In my previous post on USB Audio Output, I shared my experience developing my own USB filter as I was not happy with Elfidelity USB filter. The DIY USB filter is much simpler but resulted in sound quality (SQ) improvement, but it was not yet the ultimate SQ.
USB Audio Card
I was keen to try audiophile-grade USB card. I bought one from Europe (not JCAT) which uses Renesas / NEC µPD720201 controller. The break-in period is supposed to be up to 200 hours. It is still going through break-in (Audioquest DragonFly connected to USB port as the USB DAC) even though I am not hearing any more improvements.
Here is a quick summary of what I heard when using this USB card:
- very analog sound, no digital glares
- the sound has more body with intimate expression
- more enveloping sound with deeper soundstage but unfortunately the width shrunk a bit
- good vocal
- very low background noise; can hear more micro details without being digital
Listening to music is now more enjoyable. I think anyone using desktop computer as audio source should consider using a good USB regen + retimer card. Cost wise, it’s a fraction compared to buying stand-alone units like Innuos Phoenix (USD3.5k).
However, I don’t like the soundstage width being smaller now even though it is deeper. There are 2-channel recordings which the sound is supposed to come from behind our listening position. I am not getting that when using this USB card.
Updated DIY USB Filter
My DIY USB filter has been improved with a tiny PCB. I did not take any pictures when building the first unit which uses pure silver wire. The pictures below are for the second unit where I found out that balanced audio interconnect cable by DH Labs (Silver Sonic BL-1) has perfect 90 ohm characteristic impedance for the signal wires and around 45 ohm between signal wire and ground/shield.
UPDATE: The DH Labs Silver Sonic BL-1 cable sounds a bit different compared to Audio Consulting 24 AWG pure silver with cotton sleeve. Thicker sounding and more slam compared to more detailed with silver.
The holes for PCI bracket were done by hand! 2 M2 button head cap screws hold the USB2 receptacle to the bracket.
TI USB2 Redriver Evaluation Board
I ordered an evaluation board (very expensive given that the chip being evaluated is relatively cheap) from Texas Instruments (TI). TI has a range of USB2 Redriver products meant for automotive market. I don’t know whether it works for pure audio. The only way to know is to try it.
I only tried the updated DIY USB Filter in stand-alone mode briefly since I was so eager to discover what TI’s USB2 Redriver can do. The evaluation board is not FCC-approved and can only be used for evaluation and product development. I need to use 2 USB cables:
- from updated DIY USB Audio Filter to USB2 Redriver board
- from USB2 Redriver board to USB DAC
I know in the picture above, the right-side connection is not perfect. I was stretching the cable for picture taking. The better and/or the longer USB cable should be used at the output side into USB DAC. A very short USB cable is used between streamer USB Audio Filter output to the evaluation board.
After running a few days, I actually prefer the sound from TI USB2 Redriver compared to USB Audio card. The sound is faster with better PRAT. The USB Audio card is too smooth to my liking and it sounds slow. The USB Audio card has lower background noise though, hence the extraction of micro details is better.
TI is correct in saying both USB hub controllers and reclockers / retimers have high latency. The SQ improvement from USB Audio card is a side-way improvement instead of absolute improvement. It means we will hear different sound, not necessarily better sound. I feel the sound with USB Sound card is a bit unreal whereas with TI USB2 Redriver, it’s more life-like.
Another advantage of USB2 Redriver is that there is no need for drivers. It is transparent to operating systems, unlike USB hub controllers which require drivers. Another feature I like about USB2 Redriver is the ability to adjust signal boost and EQ depending on USB cable length so that perfect eye diagram is seen at the receiver side.
I plan to develop my own USB Audio card using one of the USB2 redriver chips offered by TI. The challenge is not with PCB design and fabrication but with the PCIe custom bracket required. Most stamping factories need minimum order quantity (MOQ) of 500 to 1000 pcs.
If you have any comments, please leave it here.