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tda1387 dac pcb "front end"
tda1387 dac pcb "front end"
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Old 19th November 2017, 06:05 PM   #21
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
I ordered PCBs for the RPi hat shown above. In the meantime, I whipped up a balanced RPI hat.

By the way, the latest nightly build of Kicad has a new raytracing 3d render engine (in addition to the existing OpenGL engine). I have a decent CPU (i5-6500) and the raytraced render is somewhat slow, but they look beautiful.
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Old 7th December 2017, 03:06 AM   #22
museguy is offline museguy  Mexico
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tda1387 dac pcb "front end"
Quote:
Originally Posted by matt_garman View Post
Playing music as I type this.
Very impressive Matt !
I am still a long way from creating my own PCB. I have been following your journey with the TDA1387.

How does your design sound ?

What is the amp to the right ?

Best,
- Mark
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Internet Radio > Raspberry Pi or MacBook Pro > TDA1387 x8 DAC or ifi Nano >JLH1969 Headphone Amp >Sennheiser HD650 or Sony MDR7506 or Grado SR80 or ACS Custom IEM or Denon D2000
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Old 7th December 2017, 07:45 PM   #23
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Quote:
Originally Posted by museguy View Post
I am still a long way from creating my own PCB. I have been following your journey with the TDA1387.
I don't claim any expertise in PCB design, but I find it quite enjoyable. Here's the thread of my first PCB design: My tpa3118 board - comments/critiques?. As you can see, I received a ton of hand-holding from the diyAudio community, and for that I'm very grateful!

Quote:
Originally Posted by museguy View Post
How does your design sound?
Once I got it working, and all the obvious problems cleaned up, I was out of time. I haven't had a chance yet to go back and give it any kind of critical listening test. And also, right now, I'm kind of putting that on hold while I focus on the single-ended Raspberry Pi hat (go back a page or two). I just received the first PCB run for that, but realized I used the wrong footprint for the tda1387 chip, so I'll have to fix that and re-order. With the holidays and such coming up, free time will be a rare luxury.

Quote:
Originally Posted by museguy View Post
What is the amp to the right?
That's the Folsom tda7297 amp. Here's a big thread on AudioCircle about it: Folsom's great little 7297 Chip Amp, and his group buy thread: Folsom DIY7297 Amp & Antipole PSU. I have more amps than any sane person needs. It was handy so I grabbed it for my testing.
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Old 8th December 2017, 03:26 AM   #24
museguy is offline museguy  Mexico
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tda1387 dac pcb "front end"
Thank you matt_garman,
Have enjoyed following you along on your journey.
I am currently using HD650 > JLH 1969 Headphone Amp > TDA 1387 x8 > Hifiberry Digi Pro, sounds good to me. I am very curious about balanced and would like to try a balanced amp and maybe your TDA1387 PCB.

Would the Salas Reflektor work with your TDA1387 ?

I have ordered Ian's McFIFO.

Curious, why the Raspberry Pi hat ? I would think the SQ of the x8 TDA1387 would be better.

Best,
- Mark

I need to review your other links, thank you.
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Old 8th December 2017, 04:20 AM   #25
abraxalito is online now abraxalito  United Kingdom
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Quote:
Originally Posted by matt_garman View Post
Here's another spin on the tda1387 theme: a Raspberry Pi HAT DAC.
I realize I'm probably too late with the comments to intercept this board before it goes to fabrication but I'll just point out anyway that the TL431 reference can be shared between the two I/V transistors. This'll save you a few parts - each transistor needs its own 22ohm base resistor but beyond that you only need one instance of the voltage reference.
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Old 8th December 2017, 02:08 PM   #26
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Definitely not too late. I want to have the single ended hat working first, well before I have the balanced hat fabbed. So thank you! Board space is tight with the balanced implementation - and I just found out the tda1387 footprint I used is too small. So removing a couple components will help offset the larger (correct) footprint needed for the DAC ICs.

