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PostPosted: Fri Apr 18, 2008 4:43 pm 
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Layout for the motherboard which will receive the FPGA module is done. It is a standard double sided board with ground plane, 100x120 mm. I will have it made by Olimex, their prices are unreal.

It is for experimentation, but it will probably be included as-is in the finished DAC (that's the idea).

Features :

- 5V -> 3.3V regulator (the digital supply will be 5V then, but using a 3.3V external SMPS is still possible, I put a connector for that).
- CS8406 SPDIF output : 1 optical + 1 transformer isolated, same signal on both.
- CS8416 SPDIF inputs : 2 isolated + 4 non-isolated + 1 optical
(optical SPDIF input also connected to a FPGA input pin, in case we want to input some ADAT or any optical signal).
- General purpose optical output (tied to FPGA pin) : for ADAT, Wordclock, sending clock to transport, whatever.
- SATA port with 1 clock output and 1 SPDIF input, impedance 100 ohms, differential twisted pair.
- General purpose differential output port (isolated) : wordclock, etc.
- Big connector to plug the FPGA module (it goes above like a sandwich, takes less space this way).
- Connector for the actual DAC module with 24 outputs, 8 inputs, translated from 3.3 to 5V, and I²C.
- I²C EEPROM for identification.
- Flat cable connector with remaining FPGA IOs (9 IO, 6 IN, 3.3V).
- a very nice LED.

Now I will need a reflow oven. I will get a cheapo oven from the thrift store, but I will need a controller. Did any of you try any of them ?


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PostPosted: Fri Apr 18, 2008 8:28 pm 
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Location: Kansas City, MO
Peufeu, I just did some toaster oven soldering for the first time the other day. No controller. Just turned up the oven to 425F (225C) and waited for the paste to bubble up and turn shiny. Here are some before and after pics (the board worked, so I assumed the chips are fine). Of course, it helps to get a stencil (I got mine from Stencils Unlimited). There still may be some bridging (see third pic), but these are easily cleaned up with the usual methods. Of course, I realize you may have special requirements that I am not aware of, so YMMV. Good luck!

Before toasting paste is dull gray
Image

I used an Oster convection oven (~$60 USD)
Image

After coming out of the oven
Image

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He's not hi-fi, he's my stereo.
DIY projects:
http://www.ezdiyaudio.com


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PostPosted: Fri Apr 18, 2008 10:13 pm 
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I ordered the reflow toaster controller from Spark Fun.
Now I need to find a cheap oven (should be easy).

And SMD stencils...


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PostPosted: Tue Apr 22, 2008 8:58 pm 
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Those damn boards are finally ordered.


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PostPosted: Sat Apr 26, 2008 4:19 pm 
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I was really fed up with the TDA1545 DAC, so I got myself a Terratec DMX 6Fire USB, 24-192, 6 channels, over USB2, windows only of course, € 220.

The construction feels solid, metallic enclosure, lots of ports, this box is very neat.
This device is a clock master, it doesn't use USB for clocking.

Overall sound quality is revolting. Bass is quite dynamic, there are some details present, and all the rest is harsh, thin, aggressive, and uninteresting. It sounds like a badly implemented 1-bit, from the good old days when digital really sucked.

The sound of the headphone jack is remarkably identical to the sound through the speakers, except the bass has been murdered and it is still more agressive and harsh.

After listening to it for 15 minutes, I got bored, opened it, screamed, closed it, and will pack it and return it for refund.

in a word, worse than a 30 € divx player, in absolute quality, and obviously the price/performance ratio is a total failure.

Opening it reveals :

- Cypress USB/CPU chip
- Xilinx Spartan-3E 100
- 24.576 and 22.592 MHz clocks fed from unbypassed supplies (just a choke)
- Obviously the clock (instead of being properly routed) goes through the FPGA, then through about 7 cm of trace, then to the DAC.
- DAC is CS42426
- Opamps are JRC4580
- Not a single film cap in sight, everything is either ceramic or no-name electrolytics (Evercon, Suncap, all signal caps are Canicon), so probably rather low lifetime...
- All audio filter caps are ceramic of course
- A couple low-ESR caps around the ADC, one at the DAC
- And a bit of green wire ! (which is actually red) so apparently Terratec is too cheap to respin a failed PCB.

