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SMSL D300 Review (Balanced DAC)

Krampi

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Sorry, but no one will be able to tell you, since the marking of operational amplifiers has been specially erased by the manufacturer.
View attachment 303053
This is usually done when operating amplifiers of medium or low quality are installed...
:(
There was an accident and 2 op amps out of 3 were destroyed, that's why it would be necessary for me to know, what opa to put in the right positions. I asked SMSL-Mandy but she hasn't answered, yet.
 

v1adpetrov2

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There was an accident and 2 op amps out of 3 were destroyed, that's why it would be necessary for me to know, what opa to put in the right positions. I asked SMSL-Mandy but she hasn't answered, yet.
If the manufacturer erases the marking of the op-amp, it means that he has installed the cheapest op-amp, such as NE5532 or JRC2068.
At best it will be OPA2132...
Therefore, feel free to install all three OPA1612 op-amps and you will be happy!...
...And if you like the imitation of "warm tube sound", then you can put OPA1656. ;)
 
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Krampi

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If the manufacturer erases the marking of the op-amp, it means that he has installed the cheapest op-amp, such as NE5532 or JRC2068.
At best it will be OPA2132...
Therefore, feel free to install all three OPA1612 op-amps and you will be happy!...
...And if you like the imitation of "warm tube sound", then you can put OPA1656. ;)
It is a pathetic solution that the manufacturer deletes the type designation of the cheap part. It doesn't even take responsibility for the decision to use a low-quality component in its product.
SMSL-Mandy is also gone, maybe she never existed. (S)He's on vacation, that's why she doesn't respond to my inquiry. :D
Thanks for the advice on op amps!
Have you changed opas in the D300 yourself? Have you done any tuning? :)
I tried the AD8397 in place of the subtractor circuit, it had an amazing sound, but it was terribly hot. In the I/V stage, the OPA1656s make great music! :) But in the subtractive position, I hear their sound as "thin, disembodied". Of course, this statement applies to my current sound system :)
 
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v1adpetrov2

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It is a pathetic solution that the manufacturer deletes the type designation of the cheap part. It doesn't even take responsibility for the decision to use a low-quality component in its product.
SMSL-Mandy is also gone, maybe she never existed. (S)He's on vacation, that's why she doesn't respond to my inquiry. :D
Thanks for the advice on op amps!
Have you changed opas in the D300 yourself? Have you done any tuning? :)
I tried the AD8397 in place of the subtractor circuit, it had an amazing sound, but it was terribly hot. In the I/V stage, the OPA1656s make great music! :) But in the subtractive position, I hear their sound as "thin, disembodied". Of course, this statement applies to my current sound system :)
No, I didn't change anything in the D300.
I used op-amps OPA1656 when modifying the BRZHIFI 3255XLR amplifier .
There, these op-amps are used as a pre-amplifier with a gain of = 3.2
 

Krampi

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We took a peek inside the D300, what's under the hood? After the I/V stage, resistors of different values were installed in the two channels by SMSL. What can be seen in the attached picture, is the factory condition! The difference between the resistance values of the two channels is 10x.
In my friend's D300, 2pcs 10 ohms were installed in one channel, 1pcs 20 ohm and 1pcs 50 ohm in the other channel, in the same position.
What's going on at SMSL??! It's a shame!
 

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Peerke007

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We took a peek inside the D300, what's under the hood? After the I/V stage, resistors of different values were installed in the two channels by SMSL. What can be seen in the attached picture, is the factory condition! The difference between the resistance values of the two channels is 10x.
In my friend's D300, 2pcs 10 ohms were installed in one channel, 1pcs 20 ohm and 1pcs 50 ohm in the other channel, in the same position.
What's going on at SMSL??! It's a shame!
But how did it sound?
 

Peerke007

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We also looked under the hood because there was an audible difference between the two channels. Mainly in volume.
And you didn't sent the unit back under warranty?
 

Snoopy

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I wonder if this is a thing with other units also.
Just use whatever parts are available or if this was a refurbished unit that got fixed ..
 

Krampi

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I have reverse enginered this schematic from D300, if anyone is interested
 

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Vannel

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I have rolled back the MCU and now it's back to normal for PRE amp mode again.

Trick is to only attach USB cable AFTER you have the program loaded and the box prevented from booting via the power/ ftn button method

V1.0 MCU Hex file attached, just added .zip to file name so I could attch
..I resume this old post and resume my experience :

I've got a D300 unit , did not working whit any Mac Book I have tried ( plaing Spotify in USB INPUT display shown an high sample rate whit audio distorted ).
It worked ok whit a Lenovo pc but there was no PREAMP mode, only FIXED VOLUME.

