Higher End DACs

I have a lowly celeron NUC as my server.  Its inside a 90dB RF-STOP isolation chamber with only optical I/O. This means zero RF noise escapes to impinge on my DAC and sounds, IMO, like endgame quality.  If we are all pragmatic, we know that the SGM Extreme bitstream is the same as my NUC's.  Exactly the same. The SGM is just a very very low RF noise source. All that metal and engineering buries the noise to be highly uncorrelated or at a level below where it matters to the DAC.  Yes, you can go in the $GM direction or be objective and focus on RF reduction with a few simple principles to get essentially the same result.

@mikelavigne
Mike - how can local vs streamed files sound better? How can you sense ’edgyness’ from one vs the other if the bitstream is the same. The MSB Select II supports a bit-perfect test file. Play the test file from SGM Extreme or ’pick any server’ using local or streamed and it will be reported by the MSB as being ’bitperfect’. So the innards of the MSB get all the bits 100%. So its not data corruption; its not jitter ...but the sound is different? Follow the evidence, Mike, it’s all about analog noise. Each server throws off a field of RF energy that gets into the DAC. Via signal, via power or through the air. This is the core issue here.

Audiophiles have to start behaving like Ham Radio operators who know and understand its all about RF noise mitigation that allows them to pick up the voice from distant Australia. You can apply common sense about the physics and technology involved ..and save a ton of money.

@yyzsantabarbara
@tomic601
RF is insidious. If we had eyes that revealed the full EM spectrum we would see fire hoses of radiated energy everywhere. I don’t know why DACs are so sensitive to RF noise but as our systems become more transparent, its clear to me that less RF noise impinging on a DAC improves the sound. I can’t delve into a DAC to measure whats going on (and in fact the levels are below test equipment noise floor). What I do is measure is the full spectrum (audio band and RF) coming into and leaving a DAC. My corollary for better sound is less measured RF energy in all cases. So the challenge for audiophiles is to get the RF level down to ambient.

To answer your questions: using optical where possible helps, using battery power helps, using low powered sources reduces their potential RF and that helps. I am all about optical isolation (DX and USB in my case), lifting the digital chain off the AC mains with battery and moving the digital components as far away from the DAC as possible. In the case of using best practices with an RF-STOP faraday cage, you have an equivalent separation of 1000 meters, optical to the DAC and optical to the (distant) network switch. It requires an audiophile to appreciate and understand that it’s a whole chain process ...no single product is a fix. But then the isolation is guaranteed by physics.

RF is the elephant in the room. The invisible elephant that changes shape and size with every digital tweak ...but still remains to affect the DAC. It's all because we have clocked digital devices proximate to the highly sensitive D/A.

Ahhh...but what if you could reduce RF to the minimum. So only room ambient remains?  Easy: put your entire digital chain inside a RF shielded enclosure (like my RF-STOP box). Only optical out; only optical in; and well isolated AC input.
It means audiophiles have to reconsider how they deal with high end audio tweaks. No single point product fixes the RF issue. No single manufacturer is dealing with all products RF emissions.
But today we can put our whole works into a Faraday box, follow a few simple principles for I/O and the elephant goes away.

@geoffkait
I considered the problem as a DAC being an antenna. I analyzed the DAC outputs while the DAC and device-under-test was in a Faraday cage. So it’s quite clear that when a generator of RF is even just proximate to a DAC (no connection) the outputs of a DAC are affected. This means the energy gets inside the DAC. And I have the corollary that when the energy bis there (even a high MHz) the sound is less transparent. So the DAC’s designed performance is affected by:
- the xtal clocking the output is perturbed
- the multiple harmonics at MHz affect the noise floor in the audio band
- reference voltage levels disturbances

None of this is measurable directly. The audio band (to 21khz in my case) shows no added jitter or noise floor changes to 150dB. Even in my conversation with Rob Watts, he says he can see nothing to 190dB. But we’re talking High End DACs here...where these effects are plainly audible.

@cleeds 
I have a signal hound BB60 and have done the tests (see my whitepaper). I have done the checks for alternative explanations. Repeated the tests. It's quite clear that a DAC fully isolated (say runing off a battery with a source chain buried in a Faraday cage and only optical I/O) sounds better ...and by that I mean exposes increased transparency. Open the lid of the cage or get lazy with what could be a source of RF...and the magic goes away.

And I'll have to say again. If you are asking questions about measurements to point the finger at a causal issue ...no test gear will suffice to find those for you.. the effects are real but must be down below 200dB.  There is something remarkable going on with our ear/brain that lets us hear these things.

heaudio123

the link to my whitepaper

i'll have my isolation units out to influential users over the course of the year. more ears and more voices will change minds.

I'm going to start my own thread on RF isolation of DACs. It's a topic whose time has come. It good to be pragmatic but it's also good to accept new ideas. Understanding is the first step toward a full resolution. 

