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Chinese 16x TDA1543 DAC modification
Chinese 16x TDA1543 DAC modification
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Old 2nd December 2017, 02:15 AM   #11
abraxalito is offline abraxalito  United Kingdom
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Quote:
Originally Posted by matt_garman View Post
Where is the I/V resistor on this DAC? (I don't own one, just looking at the pics.)
Hi Matt - I just buzzed mine out to double check and the I/V resistors are the two marked '140' between the DAC chips and the large output caps. The 2n2s are in parallel with them.

Quote:
But if you start pulling tda1543 chips, you'll have to adjust the I/V resistor accordingly.
I discovered something strange when I got into checking the I/V resistor's value. The power supply reg (LM317T fitted to mine, not the higher current LM338 as shown on silkscreen) has 270ohm and 1k for the voltage setting. This makes for a supply about 5.9V so the output compliance range for the DAC should be from +1.8V to +4.7V or 2.9V p-p (~1VRMS). With 140ohm for I/V this entails a current of almost 21mA but an array of 16 chips should give a total current of 16*2.3 = 37mA. I did not ever see any clipping on the analog output waveform though.

From poking around with my scope it looks like the digital format output from the S/PDIF receiver is resulting in only 15 useful bits reaching the DAC chips. I plan to fix this by some means - adding a flip flop for a 1CLK delay is one possibility.

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I can't tell from the pictures how clean the soldering job is. In my own tda1387 project, I did a sloppy soldering job and created several solder bridges. The results of the solder bridges ranged from total noise output, to more subtle noise...
Mine looks hand-soldered to me and the soldering quality isn't wonderful. Too much solder is used on the SMT parts but the through-hole soldering is good.
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Old 2nd December 2017, 09:40 AM   #12
pistollero is offline pistollero  Portugal
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Quote:
Originally Posted by abraxalito View Post
Keep the big caps if your amp or preamp doesn't have input capacitors. If you mean the two '140' resistors then yeah, they stay.
ok caps removed.... (i will bridge with wire the big ones)
theres is a 3k resistor also beneath yellow caps... remove also???

next:
pin7, what do i do with it??? lift from socket? or is from the bottom of the board that i have to do the surgery?

thanks
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Old 2nd December 2017, 09:47 AM   #13
abraxalito is offline abraxalito  United Kingdom
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About the 3k resistors - yes remove them. They'd slipped under my radar, I need to remove mine too

On pin7, I found its sufficient just to pull out the blue multiturn preset pot - behind the source selector button.
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Old 2nd December 2017, 09:56 AM   #14
Insanoff is offline Insanoff  Azerbaijan
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I brought my another laptop from work to home that runs Windows 10. It has immediately detected the driver when I pluged the USB cable. After playing just few seconds I could not believe my ears. It is nothing comparable with my older laptop. I never thought that SQ so heavily depends on digital source. Now there is another problem, it has random punchy clicks sometimes. Strangely when I play music directly from its output same thing happens. Internal DAC also suffers from the same problem.

Quote:
Originally Posted by abraxalito View Post
First mods I'd suggest are to delete the blue 2n2s and the yellow '3K's right at the output.
I made it. But I am not quite sure how to do with discrete current source and pin7s. Currently studying different designs.
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Old 2nd December 2017, 10:13 AM   #15
pistollero is offline pistollero  Portugal
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Quote:
Originally Posted by abraxalito View Post
About the 3k resistors - yes remove them. They'd slipped under my radar, I need to remove mine too

On pin7, I found its sufficient just to pull out the blue multiturn preset pot - behind the source selector button.
Thanks Abraxalito

done...
next, what i need to do???
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Old 2nd December 2017, 10:31 AM   #16
abraxalito is offline abraxalito  United Kingdom
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Quote:
Originally Posted by Insanoff View Post
I brought my another laptop from work to home that runs Windows 10. It has immediately detected the driver when I pluged the USB cable. After playing just few seconds I could not believe my ears. It is nothing comparable with my older laptop. I never thought that SQ so heavily depends on digital source. Now there is another problem, it has random punchy clicks sometimes. Strangely when I play music directly from its output same thing happens. Internal DAC also suffers from the same problem.
Given you've the same issue from both the Taobao and the internal DAC this sounds like a Windows latency problem to me. You can find some online checker for DPC latency I believe though on a laptop I've no idea how you can reduce it.

Quote:
I made it. But I am not quite sure how to do with discrete current source and pin7s. Currently studying different designs.
I use the standard two-transistor version - attached.

@pistollero : You'll need a couple of current sources like the picture I'm showing here, one for each channel. The 24ohm resistor sets the current, its just a rough guess at present for the value you'll need. The 3k3 resistor goes to 0V, the top rail is the DAC's +5.9V supply.
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Last edited by abraxalito; 2nd December 2017 at 10:35 AM.
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Old 3rd December 2017, 10:48 AM   #17
pistollero is offline pistollero  Portugal
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Quote:
Originally Posted by abraxalito View Post
Given you've the same issue from both the Taobao and the internal DAC this sounds like a Windows latency problem to me. You can find some online checker for DPC latency I believe though on a laptop I've no idea how you can reduce it.

I use the standard two-transistor version - attached.

@pistollero : You'll need a couple of current sources like the picture I'm showing here, one for each channel. The 24ohm resistor sets the current, its just a rough guess at present for the value you'll need. The 3k3 resistor goes to 0V, the top rail is the DAC's +5.9V supply.
ths
is this correct??
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Old 3rd December 2017, 10:57 AM   #18
abraxalito is offline abraxalito  United Kingdom
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Yes, that's the idea - the output you've marked 'regulator' goes to pin6 (and the other channel, pin8) of the TDA1543As. The I/V resistor goes between that output pin and 0V, which is the same configuration as its shipped in. So no need to change anything there.
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Old 3rd December 2017, 11:15 AM   #19
pistollero is offline pistollero  Portugal
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Quote:
Originally Posted by abraxalito View Post
Yes, that's the idea - the output you've marked 'regulator' goes to pin6 (and the other channel, pin8) of the TDA1543As. The I/V resistor goes between that output pin and 0V, which is the same configuration as its shipped in. So no need to change anything there.
ok... but m a little confused....
is this??? correct??
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Old 3rd December 2017, 11:17 AM   #20
abraxalito is offline abraxalito  United Kingdom
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Yes this is correct - the I/V resistor is already present on the PCB - marked '140'.
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