more improvements coming up in DS firmware?


#1

Are there going to be any more improvements coming up in DS firmware (FPGA coding) in the coming months? I am wondering whether a slightly more 'rich' sound is possible for PCM 16 bit recordings using better firmware?

@Ted: can you share your thoughts?


#2

Ted’s always slaving away at making improvements and I suspect that within time, new firmware will come available that keeps stepping the performance of DirectStream higher and higher. It’s truly one of the beauties of the design; to be able to dream up new innovations and them email those out all over the world. Truly an amazing machine, the DirectStream.


#3

Thanks Paul, it is indeed great that improvements can be achieved using software in stead of hardware.


#4

Out of curiosity, how many lines of code are they up to in the DS firmware?

And what percentage of the gates in the FPGA are still available?


#5

Paul/Ted

I just updated my DS to the 1.19 firmware. My DS was kit upgraded from the DAC II. One of the things that I liked about the DS over the DAC II was that the overall output level was lowered which allowed me to run my Audio Research Reference 5SE at a higher volume level which is more in the sweet spot of the unit. Now with the 1.19 upgrade the output level is more like the DAC II was. Is there any thought on the new firmware but at the lower output levels. I realize I could lower the level on the DS but I don’t want to run it below 100 and potentially degrade the sound. I realize you suggest that it doesn’t.

Jeff


#6

I’ve never heard anyone say that the firmware update resulted in a higher volume and I did not notice that in my case. Is it possible you had engaged the 20 dB reduction prior to the update and not after? You can toggle it using the filter button on your remote. Also, unlike with the PWD, you can run the DS significantly below 100 without any sound degradation as the volume is adjusted internally in a different way.


#7

Welcome, Jeff!

Are you certain the level is objectively higher? There is not nothing in the newer firmware which would change the level. In fact, the sound should not change at all - although some, of course, have noted differences. :)


#8
adriaan said

I am wondering whether a slightly more 'rich' sound is possible for PCM 16 bit recordings using better firmware?

What do you mean by "rich?"

I have not found the DS threadbare. Instead, the clarity of timbre and texture is better and richer than the vast majority of DACs.


#9
brodricj said Out of curiosity, how many lines of code are they up to in the DS firmware?

And what percentage of the gates in the FPGA are still available?


It’s hard to answer directly: I have multiple implementations of various pieces I pick between depending on my needs. Also the Xilinx tools can produce code from specs and that code isn’t dense at all.

The modules currently in the FPGA comprise about 5000 lines that I wrote and then there are things like FIFOs and FIR filters generated by the Xilinx tools from specs and coefficients I provide (the coefficients in one case were generated by a small program in my HP-48 calculator :) )

I don’t know if you were only asking about the FPGA but the PIC in the control processor is in C and has a lot of generated code too. Also the XMOS code for USB is non-trivial, but mostly not written by us. Then there’s the bridge…

FPGAs these days are much more than just a sea of gates – there are specialized resources like clock PLLs, blocks of RAM, DSP blocks, etc. With different compile options you can choose to slosh, say, a multiplier to use mostly DSP blocks or mostly simple gates and similarly for hunks of memory. One of the previous releases used about 140% of the FPGA but with optimizations got squeezed to 98% of the FPGA. Conversely another version uses about 80% of the gates and has a lot of memory and DSP blocks left over.

I have a lot of parameters I can tweak in the source to balance speed vs. size, etc. and when I need more of one or the other the FPGA resource balance changes wildly.

There is room for a few more non-trivial features and if needed there are a few things that I can get rid of that aren’t being used at the moment.

(I assume you weren’t asking about unit testing harnesses, etc. which is another whole hunk of code.)


#10

For sure there is a real 6-7 DB change in the output level. I always have a SPL meter on beside my listening seat when I listen. I know I always have the same relative volume when comparing things. I have been playing around with the DS volume since I posted and I need to run it at 90 to have the level on the SPL meter with the volume set to the previous level I was used to on my Ref 5.


#11

Another issue that happened this week with my DS before the firmware upgrade is that the channels completely reversed themselves. All the information that usually comes from the left channel was now on the right and vice versa. Anyone have this issue? I turned the unit off via the rear switch waited a few minutes and powered back on and the issue went away.


#12

I believe the reversed channel issue has been reported by one or two others and the solution was the same as yours. On the volume, stranger things have happened so who knows. I would have no concern about losing sound quality running at 90 on the DS.


