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Old 24th October 2012, 06:53 PM   #4531
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hello,

apologies for the abrupt enterance. i have retrofitted mr. john b's 2sk170 output (from mark3) on this dac. HiEnd TDA1541 A DAC CS8412 SAA7220 OS Assembled Borad | eBay
i rerouted some traces and cut the others trying my best to disable the discrete circuit, and the sound for the most part a big improvement . (thank you john!) but i'm getting random hf hiss. it's not constant but more of a irregular pulse. any idea what might be causing this?

also i have implemented grundig 9009 dem clock mod which i feel is a must have. what other significant upgrade am i missing out besides the regulators?

i'm eventually wanting to breadboard my own 1541dac following ecdesigns' guidelines and wanting to know what i should put on the must do list.

Last edited by PreSapian; 24th October 2012 at 06:57 PM.
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Old 25th October 2012, 02:27 AM   #4532
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There is a thread somewhere in which ThorstenL gives his guidelines for doing a breadboard TDA1541a dac which beats most of the commercial tda1541a dacs out there. He incorporates some of his own ideas as well as some of John's.

Look for it using the search function, it's called something like 'best tda1541a implementation' and was running in 2011 I believe...
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Old 25th October 2012, 11:07 AM   #4533
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Hi koldby,

Quote:
Is this capacitor not as much in the signal path as a coupling capacitor?
It is in the signal path like elco's in the power supply, but the cap is bypassed by a relatively low resistor value. This improves performance compared to only a cap in the signal path.

Quote:
The other thing is a suggestion to a buffer / level shifter to act on the I2S signals.
The 3 resistor I2S attenuator has proven its effectivity. For BCK I added a RF Schottky diode to split-up the transients in zones with different speed. This enables both, extreme low jitter levels (low ground-bounce) and fast transient within the trigger zone.

Quote:
It is a very clean BCK that comes out of this - look at the pictures. Even from the very rude circuit as seen in the last photo.
Digital scopes have limited resolution (A/D converter), so signals are "forced" to fit in the few pixels on the LCD. This prevents accurate analysis of wave form shape. If you want to observe signals in more detail you will need a suitable large bandwidth analogue scope.

Quote:
I just found a Pass Lab B1 buffer amp ready made board.
If you -have- to use passive I/V conversion with the I/V resistor tied to GND you have to add a super clean +2mA bias current. This is necessary to create equal signal swing around GND and thus maximise output signal swing with given -25mV and +25mV output compliance.

CCS usually cause problems with perceived sound quality in these applications. If you -have- to use a CCS, then I suggest to use the Aikido circuit where issues with non-linear properties of active elements are largely canceled out. The Aikido circuit can also be translated to JFETs, but I personally prefer the tube version.
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Old 25th October 2012, 11:12 AM   #4534
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Hi PreSapian,

Quote:
apologies for the abrupt enterance. i have retrofitted mr. john b's 2sk170 output (from mark3) on this dac. HiEnd TDA1541 A DAC CS8412 SAA7220 OS Assembled Borad | eBay
Just like a house requires a solid base, a DAC requires ultra low jitter timing source and ultra clean supply voltages as solid base to build on.

Tweaking a DAC driven by jittery timing signals and noisy supplies is like attempting to build a house on quick sand without solid base and this is likely to end in disaster.

So before even thinking of tweaking the I/V stage it would be wise to make sure you are building on a solid base (ultra low jitter timing signals and ultra clean supply voltages). This will save you years of tweaking that basically lead nowhere. I am speaking out of own experience as I have spent over 6 years tweaking DACs.

Quote:
also i have implemented grundig 9009 dem clock mod which i feel is a must have.
Please note that this DAC has massive amounts of jitter. So it is basically impossible to tell if a mod would really improve things without using an ultra low jitter source and ulta clean power supplies as base. Subjective "improvements" could well be a result of added distortion or changed distortion spectrum.

Quote:
what other significant upgrade am i missing out besides the regulators?
There are many but reducing jitter to lowest possible levels and getting rid of the SAA7220 would be a good start.
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Old 25th October 2012, 11:38 AM   #4535
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Hi SSerg,


Quote:
But on TDA1541A I have studied much material and can confirm that you mistaken.
As be with reflected signals? Furthermore, signal fronts have too low slew rate. This enlarges jitter.
TDA1541 info

Post #29 and following posts of HtP.

Quote:
Do not forget that WS defines the moment of the issue of the output signal. The flutter of this moment of time will bring about front flutter of analog signal. Well it?
TDA1541A datasheet page 4:

"Input data selection (see also Table 1)

With the input OB/TWC connected to ground, data input (offset binary format) must be in time multiplexed mode. It is accompanied with a word select (WS) and a bit clock input (BCK) signal. 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.

With OB/TWC connected to VDD the mode is the same but the data format must be in the two’s complement."
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Old 25th October 2012, 12:22 PM   #4536
koldby is offline koldby  Denmark
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-ecdesigns-

I have been using the original I2S attenuator on "The Red Baron Dac" and my Audio Widget usb to I2S is 3,3 V logic so I was forced to have a buffer to increase to 5 V I2S.
Therefor I was planning to replace buffer + attenuator with the suggested buffer as a better way?
Maybe the original solution is better, time will tell.
Thanks for your reply.

Koldby
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Old 25th October 2012, 12:25 PM   #4537
koldby is offline koldby  Denmark
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By the way , I tried the DC shift solution insted of a russian PIO coupling capacitor and you know what?

The DC shift stays in..!

Koldby
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Old 25th October 2012, 01:11 PM   #4538
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Quote:
Originally Posted by -ecdesigns- View Post

If you -have- to use passive I/V conversion with the I/V resistor tied to GND you have to add a super clean +2mA bias current. This is necessary to create equal signal swing around GND and thus maximise output signal swing with given -25mV and +25mV output compliance.

CCS usually cause problems with perceived sound quality in these applications. If you -have- to use a CCS, then I suggest to use the Aikido circuit where issues with non-linear properties of active elements are largely canceled out. The Aikido circuit can also be translated to JFETs, but I personally prefer the tube version.

Hello

So I just use a 2.5k resistor between 1541 output and the +5 volt, like in my image ?

Thank

Bye

Gaetan
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Old 25th October 2012, 01:37 PM   #4539
CeeVee is offline CeeVee  Portugal
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Quote:
Originally Posted by studiostevus View Post
There is a thread somewhere in which ThorstenL gives his guidelines for doing a breadboard TDA1541a dac which beats most of the commercial tda1541a dacs out there. He incorporates some of his own ideas as well as some of John's.

Look for it using the search function, it's called something like 'best tda1541a implementation' and was running in 2011 I believe...
Thorsten L is reference on how to do the TDA 1541 right as is John :-) but such a thread with that title does not exist....

Ofcourse his AMR solution is out of our reach ( IPR and too complex for us ) but all his other solutions are precious material.

...would love to read the text...whatever the title.

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Old 25th October 2012, 02:36 PM   #4540
ide2003 is offline ide2003  Indonesia
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I think I kept a copy of this 2011 thread, sure one of many

decoupling TDA1541A

that was when I tried to do pcb layout, so did studiostevus
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