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tda1387 dac pcb "front end"
tda1387 dac pcb "front end"
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Old Today, 12:05 AM   #281
PJN is offline PJN  United States
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Join Date: Dec 2004
Location: Pa, USA
I finally got around to auditioning my "little giant" TDA 1387 board in a decent system. I let the dac burn in for about 8 hours over a few days. Mine is powered from the on board regulators, I just hooked up two torroids to feed it AC. Feeding it through the coax input from the coax out of a CD player. The system I used is pretty easy to hear differences, Pass VFet amp fed by a Salas DG3 preamp. I compared it head to head with a AK4490 DAC from JLSounds, using an isolated Xmos USB fed from separate power supplies. Used Foobar running DSD at 32 bit. I used the same CD in the CD and in Foobar and switched between the DACs using the source selector on the preamp. The TDA1387 had a slightly lower output which I compensated for when listening. The base on both DACs was about the same as was the imaging. The soundstage was large for both also. The AK4490 had a lower noise floor and more mid and upper end detail, and sounded a little bit more liquid. That said the TDA1387 was very impressive and easy to listen to, the vocals were nice and smooth. It seemed to sound warmer, but I think the impression of warmth came from the more muted detail in the mids and highs (NOS droop ?).

That said I think it sounds great for the money. The board looks nicely made, but seems that it may be difficult to modify with all of those teeney weeny SMDs. The AK4490 cost many times more to put together and I think that's its a nice DAC, I do enjoy it. Nothing really jumped out at me regarding multi bit NOS vs delta sigma, they sounded a lot alike to me. I have another R2R cheapy NOS (AD1865) from the same maker on the way, I'll see how that sounds in a few weeks.
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Old Today, 03:05 AM   #282
matt_garman is offline matt_garman  United States
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Join Date: Feb 2008
Location: Chicago, Illinois, USA
tda1387 dac pcb "front end"
Quote:
Originally Posted by drpro View Post
I am having no joy with this build. I am guessing I may have soldered the ICs incorrectly or overcooked them on the hot plate. Also, when I configure Volumio it asks for which DAC is installed. Quite a few listed, so perhaps that is also a problem.
Hi David! Nice to see another build in the wild, even if it's not currently working. Hopefully we can get you squared away! (I can't remember, did I send you that board, or did you fab it yourself?)

*** I typed up everything below, but as I was reviewing, I noticed something in your pic. See the two orange circles in the upper-right in the image below? You need to jumper those (I use left-over component leads). The board has multiple ground planes, this is the "star" connection point for those separate grounds. If you don't jumper those, much of the circuit will be open. So that's step one. After you address that, I'd suggest running through some of what I wrote below, at least the powered-off sanity continuity checks.

Anyway: it's been a while since I've used Volumio, and it somewhat abstracts the low-level details, which is what I'm more familiar with (since I do everything from the commandline using DietPi). That said: does Volumio offer a "hifiberry-dac" option, or something similar? At the low-level, that is the "device_tree_overlay" (also called "dtoverlay") you want for use with this DAC. Here's what you can do: make the setting change, reboot your RPI. Then, go into the shell via ssh, and run this command:
Code:
egrep '^(dtoverlay|device_tree_overlay)' /boot/config.txt
Hopefully that works on Volumio's shell. Here's what I get when I run it on DietPi:
Code:
root@basement-music:~# egrep '^(dtoverlay|device_tree_overlay)' /boot/config.txt
dtoverlay=hifiberry-dac
Hopefully that gets you going on the RPI front.

Next up, with the board not powered on, you can do some basic sanity checking with your continuity checker. See the image below, I marked it up a bit. Check for continuity (zero or near-zero resistance) between the following tda1387 pins:
1 - BCK
2 - WS
4 - GND
5 - VDD
In other words, pin 1 on both tda1387 chips should be connected. The same goes for the other pins listed above.

Then you can also check for continuity between the following HC86 pins and the corresponding tda1387 pins:
HC86 pin 3 - tda1387 pin 1 (BCK)
HC86 pin 6 - tda1387 pin 2 (WS)
HC86 pin 8 - tda1387 pin 3 (one chip only)
HC86 pin 11 - tda1387 pin 3 (the "other" chip)

HC86 pins 7 and 10 - GND
HC86 pins 13 and 14 should be connected

Next, for each tda1387 chip, check that no pin is shorted to any other pin. This is very tedious! Do the same for the HC86 pins, noting the above pins that are supposed to be common (7/10, 13/14).

Looks like you figured out (or maybe I told you?) about the tl431 silkscreen being misleading. Next step is to power up the board and check voltages. Pins 13 and 14 (yellow circle) of the HC86 should be at 2.5v.

On the tda1387 ICs, pin 5 (orange circle) should be at 5.0v.

What kind of transistors are you using for the "active" I/V? Where I've made the four circles in red, those should be at 2.8v - assuming you're using BC857, BC807 or similar. Do make sure you have the leads soldered correctly! In particular:
Emitter connects to the ferrite bead
Base connects to the 22R
Collector connects to the RC network

Hopefully we get you playing sweet sweet music!
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Old Today, 03:18 AM   #283
drpro is online now drpro  United States
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Join Date: Jan 2014
Location: Nashvegas
tda1387 dac pcb "front end"
Yes the boards you sent Matt, thank you. A big oops on the jumpers. I will try that, perhaps it will play, fingers crossed. I will double check my work and the voltages. You are most kind to lay out the points to check. Volumio does offer a hifi berry dac.
I will work through this tomorrow during the day.
Thanks
David
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I must build. Pass F4s, F6, M2, BA-3 preamp, MoFo, ImPasse preamp, Whammy headamp, Aksa's Lender preamp, Salas DCG3 headphone/preamp, XRK971 PCA & DCA headamp Bruno Putzey's balanced preamp, Doug Self preamp, Pete Millet Korg headamp.
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Old Today, 09:01 PM   #284
drpro is online now drpro  United States
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Join Date: Jan 2014
Location: Nashvegas
tda1387 dac pcb "front end"
Thanks for these suggestions, Matt. Added jumpers, check continuity and voltages. All good. I have a dedicated Pi, Kali, Piano rig. In order to leave that setup alone I ordered another Pi and will go the DietPi route you are using. I think this will be easier than going back and forth with the only Pi I have in house.
So new Pi should be here on Thursday. Plus I get to learn some programming.
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I must build. Pass F4s, F6, M2, BA-3 preamp, MoFo, ImPasse preamp, Whammy headamp, Aksa's Lender preamp, Salas DCG3 headphone/preamp, XRK971 PCA & DCA headamp Bruno Putzey's balanced preamp, Doug Self preamp, Pete Millet Korg headamp.
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