Measurements of a $5 DAC

[m8o]

Lives up to every penny spent.

 

[Scytales]

Frequency response
This is what happens when you buy the cheapest DAC because all looks the same. It has an incredibly poor frequency response that drops off after 1 kHz.

View attachment 406166

This curve reminds me the frequency response of the FN1242 DAC chip from Niigata Seimitsu Luxman used to call "Fluency DAC". From the datasheet of said chip :

Luxman devices with this unusual DAC inside were not cheap, by any standard.

 

[VientoB]

I'm surprised jitter isnt worse, but the distortion is just so bad anyway.

 

[Natal]

This fr is clearly audible maybe not to some of these reviewers >80 years old .

I have this DAC for my TV. I wondered why it sounded fine as I see it rolls off after 1000 khz when my hearing loss takes place. I'm 83. No need to buy anything more expensive.

 

[torgeirs]

Dont know with this chip but the cheap dacs with western chips are hampered with too small components in output filter. So if you hear the distortion it is pure analog disortion from caps and resistors.
The chip itself is much, much better.
Here they propably have messed up the component values also.
But the nice ting is that they are quiet if one use spdif. Then there is no ground loop hum

 

[torgeirs]

https://www.ti.com/lit/an/slyt796a/slyt796a.pdf?ts=1731612114047

So in the olden days the chip was the expensive and limiting part regarding distortion. Now it has become the analog output filter that is the limiting factor on a lot of dacs

 

[solderdude]

This curve reminds me the frequency response of the FN1242 DAC chip from Niigata Seimitsu Luxman used to call "Fluency DAC". From the datasheet of said chip :

View attachment 406523

Luxman devices with this unusual DAC inside were not cheap, by any standard.

Looks like the response of a filterless DAC.
9kHz -0.2dB, 13kHz -1dB (44.1kHz), 18kHz -2.5dB

 

[torgeirs]

The spec cheet says internal filter in dac chip. But maybe the chips are rejects

 

[solderdude]

All DACs have filters unless they are totally broken by design (the filterless NOS DACs).
This particular DAC is too 'broken' and one can only guess why these were sold and what the f-up was (most likely assembly error of post filter component values).

 

[JSmith]

5$ DAC

JSmith

 

[johny_2000]

If GC8418 is indeed the chip used in this DAC, here is the datasheet

GC8418 is a CMOS monolithic receiver and converter circuit for digital audio signals. It has eight-to-one inputs and supports IEC60958, S/PDIF, EIAJ CP1201 and AES3 audio interfaces. GC8418 integrates a serial digital audio output interface, an interpolation filter, a multi-bit digital-to-analog converter, and an output analog filter. The internal phase-locked loop can recover a clean clock signal from the AES3 data stream.

105 dB dynamic range (18-24 bit, A-weighted)
-90 dB THD+N (18-24 bit, 0 dBFS)
Output amplitude Peak-to-Peak = 1/2 power supply voltage. In case of 5V supply it will be 2.5Vpp = 0.88Vrms.

Price: $0.45 for 1000+ pcs.

 

[johny_2000]

All DACs have filters unless they are totally broken by design (the filterless NOS DACs).
This particular DAC is too 'broken' and one can only guess why these were sold and what the f-up was (most likely assembly error of post filter component values).

From the chip datasheet:
The analog filter of GC8418 is a switched capacitor filter connected to a low-pass filter.
Its frequency response is shown in the following typical characteristic curve.

There are three oversampling modes based on the input sample rate:
SSM = Single-Speed Mode, up to 50 kHz SR, 128x oversample ratio,
DSM = Double-Speed Mode, up to 100 kHz SR, 64x oversample ratio
QSM = Quad-Speed Mode, up to 192 kHz SR, 32x oversample ratio.

 

[Chrispy]

Nobody does.

Yes, I prefer most make no audible difference unless quite compromised.

 

[Curupira]

And this is why I don't say all DACs sound the same

I daresay some would call it euohonic and warm with that FR and distortion profile!

 

[WalterW]

Nobody should be so poor to need to buy this one.

 

[AnalogSteph]

Here they propably have messed up the component values also.

Agree. Looks like there might be an RC filter on the output with the capacitor being orders of magnitude larger than it should be. That would explain both the frequency response and the excessive distortion that goes up with frequency.

 

[johny_2000]

Agree. Looks like there might be an RC filter on the output with the capacitor being orders of magnitude larger than it should be. That would explain both the frequency response and the excessive distortion that goes up with frequency.

The schematic diagram suggested in the datasheet:

In this design, 33 Ohms and 39 nF give us a cutoff frequency of 123'663 Hz (-3 dB).

But it is not known what exactly is installed on the real board. It can be seen that at the output there were places for installing decoupling electrolytic capacitors and an operational amplifier. But all this is bypassed with jumpers, to reduce the price at the expense of output characteristics.

 

[gvl]

My expectations were fully met, thank you.

 

[AnalogSteph]

In this design, 33 Ohms and 39 nF give us a cutoff frequency of 123'663 Hz (-3 dB).

But it is not known what exactly is installed on the real board.

I spy some "331" = 330 ohm resistors (R23 and ?), along with what I think is the capacitors to go along with them (C23 and C22). I can only assume that they intended to put 3n9s on there but a random other value of same physical size got picked instead (doing the math, it could be 68n). Crummy dielectric, of course. All the odd-order harmonics we're seeing are probably from that and/or an unhappy output stage.

 

[Billy Budapest]

I’ll stick with the Apple dongle DAC. $9.00 for pretty decent performance. Although USB-C input only.