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tda1387 dac pcb "front end"
tda1387 dac pcb "front end"
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Old 1st January 2018, 03:39 PM   #41
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Quote:
Originally Posted by didiet78 View Post
Add i2c pin and some gpio pin.
Can you elaborate? Do you mean just for pass-through if someone wants to stack another hat? Or do you have a specific use in mind for i2c/gpio on the DAC board itself?
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Old 1st January 2018, 08:50 PM   #42
didiet78 is offline didiet78  Indonesia
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Maybe someone want to add ic2 display, add some button or ir receiver. Just add some hole/pad or pin header.
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Old 1st January 2018, 09:55 PM   #43
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
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Originally Posted by robert1325 View Post
Have you had a chance to compare your front end to the 8x dac yet? I'm curious to hear what the tda1387 sounds like without the op amps.
Since you asked, it motivated me to spend some more time with the x8 front end. I have it in a case now, along with an Amanero and 5v regulated power supply. Listening to it on test speakers now (still not confident enough to put it in front of a powerful amp and expensive speakers).

I did find one of the boards has a problem, didn't feel like debugging today. (The GND+NEG output pins are totally noisy, in either single-ended or balanced mode. Suggests I have another solder bridge somewhere on the "lower" four tda1387 chips.)

The board in the picture works, but I think one of the tda1387 chips isn't soldered correctly (or I have a bum chip, but most likely it's my bad soldering job). I have the output wired for single-ended mode (POS and NEG pins tied together), but accidentally configured the HC86 for balanced mode. This I believe should have resulted in no sound at all (i.e. the signals should have cancelled each other out). But I still got sound, although it was very faint. I fixed the HC86 jumper, and now there's a lot of gain (relatively speaking anyway). FWIW, I'm using software volume control, and have it turned almost all the way down.

In short, still feeling the pain of the initial sloppy soldering job.

Hopefully I'll have time tomorrow to finish the case work. I just need to drill out the real panel.
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Old 3rd January 2018, 10:34 PM   #44
nige2000 is offline nige2000  Ireland
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u got a bom for this, ill get it ordered up
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Old 4th January 2018, 02:05 AM   #45
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Here's the BOM for the v1.0 board (i.e. what I originally posted in this thread, and what I've built up and am currently testing). The attached zip file has the BOM in several different formats - MS Excel, ODS, PDF and CSV.

You'll see one of my errors - the tda1387 pin5 (supply voltage) decoupling caps are inconsistently sized. Some are 805 size and some are 1206 size. Either way, they go on the bottom of the board.

I also included Mouser part numbers for reference. Obviously you don't need to pick the exact same parts, but I always like having an explicit reference. I put some basic notes in there too... e.g. if you're building this up strictly as a front-end (i.e. direct current-out, some external I/V), many of the parts can be omitted.

Let me know if you have any questions!
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Old 6th January 2018, 08:42 PM   #46
robert1325 is offline robert1325  Netherlands
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Quote:
Originally Posted by matt_garman View Post
Since you asked, it motivated me to spend some more time with the x8 front end.
Looks very neat! Are you planning to add an active I/V also at some point? I am hesitating to do more mods on my taobao 8x (like the CCS and filter) lest it stops making music.
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Old 6th January 2018, 11:14 PM   #47
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
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Originally Posted by robert1325 View Post
Looks very neat! Are you planning to add an active I/V also at some point? I am hesitating to do more mods on my taobao 8x (like the CCS and filter) lest it stops making music.
I hope to, time permitting. That was the idea behind this design, to make it easy to try different I/V stages, or just go with a simple passive. The I/V I'm most interested to try is Abraxalito's.
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Old 11th January 2018, 03:36 AM   #48
abraxalito is offline abraxalito  United Kingdom
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My gf's first PCB design has just come back from fabrication - its a quad chip version of Matt's board, 5*5cm, so we've panelized four to fit the 10*10 footprint that PCB vendors seem to offer their best prices on. Once its stuffed and proved working then anyone can build one - not that I'll be shipping out boards (as Matt's shown, that's not cost-effective), rather the data will be free to use on request. The cost of this first batch worked out to be around four boards for 1 USD.

One of these boards, together with the up-coming filter I/V board (about to enter layout any day now) will allow construction of a lingDAC.
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Old 11th January 2018, 03:57 AM   #49
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Looks great Richard! Can't wait to give your design a listen.
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Old 11th January 2018, 04:08 AM   #50
abraxalito is offline abraxalito  United Kingdom
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Thanks Matt - I haven't listened to lingDAC on speakers yet as I need an amp which is up to the job, haven't built it yet. Have been working lately on an amp to drive my 600ohm DT880s from this - the trafos for that are in the top-left of the DAC boards pic
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