I did the Firmware upgrade 1v1 ( the first one posted by TOKU ) , now I've got the PREAMP mode but no audio come out from the box , not from XLR neither RCA.

I've tried to flash the firmware version you posted but I can download it only as a zip file I can not unzip whit anything ..

Any advice ?..

Thank you so much
 
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Vannel

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Thank you very much!!!
I flashed my D300 with your file - the pops disappeared and the preamp functions were restored! :)
If it's not a secret, on which site were you able to find this file?
Hello there, I've tried to flash the same file but I can download it as a Zipped file that I can unzip whit anything I tried....where am I doing wrong ?..
Thank you
m
 

TK750

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Hello there, I've tried to flash the same file but I can download it as a Zipped file that I can unzip whit anything I tried....where am I doing wrong ?..
Thank you
m

It is not a zipped file, the person that uploaded it just added .zip to the filename in order to be allowed to upload it to ASR. Once you have downloaded it, simply remove the .zip from the filename
 

DrSalvia

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We took a peek inside the D300, what's under the hood? After the I/V stage, resistors of different values were installed in the two channels by SMSL. What can be seen in the attached picture, is the factory condition! The difference between the resistance values of the two channels is 10x.
In my friend's D300, 2pcs 10 ohms were installed in one channel, 1pcs 20 ohm and 1pcs 50 ohm in the other channel, in the same position.
What's going on at SMSL??! It's a shame!
I have 75 + 75 ohm in one, and 5+10 ohm in other channel. What the...
 

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Vannel

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It is not a zipped file, the person that uploaded it just added .zip to the filename in order to be allowed to upload it to ASR. Once you have downloaded it, simply remove the .zip from the filename
..thank you for reply.
Yes, after some work I realized it , did the upgrade but same result : seems everything work as it should except no audio signal out from every output in every mode.
I returned it to the Italian seller that told me he will try to contact SMSL..I wrote them too but in 2 months no reply yet.
 

Krampi

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I have 75 + 75 ohm in one, and 5+10 ohm in other channel. What the...
For example, if you can send a 1kHz signal to the D300, you may want to measure the signal level at the XLR outputs. According to the signals, the magnitude of the +/- phase signals on the symmetrical outputs is different! The signal on the IOUT_LP/IOUT_LN and IOUT_RP/IOUT_RN outputs of the DAC chip are different, although they should be the same! The signal levels at the I/V stage outputs are also different! This is (presumably) a variance inaccuracy of the DAC chip. It really is a malicious assumption that SMSL has selectively fitted the D300 with out-of-tolerance specification chips. And facts are stubborn things, as I have -so far- encountered at least 4 pcs such D300s. The 75+75 ohm/5+10 ohm is to compensate for this signal level difference (?) I hope no more things come out about the D300! :( There is a solution for all these - fortunately - but it takes a lot of time to trim and adjust. But at the end of the process, you get sound quality that is several times higher than its price range! :)
 

DrSalvia

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For example, if you can send a 1kHz signal to the D300, you may want to measure the signal level at the XLR outputs. According to the signals, the magnitude of the +/- phase signals on the symmetrical outputs is different! The signal on the IOUT_LP/IOUT_LN and IOUT_RP/IOUT_RN outputs of the DAC chip are different, although they should be the same! The signal levels at the I/V stage outputs are also different! This is (presumably) a variance inaccuracy of the DAC chip. It really is a malicious assumption that SMSL has selectively fitted the D300 with out-of-tolerance specification chips. And facts are stubborn things, as I have -so far- encountered at least 4 pcs such D300s. The 75+75 ohm/5+10 ohm is to compensate for this signal level difference (?) I hope no more things come out about the D300! :( There is a solution for all these - fortunately - but it takes a lot of time to trim and adjust. But at the end of the process, you get sound quality that is several times higher than its price range! :)
Two options, either rejecting the chips or confusing the resistors on each(?!) device. This looks either like deception of the consumer, or simply incompetence. Representatives of SMSL do not want to comment? I will think twice about buying devices from this company in the future.
 

Krampi

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Two options, either rejecting the chips or confusing the resistors on each(?!) device. This looks either like deception of the consumer, or simply incompetence. Representatives of SMSL do not want to comment? I will think twice about buying devices from this company in the future.
It's certainly true that their support is terrible! This is reflected in this forum. The firmware and other problems raised, which are not responded to at all.
 
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