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Building the ultimate NOS DAC using TDA1541A
Building the ultimate NOS DAC using TDA1541A
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Old 3rd October 2007, 07:13 PM   #1691
Sandor is offline Sandor  Italy
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Hello EC,
Can you, please, post details about your selfmade S/P-DIF input transformer?
Best regards.

Paul
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Old 3rd October 2007, 07:53 PM   #1692
tubee is offline tubee  Netherlands
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Hi John

How is the sound of the spdif connection compared to the usb to I2S? I still want to build a usbto I2S converter, and try a linux laptop as music source.
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Old 3rd October 2007, 08:53 PM   #1693
ecdesigns is offline ecdesigns  Netherlands
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Hi Sandor,


Quote:
Can you, please, post details about your selfmade S/P-DIF input transformer?
This transformer is just a temporary solution, as the new one I bought was defective. It's nothing special, took me only a few minutes to make, it's just a small ringcore (approx. 10mm diameter) with two windings of approx. 20 turns on it (wire diameter 0.2mm).
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Old 3rd October 2007, 09:00 PM   #1694
ecdesigns is offline ecdesigns  Netherlands
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Hi tubee,


Quote:
how is the sound of the spdif connection compared to the usb to I2S?
As far as I have been able to test it, they sound exactly the same by direct comparison (toggling between USB and SPDIF). I used a fully modded DI 8M for testing. If there was even the slightest difference in sound quality, the DI 8M would reveal it.

This is good news as it shows that it's possible to achieve identical sound quality from two completely different digital sound sources (I used an old 500 MHz iMac for USB, and a very old Sony CD player with SPDIF coax output). The test CD was ripped and imported in iTunes, then placed in the Sony transport.

The tracks were started almost simultaneous, the sources were toggled by pulling the USB plug (this causes automatically switching to the SPDIF source). If there was a difference, this direct comparison of exactly the same tracks would show it.

Verification of BCK jitter showed the same clean very low jitter signal for both digital input sources. The BCK signal from the CS8412 (before reclocking) clearly showed jitter (approx. 250ps rms).
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Old 3rd October 2007, 10:12 PM   #1695
maxlorenz is online now maxlorenz  Chile
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Hi -ecdesigns-

Thanks for your tips (Post #1689)
As usual, very nice solution for your 8*3DAC.

My original plan was to place the main DI16PCB on the vertical axis to benefit from convective air cooling. I will try that if the horizontal position causes excessive heating. I think my construction is tight but will always fear accidental displacement of the towers and catastrophic short if horizontally placed.
I did not have cement/heat compound which would have helped to this problem and also to eventually put a folded heatsink on top of the present one. I will figure out a way to improve it if it is required.

Quote:
About testing, one vital part is still missing.
Sorry, I did not get it. Would you explain?

Cheers,
M
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Old 4th October 2007, 06:57 AM   #1696
ecdesigns is offline ecdesigns  Netherlands
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Hi maxlorenz,


Quote:
Thanks for your tips (Post #1689)
As usual, very nice solution for your 8*3DAC.
These heatsinks parts were CNC milled, but it was still quite difficult to assemble them. The heat dissipation works fine, the chips stay relatively cool and perform well. I already installed Arcol 0.1% resistors for I/V, diff amp and output attenuator. I still need to install the improved current source modules for pulling the LM4562 into class A.

I added a photograph of these new current source modules,

The IVDIF module on the left has the constant current source piggyback module installed. The module contains 3 precision current sources plus series resistor, and two decoupling capacitors (placed between +15V and -15V). I used low profile IC sockets to enable easy module removal.

The IVDIF module in the centre shows the gold-plated pins I soldered directly to the OP-amp sockets.

The piggyback module component side (bottom right), the current sources consist of 3 JFETs and two resistors. They provide approx. 3mA each.

The smaller single current source modules (top right) can be used for the DI 16, and tubediff input stage. I already experimented with a high voltage version for the cathode follower in the tubediff module, 4 JFETs, 2 resistors and a high-voltage power MOSFET. The result was even lower distortion in the tubedif amp.


Quote:
I did not have cement/heat compound which would have helped to this problem and also to eventually put a folded heatsink on top of the present one. I will figure out a way to improve it if it is required.
You could use TO-220 silicone insulators and use them for both, heat transfer and insulation between heatsink and IC pins.
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Old 4th October 2007, 08:01 AM   #1697
anbello is offline anbello  Italy
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Hi -ecdesigns-
i would like to see the schematics of the spdif receiver in Post #1690,
or at least to know in which mode is set the cs8412/14 (m0, m1, m2).

Thanks
Andrea
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Old 4th October 2007, 04:24 PM   #1698
maxlorenz is online now maxlorenz  Chile
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Hi -ecdesigns-

Quote:
These heatsinks parts were CNC milled, but it was still quite difficult to assemble them.
You tell me!
(I sadly know how dificult is to put that together)

Quote:
About testing, one vital part is still missing.
I asume you were talking about the current sources...I thought you were talking about my project...

Very nice little circuit for the lazy and ignorant amongst us

How about using silicone glue between IC pins and heatsinks? Will this degrade sound?

Regards,
M
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Old 5th October 2007, 12:17 AM   #1699
tubee is offline tubee  Netherlands
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Thanks for reply John. Good news the spdif finally sound as good as from pc. I have a CS8414 unused here so can build a dac input from it. Do you have a pcb available? And which make xtal is used?
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Old 5th October 2007, 07:47 AM   #1700
ecdesigns is offline ecdesigns  Netherlands
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Default SPDIF > (D)I2S schematics

Hi anbello,


Quote:
Hi -ecdesigns-
i would like to see the schematics of the spdif receiver in Post #1690,
or at least to know in which mode is set the cs8412/14 (m0, m1, m2).
I added the schematic of the SPDIF to (D)I2S converter prototype.

CS8412 / CS8414 is put in the following mode:

Normal audio port mode (M3, pin17 = GND)

OUT, L/R, I2S Compatible. M0, pin23 = GND, M1, pin24 = VCC, M2, pin18 = GND)

Short explanation of schematic diagram:

SPDIF enters at J1 pin 3,4, and is fed to the CS8412 through a pulse transformer. A small ring core can be used for this, each winding should have approx. 225uH. L1 indicates PLL lock. CS8412/14 PLL jitter isn't critical.

Both SDATA, pin26 and FSYNC (WS) pin11 are available on J2 (I2S out), and converted to differential signals by U7 for the DI2S interface J3.

SCK (BCK) pin12 enters the shiftregister reclocker first (U2, U3, U4). The shiftregister reclocker is clocked by a very low jitter (<1ps) 48 MHz master clock (U5).

The reclocked BCK signal is available at U2, QB, pin4. It's then fed to the I2S interface, and converted to DI2S by U6.

I used a separate chip (U6) for BCK in order to reduce crosstalk. additional jitter problems can be caused by the DATA signal interfering (crosstalk) with BCK. I used miniature coax wire from Nexans for the I2S connections between modules.
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