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SMSL D400EX & D400ES - Impressions Thread
Nov 17, 2022 at 8:42 PM Post #61 of 284
I think I’ll wait for another AKM DAC.

The D400ES I received in error is sounding good after a few days of non-stop music playing but I’m not impressed with the unit due to the fact when I turn off the PCM Filters all I heard is noise. I’ve had a few SMSL misgivings over the years … I guess they got me once again

Maybe I’ll try a future AKM Gustard next time. As far as R2R DAC’s I’m sure they are great and all but I really don’t like leaving them on all the time … it is just me … I like things ‘on’ when using and ‘off’ when I’m not using … I hate standby buttons as well …
 
Nov 18, 2022 at 2:02 AM Post #62 of 284
jraheel said:
Hi @HermannS
I got mine ten days back and it’s been burning in. You mentioned you have had Topping’s D90SE which was my own previous dac (still lying around). I use it with Topping’s A90 amp feeding to Focal’s Utopia. I have noticed a very noticeable difference in loudness compared to D90SE. Did you notice the same thing?

I have contacted Apos about it, and thinking of either replacing it or returning for a refund (I have had bad experience with SMSL products over the years). So kindly tell me is this a faulty unit that I got or you are experiencing the same
Click to expand...
Would this just be a different output voltage?
 
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Nov 18, 2022 at 2:58 AM Post #63 of 284
I got mine ten days back and it’s been burning in. You mentioned you have had Topping’s D90SE which was my own previous dac (still lying around). I use it with Topping’s A90 amp feeding to Focal’s Utopia. I have noticed a very noticeable difference in loudness compared to D90SE. Did you notice the same thing?

I have contacted Apos about it, and thinking of either replacing it or returning for a refund (I have had bad experience with SMSL products over the years). So kindly tell me is this a faulty unit that I got or you are experiencing the same
Click to expand...
I run mine at 0dB. Can't say that the Topping is significantly louder. It's roughly in the same ballpark. Is it possible that the Topping is configured for high output level? That difference is substantial.
 
Nov 18, 2022 at 3:03 AM Post #65 of 284
HermannS said:
I run mine at 0dB. Can't say that the Topping is significantly louder. It's roughly in the same ballpark. Is it possible that the Topping is configured for high output level? That difference is substantial.
Click to expand...
could be. I bought mine from Apos, and I have contacted them about it for a replacement. Once that arrives, I might check it out using a voltmeter, if that one is quieter too. I just wanted to know if you are experiencing the same. Thanks
 
Nov 18, 2022 at 7:22 PM Post #67 of 284
Well, I couldn't wait and have started the modifications. I found a couple of things to improve.
This is probably a world premiere :grin: . The overview of the D400EX board.

A funny thing is that it's mounted upside-down. This must be a design mistake. Any other manufacturer would have put it upright with the mains plug to the left. It looks as if it had been designed that way. However, the front panel is 180° flipped. This makes no sense. I think they accidentally designed the front the wrong way around and then it was too late to fix it cheaply, wanting to be the first manufacturer with the new AKM chipset. So they just flipped everything.

What immediately grabbed my attention are the big, blue coupling caps. I-do-not-want-caps-in-the-signal-path (dammit)!! They block the 2.5V bias offset voltage from the I/V stage. Luckily the AKM datasheet presents a formula as to how to size a specific resistor to get rid of the offset. I have done that experimentally on one channel and the result is good. The coupling caps smear the treble texture and put some ringing on top. Not terribly much, but it's there.

The yellow caps are Nichicon FW (budget), the black ones in the lower left are Nichicon KZ (top notch). The FWs will be replaced with FG ("fine gold"). KZs are too big.

There is a mains filter with over-voltage protection and inrush current limiter. Bravo!
The biggest shocker in terms of sound change was the replacement of the fuse, which is soldered to the board. Totally absurd, but true.

The main power supply consists of two switching sups, +/- 12V. The digital domain is branched off from +12V and goes into a 6V step-down regulator. Two 11V linear regulators feed the opamps. For the AKM chips, there are a number of dedicated little linear regs. For the 5V VRef of the DAC there are four step-down regs with the marking scratched off.

I'll be mostly busy with the I/V stage and the DAC's VRef because that's where the sound color primarily comes from. I've learned that with the D90SE.
 

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Nov 19, 2022 at 1:18 AM Post #68 of 284
jraheel said:
yes there is a difference at the 0db for both DACs, ~5.25V vs ~4.7V, but that should not lead to this much drop in volume level
Click to expand...
Hello.You didn't think to put a 4.2 volt output on the D90SE to compare correctly!So set 4.2 volts and then write the impressions. :smile_phones:
 
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Nov 19, 2022 at 1:30 AM Post #69 of 284
HermannS said:
A funny thing is that it's mounted upside-down. This must be a design mistake. Any other manufacturer would have put it upright with the mains plug to the left. It looks as if it had been designed that way. However, the front panel is 180° flipped.


The biggest shocker in terms of sound change was the replacement of the fuse, which is soldered to the board. Totally absurd, but true.
Click to expand...
This is a new design from SMSL, it's not a design error. :slight_smile: On the SU10, the board is also inverted.
The fuse is soldered on the board where?I didn't find it.
 
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