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...
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.
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...