[wackyterbacky]

This is my first post. I have learned quite a bit from reading the various forums, and I am giving a little in return.

I will get some diagrams posted, but for now just wanted to document this idea. Pictures of the Juli@ can be found on http://www.digit-life.com/articles2/...lia/index.html and the I2S pinout on http://www.diyaudio.com/forums/showt...?postid=179778

I upgraded to a used Perpetual P-3A and wanted to investigate an I2S connection. I use foobar2000 and Kernel Streaming and flac files.

The Juli@ has an interesting design - there are two circuit boards connected by dual in line headers ( a 20 pin designated J3 and a 10 pin designated J7). The "digital" board has the PCI connection and the Envy-24 HT ( 1724 ) controller chip. The analog board has an AK4358 DAC and an AKM ADC chip as well. The "analog" board can be
rotated 180 degrees to change from RCA unbalanced connectors to Balanced 1/4" Phono plugs. Therefore there are matching connectors on opposite sides of the analog board.

I downloaded the datasheets for the Envy and the AKM DAC. The 1724 is capable of multichannel I2S outputs, and the AK4358 has multiple I2S inputs. I figured the I2S interface was going through the pin headers from digital to analog boards.

I took a multimeter and buzzed out the connectors and the chips, and found the following signals:

J3 ( 20 pin header )

J3 Pin 1 -> 1724 PSDOUT[0] ( I2S data out) -> AK4358 SDTI1 (I2S data in)

J3 Pin 5 -> 1724 PSYNC ( I2S Word Clock ) -> AK4358 LRCK (I2S
Left/Right Word clock)

J3 Pin 7 -> 1724 PBCLK ( I2S bit clock out ) -> AK4358 BICK ( I2S bit clock in )

J3 Pin 9 - > Xilinx on the digital board -> AK4358 MCLK ( I2S Master Clock in )

J7 ( 10 pin header )

J7 Pin 5 -> Digital VSS ( Actually several pins on J7 are VSS )

Here I had all the I2S signals ( Except DEEM as in Audio alchemy, but that does not exist on the Juli@ board )

Since there are two sets of headers, one set is on the top edge of the analog board, and has nothing plugged into it. I took an old keyboard cable with a 6 pin mini-Din connector and soldered the loose wire ends to wire wrap type pins, and plugged them into the signals listed above.
The cable is shielded and the shield drain wire is connected to the mini-din connector shroud.

I simply broke off the sixth pin inside the mini-din to yield a 5 pin mini-din, and connected it up.

Believe it or not, this works perfectly with the P-3A DAC. I get I2S lock and can drive it with 16/44 up to 24/96 signals. It sounds great on my system, much better than the spdif connection. The only weirdness is the P-3A phase invert light is on all the time. I may send an email to
Perpetual Tech and see what they say.

If you have a Juli@, you know there are three installed devices - Ch12, Ch34 and Ch1234. Ch12 is the analog out, Ch34 is the spdif out and Ch1234 is supposed to be both out. You have to use Ch12 or Ch1234 for my idea to work, since you are tapping the signals going to the onboard DAC. I tried to use Ch1234 and compare I2S with spdif but Juli@ is not cooperating.

Now, I admit this is cheap and dirty. I should use better quality cable, connectors and probably buffer the signals with a 74LS244 or something. But it works and I am digging it for now.

I may do a version 2 with active drivers and terminated 50 ohm mini-coax cable for each signal, as described somewhere by elso kwak. I lost the link.

When I have time I will post pictures, scope tracings, etc . . .

 

[003]

If I sent you my Juli@ and paid you, would you mod it for me?

 

[003]

Bump for a great thread!!!

If I understand correctly, does this mean the juli@ supports some form of click-sync with this mod?? That would be amazing news, afaik the only way to get that now is with the E-MU line of sound cards which have buggy and confusing drivers, and they only support clock-sync with an add on pci card (so the sound card takes two pci slots).

 

[wackyterbacky]

The Juli@ natively supports an external clock. There are two RCA connectors on the extension cable. One is digital out (spdif) and the other digital input. The control panel (JuliPan.exe) allows you to select internal or external clock. I have not tested this.

What I built uses the Juli@ internal clock but outputs the 4 I2S signals that make up the native synchronous DAC inputs.

I wonder if you do both - externally clock from a DAC and output the I2S data?

 

[003]

Remind me again what the advantage of I2S is? And what exactly IS i2s?

I thought the Juli@ had no way of syncing clocks. How exactly do you do it? What connectors and cables are necessary and what external hardware and software is needed?

 

[Joshatdot]

http://en.wikipedia.org/wiki/I2S

 

[wackyterbacky]

I2S was designed as a "chip to chip" 3 wire interface with separate but synchronous serial data, word clock ( Left/Right) and bit clock. Here is a link to the Philips I2S specification. It was adopted by several companies ( Audio Alchemy, Perpetual Tech, Camelot, Northstar, Muse ) as a connection between CD players, DAC and digital processors.

There seem to be several connector standards: Alchemy, Perpetual and Camelot are plug compatible. There are at least two others out there.

http://www.nxp.com/acrobat_download/various/I2SBUS.pdf

 

[003]

So is it the same thing (or can it achieve the same result) as the word clock sync feature on the E-MU cards? Why would it be preferred to spdif?

 

[pantapei10]

great thread

 

[dahlhaus]

Hi. I'm using Juli@ card and April Music stello DA100 Signature DAC.
I2S pin-out is on the manual of the DAC and also on my blog:

http://wagnerian.textcube.com/339

I removed the analog board of Juli@ card and plugged in a digital audio connector of a CD-ROM drive instead.
J3 Pin 1, 5, 7, 9 from the Juli@ card is connected via this connector to a PS/2 mouse cable.
I verified all the connections with a multimeter and plugged the cable into the DAC.

And now what? No sound!
Does anybody have an idea what's wrong?

 

[FallenAngel]

Got the ground?

Also, what length is your I2S cable?

 

[b0dhi]

Thanks wackyterbacky. Valuable info.

 

[dahlhaus]

Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif Got the ground? Also, what length is your I2S cable?

Today I bought an I2S cable from April Music, the DAC maker, and a 5 pin mini DIN connector.
I verified all the connection, including ground, with a multimeter.
I don't know the GND pin of the J3 header, but I got the ground anyway.
The length of the cable is less than one meter.

 

[audioengr]

Having modded a LOT of P-3A DAC's in the past (not anymore), and having several I2S interfaces that can drive this, I can give you some tips on this:

1) the P-3A needs 5V signal levels, not 3.3V
2) The inputs are terminated with 100 ohms to ground
3) MCLK needs to be 128Fs or 96kHz will not work (this is usually 256Fs (Fs is the sample-rate frequency)) You will probably have to divide MCLK by 2.
4) the input receiver on the P-3A for the I2S is a rather slow RS-422 receiver - (I replaced it in my mods with a faster device and changed the voltage to 3.3V)

I used to have a special Off-Ramp and generated this for the P-3A.

I2S is the lowest jitter interface to a DAC, provided the implemetation is well-executed.

Warning: Not all DAC's handle I2S well as far as muting. Even Northstar does it differently for the 192 versus the Extremo. If you kludge I2S into a DAC that does not have this interface, you risk loud pops and even DC at the output when the power is removed from the driving card or the I2S cable is pulled.

Steve N.
Empirical Audio

 

[dahlhaus]

I've found out something strange.
My multimeter says the voltage of the signal is half the normal.
The three clock pins are 1.65V while the data pin is only 0.85V.
The multimeter reads 5V normally from USB.
What can I do?