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I wonder why there are no products from Topping or SMSL in this category? They could probably do better.

I find it interesting that SINAD plus gain is about 125dB (124 and 126 for two types of inputs). This is roughly the same as AP's best SINAD. I wonder how the low-level test voltage is generated by AP? Is it limited by the intrinsic noise level of the AP's output? It might be interesting to test...

The low-frequency end of multi-tone test is rather poor, in many good DACs it is all below -130dB

I think this description is backwards. The input of the circuit is on the left, with a differential amplifier that has a gain of 1 or 2 (6db). Then there is the notch filter and finally a 20 dB amplifier with single-ended output. It would make no sense to put an amplifier before notch filter.

Has anyone opened their E30 II to take a look inside? If so, please share a picture :) There is already a picture posted of SMSL D-6, so I am curious to compare https://www.audiosciencereview.com/forum/index.php?threads/smsl-d-6-dac-review.36235/page-10#post-1278363

Yes, it would be a balancing act. The output noise of best DACs is about 10 nV/Hz^1/2. The Johnson noise of a 1 kOhm resistor is 4 nV/Hz^(1/2), for 10 kOhm it is already 13 nV/Hz^{1/2}. So most circuits use less than 1 kOhm resistors to squeeze every fraction of dB of noise. One can use...

Thanks, I probably should look at Topping E30 II DAC or SMSL D-6, which use AK4493S. It's true that output filters typically use pretty low value resistors. Would be interesting if one added a simple follower and used high-stability resistors in the filters or maybe just use larger resistor...

Most high end DACs (eg. ES9038Pro-based) operate in current mode. The outputs of the DAC are held at virtual ground and the current flowing out of them is converted to a voltage using an I/V converter (eg. using OPA1612). This gives a lower distortion (according to ESS datasheet). But it also...

It doesn't matter if the inputs are shorted or open. It has AC coupling, so after input is connected or disconnected there is a little transient, but at the end it settles to the same value. The gain setting also doesn't make a difference.

Yes, I just got one, but the offset seems a little high, 15 and 16 mV in two channels.

I am wondering what is a typical DC offset on the output of the amplifier with inputs shorted. Has anyone measured it with a DC voltmeter?

Would anyone be willing to open an SU-9n and take some pictures? It would be interesting to compare with SU-9: https://www.audiosciencereview.com/forum/index.php?threads/smsl-su-9-balanced-dac-review.16150/page-23

It would be interesting to see what are the changes in the analog output section compared with SU-9. There is a clear reduction in THD and perhaps some reduction in noise on high frequency side. The second and third harmonic distortions can be compensated by ES9038PRO, but the 5th harmonic is...

It looks like OPA1612s are being used to drive the power to the analog rails. It is probably better than ES9311 or LT3045 which have about 2 nV/Hz^(1/2) noise vs 1.2 nV for OPA1612 above 1 kHz. I guess using 2 op-amps provides enough current. The low-pass filter (with 470 uF and 3 k) has a...

Thanks for the overview. I didn't quite follow the purpose of 250 Hz modulation of the square wave in J-test file. Is it modulating the amplitude, frequency or phase of the 12 kHz square wave? Using a square wave as the main signal makes intuitive sense since the transitions are sharper. An...

This is actually easy to measure with a medium-grade AC voltmeter. Simply setup the DAC to output a continuous tone and measure the AC output voltage. It will drift at start-up and with temperature. Another effect I found is that when the signal is alternated between silence and constant high...

Not that I know. Like I said, it hasn't caught people's attention. There are just a few mentions on diyaudio, but I don't think anyone has implemented it.

It is still on the order of a few dollars, unless one uses LTZ1000, which would take a couple hundred dollars to implement property.

I suppose it's the difference between a mid-priced DAC like SMSL and some of the fancier ones. For example, Okto uses LT3045 regulators. People spend a lot of money on all kinds of things, like cables, that don't even make any measurable difference at all. In this case, there is a clear...

The output voltage is directly proportional to reference voltage. Of course, there could be other sources of drifts (in the DAC V/I conversion and op-amp I/V conversion), but they appear to be much smaller than the voltage reference drifts.