jack input has huge gain

[AAA]

Distro: manjaro
Jack2 started with cadence
Soundcard: M-audio fast track pro

Even at the lowest gain on the soundcard, the microphone clips hard with any sound. If I sing at this lowest level, it's obvious that audacity is getting only a handful of bits of depth. It almost looks like the signal is shifted to the left 8 bits or something.

I'm positive this isn't the result of underruns. Everything sounds "fine" - just with the bit depth weirdness - it just has lots of digital gain it shouldn't have. Audacity is recording in 32bit float, so I think jack is already getting that bit shifted and clipped signal from something at a lower level.

This is probably not enough information, so feel free to ask for more.

[Luc]

I see the M-Audio Fast Track Pro has pads. Have you tried using them?

[AAA]

I tried all four combinations of Ins/Line and Pad on/off.

[AAA]

This morning I even got the opposite problem after booting up: I now clip only at full gain on my audio interface, but the bit crush effect is even worse. So now it looks like the audio is doing something like discarding the least significant byte and then shift to the right a bunch of bits? I have no idea anymore.

[CrocoDuck]

What are the levels set in alsamixer?

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alsamixer

[AAA]

In alsamixer, after selecting my audio interface, I get:

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│                This sound device does not have any controls.                 │

[CrocoDuck]

Uhm... pretty tricky to troubleshoot I would say. Let's start by looking at what kernel modules are involved with your soundcard. Bootup your system with the card disconnected, open a terminal and type

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dmesg -wH

Then, connect your soundcard and copy and paste here the lines that are added to the log.

[AAA]

I'll do that as soon as I do another install. dd'd the wrong partition trying to burn an usb drive, haha.

[CrocoDuck]

I'll do that as soon as I do another install. dd'd the wrong partition trying to burn an usb drive, haha.

OH NO!!!

[AAA]

Here is what I get:

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[ +21.242584] usb 2-1.5: new full-speed USB device number 4 using ehci-pci
[  +0.719946] usb 2-1.5: Fast Track Pro switching to config #2
[  +0.000153] usbcore: registered new interface driver snd-usb-audio
[  +0.002111] usb 2-1.5: Fast Track Pro config OK

I'm from antergos now, but the problem is completely identical, and there shouldn't be too many differences from manjaro.

[CrocoDuck]

OK, looks legit at first sight. This is what happens when I plug my scarlett on my Arch Linux box:

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[24564.149904] usb 2-2: new high-speed USB device number 4 using xhci_hcd
[24565.291620] usbcore: registered new interface driver snd-usb-audio

In the past I had problems related to the kernel driver for USB. Not sure whether there is something wrong with ehci-pci, the driver that gave me troubles is ehci-hcd (see here).

Let's have a look at the kernel version:

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uname -a

And also ALSA version (should be the same as the kernel):

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cat /proc/asound/version

And since we are here, also the rest of the hardware:

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lspci -vnn

[AAA]

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[inventory@magazzino ~]$ uname -a
Linux magazzino 4.12.10-1-ARCH #1 SMP PREEMPT Wed Aug 30 12:18:42 CEST 2017 x86_64 GNU/Linux

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[inventory@magazzino ~]$ cat /proc/asound/version
Advanced Linux Sound Architecture Driver Version k4.12.10-1-ARCH.

Since I'm not sure how I need to run this, and I see lots of access denied...
lscpi from user: https://pastebin.com/raw/Z4Le1yap
lscpi from root: https://pastebin.com/raw/JbmeTYwa

I also saw some Xeon in there. I assume the motherboard supports both, but I'm running on an i7 3700.

[CrocoDuck]

OK, this is good info. I see you actually have an USB controller served by xhci_pci:

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00:14.0 USB controller [0c03]: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller [8086:1e31] (rev 04) (prog-if 30 [XHCI])
	Subsystem: ASUSTeK Computer Inc. P8 series motherboard [1043:84ca]
	Flags: bus master, medium devsel, latency 0, IRQ 26
	Memory at f7120000 (64-bit, non-prefetchable) [size=64K]
	Capabilities: [70] Power Management version 2
	Capabilities: [80] MSI: Enable+ Count=1/8 Maskable- 64bit+
	Kernel driver in use: xhci_hcd
	Kernel modules: xhci_pci

Not all USB ports on a computer are equal, as they are routed through different hubs and controllers. Sometimes quirky things happen. For example, I had a soundcard malfunctioning when using the USB connectors on the front of my desktop. It turned out that the wires that connect them to the motherboard dropped too much voltage and the soundcard was not powered up properly. Recently at work we had a data acquisition piece of hardware malfunctioning on Windows. It started working alright when connected to the USB through a passive external hub... go figure... I think it was related to the USB 2.0 retro-compatibility of the motherboard 3.0 controller chips...

As such, I would be curious to see whether something changes by plugging your device in a port served by the xHCI controller. Not sure how to locate it. Perhaps, it is easiest to test if the same problem happens on all USB ports, if you didn't already.

[AAA]

I'm still here, I just have been busy with some great news: I got my university of choice! yes!!!
I'll update this thread with results from both all my desktop ports, and if I can find an old laptop I used, I'll see if it's different there in manjaro, and if it isn't, I'll install a couple other distros there so we can diff and maybe even binary search through the versions of everything if we can get it working!

In the meantime, since I haven't told you yet, thanks! You have been incredibly helpful.

[AAA]

I cannot believe this... it was the usb port!!! The front works 100% correctly! I would have never ever thought of this. Two weeks later and I can record again!!!

Tesi di Laurea: Sintesi digitale di suoni: il metodo della trasformata funzionale (in Italian).

(For the English speakers: nothing important is said here. Just ramblings about audio synthesis and me also being Italian)
Wow, chi l'avrebbe mai detto? Ci credi se ti dico che un progetto che spero di riuscire a fare prima o poi e' un sintetizzatore orchestrale basato sul modelling fisico (piu' o meno, e "barando" un po') e non sul campionamento? Ho un conservatorio relativamente vicino, e conosco alcuni professori, quindi dovrei anche avere le cavie per sperimentare i modelli.