How's progress coming on your 1387 project?
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Old 8th December 2017, 02:32 PM   #27
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Quote:
Originally Posted by museguy View Post
Would the Salas Reflektor work with your TDA1387 ?

Curious, why the Raspberry Pi hat ? I would think the SQ of the x8 TDA1387 would be better.
I don't see any reason why the Salas PSU wouldn't work with my tda1387 board (though it might be overkill). I haven't worked out it's power consumption, which you'd want to know for optimal buildup of the Salas. But the power requirements should be quite low.

As for RPi vs x8... Kind of an apples and oranges thing. The x8 is designed to be either one component in a fancier DAC (I.e. assumes you have an active IV stage and/or filtering and/or buffers on downstream boards). That, or you want a simple passive IV stage, and are ok with the limitations of such.

The RPi hat is designed to be a complete (albeit simple) solution. Also, for me personally, single board computers like the RPi have become my preferred source. The pi hat is purpose built while the x8 board is more generic (and there's no reason you couldn't use the x8 board with an RPi). Technically, you could use the pi hat as a standalone DAC as well, it would just be somewhat awkward.

As for which would have superior sound quality... Way too soon to even guess. The x8 board, if used with passive IV, will be highly dependent on downstream components. With active IV, I believe the IV stage itself would likely make or break the sound quality.

The RPi hat is active IV, but a deliberately very simple one. The goal is an "80-20" design where you get 80% of the benefit with 20% of the effort.
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Old 8th December 2017, 02:47 PM   #28
abraxalito is online now abraxalito  United Kingdom
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Quote:
Originally Posted by matt_garman View Post
Definitely not too late. I want to have the single ended hat working first, well before I have the balanced hat fabbed. So thank you! Board space is tight with the balanced implementation - and I just found out the tda1387 footprint I used is too small. So removing a couple components will help offset the larger (correct) footprint needed for the DAC ICs.
Ah glad to hear my belated feedback isn't in vain. You'll save 3 resistors, an electrolytic and a SOT23.

Quote:
How's progress coming on your 1387 project?
I've been measuring frequency response of my first prototype batch of NOS droop correcting filters. I have 3 prototype USB-fed DACs fully assembled now and one S/PDIF-fed one, going to build a couple more USB ones and send them out for listening evaluation. After more than 5 years of DAC development I've finally got a DAC where I'm totally happy with the sound

Incidentally I just posted up a schematic of the I/V and filter stage on IanCanada's thread - Design DSD/I2S DAC HATs for Raspberry Pi, start from ES9018K2M
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Old 8th December 2017, 05:50 PM   #29
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Quote:
Originally Posted by abraxalito View Post
Ah glad to hear my belated feedback isn't in vain. You'll save 3 resistors, an electrolytic and a SOT23.
I just realized you were talking about the single-ended HAT board; when I replied earlier I thought you were talking about the balanced board.

Yeah, I already had the single-ended one fabbed, but the tda1387 footprint is wrong, so I have to have them re-made anyway. So your feedback, though technically late, is still not in vain. And certainly still appreciated!

The component savings won't hurt on the single-ended board by any means; and will be a big help on the balanced board.


Quote:
Originally Posted by abraxalito View Post
After more than 5 years of DAC development I've finally got a DAC where I'm totally happy with the sound
Famous last words.

Are you going to update your Hackaday page with your latest developments? Pics of the completed DACs?
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Old 12th December 2017, 09:19 PM   #30
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Here's revision 1.1 of the single-ended RPi HAT. I fixed the tda1387 footprint, and also simplified the tl431 voltage reference per Abraxalito's suggestion.

The only other change was to add resistors in front of the tda1387's I2S input pins (1/BCK, 2/WS, 3/DATA). Not sure if that's really necessary, and if so, what the values should be... easy enough to use a 0R if they don't need to be there.

These KiCAD raytraced renders look better than the real thing IMO!
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File Type: jpg pcb_v1.1_raytrace_angle_20171210.jpg (387.4 KB, 21 views)
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