08-16-2006, 06:17 AM
Aside from the jumpers, what changed in the new schematics and why are they better ? Also why do you use two preamps for the Analog-2 design ?
Did you test your design ?
We are very interested in this, but since electronics is not our field, we're a bit afraid of frying the head unit (or the ipod)
08-16-2006, 06:53 AM
Originally Posted by FroMage
The changes mostly effect the power suply. It is improved to have better realitility.
The second analog alternative needs 2 op.amps, because the analog input ground also needs to be connected to the op.amp. I don't see the reason why, but the datasheet says so.
I didn't have the time to test them. I'm currently working on that.
It is impossible to fry the the head unit, becsuse if the CS8406 doesen't get the master clock or the data itself the output is connected to the ground. It also has a transformer, witch makes it even safer and reduces ground noises.
Tha analog input ( example Ipod ) also can not be fryed. The capacitor ( 6.8 uF ) gives some protection, and the op. amp shouldn't allow any chargebacks.
I found another desing on the net witch is a wireless audio transmitter. It uses cs5330 for AD and another CS ic to make it back to analog. It doesen't have op amp before the cs5330. I want to test this desing also. Maybe today
But there is a mutch simpler way to connect analog source to hu. I'v tried it and it works, but I don't think anybody should use it. In this case you have to connect the analog input directly to the HU's main chip's analog input pins. If you do this then the analog input will work even in radio or casette mode, and I don't know how it will effect the lifetime of the HU.
08-16-2006, 09:37 AM
OK thanks, that sounds great. Let us know how that works out.
I think I'll stick on the 18bit design, since it seems the connects2 uses that too.
Is there a reason why you use the TLC27L2 on this one instead of the TLC272 on the first design and the Analog-2 ?
08-16-2006, 10:37 AM
No special reason for TLC27L2.
I only found this in the schematics libary. But I think any op.amp would do fine instead of TLC272.
08-16-2006, 01:44 PM
Finally after a few month of design and a few unsuccesfull prototipes I have DONE it !!!!
The analog is now in SPDIF format !!!
The prototipe I've build today WORKS !!!
I'm so happy about it.
Aldough it has a few bugs too.
It's quality is like an old casette tape. It is very noisey. And only one channel works. I don't understand the problem yet, but I will solve it. My oppinion is thet the problems are mostly from using ceramic capacitors insted of mylar.
Here is the picture of the board.
08-16-2006, 02:22 PM
Terrific! Now let's hope you manage to get good sound too.
I see you use the headphone output of the ipod instead of the line output from the dock, perhaps the signal is too high for the preamp ?
08-16-2006, 02:27 PM
Sorry, but I don't have a dock connector.
And this prototipe doesen't have op.amp
I will try it with the op.amp too
08-17-2006, 04:34 AM
I've attached the pcb printout just in case someone wants to experiment also. It is now almost noiseless, but only the left or right channel works. To make it work you have to short circuit the other channel's pin of cs5330 to the ground . The Cs5331 wont work in this connection, because it has different output data format. If you want to use cs5331 you have to disconnect pin 5 of cs8406 from ground and connect it to 5 volt.
This connection doesen't have op amp, but the connector on the bottom makes it possible to connect it. The 4 pads on the upper right represents the transformer, and the wide lines are the spdif output.
I wont be reachable for 1 week, and I can't test during this period.
08-17-2006, 05:32 AM
This is annoying, only one channel... Perhaps with an oscilloscope you can check the data sent by the 5330, at least the docs say what it should look like, whereas I'm not sure what the SPDIF signal should look like. What do you plug the SPDIF output into to test it ? If it's a computer there should be a way of figuring what type of signal is output. In particular I didn't find in the docs of the 8406 where you specify whether the stream is 2 or 4 channels. Perhaps it's outputting in 4 channels ?
08-17-2006, 06:02 AM
I plug the SPDIF output to a home cinema amplifier not a computer.
I will test the circuit with different op.amps to see if they work out.
I'll inform you, but you have to wait at least 1 week for this.