Since people have been fishing for information about the FPGA changes in the upcoming software release for the DS and DS Jr I thought I’d start a separate thread to avoid hijacking other threads.
I don’t know PS Audio’s release schedule and can’t guess because I have no idea what else they will be doing for the release.
I have sent the first potential release of the FPGA code to PS Audio: I want to see if the changes I’m doing have the desired effect. If not I’ll have to think more.
The changes are based on the things that were done for Snowmass: doing a little more shuffling of function from noisier FPGA resources to the resources I have more control over. (e.g. using distributed ram instead of the block rams.)
Also I realized that one of the things I designed in the TSS hardware can also be done in the DS Sr’s hardware. It deals with how to use the digital switches more effectively. The Jr only has one digital switch per channel so I can’t do it there.
I’d figured out how to do better filtering with the available multiply/add units in the FPGA, but I’d forgotten that the memory for filter coefficients was the actual bottleneck right now in the DS and DS Jr. I’m still looking at compressing the coefficients and other tricks to enable some other ideas I have, but I doubt they’ll make it into this release.
I have fixed the slow ramp up after a discontinuity in sample rates, transitions to and from DSD, etc.
Also, we’ll have to wait for impressions from PS Audio about changes in sound quality. We know that the other changes in the control processor (and possibly Bridge software) can affect the sound and I don’t have their new code yet. But more practically my tinnitus really gets in the way of distinguishing details these days. I have to rely on impressions over a length of time which isn’t really that accurate. I still make sure that my wife and daughter don’t hear untoward changes. I’ve been using feedback from others (especially this forum) to guide my changes for many releases now and feel comfortable that I can make positive sound quality changes even if I can’t hear them.
No, not a major change. I spent a couple of weeks looking for a major change that could be done without a high probability of introducing bugs - no luck. I’ve still got some interesting things that I need to finish, listen to, etc. But they aren’t fully baked yet. I’m rewriting some of the code for the TSS, after the TSS is out I’ll port back to the DS and DS Jr those things that I can.
I don’t want to go into too much detail, but the four digital switches in the DS are arranged into dual balanced pairs, each of which is differential. That is there are two sets of balanced digital switches in parallel. Each balanced digital switch is implemented with a differential opamp.
What does this mean?
Putting two sets of hardware in parallel will lower the noise by 3dB assuming the noise is not correlated between the two sets. Putting four sets in parallel will lower noise by 6dB.
Having balanced sets of hardware means that something is always going up when something else is going down. I.e. ideally even order distortion is canceled. Also (ideally) the correlated noise between the positive power rail and the negative power rail is canceled.
This is all independent of the output of each digital switch being differential so that there can be a differential output…
Anyway TSS and DS have separate control of the dual parts of the digital switches so the software can take advantage of the freedom to not always drive them identically.
Well, this is exciting news. Looking forward to it, Ted!
Forgive me if this has been answered in the TSS thread, but will the TSS accept DSD256 via I2S? DSD512? (In terms of jitter, I know you believe the sweat spot is somewhere between 128 and 256.)
The TSS will accept quadrate DSD via I2S with the initial software, quad rate via USB may take a little longer (PS drivers and all that.) The TSS digital box can’t talk to the TSS analog box fast enough to support DSD512. I don’t know if taking DSD512 and converting it to DSD256 internally would go over too well marketing-wise.
No, I’ve had tinnitus continuously so long I can’t remember not having it (decades at least) and I hear music the same as I hear the world. I’m very glad that tinnitus causes me no distress (unlike many.)
About 15 to 20 years ago my tinnitus was great for detecting jitter: jitter would cause more stress and more stress would cause more tinnitus. It was instantaneous and repeatable in a double blind test. So at least for a while my tinnitus was very useful
The bigger problem is that I have a > 70dB loss in the left ear at about 4K which I don’t normally notice (I didn’t notice it for 20 years after I got it ) but now recruitment is causing me to hear fuzz that isn’t really there. At times I need to turn my head sideways (listen with only one ear) to hear clearly. Still almost all well recorded music sounds great and even poorly recorded music that I listened to when I was younger still sounds better than it used to on my earlier systems.
IMO the best thing to do with tinnitus is to relax and ignore it (unfortunately easier said than done for many.) I hold out hope that a reliable treatment or amelioration will be found.
It is amazing how a trained brain can distinguish sounds that would not seem to be possible. I too have high-frequency hearing loss, but I can still easily appreciate how well the DSD reproduces cymbals and tell when they are poorly or well-recorded, and sibilant exaggeration is still annoying to me.
) but now recruitment is causing me to hear fuzz that isn’t really there. At times I need to turn my head sideways (listen with only one ear) to hear clearly. Still almost all well recorded music sounds great and even poorly recorded music that I listened to when I was younger still sounds better than it used to on my earlier systems.