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Old 4th November 2012, 08:01 AM   #4581
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The treble boost is necessary since the Dac is reconstructing the analog signal with square steps and not infinitely short pulses at the sampling instants.

Rectangles in the time domain having the spectra of a sinc functions in in the frequency domain having more energy content at low frequencies, thus you need to apply the inverse of a sinc in the frequency domain to get a summed flat frequency response.

If you are using 1.5K I/V resistors you can use a 8.2mH inductor in series with the I/V resistor and 3.3nF across the R-L combo to form a resonable accurate sinc compensation filter.

If you have an analog anti aliasing filter you can modify it by adjusting the Q as s3tup says to get some sinc compensation, you can use the R+L//C combo above as a model to mimic across the audio band.
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Old 4th November 2012, 07:10 PM   #4582
oshifis is online now oshifis  Hungary
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You could avoid the need of sinc related treble boost by using an approximation of infinitely short pulses. Such pulses can be produced by a differentiating C-R circuit. The energy content will be very low after this circuit, that effect can be partly compensated by using high supply voltage (with a tube circuit). Another advantage of this circuit would be the natural insensitivity to jitter.
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Old 5th November 2012, 12:50 AM   #4583
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Quote:
Originally Posted by -ecdesigns- View Post

Too expensive, too low resolution (A/D conversion), and it doesn't capture the information I am interested in.
I reviewed your interferences.
The 2,5 kHz interferences are only ca. -16 dB below the 50 Hz.

Even the worst playtoy analyzer with 8 bit resolution = 48 dB dynamic range will show that and many more things you can not see with your scope.

As far as I know, energy from various sources is bundled together in the net, even from foreign power plants on demand. Either one of these sources is dirty or you have a big maschine somewhere in a factory spoiling the energy net.

Anyway, the 2,5 kHz will be smoothed out 99% by the first cap in your psu.
Can you still measure it after a simple regulator ?
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Old 7th November 2012, 12:56 PM   #4584
SSerg is offline SSerg  Russian Federation
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Hi -ecdesigns-
Quote:
Originally Posted by -ecdesigns- View Post
At the beginning of this thread I was focussing on sample amplitude, smooth signals, low THD and so on. This resulted in the DI system that smoothens the NOS DAC output signal.

I supposed that you interest in the first place quality of the sound, rather then «
sample duration and sample shape».

Quote:
Originally Posted by -ecdesigns- View Post
This has resulted in reverting to one DAC chip, placing main focus on sample duration and sample shape.
You wrote that with increase the chip number sound became much clearer, detailed (for instance, posts #1, #9, #73 and so on). Was this an illusion?

Serg
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Old 7th November 2012, 02:33 PM   #4585
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Quote:
Originally Posted by SSerg View Post
Hi -ecdesigns-

I supposed that you interest in the first place quality of the sound, rather then «
sample duration and sample shape».


You wrote that with increase the chip number sound became much clearer, detailed (for instance, posts #1, #9, #73 and so on). Was this an illusion?

Serg
Audio is an illusion

A DAC signal that passes a brickwall filter is a smooth signal.
Everything else is
Ok. Everything else is a staircase.

And before EC will teach me that a brickwall is not acceptable for highly transparent sound because many reasons and his many listening tests...
( But a staircase is... because the speakers... and the ear... )

I did listening tests too. With a different result.

Fact is: Unfiltered nonos is a staircase signal with hf loss.
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Old 7th November 2012, 03:18 PM   #4586
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Here is my ac power one day.

I have a 16 bit plugin but measurement is done with a 8 bit plugin.

It has spurious at 12,5 kHz and 13,8 kHz.

Click the image to open in full size.



Next day clean.

Click the image to open in full size.

Last edited by Bernhard; 7th November 2012 at 03:30 PM.
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Old 8th November 2012, 02:30 PM   #4587
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Hi SSerg,

Quote:
I supposed that you interest in the first place quality of the sound, rather then «sample duration and sample shape».
Yes, at the beginning I focussed on perceived sound quality and signal shape.

Quote:
You wrote that with increase the chip number sound became much clearer, detailed (for instance, posts #1, #9, #73 and so on). Was this an illusion?
This was the conclusion made many years ago when digital audio source jitter levels were rather high.

Now I make conclusions based on low jitter systems and I got much more critical.

As far as paralleling DAC chips is concerned, each DAC chip has tolerances, including tolerances in propagation delay.
Propagation delay also depends on chip temperature and supply voltage.

So when paralleling DAC chips, each DAC chip can have slightly different temperature and supply voltage.

The samples of each DAC chip will not arrive at the summed output at exactly the same time. This would translate to a "rattling" sound (asynchronous sample latching) instead of a single click (synchronous sample latching).

This effect alone will significantly increase timing errors (jitter). So this type of DAC is more "compatible" with high jitter sources.
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Old 9th November 2012, 08:56 AM   #4588
SSerg is offline SSerg  Russian Federation
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Hi -ecdesigns-,
Quote:
Originally Posted by -ecdesigns- View Post
Now I make conclusions based on low jitter systems and I got much more critical...
As far as paralleling DAC chips is concerned, each DAC chip has tolerances, including tolerances in propagation delay...
So this type of DAC is more "compatible" with high jitter sources.

Well
, that we have? Mountain gave birth to mouse.
The result of the gigantic thread became the confession to fallaciousness of initial ideas.

I'm sad.

Serg
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Old 9th November 2012, 09:25 AM   #4589
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Again, SSerg, I fail to see how your posts contribute to anything at all...in the Universe.

And don't repeat that your intentions are good.

Have a nice year.

M.
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Old 9th November 2012, 09:29 AM   #4590
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Quote:
Originally Posted by maxlorenz View Post
Again, SSerg, I fail to see how your posts contribute to anything at all...in the Universe.

And don't repeat that your intentions are good.

Have a nice year.

M.
Thank you Maxlorenz, my thoughts........you say it!

Ed
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