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tda1387 dac pcb "front end"
tda1387 dac pcb "front end"
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Old 15th September 2018, 07:13 PM   #241
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Here's a semi-decent detail picture of the board. About the best I can do without turning it off, which I'm not ready to do yet. But hopefully later today or tomorrow I'll give it a rest and then be able to get some more pics, including the back.
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File Type: jpg fd_tda1387nas_detail_20180915.jpg (380.6 KB, 233 views)
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Old 16th September 2018, 03:36 AM   #242
stellarelephant is offline stellarelephant  United States
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Cool find, Matt. If you're already talking about a case, the "Little Giant" must be living up to your expectations...and a bargain too! I will look forward to your direct I2S mod. On-board rectification is an interesting approach. Do you have a link for that transformer you're using?
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Old 16th September 2018, 07:21 PM   #243
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
I don't have a link for that particular transformer, I've had it for quite a while. But I bought it off ebay, just search for "R core transformer", and select the right VA rating, along with the right secondary(ies) you want. IIRC, some of the vendors will even make custom secondary voltages for you.
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Old 16th September 2018, 07:31 PM   #244
zgtc is offline zgtc  Europe
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tda1387 dac pcb "front end"
Quote:
Originally Posted by matt_garman View Post
Here's a semi-decent detail picture of the board. About the best I can do without turning it off, which I'm not ready to do yet. But hopefully later today or tomorrow I'll give it a rest and then be able to get some more pics, including the back.

looks pretty. does it have pins to add a potentiometer? i guess not, but would it be feasible to hack it?
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Old 16th September 2018, 08:38 PM   #245
PJN is online now PJN  United States
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Quote:
Originally Posted by matt_garman View Post
Here's a semi-decent detail picture of the board. About the best I can do without turning it off, which I'm not ready to do yet. But hopefully later today or tomorrow I'll give it a rest and then be able to get some more pics, including the back.
Hi .Matt, You I spired me to buy one, my beloved Subbu dac just died and I need a replacement. I'll be interested in hearing how it compares
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Old 19th September 2018, 02:11 PM   #246
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Quote:
Originally Posted by stellarelephant View Post
I will look forward to your direct I2S mod.
It won't really be a mod, just soldering wires directly to pins 1, 2 and 3 of the DAC IC.


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Originally Posted by zgtc View Post
looks pretty. does it have pins to add a potentiometer? i guess not, but would it be feasible to hack it?
No pins for a pot. But I don't see why you couldn't hang one off the output.


Quote:
Originally Posted by PJN View Post
Hi .Matt, You I spired me to buy one, my beloved Subbu dac just died and I need a replacement. I'll be interested in hearing how it compares
Please post your thoughts and impressions when you get it! My (decidedly non-golden) ears say it's pretty decent.


Attached are some better pics.
Attached Images
File Type: jpg top1.jpg (822.4 KB, 172 views)
File Type: jpg top2.jpg (954.0 KB, 167 views)
File Type: jpg angle_top1.jpg (891.5 KB, 151 views)
File Type: jpg angle_top2.jpg (786.4 KB, 143 views)
File Type: jpg angle_top3.jpg (782.5 KB, 30 views)
File Type: jpg back2.jpg (745.4 KB, 32 views)
File Type: jpg back3.jpg (770.9 KB, 35 views)

Last edited by matt_garman; 19th September 2018 at 02:14 PM.
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Old 19th September 2018, 02:35 PM   #247
zgtc is offline zgtc  Europe
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tda1387 dac pcb "front end"
Quote:
Originally Posted by matt_garman View Post
No pins for a pot. But I don't see why you couldn't hang one off the output.
sorry if this sounds like a very stupid question, but wouldn't that mess up w/ impedances?
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Old 19th September 2018, 02:53 PM   #248
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Certainly, hanging a pot off the output will definitely change the impedance characteristics. You may or may not be able to hear it though. I've seen lots of people do this (self included) on the amplifier end of things (quick and dirty way to turn a "power amp" into an "integrated amp").

Perhaps it's possible to hack the output buffer circuit for volume control?

You could of course also add a pre-amp with volume control to the chain.

Variable transformers are another option.

While I used to use pots between the DAC and amp input, these days I use digital volume control on the source. I know it's imperfect, but it's easy.
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Old 19th September 2018, 02:57 PM   #249
zgtc is offline zgtc  Europe
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tda1387 dac pcb "front end"
good, i wasn't so misleaded then

Quote:
Originally Posted by matt_garman View Post
While I used to use pots between the DAC and amp input, these days I use digital volume control on the source. I know it's imperfect, but it's easy.
you mean software or hardware based digital volume control on the source?
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Old 19th September 2018, 04:27 PM   #250
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
I meant software-based. My source these days is almost always a Raspberry Pi running Music Player Daemon (MPD). I have a huge music collection which lives on a networked file server. So whenever I want a new music source somewhere in my house, I just spin up a new RPi. (I already have three of these instances already: basement, living room, office.) Then I can use any number of MPD client apps (on just about any device) to control the music. In particular, the M.A.L.P. player for Android is really nice (and free/open source), and allows storing of multiple server profiles, so I can quickly and easily switch between devices.

So, as-is, it's software volume control.

To have this convenience with hardware volume control, I'd need to implement something that can be controlled by a microcontroller (i.e. the RPI), and do some hacking on my MPD/ALSA config to turn volume control operations into microcontroller commands that actually tweak the hardware. I've done exactly this with the Soekris dam1021. But so far I haven't had the time to come up with a similar arrangement for tda1387-based DACs.
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