I had a read through the TI TUSB7340 data sheet earlier, there's some interesting stuff which could be relevant to the sound quality the chip produces:

• It can be clocked from 20 to 48mhz. There is a pin select on the chip to allow for 48mhz operation without programming. A Rom or PCIe channel programming of a clock multiplier can be used to allow other clock speeds such as 24mhz etc.
  
  
• The chip is specificly designed to used with either a crystal oscillator OR an external clock (similar to what some are doing with external clocks). This is interesting has, someone realised that performance of USB links depends on clock quality or might this be to support synchronous operation with other devices ?
  
  
• The crystal occilator circuit is referenced back to a special pin on the chip where normally the circuit is referenced to the signal ground of the PCB. This could be very important, from clock experiments I'm sure ground noise in the clock signal has a [-ve] effect on sound quality.
  
  
• The clock input pin needs is 1.8v clock signal IIRC what it said in the datasheet. The data sheet specifically states that the input is NOT 3.3v tollerent so clocking with a dexa or any other 3.3v clock source will need some components to step down the clock amplitude.
  
  
• The chip has some high quality PPL implementation, not sure where but in the right place could be very good news for sound quality.
  
  
• Finally there is a spread spectrum feature which is potentially not so positive. I have not got to the bottom of wheather this is enabled all the time or has to be turned on. Personally off would be the place to be for audio.
  
  Edit actually thinking about this it may be a feature that allows the chip to be tolerant to the PC using spread spectrum. I'll take another look at the data sheet.
  

The sound of earlier TI usb 2 and usb 3 chipsets were not good IMHO. this new chipset look like a REALLY interesting chipset for audio though. I'm starting to get a sense of why Peters reports on sound quality are so much different from NEC chipset USB cards.

Need to take a listen to this card but its going to be the TI chipset version that for sure.

Nick.

Anthony,

Many thanks will take a look,

Best,

Nick.

Ed hi,

See what you mean, the links in the thread show two quite different looking card layouts.

http://www.silverstonetek.com/product.php?pid=364&area=en

This is possibly the most unusual / interesting to take a look at is anyone has one to hand to post a pic of.

Cheers,

Nick.

Hi All,

I'm interested in trying a clock change out on the card but it would be good to take a closer look before jumping in. I was looking at the card in low res pictures on-line to try to spot any anything that marks out its implementation from other cards, but the pictures are not very useful.  The crystal and nest of components around it are one of the main areas I of interest because of the crystal implementation's ability to influence the cards audio performance.

Would anyone who has the card be able to post a hi-res picture of the crystal area ?

Many thanks,

Nick.

Hey Paul,

Interesting, ill have another go with your settings and see what happens 

Best,

Nick.

Hi Peter,

I used phase alignment for the previous beta XX version, so the start position was to try XX V1.186 with phase alignment for both q5=1 and q5=5 settings.

With q5=1 and sfs low enough to cause short interruptions in playback I did not get any very large blob dc sounds as the playback was started, stopped at the end of a track or stuttered during playback. In each of these situations I get lightish tick (about 1/4 playback volume) momentarily which is what happened before with earlier versions of xx. Worth noting I play at -33db vol setting and with phase strength set to 1.

Just as a general comment after a long period using phase alignment with earlier xx versions for best sound quality result im finding I don't need to use it when playing in v1.186, which is really nice.

Regards,

Nick. 

Alain Peter hi,

To try to clarify better.

The listening impressions given are based on listening to XX V1.186 using "meduim latency" settings as listed (with Q5 = 5) vs Q5 = 1 settings which were based on your signature settings Peter.

Looking back this was not clear (now edited above).

The reason for listing the DAC changes is so that its clear the that listening system has USB clock and other changes as I you mentioned Peter that Q5=1 might be targeted to work in a similar fashion to USB clock improvements.

Hope this helps,

Regards,

Nick.

Hi,

I had a long chat with Paul this afternoon and q5 = 1 settings came up. I thought i'd post my observations. The comments are relative to the schedule of usb clock, analogue and digital pcb changes to my NOS1 in place, plus a number of other clock and usb pcb psu changes implemented.

 So the sounds.

First V1.186 makes a large posertive impact with medium latency settings (q1=25, xq1=2, SFS=60 EDIT q5=5) that i was using before still providing the best overall sound quality. With v1.186 and these settings, there is an exceptional feeling of being in the same space as the music, with the feeling of musicians in the room performing.

I tried q5=1 EDIT again with XX V1.186 and with Peters signature settings and then  spent some time experimenting with EDIT SFS, NOS Buffer size and other settings. It was a mixed result for me. First the tone and solidity of reproduction was very good, a strongly 'valve' warmth feel to it. The highs are also strong but balanced and somehow have weight at the same time. The points that do not work so well here are that the sound stage becomes flatter, musicians that were in front and behind the plan of the speaker in the room now line up between the speakers. In addition dynamics are not so strong with transients and crescendos being more compressed, in this respect the medium latency setting sound more life like without being overblown.

