Thinkpads Forum

Does the headphone jack autoswitch to S/PDIF without the dock? Ubuntu shows a 'AD198x Digital' option in 'Sound Playback'. I understand it's an undocumented feature on alot of laptops. I've got the proper cable from another laptop where that's how it worked, but now I have no way to try it. I would rather get a 20-bit capable DAC than settle for 16-bit with a USB adapter. ie., I want one of these: http://www.firestone-audio.com/cgi-bin/ ... pdtseqnm=4 without having to buy one of these: http://www.trendsaudio.com/EN/Product/U ... o_desc.htm
Thanks for any input.

This just means the chipset supports SPDIF, which is the case quite often. But often the manufacturers don't use this option of the chipset , so you don't have a place were you can connect your cable.

brnf wrote:This just means the chipset supports SPDIF, which is the case quite often. But often the manufacturers don't use this option of the chipset , so you don't have a place were you can connect your cable.

But with a dock, Lenovo does support the option. I am just wondering if anyone had tried it without a dock. Also, other ThinkPads do support this function through the headphone jack.

Why not take the cable from the other laptop and try it. My friend has a Asus Z70va that has a plug that self swtiches to S/PDIF so it's not impossible.

"other": USB to custom DIY TI PCM2702 USB/SPDIF output, transformer coupled, with 75 Ohm BNC cable to a custom modified DAC to impedance match the 75 Ohm line with another transformer and an inverter.
With a dock, i'd still use this option since nobody cares about using correct interfaces to avoid reflections...

tebore wrote:Why not take the cable from the other laptop and try it.

Because I don't have anything to plug it into, so my question was posted here. If I had something to plug it into, why on earth would I ask here? I'm deciding if, or what to order...

Troels wrote:"other": USB to custom DIY TI PCM2702 USB/SPDIF output, transformer coupled, with 75 Ohm BNC cable to a custom modified DAC to impedance match the 75 Ohm line with another transformer and an inverter.
With a dock, i'd still use this option since nobody cares about using correct interfaces to avoid reflections...

Where is more info. on building something like this? Doesn't using USB mean limited resolution? I was considering FireWire thru the ExpressCard slot, but would rather use the slot for an SSD. I want something portable for when I'm on the road.

Why do you want this feature if you have nothing to plug it into?
Also, note that Dolby Digital has a maximum bit rate of 640 kbit/s for a Blu-ray disc and the usb 2.0 interface is capable of around 480 Mbit/s, I think you should be alright with a usb-based solution for sound processing. Although really, if you're looking to hook this up to a home theatre system, you'd be best served by a docking station anyway since you could disconnect and reconnect it easily.
I don't think using USB necessarily means limited resolution... I think that resolution is determined by the quality of the DAC chip on the sound processor. It may be true that they don't make high resolution DAC's for the USB interface due to a lack of demand on the market, but I don't think it's due to the USB interface being starved for bandwidth.

Mr. The Guy wrote:Where is more info. on building something like this? Doesn't using USB mean limited resolution? I was considering FireWire thru the ExpressCard slot, but would rather use the slot for an SSD. I want something portable for when I'm on the road.

Well.. the PCM290X datasheets give some good, decent standard configurations... and there are some dicussions in http://www.head-fi.org/forums/showthread.php?t=105088.

For on the road, i'd really recommend the PCM2702, which has analog output only and no SPDIF. The PCM290X has both, but it's analog performance has been toned down a bit.
That being said, SPDIF requires transmission lines with no reflection to be 100% perfect. Funnily using RCAs and no input coupling is the first mistake and is always done in order to save some money.

On USB 1.1 the bandwidth was severely limited, and wouldn't allow more than ~16 Bit / 48 kHz SR. Good enough, but the market newer grew because multichannel audio is what sells.