#13
richfieldhunter said For sure there is a real 6-7 DB change in the output level. I always have a SPL meter on beside my listening seat when I listen. I know I always have the same relative volume when comparing things. I have been playing around with the DS volume since I posted and I need to run it at 90 to have the level on the SPL meter with the volume set to the previous level I was used to on my Ref 5.
Something else is going on. There isn't any change in the volume handling between 1.1.6 and 1.1.9 in the DS firmware. Tho I doubt it's what you are running into, there was a bug in the original release 1.1.5 which messed up the volume badly when the polarity was inverted. But I can't think of anything else in firmware that could be related to your experience. If your player supports Replay Gain, etc. or you use any volume leveling or DSP I'd look there. You could run the bit perfect test just to verify that nothing is messing with things in your player configuration or the OS: http://www.psaudio.com/ps_how/how-to-run-a-bit-perfect-test-with-directstream/
richfieldhunter said Another issue that happened this week with my DS before the firmware upgrade is that the channels completely reversed themselves. All the information that usually comes from the left channel was now on the right and vice versa. Anyone have this issue? I turned the unit off via the rear switch waited a few minutes and powered back on and the issue went away.
I suspect that you have a data integrity problem, there was a bug in the receiving of S/PDIF (and AES/EBU) signals in 1.1.5 that could in rare circumstances reverse the channels now and then. If it happens again run the bit perfect test to perhaps narrow things down a little.

#14
richfieldhunter said One of the things that I liked about the DS over the DAC II was that the overall output level was lowered which allowed me to run my Audio Research Reference 5SE at a higher volume level which is more in the sweet spot of the unit. Jeff
Interesting because the one thing I would change about the DirectStream is the output volume, I'd love it to be where the PWD Mk II was! With my "lowest" output source, my DVR, the DirectStream just isn't quite loud enough to use without the "Narrow" setting chosen, and I'm not sure I like the "Narrow" setting's sonic signature as well as the "Normal." This is not an issue if I run the DirectStream into the preamp, but I honestly prefer to run the DirectStream directly into my amp and this allows me to use my best interconnect all on its own and the sonic payoff is quite noticeable.

#15
richfieldhunter said I realize I could lower the level on the DS but I don't want to run it below 100 and potentially degrade the sound. I realize you suggest that it doesn't.
It's the reason we suggest that running it below 100 doesn't potentially degrade the sound that matters. There is nothing at all special about a volume of 100 in the DS: unlike many processors there's no shortcut in the volume multiply for any input (0 or full scale) and all output bits of the multiply are kept and are significant down stream (i.e. no dither or truncation is used). Even more to the point, there are multiplies all over the place, many in every filter and in the sigma delta modulator.

I’d not think twice about having the DS volume at whatever level works best with the rest of the system. (Some preamps have sweet spots and I guarantee that you’ll hear more of a difference when moving the volume outside the preamp’s sweet spot than changing the DS volume a little.)


#16

I too wish the DS had more output - with Ted’s great volume setup that doesn’t lose any bits/resolution, I’d much rather have a little too much and have to dial it down, then be where I’m at, which is wanting to be able to turn it up to 11. :slight_smile: My amp wants just a little bit more voltage, and I too prefer having the DS direct to the amp vs putting a preamp in between. My Oppo just has so much more density with it’s added output voltage.

Ted, is output voltage something that’s completely fixed, due to the output transformer/filters? Or can it possibly be adjusted in the future? Even just another .5v on the unblanced output would help (though I’d prefer 3v total). Right now I’m looking at building a simple balanced to unblanced converter using Jensen 1:1 transformers just to get the voltage to my amp. But as I said, I don’t like putting anything inbetween - K.I.S.S.


#17

The output voltage is set by the power rails. The design has some headroom built in, but using much more of it would cause distortion and lessen the ability to deal with very dynamic music: the DAC would loose ease.


#18

I was afraid of that.

Make note for DS V2 - 3v output on unbalanced, 10v on Balanced

I’ll be first in line. :slight_smile:


#19

Maybe you should consider a new amp. I have an octacev110 and I can barely turn it up 3 notches when the DS is attached directly without it becoming too loud??


#20

Lone Raven and I both have Decware amps which we LOVE and they are not going anywhere!