[SOLVED] Samson XPD2-insanely low volume/gain/too attenuated

[verahill]

In these Corona-times, in some countries university lecturers are expected to both teach on-campus and on-line simultaneously. To deal with this I purchased a samson XPD2 lav mic set-up: http://www.samsontech.com/samson/produc ... s/xpd2lav/

If you follow the link, you'll see that it's a 2.4 GHz wireless audio mic with a usb dongle. The usb dongle has a headphones output.

The problem: If I listen on the dongle using a pair of headphones the sound is fine -- loud and clear. On linux, however, the sounds is ridiculously muted even if I crank up the hardware gain on the PXD1 (the transmitter), and through software (pavucontrol and Gnome Sound). Everything is maxed out, but Audacity records a signal which is very, very weak. It seems to be excessively attenuated.

lsusb

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Bus 002 Device 023: ID 17a0:1616 Samson Technologies Corp

dmesg -T

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[Sun Aug 23 06:40:50 2020] usb 2-4: new full-speed USB device number 23 using xhci_hcd
[Sun Aug 23 06:40:50 2020] usb 2-4: New USB device found, idVendor=17a0, idProduct=1616, bcdDevice= 1.00
[Sun Aug 23 06:40:50 2020] usb 2-4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[Sun Aug 23 06:40:50 2020] usb 2-4: Product: Samson RXD wireless receiver
[Sun Aug 23 06:40:50 2020] usb 2-4: Manufacturer: Samson Technologies
[Sun Aug 23 06:40:50 2020] usb 2-4: Warning! Unlikely big volume range (=496), cval->res is probably wrong.
[Sun Aug 23 06:40:50 2020] usb 2-4: [50] FU [Mic Capture Volume] ch = 1, val = 0/7936/16
[Sun Aug 23 06:40:50 2020] input: Samson Technologies Samson RXD wireless receiver as /devices/pci0000:00/0000:00:14.0/usb2/2-4/2-4:1.2/0003:17A0:1616.0013/input/input59
[Sun Aug 23 06:40:50 2020] hid-generic 0003:17A0:1616.0013: input,hidraw6: USB HID v1.00 Device [Samson Technologies Samson RXD wireless receiver] on usb-0000:00:14.0-4/input2

I feel that

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[Sun Aug 23 06:40:50 2020] usb 2-4: Warning! Unlikely big volume range (=496), cval->res is probably wrong.
[Sun Aug 23 06:40:50 2020] usb 2-4: [50] FU [Mic Capture Volume] ch = 1, val = 0/7936/16

must be the key.

A similar issue is described here: https://bugzilla.redhat.com/show_bug.cgi?id=1070706 with especially this comment feeling 'right': https://bugzilla.redhat.com/show_bug.cgi?id=1070706#c4

pact list

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Card #13
	Name: alsa_card.usb-Samson_Technologies_Samson_RXD_wireless_receiver-00
	Driver: module-alsa-card.c
	Owner Module: 38
	Properties:
		alsa.card = "3"
		alsa.card_name = "Samson RXD wireless receiver"
		alsa.long_card_name = "Samson Technologies Samson RXD wireless receiver at usb-0000:00:14.0-4, full sp"
		alsa.driver_name = "snd_usb_audio"
		device.bus_path = "pci-0000:00:14.0-usb-0:4:1.0"
		sysfs.path = "/devices/pci0000:00/0000:00:14.0/usb2/2-4/2-4:1.0/sound/card3"
		udev.id = "usb-Samson_Technologies_Samson_RXD_wireless_receiver-00"
		device.bus = "usb"
		device.vendor.id = "17a0"
		device.vendor.name = "Samson Technologies Corp."
		device.product.id = "1616"
		device.product.name = "Samson RXD wireless receiver"
		device.serial = "Samson_Technologies_Samson_RXD_wireless_receiver"
		device.string = "3"
		device.description = "Samson RXD wireless receiver"
		module-udev-detect.discovered = "1"
		device.icon_name = "audio-card-usb"
	Profiles:
		input:analog-mono: Analog Mono Input (sinks: 0, sources: 1, priority: 7, available: yes)
		off: Off (sinks: 0, sources: 0, priority: 0, available: yes)
	Active Profile: input:analog-mono
	Ports:
		analog-input-mic: Microphone (priority: 8700, latency offset: 0 usec)
			Properties:
				device.icon_name = "audio-input-microphone"
			Part of profile(s): input:analog-mono

