%
amixer -c USB cset iface=MIXER,name='Line Capture Switch' on
amixer -c USB cset iface=MIXER,name='Line Capture Volume' 100%
echo "======= Configuration done."

> Trying it live at weekend, doing a lockdown mix live on Mixcloud (mainly 80s and 90s house music)

May I ask you the link of this mix please ? It's always great to listen to mixes performed with Digital-Scratch :-)

Bests,

Julien.