Adding a word clock output to the PCM4222EVM

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Here's the single layer PCB layout. I admit it could be better, but at least you get the idea if you wanna do your own layout  ;D

J1 pinout (from left to right):

1. LRCLK IN
2. GND
3. +5V

LRCLK IN connect to AUDIO SERIAL PORT pin 5.
GND connect to AUDIO SERIAL PORT pin 9.
+5V connect to DIGITAL POWER pin 1.

Supply coupling cap is standard 0.1uF X7R ceramic.
 

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metalb00b00 said:
It has to be 74HCT, because the T stands for TTL.

For living sounds' (and others') benefit:

Specifically, the HCT has TTL logic thresholds for its inputs (the outputs swing to the rail).

The LVC family (like all CMOS parts without TTL thresholds) has input thresholds which scale with supply voltage, and they're usually 0.3*VCC for a logic low and 0.7*VCC for logic high. When driven with a 3.3V logic output, you won't meet the logic high requirement.

-a
 
metalb00b00 said:
Can also replace U9 with 74LVT245PW (same footprint TSSOP-20), so BCLK and LRCLK signals going out via the AUDIO PORT header become TTL compatible.

No. TTL compatibility matters only for the input, not the output.

-a
 
metalb00b00 said:
Here's the single layer PCB layout. I admit it could be better, but at least you get the idea if you wanna do your own layout  ;D

J1 pinout (from left to right):

1. LRCLK IN
2. GND
3. +5V

LRCLK IN connect to AUDIO SERIAL PORT pin 5.
GND connect to AUDIO SERIAL PORT pin 9.
+5V connect to DIGITAL POWER pin 1.

Supply coupling cap is standard 0.1uF X7R ceramic.

Thanks. So there's no benefit of creating a seperate line to the PSU ground for the unused inputs or the decoupling cap? I will breadboard the design anyway, so it won't have to look pretty.  ;-)

I'm new to digital stuff, but I've learned from analog design that proper grounding can make all the difference. I don't want to inject dirt into the ground that might impact the converter's performance.
 
Andy Peters said:
metalb00b00 said:
Can also replace U9 with 74LVT245PW (same footprint TSSOP-20), so BCLK and LRCLK signals going out via the AUDIO PORT header become TTL compatible.

No. TTL compatibility matters only for the input, not the output.

-a

Ok, thanks for pointing out my mistake.
 
Thanks. So there's no benefit of creating a seperate line to the PSU ground for the unused inputs or the decoupling cap? I will breadboard the design anyway, so it won't have to look pretty.  ;-)

Why not etch that layout I made? Size is only 2" x 1".  You can make a nice looking single layer board with a transparency film and some UV solder mask paints. The board will not budge when the BNC connector is securely fixed on the back panel, if not, you can always drill a few holes at the corner for screws.

I'm new to digital stuff, but I've learned from analog design that proper grounding can make all the difference. I don't want to inject dirt into the ground that might impact the converter's performance.

You won't be injecting dirt because the digital stuff are not crossing over to the analog domain.
 
I didn't realize you went through the trouble of creating a layout, thanks alot!

I built the whole thing on veroboard, it puts out a very strong clock signal now and the Aurora has no trouble syncing to it, works great.

If I need more clock outs, can I simply add another 100R on pin 13 of the SN74ALVC245PW and connect this to another input of the PC74HTC125P, for a maximum of 4 word clock outputs?

Thanks again everybody, much obliged.
 
Glad to know it's working! :)

If you need more, probably can just connect the LRCLK signal to all of the 74HCT125 inputs (pin 2, 5, 9, and 12).
Add another three 51R resistors and BNC female connectors to the outputs.
 
Thanks!

One more question. Should the BNC output have a direct connection to the chassis? Besides this I have connected the analog inputs and the PSU to chassis right now. 
 
Nice to hear that it works now. What is the new pk-pk level? If it's adjustable would be interesting to see at what point the Aurora drops out.
 
metalb00b00 said:
The one I use doesn't have a direct connection to the chassis because it's encased in a plastic body.

I asked because I still had a little trace of hum in the audio signal and suspected a ground loop. But it was the cables positions, changed them and it's perfect now.  :)
 
Hi i'd like to cook a multichannel AD using the infamous PCM4222EVM, so i've buyed and external DIY clock by audio-gd

http://www.audio-gd.com/Pro/diy/JZ1/JZEN.htm

cause reading the pcm4222 TI's datasheet seems that there's an clock in on that board ( i hope i don't misunderstand that ).

I've pointed that out for two means:

1) Report @livingsound a possible "reliable and easy" solution for his purpose ( i hope)

2) Receive some help to manage the multichannel AD goal using the pcm4222evm

So my questions are:

1) Is it possible to use ( as i've think ) an external clock ( as the audio-gd jz1) to pilot "many" pcm4222evm setted to use external clock ?

2) Which is the "best and reliable way" to switch among different freq on JZ1 clock out ? ( The JZ1 got many out ..that is one for each  freq ...as showed in picture ...so is possible to use a plain mechanical rotary switch?)

JZ1.15.JPG


3) Finally which is the "best and reliable way" to distribute the clock among the pcm4222evm ? (  is possible to use a split trasformer like the lundhal LL1589  or the like or is not necessary all that?)

thanks for the help

Rob
 
The PCM4222EVM doesn't support word clock input, the BNC connector input on the PCB requires a multiple of the sample rate to work. You could buy a super clock with x256 out, I guess these would work with the PCM4222EVM, see these:

http://www.soundonsound.com/techniques/does-your-studio-need-digital-master-clock
 
i've figured out to use the audio-gd jz1 as master clock and all the pcm4222evm as slave using the bcn in on the board...but maybe i miss something of the puzzle??!!
 
To use that JZ1 clock module...

First step, tell me, which type did you buy? Only Type3 outputs a suitable frequency.

Second step, if that's the one you bought, assuming you don't have an oscilloscope, ask the manufacturer what is the supply voltage for the module to output a 5V signal level.

Third step, make yourself a short 75 ohm impedance BNC cable for the module FO output. Connect this cable to the BNC connector (marked J11) on the first EVM board.  Set this EVM board as master.

Fourth step, make the rest of the EVM boards as slaves.

Fifth step, make yourself a multi way 2x3 IDC cable. Connect this cable to the AUDIO SERIAL PORT header (bend pin 1), with one end at the master, and the rest at the slaves.

Power them up, pray, and hope it works.
 
living sounds said:
The PCM4222EVM doesn't support word clock input, the BNC connector input on the PCB requires a multiple of the sample rate to work. You could buy a super clock with x256 out, I guess these would work with the PCM4222EVM, see these:

http://www.soundonsound.com/techniques/does-your-studio-need-digital-master-clock

Ok...seems i have to investigate more
 
living sounds said:
The PCM4222EVM doesn't support word clock input, the BNC connector input on the PCB requires a multiple of the sample rate to work. You could buy a super clock with x256 out, I guess these would work with the PCM4222EVM, see these:

http://www.soundonsound.com/techniques/does-your-studio-need-digital-master-clock

Actually it does. So I made a mistake when I said it can't be configured as a slave.
 
living sounds said:
The PCM4222EVM doesn't support word clock input, the BNC connector input on the PCB requires a multiple of the sample rate to work. You could buy a super clock with x256 out, I guess these would work with the PCM4222EVM, see these:

http://www.soundonsound.com/techniques/does-your-studio-need-digital-master-clock

Audio-Gd Jz1 type3 at F0 seems capable of 24.576MHZ out so it should be fine to manage the pcm4222 clock, don't You ?
 
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