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Old 1st September 2012, 06:24 PM   #11
Calvin is offline Calvin  Germany
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Hi,

since the AD844 is a fast device and running openloop a smaller cap could be used and it improves the simulation results. I canīt promise that the same would apply in praxis. But since this DAC is of NOS-type, it requires heavy and low-frequency filtering. So I guess that a big cap at the DACs output is probabely more positive than the associated THD-increase is negative.
For example the TDAs output impedance and behaviour against the I/Vs input impedance is unknown (to me at least). If it would be >100kOhms the cap size wouldnīt change much in THD figures.
Personally I wouldnīt place such a burdon on a DACs output, but also I wouldnīt use an antique DAC in NOS-mode...but thatīs a wholly different matter.

jauu
Calvin
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Old 3rd September 2012, 06:59 AM   #12
ozcal is offline ozcal  Australia
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Quote:
Originally Posted by R4s3tsu View Post
Hello there. Thats my first post lol.
Some time ago I've bought this dac
(SUMMER SALE) DAC TDA1541+WM8805 1.0UI multi-input | eBay
Click the image to open in full size.

The DAC is not arrived yet, but I'v got a question:
The description says it's NON-OS.Without any analog stages. So I need some tips for this.
I've been looking for good I/V stage for this board and bought some kind of "Pedja Rogic's Buffer"
The schematic is in attachements.
So can I use this I/V stage with this DAC? Cos some people say it's can't work with TDA1541 NOS dacs. So, will it work or not?
Hi R4 , I recently purchased one of these boards and it sounds better than I expected.
I went for passive I/V conversion by fitting 2 Shinkoh Tantalum 47 ohm resistors in the place provided for them at the top left of the board. I then added a Universal valve stage form DIYHIFISUPPLY : Universal Stereo Tube Output Stage with Standard copper cap (Complete with Power Transformer) | Diy HiFi Supply and the sound is very acceptable on rca input ( haven't tried the other inputs ).
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Old 3rd September 2012, 12:56 PM   #13
R4s3tsu is offline R4s3tsu  Russian Federation
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ozcal,
Thanks for your review.
Quote:
2 Shinkoh Tantalum 47 ohm resistors in the place provided for them at the top left of the board.
What is the purpose of this resistors? Do you use original TDA chip provided by the seller? Did you tried TDA1541A? S1?
Do you know which 14 decoupling caps placed around DAC chip?
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Old 4th September 2012, 03:08 AM   #14
ozcal is offline ozcal  Australia
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Quote:
Originally Posted by R4s3tsu View Post
ozcal,
Thanks for your review.

What is the purpose of this resistors? Do you use original TDA chip provided by the seller? Did you tried TDA1541A? S1?
Do you know which 14 decoupling caps placed around DAC chip?
The resistors are used to do the current to voltage conversion(I to V),then all you need is a valve / solid state output stage to amplify the signal to normal cd player output levels .
Using the tda1541a chip supplied by Hui. I have not tried S1 or S2 chips as they are getting rare and therefore expensive.
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Old 4th September 2012, 07:32 PM   #15
R4s3tsu is offline R4s3tsu  Russian Federation
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Quote:
Originally Posted by ozcal View Post
The resistors are used to do the current to voltage conversion(I to V),then all you need is a valve / solid state output stage to amplify the signal to normal cd player output levels .
Using the tda1541a chip supplied by Hui. I have not tried S1 or S2 chips as they are getting rare and therefore expensive.
How should I know which resistors I need with my stage? Or they not so necessary?
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Old 16th September 2012, 10:23 AM   #16
R4s3tsu is offline R4s3tsu  Russian Federation
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I've received the board. It's very fine. Waiting for transformers now.
As for I/V stage I should build a good 18V PSU - all I need is Rectifiers and big filter caps. As for caps I'll use Nichicon KGs. So the question about rectifier diodes.
Which diodes are the best for audio?
Are the Shottky diodes will be fine? I heard that they has very good qualities for audio applications. Can I use 4 x SB3100 100V 3A or 4 x 1N5822 40V 3a shottky diodes? Will it be enough?
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