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Building the ultimate NOS DAC using TDA1541A
Building the ultimate NOS DAC using TDA1541A
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Old 25th July 2009, 02:53 AM   #2991
jameshillj is offline jameshillj  Australia
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Current flo J2 - add a temparary small R between rail and J2 and measure.
Actually, perhaps consider changing the o/p buffer to the variation of the B1 with the +/- rails (with the Shunt reg in group buy section)
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Old 25th July 2009, 09:27 AM   #2992
ccschua is offline ccschua  Malaysia
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I will try a simplify version and test. The shunt reg with B1 is what I am looking for. I regreted not buying enough of the 2sk170BL/2sj74BL.
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Old 25th July 2009, 09:38 PM   #2993
omainik is offline omainik  Austria
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Originally posted by jameshillj

With the 4 x 41A chips in //, o/p current max is 16mA amd this feeds the transformer directly (Sowter number?) - if the reflected impedance at max setting = 6R, dac o/p pin would have about 100 mV on it, yes?

Do you source current for the transformer (to dac o/p pin) from a -ve voltage, or just to 0volt? [/B]


transformer is 8347

4mA * 4 DAC = 16mA
0.016 A * 6 R = 0.096 V on the loudest position
in normal use for my system
0.016 A * 0.4 R = 0,0064 V

transformer is connected to 0V
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Old 28th July 2009, 01:19 PM   #2994
Builder Brad is offline Builder Brad  United Kingdom
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Location: Kent, UK
Default Battery Power for TDA1541

Hi John,

I am just about to implement battery power on my D14M, and have sourced 3 x 12v 20Ah SLA batteries. Is it acceptable to directly feed +12v -12v and -24v to the D14M main board and let the LED regulators produce +5, -5 and -15, or would I need to use some kind of pre-regulation before the LED regulators.

I am also looking for 3 x 1f car audio capacitors for each of those voltage rails and it seems a shame to put pre-regulators in if I can get away without them.

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Old 30th July 2009, 08:15 PM   #2995
Bernhard is offline Bernhard  Germany
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Originally posted by Bernhard

What does the dV -36.25 mean ?
K2 is -36.25 dB below the fundamental ?

I would appreciate your comment.

While I was on my analyzer for another thread, I did a FFT of my DAC with passive I/V @ 1 kHz / 0dB.

As you can see, it is totally clean down to the noise floor of ca. -90 dB.
I was lazy to program averaging to remove the noise floor, it would be clean down to and below the limit of my analyzer = -95 dB also...

Vpp on each leg of the balanced DAC is 395 mV, that combines to 1,3 Vpp after the TVC
The measurement was made on the output of the transformer volume control, thus includes the distortion of the TVC.

Click the image to open in full size.
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Old 31st July 2009, 07:14 AM   #2996
Radian is offline Radian  Germany
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Location: Wiesbaden
Originally posted by omainik
transformer is from sowter.

I compared a lot of other possibilities. The sound characteristics I like were only present with the transformer and some tube based output stages with a rather complex psu, so the transformer wins soundwise and is the simpler solution.
Would you mind showing a basic schematic of your output stage.
I got two sowter transformers here that have a 1:19 ratio and I
would really like to compare your solution to my simple passive I/V.

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Old 31st July 2009, 01:13 PM   #2997
jstang is offline jstang  United States
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This is such a great post.... John has done a great job of working with us and sharing...providing products on his site.

But is there any way to down the whole thread? Into a word doc or some thing like that....

I would like organize the thread into a bits and pieces that are really meaningful for me....

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Old 31st July 2009, 05:05 PM   #2998
2A3SET is offline 2A3SET  Canada
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Location: Toronto
Default Re: Dynamic jitter attenuator.

I am using 220R-3xBAT43-(to BCK)-154R-499R//220n, I only got 1V at BCK, should I keep it or replace the 499R with a trimmer?

The forwarding volt of BAT43 (VISHAY) from DMM is only 0.27V, is that normal? The datasheet shows 2.7V-3.3V under 2MA, which should be correct. Maybe I need to add another BAT43?

BTW, I am getting 1.2V from WS and 1V from DATA with 1K//3.3K attenuator network. PCM2707 datasheet shows 2.8V output from FUNC1 and 2.4V from DOUT.


Originally posted by maxlorenz
Thanks EC for your detailed and informative reply about volume control.
Thanks 2A3SET for you tip. I recently saw that ligthspeed attenuator. It sounds interesting and can be driven by 5V PS.

Dear EC, yesterday I made my first attempt with the dynamic jitter attenuator for my D1M. BCK is taken from PCM2707. I put a trimer resistor parallel with 220nf, in series with 150R to ground as per your diagram. The trimer set at 283R (rheostat mode) gave 1,22V DC for BCK. Ripple measured between 150R and 283R (trimer) and ground was around 10mV, even with 230nf or 320nf...is it good enough? Shall I try lower capacitances?

Today I will try to replace the trimer resistor by a better quality fixed R.

Another question> could you advice what tweak would be better for the BCK signals of the multiple DAC chips (DI4 and scrambled versions) converters-> conventional signal attenuator or dynamic jitter attenuator???

Many thanks,

PS> the 220R series BCK resistor is place AFTER the bat 85 (in my case) and after the dynamic jitter attenuator. Must I change it?
Attached Images
File Type: jpg 2707 attenuator.jpg (28.2 KB, 910 views)
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Old 1st August 2009, 07:39 PM   #2999
maxlorenz is offline maxlorenz  Chile
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Hi 2A3SET,

I would recommend using trimer resistors on daughter boards when playing with attenuators and dynamic jitter attenuator (DJA), to set for optimal values and optimal sound, IF you have a scope to check. I would do it just for the fun of learning how the waves move up an down.
After that it is easy to measure and replace by better fixed R.

A question> do you get sound coming out?

I report that, even if not optimal, my own version of the DJA made a significant improvement in sonics.

Another philosophical/technical question to John> do you think using inductors from attenuators R TO GROUND will improve sound???

Good luck,
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Old 2nd August 2009, 01:05 AM   #3000
2A3SET is offline 2A3SET  Canada
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Default Dynamic jitter attenuator

I do get sound out with 1V at BCK, does the lower volt means better sound? I cannot get 1.2V BCK as the forward volt of BAT43 is only 0.27-0.33V. The DATA after attenutating is 1V as well.
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