Table of Contents
Yoga AD-100
The chip is from C-Media and appears to be the CM102A. You can download the Technical Brief or Data Sheet.
I picked up a Yoga AD-100 Virtual 5.1 Channel USB Adapter from Jaycar. It's a standard USB-Audio chip (0x0d8c/0x0001) running at 12Mbps with a stereo audio socket. It has a reasonably beefy ampliier on-chip, at maximum volume it can over-drive headphones easily, and put out a respectable volume from a pair of small un-powered speakers. A switch on the side triggers a shutdown of the output stage of the chip, leaving the USB interface and decoder running.
Using my power monitoring board, I measured the current draw of the AD-100. Plugged in to USB, but with the switch off it draws 12mA. With the switch on it jumps to 49mA, but that includes the blue LED. Plugging in a pair of amplified speakers has no effect of power use, while a pair of 8ohm 2 Watt unpowered speakers takes it to 55mA to 80mA, depending on what music is playing.
It appears the onboard 0.5 Watt amplifier is good enough for smaller speakers. For volumes above what it's able to drive, a good amp will give much better sound than most amplified PC speakers.
C-Media blurb
CM102A/CM102S USB Audio Controller
Features
- USB v2.0 full speed operatible.
- Fully compliant with USB audio device class specification v2.0
- USB bus powered 500mA operation with suspend mode support
- Single 12MHz crystal input with on-chip PLL and embedded USB transceiver
- USB audio function topology has 1 input terminal, 1 output terminal, and 1 feature unit
- Alternate zero bandwidth setting for releasing bandwidth on USB bus during inactive operation
- Isochronous transfer using adaptive synchronization with internal PLL
- High performance 48KHz sampling rate for audio playback
- Embedded high performance 16 bit audio DAC
- Embedded class AB power amplifier for speaker driving and enable/disable control pin
- Volume control input with simple external VR circuit
- Embedded power on reset block
- Single 5V external power supply with internal power regulation
- 3.3V IO with 5V tolerance; 3.3V core logics design
- Compatible with Win98 SE / Win ME / Win 2000 / Win XP, and Mac OS 9 / OS X without additional driver
- 18 pin PDIP (CM102)or SOP (CM102S) package
Kernel messages
usb 3-1: new full speed USB device using ohci_hcd and address 4 usbaudio: device 4 audiocontrol interface 0 has 0 input and 1 output AudioStreaming interfaces usbaudio: valid output sample rate 48000 usbaudio: device 4 interface 1 altsetting 1: format 0x80000010 sratelo 48000 sratehi 48000 attributes 0x00 usbaudio: registered dsp 14,3 usbaudio: registered mixer 14,0
lsusb -v
Bus 003 Device 020: ID 0d8c:0001 C-Media Electronics, Inc.
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 1.10
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x0d8c C-Media Electronics, Inc.
idProduct 0x0001
bcdDevice 0.10
iManufacturer 1
iProduct 2
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 110
bNumInterfaces 2
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
MaxPower 500mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 1 Control Device
bInterfaceProtocol 0
iInterface 0
AudioControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 1 (HEADER)
bcdADC 1.00
wTotalLength 40
bInCollection 1
baInterfaceNr( 0) 1
AudioControl Interface Descriptor:
bLength 12
bDescriptorType 36
bDescriptorSubtype 2 (INPUT_TERMINAL)
bTerminalID 1
wTerminalType 0x0101 USB Streaming
bAssocTerminal 0
bNrChannels 2
wChannelConfig 0x0003
Left Front (L)
Right Front (R)
iChannelNames 0
iTerminal 0
AudioControl Interface Descriptor:
bLength 10
bDescriptorType 36
bDescriptorSubtype 6 (FEATURE_UNIT)
bUnitID 13
bSourceID 1
bControlSize 1
bmaControls( 0) 0x03
Mute
Volume
bmaControls( 1) 0x00
bmaControls( 2) 0x00
iFeature 0
AudioControl Interface Descriptor:
bLength 9
bDescriptorType 36
bDescriptorSubtype 3 (OUTPUT_TERMINAL)
bTerminalID 3
wTerminalType 0x0301 Speaker
bAssocTerminal 0
bSourceID 13
iTerminal 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 0
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 0
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 1
bNumEndpoints 1
bInterfaceClass 1 Audio
bInterfaceSubClass 2 Streaming
bInterfaceProtocol 0
iInterface 0
AudioStreaming Interface Descriptor:
bLength 7
bDescriptorType 36
bDescriptorSubtype 1 (AS_GENERAL)
bTerminalLink 1
bDelay 1 frames
wFormatTag 1 PCM
AudioStreaming Interface Descriptor:
bLength 11
bDescriptorType 36
bDescriptorSubtype 2 (FORMAT_TYPE)
bFormatType 1 (FORMAT_TYPE_I)
bNrChannels 2
bSubframeSize 2
bBitResolution 16
bSamFreqType 1 Discrete
tSamFreq[ 0] 48000
Endpoint Descriptor:
bLength 9
bDescriptorType 5
bEndpointAddress 0x06 EP 6 OUT
bmAttributes 9
Transfer Type Isochronous
Synch Type Adaptive
Usage Type Data
wMaxPacketSize 0x00c0 1x 192 bytes
bInterval 1
bRefresh 0
bSynchAddress 0
AudioControl Endpoint Descriptor:
bLength 7
bDescriptorType 37
bDescriptorSubtype 1 (EP_GENERAL)
bmAttributes 0x00
bLockDelayUnits 0 Undefined
wLockDelay 0 Undefined
