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tda1387 dac pcb "front end"
tda1387 dac pcb "front end"
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Old 29th October 2017, 08:16 AM   #11
abraxalito is online now abraxalito  United Kingdom
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Quote:
Originally Posted by hollowman View Post
How much sonic benefits actually (subjectively) accrue when more than one TDA1387 are stacked?
I've not noticed there being sonic benefits from paralleling chips. Rather paralleling gives more flexibility over design of the I/V stage - for example it allows lower output impedance by virtue of switching higher currents. The 1mA total swing of a single chip is low by DAC standards - the lowest of any multibit DAC that I'm aware of.
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Old 29th October 2017, 02:17 PM   #12
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
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Originally Posted by hollowman View Post
I know much of the romance with this DAC chip began with the parallel x 8 design orig. offered a few years ago.
That was, quite literally, my inspiration for this design. Romance is an apt word. I was underwhelmed with my first foray into NOS DACs, but that x8 DAC changed my mind. But there comes a point where it just gets messy to continue to hack on the x8 board. So my intent here is to create a modular "framework" for folks wanting to play with the tda1387 chip. Folks might be limited to Richard and I, but I'm OK with that! At the end of the day, I simply enjoy designing PCBs, and ever since I first took a soldering iron to that x8 DAC, I've wanted to design my own tda1387 board.


Quote:
Originally Posted by hollowman View Post
How much sonic benefits actually (subjectively) accrue when more than one TDA1387 are stacked? I'm assuming parallel x 8 is some sort of sweet-spot?
Dunno. I used eight only because that's what the x8 DAC used. But you do need at least two chips if you want balanced output (which I do). Other than wasting PCB space, there's no reason you have to populate all eight chips. The intent is to be flexible, to allow for relatively easy trial-and-error.
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Old 29th October 2017, 04:21 PM   #13
hollowman is offline hollowman  United States
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Default TDA1387 Dragonfly

Quote:
Originally Posted by matt_garman View Post
I've wanted to design my own tda1387 board.
Hmmm...
1387's low power consumption makes it ripe for, say, an iPhone dongle.
If you/someone were to design a thumbnail-sized PCB (form actor: Dragonfly), you may get more interest.
Here on DIYA, I think I have seen a few TDA1387 projects (??) with pretty small form factors.
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Old 5th November 2017, 01:14 AM   #14
nige2000 is offline nige2000  Ireland
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Ill take two boards if u have them matt
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Old 5th November 2017, 08:19 AM   #15
Mayday is offline Mayday  Sweden
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tda1387 dac pcb "front end"
I'll take a board if still available
Nice of you to offer them for just shipping cost.
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Old 5th November 2017, 02:31 PM   #16
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Quote:
Originally Posted by nige2000 View Post
Ill take two boards if u have them matt
Quote:
Originally Posted by Mayday View Post
I'll take a board if still available
Nice of you to offer them for just shipping cost.
Yup, still have all 13 boards! Only just now ordered the parts to do the build up. I need only two or three at most, the rest are free to whoever wants them.

However, nige2000 and Mayday, based on shipping costs, I suspect it might be cheaper for you just to order your own boards straight from Elecrow. When I placed my order, it was $5 for the boards and $5 shipping from China to the USA. I'm assuming Elecrow shipping to your countries is the same as it is for the USA.

Some quick Internet research suggests $20 might be as cheap as I can get to ship to Ireland or Sweden.

Not trying to discourage you, just don't want you to waste money. At a minimum, you might want to wait until I build up the first one to make sure I didn't make any mistakes!

I attached the Gerber files I sent to Elecrow, if you want to go that route.
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File Type: zip tda1387x8_front_end_gerber-20171013.zip (153.7 KB, 47 views)
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Old 5th November 2017, 02:37 PM   #17
Mayday is offline Mayday  Sweden
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tda1387 dac pcb "front end"
Wow, that's alot to send one PCB. I understand why you wanted to mention that.
I'll hold off for now.
Thanks for the heads up
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Old 7th November 2017, 03:09 PM   #18
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Here's another spin on the tda1387 theme: a Raspberry Pi HAT DAC. This was inspired by didiet78's tda1387 DAC for Orange Pi.
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File Type: jpg image-schematic-20171107.jpg (236.8 KB, 430 views)
File Type: jpg image-board-20171107.jpg (249.4 KB, 426 views)
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Old 11th November 2017, 10:44 PM   #19
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Default Hope they work!

Spent way longer than I expected soldering a couple of these up. For the ICs and SMD components, I used solder paste and a skillet. I used too much solder paste, so ended up spending way too much time fixing solder bridges. Lesson learned: less is more with ICs and solder paste. Very frustrating.

Anyway... here's to hoping they actually work!
Attached Images
File Type: jpg IMG_20171111_172707746.jpg (188.5 KB, 360 views)
File Type: jpg IMG_20171111_172729083.jpg (196.4 KB, 349 views)
File Type: jpg IMG_20171111_172800118.jpg (219.4 KB, 349 views)
File Type: jpg IMG_20171111_172813695.jpg (216.0 KB, 138 views)
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Old 12th November 2017, 07:39 PM   #20
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Default They actually work!

Playing music as I type this.

The first test with the first board was a total failure: sound was complete noise. Turns out I missed a solder bridge across two pins of the HC86 logic chip. Before fixing that, I tried the second board: I got something recognizable as music, but still fairly distorted. I removed the solder bridge on the first board, and it was now the better sounding of the two boards, but still not perfect.

For I2S source, I'm using an Amanero (USB to I2S) device that I've had now for a couple years. I had to tweak the settings a bit. The sound cleaned up further with the right settings; see attached screenshot.

There was still a bit of "fuzz" on both boards, so I used a flashlight to look more closely at the tda1387 IC pins. Yup, more solder bridges (or at least partial ones). Thank goodness for copper solder wick!

Now they are definitely both playing pretty clean as far as I can tell.

The laptop didn't have ASIO drivers set up, so I installed that Foobar plugin. That seemed to clean things up a tiny bit too (or maybe my imagination). But I definitely wasn't "bit perfect" prior to that, as I could still hear Windows system sounds layered on top of the music. Now those are gone, Foobar has exclusive control of the Amanero.

I went ahead and added another eight pin7 caps to one of the boards, and installed the pin5 polymer caps on the board's bottom. Can't really tell any difference. But then again, I'm still in a pure test config.

Main lesson here, for me anyway, is to use the solder paste very sparingly. I'm certain I spent more time cleaning solder bridges than if I'd just hand-soldered the SMD stuff in the first place.

Thus far all tests have been with single-ended output. Next step is to solder up some XLR connectors so I can do a test of the balanced output.
Attached Images
File Type: jpg amanero_settings_tda1387x8-20171112.jpg (92.5 KB, 135 views)
File Type: jpg IMG_20171112_134644648.jpg (176.0 KB, 150 views)
File Type: jpg IMG_20171112_134629470.jpg (273.9 KB, 176 views)
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