Master channel stops sending signals (due to Plug-in?)

Hey there!

I encounter a problem with my Ardour 2.8.1 (5337) on a AMD Athlon 64 with M-Audio Audiophile 24/96.

At a certain point in my song, the master channel simply stops sending a signal. Always first on the right channel and some seconds later on the left one. Every other channel still has the meter working but the master channel is dead by means of meter and sound coming out.

On the other channels there’s at least the meter working but when I plug on of those directly to the output of my soundcard (through JACK) there’s no sound either so more or less Ardour simply stops singing my melody and is just whistling unheard air :slight_smile:

Obviously this started to happen after I created a Gain automation for a Valve Rectifier (LADSPA). May it be that simply Ardour doesn’t like this plug-in and I have to search for another one? Or may there be another explanation.

CPU is at 99% (it’s always there) and DSP at around 20 - 30%…

Thanks for any advice, tips and help!!!

My understanding is that it isn’t a LADSPA vs LV2 problem per se but depends on the algorithms used, denormal handling and such. And the TAP plugins have had problems with that, but I think the 0.7.1 release has fixed most of it.

As for SWH-LV2 at least the triple parametric EQ is buggy whereas the LADSPA version works fine (after you set every frequency slider above zero)

Do LV2 plugins suffer from the same problems? Would it be worth trying the LV2 version of a plugin? The SWH-plugins (from wich the Valve Rectifier is) are also available in LV2 format.


Yes, try to look the plugin way. I had somehow a similar issue with a plugin that caused a click and muted output until restarting Ardour. Changed the plugin (with other things), and no more issue since.

I didn’t know what caused this at first, but someone on IRC helped me understand the problem and trace the cause to that plugin.


There are plugins with known issues. Unfortunately there isn’t much Ardour can do about those plugins. The best thing to do when you find one is just not use it.


I was having problems using the TAP equalizer (loud “crackling” with multiple tracks muted; pops and clicks; high CPU usage) until I installed the latest TAP plugin source, replacing the deb packages that were installed. For what it is worth…

Just to let you know:
Changing (in fact: deleting - too many Plug-Ins is never too good anyway I think) the Plug-In stopped the problem…

i use ubuntu on amd64 with ardour and the TAP plugins did not work. some months ago i recompiled them and got them working by switching a compiler option and mailed it to tom who gave me another solution. here is a part of a mail with tom szilagyi:

Hi Steve,

could you achieve the same effect by simply adding
-fno-strict-aliasing to the GCC options, instead of the above?

I would be interested in the simplest solution. :slight_smile:

So I would just change one line in the Makefile to:
CFLAGS = -I. -O3 -Wall -fomit-frame-pointer
-fstrength-reduce -funroll-loops -ffast-math -fno-strict-aliasing -c

(I just added -fno-strict-aliasing to the end of the -f* list)

Could you confirm if this works the same as your solution?


this helped me and i work a lot with these plugins as they have a parametric equalizer.

i have similar problems with the holap plugins (exciter !!) on ardour - they still don’t work in ardour but in jackrack as i detected now. so for any non-working ardour plugin start jackrack and insert it into the main channel of your mixer, connecting your outs/ins to jackrack, then load the desired plugins into jackrack and test them.

best wishes,


i found out, how you can use the holap exciter in ardour, which was not possible yet. i think the problem is, that the runexiter() method is used for LADSPA and DSSI.

in src/exciter.c, in the runexciter(…) method, just comment these code lines in 312, 313 with “//” :

// memset (exc->efxoutl, 0, sizeof (LADSPA_Data) * sample_count);
// memset (exc->efxoutr, 0, sizeof (LADSPA_Data) * sample_count);

as this is used in DSSI and LADSPA i guess that DSSI is not affected by nulling the output. LADSPA doesn’t like it anyway.