Heaudio123
It's worse than you just galvanic conduction of RF.  Even with optical from server to DAC, you can tweak the server to change the sound. Why? Because the RF conducts along the metal AC power cord to the wall and to the household grid. You then have a room sized mesh of metal to contend with. Also the phenomenon plainly affects DACs across open air. 
If I have a RF analyzer at the output of a DAC and just power on a disconnected NUC 15' away,I can see the MHz,GHz noise that varies as the NUC is doing it's thing.
So ...distance  battery power and optical are the factors to focus on. And as you say,lower power helps and your mention of a Faraday cage is on the right track to an objective solution. 

And despite the resistance, ll keep working to break the spell that so many are under. 

RF isolation is needed to determine DAC differences. That is, RF noise in signal, power or radiated thru free air affects how a DAC sounds. 
Regards xtreme servers ...well if the output is optical and the server is 100% RF isolated from the DAC, they sound the same as a $100 raspberry Pi. Exact same.
Im in the Toronto area and able to plainly demonstrate this.

@lalitk
Thanks. I will (gingerly) post on that thread. I am going to turn this industry on its head so i need to be careful. The issue of RF noise (basically any EM energy above the audio band) is grossly under-appreciated as being detrimental to ultimate sound from a DAC. There is so much misinformation about tweaks to the upstream digital chain. Servers, cables, power supplies, switches, reclockers, etc. - all do nothing to the fidelity of the digital stream to the DAC. It’s always 100% perfect. The bugaboo of jitter is a 1990’s issue - modern DACs are impervious with double-buffers and separately clocked outputs.
It may be incredulous to many (most) that digital electronics radiate RF noise across meters of open air or via galvanic signal paths or AC mains to enter a DAC to affect the final D/A stage through perturbations in clocking or reference voltages. So all those tweaks ...all they do is change the radiated emissions profile; modulating the RF correlation to become manifest as subtle deviations in a DACs output waveform timing and amplitude: hence staging, timbre, detail.
I wanted a solution not a partial fix so I solved this for myself (and its a commercial Audiowise product) by putting my entire digital chain inside an RF isolation chamber (a 90dB attenuation Faraday cage) with only optical allowed in/out. Bingo - zero audible difference between a Raspberry Pi, an Intel NUC or an ’audiophile’ server. No difference between a $5 USB cable or a $500 one. No difference between using a factory switch-mode power supply or a $1500 LPS. When all these tweaks are contained inside a RF chamber, no RF noise escapes and the DAC always sounds its best (as it was designed).

@audiotroy 

I have Chord Hugo TT2 to headphones (or direct to Voxativs) isolated from AC noise on a battery and Toslink signal input. With such a configuration, nothing upstream should make a sonic difference, right?  The TT2 is impervious to input jitter, so why does a server make a difference? Please don't claim that that bits are 'better' in any way ...yet in open air any upstream changes can sound different, why?  If a switch or power supply or cable changes the sound but the bits are the same going into the DAC, what else could account for this? Hint: its all about RF noise.

My test server was a Baetis (circa 2016), my NUC is a 5i5RYK, my Pi has a HifiBerry Digi+ module.  My test equipment is my ears combined with a SignalHound BB60c to correlate measured RF noise in the signal and proximate to the DAC.

@audiotroy,

Dave,
I don’t doubt your experience of differences in sound quality - perhaps your DACs are intolerant of jitter. Yes,Toslink is synchronous and maxed at 192/24 but apart from that its the same as any other digital transport...from the motherboard, from a custom board, etc. If there was any digital error in the stream you would be hearing dropouts, pops and clicks. So, apart from their innate bandwidth and protocol differences, toslink, coax, USB, AES all gets the bitstream to the DAC with 100% fidelity ...at least to Chord DACs.
My comments regarding RF noise and Toslink was in the context of this thread (High End DACs) as a means to get data from source to my chord DAC without any conducted RF noise, which i am convinced is the big elephant in the room.
I was just at CanJan, I should have taken the extra day to come see you. I have other NYC trips planned soon, ive messaged you.
Dan

Not just Playback has an optical link .... Chord DX DACs can have the benefit of a high resolution optical link from source/upscaler to DAC using OPTO-DX. And for those totally on digital streaming, the combination of a software PCM upsampler (Roon+HQPlayer) direct to DAC (Dave or Hugo TT2) gets pretty close to endgame. No galvanic link means zero conducted RF noise on the signal as all the computational heavy lifting is separated from the DAC. And then paying attention to DAC power RF isolation and radiated RF (and magnetic field) isolation means you don't need to jump to an uber expensive DAC. At this high level, it's all about RF elimination.

Recently,  REMASTERO (https://www.remastero.com/pggb.html) announced PGGB offline remastering with sinc filter reconstruction using hundreds of millions of taps and advanced noise shaping. The process is offline ...meaning a source file is converted to a ultra high resolution WAV file and fed to DACs capable of 8fs, 16fs or higher sample-rate USB/DX input.  I recently evaluated this with my Chord Dave and compared it to Chord MSCALER or HQPlayer upsampled source files.
No contest ... the PGGB version was stunningly better and points to the possibility that essentially infinitely wide filters can achieve optimal Nyquist-Shannon reconstruction. And since all the intellectual property is offline, I think this opens the door to inexpensive end-game DACs.

Its worth your own eval and listen using the free 30-day trial.