Worlds Worst USB Interface?!

[Lambda]

How bad can it be?
is it "transparent"
whats SINAD, THD, Noise and output voltage?
Make a guess and i will later post some Measurements.

 

[JayGilb]

I can't wait for the tear down where you peel the block dot off.

 

[Killingbeans]

@JayGilb Because it's a piece of silicon substrate soldered directly to the PCB?

BTW, there's a short between two of the USB pins?

 

[tomtoo]

Is the mic input stereo?

 

[Lambda]

BTW, there's a short between two of the USB pins?

It looks like this but it works...
Maybe the solder is so oxidated it has an isolating layer.

Also the USB plug Case is not soldered at all

Is the mic input stereo?

sadly no.

 

[Lambda]

This is the output of the DAC.
SINAD of around 47dB
Output level -1.2dBV
Noise is lower then exacted-

-84dbV (-86.5dbV A) noise with a peak from the 1khz USB Clock viable.

With smoothing.
Green: 0dBFS
Orange: Output disabled
Blue:150Ohm reference (DAC noise)

 

[dasdoing]

I wonder if you could abx it vs your go-to DAC

 

[Lambda]

A THD+N of 38dB at around 300Hz is relay bad...

IMD -25dB

IMD AES:
-32dB
Super bad imaging and filter.

1/3okt 31 band multi tone:

I wonder if you could abx it vs your go-to DAC

I need build a setup to test this.
but looking at the AES IMD test im sure i can hear this giving the right test signal.
with "normal" music it might be harder.

 

[Feargal]

Maybe they could market this as the ADC for electric guitarists - no distortion pedal needed!

[edit - whoops, helps to wait until the ADC graph has been posted!]

 

[Lambda]

The ADC is surprisingly good!
-72dBFS /-79.5dBV noise with 150ohm

No clipping till -9dBV input voltage.
THD is exceptionally low with -87dB
So Almost 70dB dynamic range.
SINAD of 51dB is also ok.

 

[mansr]

Can you zoom in on the 1 kHz fundamental? I'd like to see how it compares to this monstrosity:

 

[Lambda]

Can you zoom in on the 1 kHz fundamental? I'd like to see how it compares to this monstrosity:

What Window function and FFT length did you use?

I think this is Hann and 2M

 

[garbulky]

Super bad imaging and filter.

Clearly you were listening to it wrong. It says 3d sound on the DAC not 2d.

 

[Freeway]

This thing cost all of a couple bucks at most.

 

[Gradius]

Clearly you were listening to it wrong. It says 3d sound on the DAC not 2d.

DAMN IT!

I was posting something similar.

 

[AnalogSteph]

This is the output of the DAC.
SINAD of around 47dB

It's clearly Not Happy like this, try reducing the output by 1...3 dB and see what that does. Looks like it's clipping to me. I would expect the output stage to be running on the same supply as the DAC, in which case you will never quite get to 0 dBFS. -1.2 dBV (0.87 Vrms) is almost exactly 2.5 Vpp. Alternatively, similar max output has been observed with misc. Realtek chips on +3.3VA.

 

[Lambda]

It's clearly Not Happy like this, try reducing the output by 1...3 dB and see what that does. Looks like it's clipping to me.

I have tied to find an point of better performance.

to me this looks like THD+N is failing linearly with the output.

in which case you will never quite get to 0 dBFS. -1.2 dBV (0.87 Vrms) is almost exactly 2.5 Vpp. Alternatively, similar max output has been observed with misc. Realtek chips on +3.3VA.

The output is DC coupled and at 2.5V with no signal.

i also measured this when connecting input straight to the output with a short cable

Not sure whats going on.
Looks like comb filtering to me but i cant make sense of it.

 

[tomtoo]

It

I have tied to find an point of better performance.
View attachment 167085
View attachment 167087
to me this looks like THD+N is failing linearly with the output.


The output is DC coupled and at 2.5V with no signal.

i also measured this when connecting input straight to the output with a short cable
View attachment 167089
Not sure whats going on.
Looks like comb filtering to me but i cant make sense of it.

it makes sense if you bring two timedelayd signals togheter.

 

[Roland68]

That will be a PCM2912 or something similar in economy circuit.
What does that cost?

 

[Lambda]

What does that cost?

2$ including shipping.

But there are at least 5 different version with the same caes on ebay and you don't now what version you gonna get.
Some have the chip on the front some on the back of the pcb.
some have solder ic some have epoxy blob
some have decoupling output caps (this one don't)
some have a Quartz (this one don't)

it is one of this products that might started out ok but it got "cost optimized" so often so now you don't even have output capacitors.