DIY Analog-to-Digital Converter project.Audio measurements tool

[Frex]

Yeah !

PCBs are arrived today, i will post pictures this evening.
Now, some work to soldered all....

Frex

[Frex]

Hello,

PCBcart has made a very good job again...
Top quality pcb.
Now, just need to find the time to soldered all of that. I love that !
I will also post pictures when it will be soldered.
The pcb fit very well in it's housing !

Frex


Top and bottom view of the prototype pcb :




To follow...

[Frex]

Hello,

I have made a false front/rear panel in cardboard, for checking the positions of mechanical parts. All seem to be ok, i can drill the real panels.
For the SMD soldering, i must unfortunately wait until saturday or sunday to have enough time and tranquility.




and anothers pictures :
front view

top view




Frex.

[Frex]

Hi,

The first board is just finished to wiring. Phew !
Now, need to take the time to test that
It's the job i love

Frex

Two picture of what it look like now.

[ikoflexer]

Impressive! What do you use for the pcb design, btw?

Looking forward to your final result!

Edit: what's the approximate total cost of building this project?

[Frex]

Hello ikoflexer,

I'm happy that my job pleased you.
I use PCAD as EDA software (it is now part of Altium).

The price for me (including the PCB) is about 300€.
If i buy others pcbs, their price will be much less because tolling cost has been
already payed.

Also, some component are optional.
The clock can be a low cost SMD oscillator (~5€) or a ultra low jitter TenT-Lab XO (40€).
The SPDIF transformer can be a low cost Murata (3€) or the high-end high CMRR digital transformer SC947-02 from Scientific-Conversion.
These different choice can also change of course the final price.

FRex.

[ghg]

Perfect job, I wish I could handle these SMD's ...

As promised, some measurements of the PCM4222 eval. board for comparison.

Test chain:

Krohn Hite 4400A ( 50 Ohm output impedance, SLA battery driven ) ->
PCM 4222 eval. board ( 560 Ohm input impedance, unbalanced input, SLA battery driven ) ->
E-MU 1616m ( coax spdif input )

At 192k, I had to replace the E-MU PS with a linear one, cause it gives a 63kHz switching artefact.

Although I own a license of HpW works and Dr. Jordan Win Audio MLS, I decided to use the latest SpectraPLUS 5.0 demo, fully functional for 30 days.

http://www.spectraplus.com/Downloads...s_50_setup.exe

0dB means ADC full scale, board input 4V rms.

Next step will be to add an AD797 inverter to the Krohn, getting balanced out,
hopefully the AD797 will drive 560 Ohm at the "sweetspot" input level ( app. -26dB ) without adding distortion.

[Frex]

Hello,

Thank you for those detailed measurements ghg.
I'm very surprised by the level of the noise floor at 192kHz!
Can you measure the RMS power level when input is shorted,
and at different sampling rate ?
(Spectraplus can display it)
I agree, it's a really interesting card, especially for this price.


For my own ADC project, powering is ok and PLD is programmed and all work fine. The 3 rear switch allow to select sampling rate (48/96/192), AC or DC input coupling, single-ended or differential input, and offset calibration for 5s.
I have start today some short measurements with my lab PSU.
When all tests will be done, i will post measurements results and some pics of
the ADC working. May be a video...What do you think ?

Frex.

[ghg]

PCM4222 eval board - Noise floor, FFT window: Hanning !!!

Some words about your measurement setup ?

Gary

[Frex]

Thank for your answer ghg.
I start to make measurements with same setup of you.
I will post all detailed result this week end.

Here, the first result, the noise floor with 50 Ohms at each inputs, differential mode, DC coupling, HPF ON, FS=48kHz (the ADC don't allow 44.1kHz)
The ADC is powered with +/-15V JRS06 PSU from P.Sjöstrom.
Digital output used is coaxial, go to SPDIF input of ESI Juli@ sound-card, ext clock mode.
FFT analysis software :Spectralplus Demo with this setup :

• FFT resolution = 1Mpts
• Average=10 (exponential)
• Fs =48kHz
• 0dB of Spectrum is 0dBFS of ADC,
• corresponding to 7.07Vrms for full-scale at the input of ADC.

(note:AOP input buffer of ADC is OPA134).

Resulting spectrum is below.
AA5381v1noisefloor48k

I post some pictures of the converter in it's box.
It's look fine

Frex.