Q5=1 is really interesting sound and could be a prefered setting for some types of music but just now the medium latency type settings provide the most realistic "in room" performance here.

Nick.

Edit Alain Peter have updated to make the compariosn an little clearer.

What a nice surprise for new years day 

I read the release notes (took half an hour !) but just to get going started with similar settings to last XX version (sort of medium latency Q1 xQ1 and SFS) just to get going.

First impression WHAT A HUGE CHANGE V1.186 gives !!!!

Without trying any of the new special settings even the sound is fantastic so live sounding. I m really looking forwards now to exploring the new settings.

Peter thank you so much, what an absolutely superb achievement Version 1 is.

Nick.
 

Hey Paul,

Position of the clocks certainly has audible effects, my nos is still looking like a project because of this. No top on the box still, maybe some time in 2014 it will finally go back on haha. Right now a long coax for the clock signal and have options regards placement. Seems the best route for SQ.

I found some extruded aluminium boxes for clock and psus at last after a long search so will give these a go within the pc and nos.  The hard drive bay sounds like a nice solution.

I'm looking forwards to a nice session listening on Friday without too much A/Bing to do.... for once  .

Best,

Nick.

Wishing you all a very Merry Christmas and a musical new year 

Kind regards,

Nick.

Coen hi,

I have not tried, but can do. I'll give alternate cables a go and report back.

Cheers,
Nick.

Wow Peter, you got out of the wrong side of bed this morning. I'm not going to dignify this with any form detailed response, it can just hang 

Anthony hi,

We are both a little sad to be trawling USB protocol information  . I have posted these points elsewhere but they may help again here.

lets assume for the USB link only that there might be four main forms of error / management interruption to data that could impact sound here (there are properly more, but for now).

1) Processing of resend requests (depends on usb transfer mode used)
2) Bit transmission errors
3) Audio word errors (out of sequence or missing words) 
4) Transfer speed management requests


USB Async transfer mode is intended for media stream transfers of video / data and as you say there is no USB protocol error checking, just signalling from the receiving end to speed up / slow down the link. So here the only point 1 of the points 1 to 4 above would not apply. The rest will apply and there will be no USB protocol handling / correction of errors so once the error has happened it will make it to the DACs as corrupt data and we hear it. Since the data lines are simplex (one set of wires carrying data for both directions) for the receiving end to issue commands to the transmitting end to speed up or slow down it has to interrupt the transfer. This is unlikely to be a "set and forget" tuning by the receiving end because the clocks at both end of the link will drift (I know even the temp stabilised Dexa clocks do this) which means that the speed up slow down requests will happen throughout replay.

Another USB transfer mode is bulk transfer mode. If you read back and look at the hunting for noise thread you will see that this is mentioned. I asked in one of these thread posts IIRC if Peter knows from the source code of the NOS USB driver if bulk transfer mode is used by the NOS interface. This could be very relevant to what we hear. With bulk transfer mode there are CRC checks performed on packets and transfer resend requests are made where there are errors. So in this mode it is possible that all four error types listed above could be happening.

The errors only have to happen at some thing like audio frequency intervals and we are going to hear the effects.

Finally wrt clock quality and the accuracy of transmission over the USB lin. Again as mentioned else where both the transmitting and receiving end of the USB link synthesize their 480mhz transfer clock speed by multiplying the 24mhz oscillator wave form by 20X. This makes phase noise in the 24mhz oscillator VERY important if there is to be a well formed 480Mhz link clock. Consider if one beat of the transmitting 24mhz xtal is say 25% faster this could mean that for 20 beats of the transmitting 480Mhz clock it runs 25% faster than the receiving clock so 20 beats at the transmitting end to a relative 15 beats so 5 beats missed.

This is an extreme (I hope  ) example, but its not hard to see that not having the 480mhz USB carrier running at consistent speed at both ends of the USB link could / will cause all sorts of data transfer problems.

Taking all this into account my view was when I started with DIY clocks and then selected the Dexas was "how would better quality clocks not improve the USB link transfer quality ?" (actually I did have some experience of improving USB clock quality from years ago  which helped. Then it was just a case of waiting for the free PSU offer that NewClassD run on Neutron stars from time to time to come round again)

Its important not to go down the "data is data" route of thinking when tuning the implementation of digital audio components. Practical experience is that if you buy into the data is data approach then there are some really big improvements that can be missed out on.

I think the best thing to do would be to use the information I sent over by email and take to plunge. Build the DIY clocks or put Dexas in. Don't get too hung up on transmission line lengths and noise etc. The effect of improved clocks is much much greater then the electrical effects. Three folks are up and running with Dexas with two more in the pipeline that I know of. Listening to the effects puts a very different perspective on the discussion  .

Kind regards,

Nick.

Hummmm there is a riddle