I /think/ this is the relevant bit from /var/lib/alsaasound.state

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state.receiver {
	control.1 {
		iface PCM
		name 'Capture Channel Map'
		value 0
		comment {
			access read
			type INTEGER
			count 1
			range '0 - 36'
		}
	}
	control.2 {
		iface MIXER
		name 'Mic Capture Switch'
		value true
		comment {
			access 'read write'
			type BOOLEAN
			count 1
		}
	}
	control.3 {
		iface MIXER
		name 'Mic Capture Volume'
		value 496
		comment {
			access 'read write'
			type INTEGER
			count 1
[b]			range '0 - 496'
			dbmin 0
			dbmax 3100[/b]
			dbvalue.0 3100
		}
	}
	control.4 {
		iface CARD
		name 'Keep Interface'
		value false
		comment {
			access 'read write'
			type BOOLEAN
			count 1
		}
	}
}

Sooo ... is there anything I as a mere mortal/user can do to fix this?

Edit:
forgot some key info:
I'm on Deb 10/Buster, running with Linux indium 5.4.0-0.bpo.4-amd64 #1 SMP Debian 5.4.19-1~bpo10+1 (2020-03-09) x86_64 GNU/Linux

[Head_on_a_Stick]

I'm on Deb 10/Buster, running with Linux indium 5.4.0-0.bpo.4-amd64 #1 SMP Debian 5.4.19-1~bpo10+1 (2020-03-09) x86_64 GNU/Linux

Why are you using such an old kernel? You should install the linux-image-amd64 metapackage to keep it updated.

Do you still have this problem with the stock Debian buster kernel?

[verahill]

I wouldn't call a kernel released in April 2020 'old'. Given that buster is currently at 4.19, I don't think tracking the meta-package over the bpo would do much good.

Either way, I've also tried 5.7.0. Latest release is 5.8.1.

The issue is present on stock too.

[Head_on_a_Stick]

Well I have no idea how to change "cval->res" but it looks like this sort of thing is supposed to be covered by kernel quirks so it may be worth opening a bug report with the kernel developers.

[verahill]

Thanks, I'll have a look at that.

I think in the meantime I might open a new post in the multimedia section. I don't know if it's possible to set up a software pre-amp to boost the input (and whether this would simply cause the noise to go through the roof). I don't have a good handle on whether you can set up rules per-device for maximum boost (e.g. norm* instead of 1.5 which seems to be the case right now).

[verahill]

The 'solution' for now is quite simple, and while terminal-centric, it works like a charm.

First, figure out what the index of your device is:

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pacm list-sources|egrep "name|index"

In my case, it was index 26

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    index: 26
	name: <alsa_input.usb-Samson_Technologies_Samson_RXD_wireless_receiver-00.analog-mono>
		alsa.name = "USB Audio"
		alsa.subdevice_name = "subdevice #0"
		alsa.card_name = "Samson RXD wireless receiver"
		alsa.long_card_name = "Samson Technologies Samson RXD wireless receiver at usb-0000:00:14.0-2, full sp"
		alsa.driver_name = "snd_usb_audio"
		device.vendor.name = "Samson Technologies Corp."
		device.product.name = "Samson RXD wireless receiver"
		device.profile.name = "analog-mono"
		alsa.mixer_name = "USB Mixer"
		device.icon_name = "audio-card-usb"

Then set the volume from the terminal:

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pactl set-sources-volume 26 270%

If you touch the settings in the GUI it'll come crashing down like a house of cards, but assuming that you can keep your fingers under control the problem with the low volume will now be gone.

I played around in audacity when I adjusted the boost, and 270% was optimal. I should also stress that /as far as I can see/ the dynamic range is absolutely fine.

I'll post an update here once I've sorted out how to make this change automatic whenever I plug in my device.

[Deb-fan]

Sounds like a udev rule is a good approach, stuff like https://linuxconfig.org/tutorial-on-how ... s-in-linux also its /lib/udev not /usr/lib/udev etc for default system file examples. At least is on the Stretch install i poked around in to check. Haven't ever learned much about using it but this type of thing is clearly what udev rules are intended for. Thanks for posting the fix you found too.

Ps, oops, yep you're already considering udev rules and yep, seems like just the thing for what you want. Anyway good luck, hopefully turns out quick n painless.

[Deb-fan]

How2 about this, http://forums.debian.net/viewtopic.php?f=16&t=147309

[verahill]

I agree -- udev is likely the most easiest way forward here, although I'll be exploring pulseaudio conf too. I'll be posting updates as I progress. For now the pactl means that sound is working fine for my students, and running a single command really isn't that much hassle for me either.

Secretly though, I want to change pulseaudio and/or gnome-settings so that it allows me to simply drag the boost up to 500% using the slider. I've already messed around with the pulseaudio src, but so far no luck. I'll get there one day though (and will report back)