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Building the ultimate NOS DAC using TDA1541A
Building the ultimate NOS DAC using TDA1541A
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Old 8th October 2018, 08:01 AM   #6591
batteryman is offline batteryman  United Kingdom
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Join Date: Jun 2011
Location: SCOTLAND
Quote:
Originally Posted by poki921 View Post
Dear EC AND batteryman
Both of you seems have some experience of transformer output
May I know the suggestion of the section?brand? Type? Value?
Is it better then op or passiveIV?
My transformers are from Sowter type 9545 which has now been superceded by: 1465 DAC Interface Transformer

They are expensive, but do an excellent job of filtering a NOS dac, especially a balanced setup and depending on how you connect it, offer a step-up ratio of x5 or x10.

I've used the transformers with a dual 1541, and an Audio Note Dac1.1 (AD1865) kit with no other filtering.
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Old 8th October 2018, 09:20 AM   #6592
marconi118 is offline marconi118  Germany
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is the passive I/V converter with CCS current feed better than the common gate jfet stage in MKV citcuit?
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Old 8th October 2018, 04:59 PM   #6593
batteryman is offline batteryman  United Kingdom
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Default Screenshot

Here's a screen shot of the latch and bck, which look okay to me and of course you can see the clock stop feature of Ian's interface.

I will try half speed mode next and if that doesn't help, I'll move the interface into a Marantz Cd65 1541 based cd player.
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File Type: jpg ckll.jpg (82.5 KB, 202 views)
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Old 9th October 2018, 09:28 AM   #6594
ecdesigns is offline ecdesigns  Netherlands
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Hi batteryman,

Quote:
Here's a screen shot of the latch and bck, which look okay to me and of course you can see the clock stop feature of Ian's interface.

I will try half speed mode next and if that doesn't help, I'll move the interface into a Marantz Cd65 1541 based cd player.
LE latches the TDA1541A outputs (simultaneous mode) at the -rising- edge of LE (datasheet spec).

When the red trace represents LE and it runs synchronous with BCK (no scope trigger issue), it latches the outputs -before- all 16 bits have been clocked in.

So if I am correct, all you have to do is invert LE. Perhaps Ian already made a provision for this (jumper setting?).
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Old 9th October 2018, 09:38 AM   #6595
3lite is offline 3lite  Poland
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Quote:
Originally Posted by ecdesigns View Post
So if I am correct, all you have to do is invert LE. Perhaps Ian already made a provision for this (jumper setting?).
I'm afraid that won't work.

I've noticed that TDA1540/TDA1541A uses falling edge of LE to clean up input register.

In short - LE cannot change during clocking-in data. That is in both ways (whether it's falling or rising).

On a side note, here is what you can achieve with TDA1540 and a proper digital filter with a dithering:

Click the image to open in full size.

That's a -96 dBFS signal which in normal conditions is on 18th bit. In general you cannot play anything below -72 dBFS on 14 bit converter since it looks like this:

Click the image to open in full size.

That is just switching noise of the MSB. Nothing else (it looks exactly the same from -73 dBFS to -100 dBFS).

Proper manipulation with dithering can in fact increase the resolution of the DAC itself.

Last edited by 3lite; 9th October 2018 at 09:44 AM.
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Old 9th October 2018, 09:45 AM   #6596
poki921 is offline poki921  Taiwan
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Hi
I’m not sure if someone read this from me already
Thus I think it might be a general problem for the digital expert here

philips cd104 tda1540 NOS modify error... - diyAudio
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Old 9th October 2018, 10:24 AM   #6597
batteryman is offline batteryman  United Kingdom
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Quote:
Originally Posted by ecdesigns View Post
Hi batteryman,



LE latches the TDA1541A outputs (simultaneous mode) at the -rising- edge of LE (datasheet spec).

When the red trace represents LE and it runs synchronous with BCK (no scope trigger issue), it latches the outputs -before- all 16 bits have been clocked in.

So if I am correct, all you have to do is invert LE. Perhaps Ian already made a provision for this (jumper setting?).
I am now confused! According to Ian's instructions, the data appears at the output on the negative transition of WE which is what my screen shot shows. But according to the data sheet, this only applies to time multiplexed TWC.

"The converted samples appear at the output, at the first positive going transition of the bit clock signal after a negative going transition of the word select signal."

You are correct in saying that in simultaneous mode, that its the positive going transition as the datasheet states:

"The converted samples appear at the output at the positive going transition of the latch enable signal."

So this might explain why the data is truncated and causing the distortion.

I will re examine the traces when I have replaced the 50cm cat5e cable with a 15cm Cat6 cable tomorrow, and in the meantime I can try Ian's suggestion of half speed mode.

Many thanks for your comments.
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Old 9th October 2018, 10:27 AM   #6598
batteryman is offline batteryman  United Kingdom
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Join Date: Jun 2011
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Quote:
Originally Posted by poki921 View Post
Hi
Iím not sure if someone read this from me already
Thus I think it might be a general problem for the digital expert here

philips cd104 tda1540 NOS modify error... - diyAudio
It looked like a psu issue to me. How hot are the regulators getting?
When they get hot, you get the problem, hence try the freezer spray as suggested, but on the regulators.
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Old 9th October 2018, 10:36 AM   #6599
3lite is offline 3lite  Poland
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Quote:
Originally Posted by batteryman View Post
So this might explain why the data is truncated and causing the distortion.

I will re examine the traces when I have replaced the 50cm cat5e cable with a 15cm Cat6 cable tomorrow, and in the meantime I can try Ian's suggestion of half speed mode.

Many thanks for your comments.
I don't think so. TDA1541A can operate at 14 bits just like TDA1540 and it does work just fine. You wouldn't hear any difference between 14 bits and 16 bits.

I can imagine there is another issue. Can you show us the DATA line (whether it's R or L, doesn't matter) along with BCLK on the same screen? If you can include 3rd graph of LE that would be lovely, but that's not necessary.
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Old 9th October 2018, 12:35 PM   #6600
ecdesigns is offline ecdesigns  Netherlands
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Hi batteryman,

Quote:
I am now confused! According to Ian's instructions, the data appears at the output on the negative transition of WE which is what my screen shot shows. But according to the data sheet, this only applies to time multiplexed TWC.
Philips TDA1541A datasheet page 4

quote:

When input OB/TWC input is connected to VDD1 the two channels of data (L/R) are input simultaneously via DATA L and DATA R, accompanied with BCK and a latch-enable input (LE). With this mode selected the data must be in offset binary. The converted samples appear at the output at the positive going transition of the latch enable signal.

The format of the data input signals is shown in Fig.5 and 6.


When you invert LE, the positive going transition (latching) will occur -after- all bits have been clocked in. This would meet datasheet specs and should work.

See attached modified oscillogram.
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File Type: jpg clk1.jpg (58.4 KB, 141 views)
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