Swenson has a lot of "theories" which he does not seem to back up with actual measurements of end devices to prove the effects he claims. I am not doubting the things the says, I am doubting his claims of how the impact what comes out.
That starts with simple things, like leakage current, which he claims is a big issue at 50/60Hz, but then claims it is hard to measure because it is small. Well no, it is not hard at all. It is easily measured and characterized. He claims it is the primary noise source if you have a great system. If you have a great system and turn the volume up, do you hear 50/60Hz hum? No? So where is this? Not to mention that differential connections eliminate pretty much eliminate this source of noise. Also note that in single ended connections this is predominantly a noise current on the ground wire, and since the current is low and the resistance low, the developed noise voltage is small.
Then lets get into his argument for clock jitter, i.e. in an Ethernet output creating an audio frequency noise spectrum in the end equipment and justifies this with talk about ground plane noise. That is all fine and good, except good power supply decoupling, which is what competent designers do, will predominantly confine that ground noise to a section of the PCB, and a competent designer will also use good layout practices, such that ground noise from the digital circuit does not impact the analog audio.
Of course, it is easy when you make claims but don't back them up with measurements (which Swenson claimed he would provide) and make baseless claims that most engineers don't know about these things and don't account for them in their designs. All his claims are super simple to prove, so why does he not have a whole suite of measurements showing the improvement with readily available off the shelf equipment?
Oh, I love this that he wrote, "Galvanic isolators—be they transformers or any form of capacitive or optical digital logic isolator—still pass AC (alternating current). " That is simply crap. Optical digital logic isolators do not pass AC. They only pass AC, IF and ONLY IF they include a power supply for the opposite end of the circuit (most do not). The capacitive coupling on most optically based isolators is near nil unless they have a built in isolated supply.
A better power supply is going to do far more to reduce noise in the digital (or analog) domain than any of these products. End Rant.
That starts with simple things, like leakage current, which he claims is a big issue at 50/60Hz, but then claims it is hard to measure because it is small. Well no, it is not hard at all. It is easily measured and characterized. He claims it is the primary noise source if you have a great system. If you have a great system and turn the volume up, do you hear 50/60Hz hum? No? So where is this? Not to mention that differential connections eliminate pretty much eliminate this source of noise. Also note that in single ended connections this is predominantly a noise current on the ground wire, and since the current is low and the resistance low, the developed noise voltage is small.
Then lets get into his argument for clock jitter, i.e. in an Ethernet output creating an audio frequency noise spectrum in the end equipment and justifies this with talk about ground plane noise. That is all fine and good, except good power supply decoupling, which is what competent designers do, will predominantly confine that ground noise to a section of the PCB, and a competent designer will also use good layout practices, such that ground noise from the digital circuit does not impact the analog audio.
Of course, it is easy when you make claims but don't back them up with measurements (which Swenson claimed he would provide) and make baseless claims that most engineers don't know about these things and don't account for them in their designs. All his claims are super simple to prove, so why does he not have a whole suite of measurements showing the improvement with readily available off the shelf equipment?
Oh, I love this that he wrote, "Galvanic isolators—be they transformers or any form of capacitive or optical digital logic isolator—still pass AC (alternating current). " That is simply crap. Optical digital logic isolators do not pass AC. They only pass AC, IF and ONLY IF they include a power supply for the opposite end of the circuit (most do not). The capacitive coupling on most optically based isolators is near nil unless they have a built in isolated supply.
A better power supply is going to do far more to reduce noise in the digital (or analog) domain than any of these products. End Rant.