Guys, those huge capacitors on VREF pins are not needed with good separated ldo's, at least tested on AK4493. On my board there are 10uF ceramic cap after LT3042 and 10uF near pins and it is enough, adding any electrolitic capacity such as 470-2200uF not does not affect anything. It really make sense when we have bad power supply realisation, such as one or only two 5V supplies for all 5V consumers. In this case those big caps matters (as smoothing and as LC filters between different circuits). Best supply is a several independent windings with several bridges and independent ldo's for VREFL / VREFR / VDDR / VDDL / AVDD / TVDD
IMHO
IMHO
Thank you!Looks great. I hope you don't make as many hard-to-find mistakes as I do!
I had two simple misstakes but it should be good 🙂
Please, share measurements. I'm curious about this.Guys, those huge capacitors on VREF pins are not needed with good separated ldo's, at least tested on AK4493.
I did everything by ears, it is enough for me, but if you want - AK4493 with measurements (also focus at capacitance on board there)Please, share measurements. I'm curious about this.
By the way, how it is measures ≠ how it sounds. Good graphs are desired but they are not all sound, and may very differ from one realization to another. Playing only with different combination of caps on my dac I've passed dozens different sounds from the same board. Different power supply is the same
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I'm using the same approach so no large caps on AK4493 Vref. Here is 1kHz@44.1kHz full scale (0 dBFS).
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Do you have the measurements at 100-200Hz?Here is 1kHz@44.1kHz full scale (0 dBFS).
Small Vref caps may provide good measurements, but not always good sound.
P.S. I often use an OP (with enough Iout) instead of an LT3042 or similar - just an RC filter from any regulated power than an OP with a larger electric capacitor.
Sometimes it named as "Active Drive" (for example - see "Design and Layout Guidelines for the AT1201", ADC from ARDA, also in ESS app.notes).
Used this with 4490/93/97, both 4499 (old and new) and others.
Here is stepped THD from 10Hz to 2kHz with -1dBFS. No issues IMO, neither with measurements nor with sound.
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One thing to note is that AK4499 is a different beast compared to AK4493/AK4497 regarding Vref. In AK4493/AK4497 Vref draws only max 1.5mA current so large caps are not needed. On AK4499 Vref current is typically 46mA so larger caps may be beneficial.
I see elevated 2,3,4th in bass...!? Maybe vRef guts?No issues IMO
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One thing to note is that AK4499 is a different beast compared to AK4493/AK4497 regarding Vref. In AK4493/AK4497 Vref draws only max 1.5mA current so large caps are not needed. On AK4499 Vref current is typically 46mA so larger caps may be beneficial.
As I am not that much interested in THD and see the Vref as the output FIR power of the AKM DAC's behaves any different as using for example fs/4 signals.
In addition different figures as the DAC FIR filter setup as on two extremes: NOS to SD SHARP.
It shows clearly like on 44.1kHz SR and fs/4 as symmetric peaks around the fundamental as +/- 310Hz spurs/jitter/AM and multiply of it. Some x 310Hz multiply do not show up but a higher clearly visible.
Even using VRef with Cap, LDO (LT3042) or output FIR with LDO (3042). This may relates also to the PB GND layout as Vref as +/- separated chip pins.
In other words the PCB layer count & layout and grounding will change the picture (RME ADI-2 Pro fs as 8 layers).
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Would be very interesting how your jitter & PN & AN (amplitude noise) shows up, while MCK needed from your USB clocks. In addition about any amplitude modulation of the Vref induced into above mentioned spectrum usually at fs/4.
Hp
Hp
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