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TDA1387 X8 NOS DAC
TDA1387 X8 NOS DAC
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Old 23rd April 2017, 10:47 AM   #21
abraxalito is offline abraxalito  United Kingdom
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Quote:
Originally Posted by Greg Stewart View Post
Nope, right on the board and it looks like the clock signal is input to the VHC574 that I suspect is used for distributing the I2S signals to the DAC chips.
My apologies, you're talking about the 'Hat' DAC for RPi, not the original topic of this Wiki.
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Old 23rd April 2017, 05:46 PM   #22
Greg Stewart is offline Greg Stewart  United States
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Quote:
Originally Posted by abraxalito View Post
My apologies, you're talking about the 'Hat' DAC for RPi, not the original topic of this Wiki.
That's funny... when you posted the link to the one on Taobao that is similar to this one AND also an R-Pi HAT DAC, I thought you realized that then. Funny, that's all that jonners' & bommetje's posts have referenced.

Interesting that the one that started this Wiki thread DOES have 8 TDA1387s, but does not have a clock used as part of the I2S distribution? The DAC HAT one from Taobao DOES appear to have a clock just like the Audiophonics board AND that area of the board also looks like it would accomodate the TCXO used by Audiophonics.

Oh well, any thoughts?

Greg in Mississippi

P.S. Jonners & bommetje, how are you powering your Pi & your Audiophonics cards?
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Old 23rd April 2017, 06:21 PM   #23
bommetje is offline bommetje  Netherlands
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I power the hat from pi to hat with ifi power. Somehow powering them separately, or from hat to pi does not work. Still have to look into that, maybe something wrong in the audiophonics dac 5V circuit? The TDA1387 hat also works with Allo Kali, which surprised me because of the ' mysterious' clock, was expecting a master slave issue. But I am not very experienced. I just got interested in diy audio. ( I did remove the 5V jumper when trying to power them separately.)

Last edited by bommetje; 23rd April 2017 at 06:24 PM.
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Old 23rd April 2017, 08:15 PM   #24
jonners is offline jonners  United Kingdom
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Quote:
Originally Posted by Greg Stewart View Post
P.S. Jonners & bommetje, how are you powering your Pi & your Audiophonics cards?
Powering Pi and DAC via Kali with iFi Power.
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Old 24th April 2017, 01:39 AM   #25
abraxalito is offline abraxalito  United Kingdom
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Quote:
Originally Posted by Greg Stewart View Post
That's funny... when you posted the link to the one on Taobao that is similar to this one AND also an R-Pi HAT DAC, I thought you realized that then. Funny, that's all that jonners' & bommetje's posts have referenced.
I realized that those other posts were about the RPi DAC, dunno why I just assumed your post had reverted to the original topic. I often have problems working out what context people are coming from....

Quote:
Interesting that the one that started this Wiki thread DOES have 8 TDA1387s, but does not have a clock used as part of the I2S distribution?
Right, no need for a clock distributor. I've built a DAC that had (I think, memory isn't what it used to be ) 19 TDA1387s in it and I didn't use any clock distribution IC, just paralleled all the BCK pins. So its definitely not a requirement on a drive ability basis.

Quote:
Oh well, any thoughts?
Having played with multiple DACs in parallel, I'm left wondering whether there's any technical reason for putting 8 in parallel beyond getting a lower output impedance. Which in itself is a decent technical objective, however active I/V achieves it more elegantly.
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Old 24th April 2017, 02:26 AM   #26
Greg Stewart is offline Greg Stewart  United States
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Abraxalito,

Thanks for the info. At some point I'll trace what they are doing with the 50mHz clock signal, but that''s low on my priority. As I said, if it looks like they are using it to gate the timing of the I2S signals (which sounds like a really dumb idea to me), I may try doing the same with the clock signal from the Kali instead of the on-board clock.

Maybe that, some really good power, and some improvements around the I/V will make it sound decent.

But in the meantime I have other projects to burn.

Jonners & bommetje, thanks for the info on the power. When I try it I'll figure out how to power it separately... I've always found separate supplies for the Pi, the Kali, and the DAC make a significant improvement... and even separate supplies for the analog and digital sides of the DAC chip if it can be powered that way, like the PCM5122 (and the PCM1793, which is one of my next DAC HAT projects).

Later!

Greg in Mississippi
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Old 9th June 2017, 10:31 AM   #27
ChuckT is offline ChuckT
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Hi, I just got the hi-hat 8 x tda1387 dac for Pi. Burning in right now, its a smooth sounding dac with decent bass. I am powering it with a portable phone battery with 2.4A current out.

This dac uses passive I/V out with caps and inductor for filter and Muses BP 10uf for coupling. My version has a 50mhz TCXO 0.1ppm crystal .
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Old 9th June 2017, 12:37 PM   #28
abraxalito is offline abraxalito  United Kingdom
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Are the tracks visible enough to work out what role the inductor's playing in the scheme of things?
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Old 10th June 2017, 03:31 AM   #29
ChuckT is offline ChuckT
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I worked out the signal out from tda1387. The inductor is use for filtering high fz noise from dac output. I suspect the passive out filter can be further optimized. I have a cheap portable scope, but I don't have the knowledge to measure the output.

TDA1387
=> I/V resistor 500 ohm
=> RC to ground 33R +3.9nf (square blue cap on board)
=> Inductor (marking 103)
=> RC to ground 2.7k + 0.22uf (round blue cap, but resistor label 2.2k)
=> Nichicon BP 10uf for coupling
=> smd cap (label 47k) piggy back with COG type at bottom (my guess as the cap looks lighter)
===> RCA out
Attached Images
File Type: jpg SAM_0324-2.jpg (1.03 MB, 480 views)
File Type: jpg SAM_0329-2.jpg (1.04 MB, 465 views)

Last edited by ChuckT; 10th June 2017 at 03:41 AM.
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Old 30th June 2017, 06:09 PM   #30
Mortenhoe is offline Mortenhoe  Denmark
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Hello. Nice thread. Me and a friend, have the portable version of this DAC. Very impressive little thing, compared to much more expensive equipment. Kind of surprised me how bright it is, for a multi-bit. We would like to remove some of that treble harshness as in the second mod on the list, but the pcb layout is quite different.

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Is it as easy as removing the blue 2n2 in the top?

The portable version has a small smd tda opamp, which I was thinking about replacing with a dip8 socket. Will also be replacing all thru hole capacitors for better spec ones.

Other mod recomandations is much obliged.

-Morten
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