Viper2001
100+ Head-Fier
- Joined
- May 21, 2011
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Quote:
AC noise issue can be troublesome for some people, depending on where you live, your neighbors, etc., but some of the points you made are not quite valid.
For example, the blue fin transformer does not have high interwinding capacitance. The interwinding capacitance starts to become a problem when you're into hundreds of VAs. This is why it is better to use EI transformers in power amplifiers instead of toroids. But for low consumption unit like the Anedio (10VA), it is not a problem.
The problem of leakage inductance on those cheap blue fin toroid is actually the bigger issue. Cheap toroids are like that. But James has done the RC damping network on the output of the transformer to kill leakage inductance induced noise spikes, so even if you replace it with a higher end unit, such as R-core, the gain will be very little. The problem with R-core would be higher radiated stray magnetic field, so unless you can make it far away, it is going to affect the clock circuit.
The hum buckers used in Berkeley are mechanically noisy (hum). So you gain some and you lose some.
Also, contrary to popular beliefs, the most damaging noise does not come from AC, it actually comes from inside your gear - the rectifiers (diodes). Silicon rectifiers or fast recovery rectifiers are "noisy". They emit tons of high freq noise at the moment of switch off. The smart designers will put a snubber across each rectifier to damp out this noise. James did the right thing on using the Cree SiC recitifiers, they have nearly zero switching noise. And the other rectifiers he used for the display are of soft recovery type.
My assessment of D2 is that power supply related noise is not a problem on this unit. The problem is actually the clocks on U2 and WM8805.
Isolation of a DAC from noise sources is far more important than jitter in my experience. The noise sources to watch
out for are the mains supply itself, and PCs. The average DAC has a connection to both. Galvanic isolation most
certainly can help a lot but the isolation is not complete at high frequencies, so its more important to know the
capacitance across the isolation barrier than know whether the isolation is of the 'galvanic' kind, or not.
If you look at the pics Viper2001 has posted of his D2, you'll see that it has a 'block' type mains filter (top left). In
my experience these aren't really adequate in taming mains-borne noise. It also shows a toroidal type mains
transformer (the blue thing with fins, bottom left). Designers keen to reduce mains noise don't use such trafos - a
good example is the extremely well regarded Berkeley Alpha DAC. Its transformers look positively pre-historic in
comparison with this one, but they've been chosen for good reason - isolation. Toroids have the two windings
(primary - mains, secondary - low voltage) wound over the top of each other. This means high interwinding
capacitance - an open window to mains noise.
If I was a D2 owner (and I wouldn't buy because I'm a multibit addict, not S-D) then I'd be looking into optimizing the
noise immunity before the clocking. That's not to say the clocking is unimportant, just getting the priorities right.
AC noise issue can be troublesome for some people, depending on where you live, your neighbors, etc., but some of the points you made are not quite valid.
For example, the blue fin transformer does not have high interwinding capacitance. The interwinding capacitance starts to become a problem when you're into hundreds of VAs. This is why it is better to use EI transformers in power amplifiers instead of toroids. But for low consumption unit like the Anedio (10VA), it is not a problem.
The problem of leakage inductance on those cheap blue fin toroid is actually the bigger issue. Cheap toroids are like that. But James has done the RC damping network on the output of the transformer to kill leakage inductance induced noise spikes, so even if you replace it with a higher end unit, such as R-core, the gain will be very little. The problem with R-core would be higher radiated stray magnetic field, so unless you can make it far away, it is going to affect the clock circuit.
The hum buckers used in Berkeley are mechanically noisy (hum). So you gain some and you lose some.
Also, contrary to popular beliefs, the most damaging noise does not come from AC, it actually comes from inside your gear - the rectifiers (diodes). Silicon rectifiers or fast recovery rectifiers are "noisy". They emit tons of high freq noise at the moment of switch off. The smart designers will put a snubber across each rectifier to damp out this noise. James did the right thing on using the Cree SiC recitifiers, they have nearly zero switching noise. And the other rectifiers he used for the display are of soft recovery type.
My assessment of D2 is that power supply related noise is not a problem on this unit. The problem is actually the clocks on U2 and WM8805.