Verdict : Complete Failure.

It is much worse than the sound from my desktop motherboard (which is below average), much worse than the sound from my RME (which is average) and it is even worse than the sound from the laptop's line out (which so totally sucks).

Innards :

http://home.peufeu.com/nik/dac/Terratec ... e_USB1.jpg
http://home.peufeu.com/nik/dac/Terratec ... e_USB2.jpg
http://home.peufeu.com/nik/dac/Terratec ... e_USB3.jpg


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PostPosted: Sat Apr 26, 2008 9:51 pm 
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Location: Norwich, UK
Disappointing - Terratec stuff is usually pretty good, although you can bet that they are being forced to make cheaper and cheaper crap in order to compete with Creative's (ha) crap.

I'm not sure if the USB Audio standard actually covers sound output above 48KHz 16-bit stereo. I haven't had any luck finding any chipsets that do 96KHz/24 bit that uses USB 2.0, although there must be some out there. The fact that this one is Windows only points to it being a custom solution rather than using any USB standard protocol.


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PostPosted: Sat Apr 26, 2008 10:14 pm 
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It's custom and asynchronous.


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PostPosted: Tue Apr 29, 2008 5:42 pm 
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I got the spark fun reflow oven kit.

I have created a private forum for discussing about the project. Those who want to participate actively may send me an email.

FireWire :

After all, seems that the Dice manufacturers don't really want us to get an eval board for less than $1500.


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PostPosted: Tue Apr 29, 2008 7:18 pm 
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Location: near Venice, Italy
peufeu wrote:
I have created a private forum for discussing about the project. Those who want to participate actively may send me an email.


You have mail (I sent you from the other place) :D


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PostPosted: Wed Apr 30, 2008 8:41 am 
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OK, er....

I got several emails... I forgot to mention that there is no DAC to listen to yet, so please join only if you can participate in the first stages of the design, that means FPGA, embedded programming, highspeed digital, etc. When the thing is usable, and stable, in a few months hopefully, we will need to test DACs and IVs, etc, but not right now.

PCBs should arrive in an hour if Fedex tracking is good. Yesssss.


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PostPosted: Wed Apr 30, 2008 10:42 am 
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Got PCBs.
Toaster over (€40) ordered.

I need stencils.


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PostPosted: Mon May 05, 2008 10:20 am 
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Joined: Sat Aug 13, 2005 11:20 pm
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Location: Italy
peufeu wrote:
I will send the FPGA PCB for fabrication on Monday. This means you, guys, only have three days to tell me where I fucked up !

Here are all the files (PDF and Altium).

http://home.peufeu.com/nik/netfpga/FPGA ... 080417.zip

What keeps me up at night is : which configuration pins work on 3.3V and which ones work on 2.5V ?


Sorry peufeu this link is intentionally dead or do you have some problem with the server?

ciao
andrea


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PostPosted: Mon May 05, 2008 9:36 pm 
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Everything is on the private forum now.
If you want to participate, send me a mail for access.

Status :

- FPGA+Ethernet proto board : still needs stencil and reflow oven
- DICE II FireWire proto board : design in progress


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PostPosted: Thu May 08, 2008 9:06 pm 
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Yesterday I received the oven. So, I assembled the Spark Fun Reflow Toaster Controller Kit.

Turns out it should have been named "PIC with a LCD that displays nothing, a relay, no software, and no manual".
And the thermocouple IC is missing from the kit.

WTF ????????

So I soldered the damn thing by hand. Twice, actually.
All that remains is to power it up. I will try that tomorrow.

WTFs of the day go to :

- Spark Fun for being so lame,
- SMC for putting TWO dots on the MAC IC (with the larger one being the wrong one, of course) => a coaster with all the ICs soldered on it
- And me for not triple checking the docs
- And me again for losing the oscillators !!! I don't know where these things are so the CPU isn't going to get very far without a clock. Now I need to explore the room for one 5x8 mm SMD oscillator. Hm.

Image

Image

Tomorrow, we'll know if it works or smokes.


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PostPosted: Thu May 08, 2008 10:16 pm 
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Location: Kansas City, MO
I don't think you need the oven controller. Just do it by inspection. That worked for me.

_________________
He's not hi-fi, he's my stereo.
DIY projects:
http://www.ezdiyaudio.com


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