[Jack-Devel] Mic won't work when Jack PortAudio is turned on

Chris Caudle chris at chriscaudle.org
Mon Dec 25 19:31:42 CET 2017

On Wed, December 20, 2017 6:22 pm, Beagtroll wrote:
> I need your help, my mic won't work when Jack PortAudio is turned on.

I never saw a reply to this on list, so I will make a best guess (I do not
have jack running on Windows, only on Linux).

> I connected my mic to a Focusrite Saffire Pro 24 DSP and am working on
> windows 10, my microphone is connected to the first XLR input, and is
> working fine when Jack PortAudio is not activated.

You established that the hardware is working, so I think you only need to
understand how jack works and connect everything appropriately within the

> When I turn on Jack PortAudio however, it suddently doesn't register any
> sound anymore on the Widnows VU metres (playback devices)

How are you starting jack, directly from a command shell, or using another
tool like qjackcontrol?

Either way works, but there are implications for how you make changes to
the jack settings depending on whether you have to use the jack control
line applications, or you can use the graphical dialogs in qjackcontrol
(or other graphical software).

First a quick description of how jack works, since you may not understand
how and  why it is used:
jack is made to take exclusive control of your audio hardware so that you
can be sure it has the correct settings for audio production, and to
ensure that all connected applications are using the same settings (so for
example you will not have one application starting and trying to make
changes to the settings which conflict with another previously started

Once jack is controlling the audio hardware, it then acts like an
electronic equivalent of a patchbay, so that no audio goes in and out of
the sound card until you make connections from jack to the applications
you want to use.

I think the reason that you no longer see any indication of audio in the
windows control application is because that application no longer has
control of the sound card, jack does, and you have not made any
connections within jack to an application which can display the level of
the incoming audio.

> is that I can't change the sample rate anymore of my mic, the Advanced tab
> is gone after I started JackPort Audio.

Correct, the sample rate is controlled strictly by how jack was configured
when started, and cannot be changed at run time.  You must stop jack and
restart it with a different sample rate if you want to record at a
different sample rate for some reason.

> I have provided you with a Imgur link to the pictures with the description
> under the pictures.

Since I am not running the Windows build at this point someone with jack
on Windows experience will need to comment on the easiest way to make the
connections between Jack applications.  From what I understand, many
Windows users are not actually using jack aware software but are just
using jack as a way to route audio between multiple ASIO aware
applications.  I think the same requirement applies, you have to have a
way to inform the jack server which applications you want connected
together, and which you want connected to the hardware interface.  On
linux there are applications named jack_lsp and jack_connect which can be
used to list ports and connect ports together, respectively, but I
typically use a graphical application called qjackcontrol which has a
graphical patch style connection display.  I think qjackcontrol can run on
Windows, but I am not positive, but there may be some other application
more commonly used on Windows.

Chris Caudle

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