It's a given that people here are intelligent & hopefully thirsty for truth. Sometimes I see more debating tactics than truth seeking in other threads I have been involved in - this thread seems to have remained pretty empty of that?
OK, I'll try to adjust my demeanor but when someone wades in with what I I think are bullish statements or accusations or pie fight arguments, I tend to get tetchy & react accordingly. Sometimes I'm wrong - I'm human & hopefully I spot it & apologize?
Maybe I'm just too direct as well but that's me - I'm more interested in the truth than the PR of persuasion
I know you don't sit there all day. It was a colloquial expression of respect towards your obvious dedication and intent. I'm actually very impressed by what you say and how you say it. So we are cool, and I will never disrespect you.
And yes, I also agree about the artifice about sound synthesis. Over the years I have come to prefer the sound of synthesisers mixed with acoustic instruments. I have had a wonderful time over this past year listening to the back catalogue of Tranglobal Underground. Check out 'Kabatronics' you would love it.
ToS
An outstanding reply. Looks like you and I are gonna get on just fine. Oh, and don't worry, I too can be very direct if I have to. I can call them out along with the best of them - but as you know, a sense of humour (and in my case, a really wicked sense of humour) goes a long way when being ambushed by the cardigans.
So everything is cool. Let's all take our time and see everybody enjoying the thread as it evolves.
ToS
Noise Floor Modulation (NFM) is my best premise to date for what I hear, what experiments I've conducted (don't know how much I can say about these) & what I see reported from others but again I'm aware that we choose our evidence to fit our conclusions & dismiss or disregard that which doesn't fit and this may very well be a case of that confirmation bias.
NFM didn't originate with me - I've seen Rob Watts (Chord designer), Martin Mallinson (ex ESS chief designer) & others refer to it. See PeuFeu's side remark about NFM not being reported on typical FFTs
But when I understood what it was it fitted into my experience & my basic understanding of auditory perception & measurements. See here for some posts on DAC measurement & why FFTs are not particularly suitable for analyzing noise & NFM
First, my definition - NFM is about how the noise floor (present in every playback) modulates while music is playing - not necessarily in correlation to the signal but often because of the processing involved in handling the signal. Its not just confined to DACs either but device that handle very low level signals (that are later amplified) are likely devices where NFM is of more import.
I'm of the opinion that NFM ultimately boils down to the signal ground (reference) not being stable (exquisitely stable when devices that handle very low level signals). This can obviously arise from many different causes - probably too many to itemize here but PS rock solid stability is a big factor; ensuring PS ground returns never mix with signal ground returns. Maybe the EEs here can talk about this, particularly with regard to digital chip transient power requirements?
If I can give an example of where I believe PS stability (or lack of ) is shown:
There is a thread on here - the DDDAC thread - he calls it NOS but it is actually a dual mono PCM1794 which bypasses the reconstruction filter. Now the PCM1794 uses a resistor from pin 20? to ground to generate a bias current internally. This should be perfectly fine & stable bias current generated as long as the internal PS rail is stable. However, when a fet (2SK208?) is used to source the same value of current into this pin an audible improvement is noted by all.
This hopefully gives people more to chew on than just auditory perception but I have more to say about NFM & auditory perception
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This is where we get to the 'extraordinary claims' part. I'm very sceptical here esp without full characterization of what these changes do to the acoustic output. I have no issue with the fact that Mark has trained his brain to pick up things I can't just the levels are so low that due diligence is required. Like Cern's neutrino experiment with the loose connector.
But boundaries are there to be pushed...
@Markw4, I see you also have similar thinking regarding NFM & mention PS impedance rather than PS noise as one of the determining factors for PS stability & hence avoidance of NFM. I agree but don't understand why you don't try using those 3.2V batteries that have been recommended to you? Forget about battery maintenance, for the moment, see if battery power improves your DACs sound first.
Just need to point out that noise floor modulation is well known from the days of tube circuits and carbon comp resistors where the excess noise (1/f) was heavily modulated by the DC current. It is also worth pointing out this is another effect sought after by a certain crowd similar to the negative HD2 group.
And to repeat myself I'm not that interested in going through the effort of hearing very subtle differences without stating preference, I suspect without any coaching or applied bias many still might prefer the $300 DAC to the $3000 DAC (for instance. or of course have no preference).
And to repeat myself I'm not that interested in going through the effort of hearing very subtle differences without stating preference, I suspect without any coaching or applied bias many still might prefer the $300 DAC to the $3000 DAC (for instance. or of course have no preference).
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Auditory processing categorizes the soundscape into foreground & background sounds. Typically we consider background as room ambiance, recording noise, playback noise & generally focus on the foreground sounds. This background noise is not inaudible to us, it's thought that it's just being analysed as a texture sound i.e by summary statistics. Unless there is a change in this background pattern we tend to continue to ignore it (or we can consciously focus on it directly).
When NFM is present, I believe, among other effects that it has, we are also unconsciously influenced by this change in background texture - perceptually, it becomes mixed into the foreground sound, not as a distinct noise but rather as an affect on how the foreground sound is subtly altered - the sound we are focused on listening to.
The signal ground is just that, a reference, as well as being the return path. Any noise rides above it, wherever it happens to be at the time. Am I missing your point?
Sure, its not a new idea - and to that, can you tell me if DAC chips are regularly tested for noise power vs DC offset to check for noise floor modulation? I don't see any sign that this happens & this is exactly what Mallinson did in ESS to uncover the NFM in their DAC chip so it appears that this is not one of the stock suite of tests done on DACs?
What do you mean by "Any noise rides above it"?
Edit: You mean in the PS ground plane, I guess?
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No idea, easy enough to do. The larger question would simply be what is the code dependent noise of your particular DAC. Remember the state variable settling tail issue is very different from this.
Yes easy to do but is it done - I was hoping you might be able to shed some light on this question?
You mean SNR?
You are referring to Mallinson's ESS video presentation & his statement about state variable settling time? I seem to remember a slide showing a plot of DC offset Vs noise floor & description from Mallinson about this test uncovered the issue?
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As does safety ground & shield.
Add to that multiple connected devices in the chain, some with earth grounding, some with SMPS (ungrounded), multiple interconnects & shields.
Add to that the different pathways audio frequency & RF current returns take
It quickly becomes an art form.
That's ok then 
yes, avoiding ground loops can be fun. What I'm saying is that any noise will be referenced to ground same as the signal is. Whilst the power supply wants to be clean, it's a two wire circuit and all that matters is the potential difference. So I'm wondering if I'm still missing your point?
yes, avoiding ground loops can be fun. What I'm saying is that any noise will be referenced to ground same as the signal is. Whilst the power supply wants to be clean, it's a two wire circuit and all that matters is the potential difference. So I'm wondering if I'm still missing your point?That's ok then
I cant actually understand what you're saying here - you say "any noise will be referenced to ground" but I'm saying that the signal ground itself is being modulated causing the modulated noise floor?
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