Not quite - the volume control in the DS doesn’t loose bits at lower levels: it takes all input bits and multiplies them with a 20 bit volume, keeping all resultant bits. These bits go into the sigma delta modulator to be converted into single bit output. At any volume > 0, any bit changing in the input will cause the pattern of 1’s and 0’s in the output stream to change appropriately.
The confounding thing is that there’s also a noise floor. When FFTs are averaged or use more bins the measured noise floor is lower. With the DS and enough bins and averages you can see the effects of any single bit difference in a repeating pattern no matter what volume.
The digital noise from the sigma delta modulator and the analog noise from the DS hardware present a practical noise floor that is reasonably close to the dynamic range of the ear so with an appropriately level matched preamp or amp, all bits that you could hear will be there at any volume.
In the real world it’s sometimes hard to match the output levels of the DS with the existing preamp and/or amp and speakers that well and then you can loose some dynamic range if volume 100 on the DS isn’t just a little above TOO LOUD.
To be fair the analog noise floor of the whole system is the practical limit for DSD or PCM with more than, say 22 bits. But in the DS if you use enough averaging you’ll see that all of the bits are there at any volume and you’ll be loosing bits off the bottom end with most PCM systems.
An analog volume control would degrade the quality of the sound.
It could be engineered not to degrade sound quality, but a stepped resistor ladder will take up quite a bit of real estate inside the chassis. I think the digital volume control of DS/DSJ is just fine, and I particularly like the way they did the volume knob on the DSJ. So if there was to be an ultimate DS, don’t limit the budget, and put a volume control knob on it rather than touch screen GUI arrows.
Yes, the DS and DS Jr share identical code for the volume (and all signal processing for that matter.) The differences are things like one less I2S input means that there’s one less instantiation of the I2S -> PCM block, the FPGA in the Jr has to generate clock signals for the bridge module, but not much else is different in the two DS’s FPGAs.
Even with perfect resistors that are perfectly trimmed, stepped resistor ladders aren’t ideal either. The switches are one of the problems - if physical, the contact resistance has to be very repeatable and they need to not oxidize or wear out very fast and you need some other kludge if you want a remote - if solid state, the parasitic inductance, capacitance, charge injection, etc. have to be at acceptable levels and they have to be fairly immune to noise on the (digital) control inputs. There’s a reason quality preamps cost.
In the real world it’s sometimes hard to match the output levels of the DS with the existing preamp and/or amp and speakers that well and then you can loose some dynamic range if volume 100 on the DS isn’t just a little above TOO LOUD.
Ted, a couple of months ago you have told about a way to use the DS DAC’s remote control in (spite of) the case that a preamp is part of the chain. When I remember right it was turning down the volume of the preamp at first, then turning up the DS DAC’s volume to 100 and then turning up the preamp’s volume as loud as it bearable to the ears (sorry for my English). Then you turn down the volume by the DS DAC’s remote control to the usual range you are listening to the music. That’s what I was practizing with my former tube preamp and now again with this Level Pilot . It’s placed between the xlr- outputs of the DS DAC and my active speakers’ xlr-inputs. The knob of the Level Pilot remains at 9 o’clock now, the volume knobs of my active speakers are at 12 o’clock (neutral) and the listening volume range of the DS DAC is between 60 and 70 now. Before without this thingy the volume knobs of the speakers were set on minimum and listening volume range of the DS DAC was around 40-50.
Not sure if it is embarassing to use the Level Pilot or if I have the “best of two worlds” now. The sound seems ‘beefier’ to me but the most important is I can adjust the volume in the lower/quieter passages better now. Before e.g., the volume jump from 0 to 1 was too big for my taste.
So, belated thanks for that (to me) very useful advice.
brodricj said
It could be engineered not to degrade sound quality, but a stepped resistor ladder will take up quite a bit of real estate inside the chassis.
This would be true only if one has access to theoretically perfect resistors which, of course, do not exist, and a flawless means in which to connect them in the DirectStream switches, wire, etc.), also non-existent. Additionally, a resistor-based volume control inherently throws away signal; this is how such controls work. An analog volume control is inferior to the DirectStream's volume control.
Compare this with Ted’s description of the method by which volume is presently controlled in the DirectStream. The volume control is not subject to the quality of analog parts and no data/signal is ever thrown away.
However, as Ted explains, the noise floor of the DS remains present and is not diminished as volume is reduced. This makes gain matching more challenging and can be a problem in some systems. An analog control throws away noise as it throws away signal.
All that said/written, I enjoy the fell of the little clicks of a stepped resistor ladder.
I have the DSJr and the BHK Sig preamp, what would be the best settings for the two volume settings? Max on the BHK and adjust with the DSJr or vice versa Max one the DSJr and adjust on the BHK? or a compromise?
A great question. Of course, the answer is what sounds best.
I would start with 100 on the DAC and adjust the volume with the preamp. I suspect the trick is to find the sweet spot of the preamp and my guess is this is with the DAC and 100. But experiment.
Please let us know in the DSJr/preamp threads what you find works best.
Sometimes it’s best to let your subconscious figure these things out: as Elk suggested start with the DS at 100 and then don’t think about whether you need to adjust the preamp or the DS, just do what feels comfortable at the time - after a while you’ll stop adjusting one and you’ll always use the volume on the other.
Great idea, Ted. I did not think of it this way. I bet you are correct that you will magically figure it out by not thinking about it and channeling your inner unicorn.
Tube rectification does sound different than solid state, including sounding different with different tubes. I would not like to see the DirectStream go this route.
Interestingly, some owners of high end tube amps (such as the $6,000 Woo Audio WA5 which has a separate tube power supply) prefer the sound of solid state rectification and replace the tube with an SS plug-in equivalent. These plug-in tube replacements were developed for owners of tubed guitar amps.
One compromise we did for the DS was to use the same power supply that the PWD used. Originally that was to allow an only two board replacements for upgraders from the PWD. We ended up using a different transformer for the DS because we could make one that sounded better for the DS so we ended up having to replace three boards anyway.
With a little more money (higher price) a custom power supply board for the DS could have made a difference and in any future DS like or better version of the DS will probably have a new power supply board.
Tho tube rectification isn’t likely there are better diodes available for the rectifiers that generate less noise, which is what I presume a tube rectifier would do and there are some other things we’d do that would make a non-trivial difference.
Always when I read about improvement potential like this, I think…“and in ten years we probably still compare DAC‘s to quite the same record players as today with similar results and discussions“
I tapped into the jumpers for selecting voltage before the transformer primaries on the power supply board, and snaked a heavily shielded power line to the front-left where I mounted another transformer. My primary objective was to test whether isolating the analog supply from line noise and noise from the digital supplies would make a difference, so I ended up using a split-bobbin EI transformer feeding a narrow regulator board. Output from the regulator board ends up close to the power supply jack on the “analog” board.
Sorry, no pictures, but will try to remember to shoot one the next time my DS is open.
(PS - This is not a simple undertaking and I do not recommend anyone actually do it.)
Puh, sounds as if you know what you do. I wonder if everyone who has knowledge about basic electronic design can easily improve such parts without risk…nice
I have no formal training in electronics, but have been building/modifying audio gear for 30+ years now. But there are definitely risks, including potential electrocution, and it was with no shortage of trepidation that I began modifying the DS. To be honest, I hadn’t really planned on doing much to the DS since it is such an amazing component out of he box, but it responded favourably to my ears and I just couldn’t help myself.
In terms of sonics, generally I’m hearing what we all love about the DS, only with more detail and smoothness. The big thing I noticed about the dedicated power supply for the analog board is that everything became more holographic and 3-dimensional.
Any pictures?