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A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)
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Old 10th November 2017, 08:04 PM   #6391
Svitjod is offline Svitjod  Sweden
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OK, DDDDDAC, ( I'm stuttering ).

You are right, your DAC probably sounds good with SCK at 64*fs.

BUT.... since the device is a sigma delta DAC, it will always obtain full 130dB resolution after a couple of samples. But it will take longer time for the DAC to "home in" at the desired value. Thats a very well known disadvantage for any S/D device, even if a PCM1794 ( with it's 6 hardware levels ) is almost as good as a 16 bit (ideal)multibit DAC.
So, since this DDDAC is supposed to be a real hi end DAC we should squeeze every possible bit of resolution out of it.

My own solution is to feed the DAC from a DSP. I'm using a fairly cheap one from Microchip. This DSP also acts as a buffer and outputs its data, clocked from a master oscillator. It's simply reclocking the input stream. It also handles a radio controlled remote control to set the volume. And other tasks.

So, this DSP feeds the PCM1794 with identical copies of the samples, so the SCK can be run as high as fs*256. And it's still in NOS-mode, since the samples are identical.

Perhaps you are interested to make a DDDAC v2.00 from my project?
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Old 15th November 2017, 11:42 AM   #6392
beardman is online now beardman  Denmark
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Hello
I will like to lower the output from Doede dac

how low can i go with the I-V resistor on my 4 deck,,i use Sowter 3575 trafo

Best Bjarne
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Old 16th November 2017, 10:55 AM   #6393
Smartdriver is offline Smartdriver  Netherlands
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Hello there,

I've been rebuilding and upgrading my DDdac for a while now and very very happy with the results i must say.

From wave-io to streaming: Rpi 3b with Volumio, ALLO Isolator with ALLO Kali.
This setup has the advantage that you don't need an extra "audioquality" PSU.
The Rpi uses it's own small crappy stock powersupply which also feeds the "unclean"
part of the Isolator just before Galvanic separation, the "clean" part of the Isolator is fed with clean audioquality power from the Kali which has the 5V from the stock PSU for the ditched wave-io.

The DDdac is upgraded from 2 to 4 decks.

I upgraded the stock 2 PSU's with one very large (500VA) transformer.
The 2 secondairy windings are manually adjusted to give the proper voltage to each PSU.
I made one upgrade to the PSU circuit, the half wave rectifier was ditched and replaced with a proper full wave bridge rectifier.

And finally i intergraded a TVC in this setup, not a Sowter but the Silk.

The endresult is much more than i wished for but it took a while to get there.
It noticed that it takes a long time, up to 250 hours of actual burn-in time, to let the new dac decks sing, these are the TENT versions.
I don't use anything special for burn-in, just music day and night, 24/7 for 2 weeks straight.

My experience was that after the 200 hours passed, the soundimage went from 4:3 to 16:9 and then slowly crept to 21:9.
The depth image did the same.

Well, as i said, it sounds breathtaking, it is deadsilent, no backroundnoise whatsoever just music!

A very happy DDdac user
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Old 16th November 2017, 12:20 PM   #6394
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by Smartdriver View Post
From wave-io to streaming: Rpi 3b with Volumio, ALLO Isolator with ALLO Kali.
This setup has the advantage that you don't need an extra "audioquality" PSU.
The Rpi uses it's own small crappy stock powersupply which also feeds the "unclean"
part of the Isolator just before Galvanic separation, the "clean" part of the Isolator is fed with clean audioquality power from the Kali which has the 5V from the stock PSU for the ditched wave-io.
This is very interesting! I tried (almost) the same, and I am getting some serious noise/hiss with the Kali (see here and followups). Did you ever observe anything similar with your setup? Do you have experience with running the setup without the Isolator?
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Old 16th November 2017, 12:32 PM   #6395
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by beardman View Post
Hello
I will like to lower the output from Doede dac

how low can i go with the I-V resistor on my 4 deck,,i use Sowter 3575 trafo

Best Bjarne
Lower resistors would indeed give lower voltage swing. However, the DAC chips would be biased at a higher current, which would increase distortion (maybe dramatically). It would be better to use a different method to reduce the output voltage. You could use two smaller series resistors in place of the single I-V resistors and tap the output signal between those resistors. Or you could use a different output transformer that has a voltage step down.

However, the signal voltage swing of the DDDAC already is a bit on the low side (that's why Doede used a step up transformer in his design). I would therefore look for excessive gain elsewhere in your system.
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Old 16th November 2017, 03:13 PM   #6396
rohot01 is offline rohot01  Taiwan
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Click the image to open in full size.
Its Broken,Can I use it??
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Old 17th November 2017, 07:55 AM   #6397
beardman is online now beardman  Denmark
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mbrennwa
I will try the idea with the 2 resistor and take the output in the middle off them
thanks
Bjarne
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Old 17th November 2017, 10:05 AM   #6398
Smartdriver is offline Smartdriver  Netherlands
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Quote:
Originally Posted by mbrennwa View Post
Did you ever observe anything similar with your setup? Do you have experience with running the setup without the Isolator?
Hello mbrennwa, sorry to hear about your problems, i do not have experience playing without the Isolator.

I've had some problems but not the one you discribe, i made one mistake with the I2S connections.
I connected GPIO 29 aka MCLK who we don't need, as soon as i disconnected this one everything was souding as it should be.

Therefore, you only need to connect GPIO 40 (DATA), 35 (LRCLK) and 12 (BCLK) for grounding i connected 39 also.

At the moment these connections aren't even shielded so i'm busy right now with creating some "air" silver shielded FMJ interconnects for the I2S connections.

Let me know if this works out for you.

Cheers, Paulus
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Old 17th November 2017, 11:49 AM   #6399
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by Smartdriver View Post
Hello mbrennwa, sorry to hear about your problems, i do not have experience playing without the Isolator.

I've had some problems but not the one you discribe, i made one mistake with the I2S connections.
I connected GPIO 29 aka MCLK who we don't need, as soon as i disconnected this one everything was souding as it should be.

Therefore, you only need to connect GPIO 40 (DATA), 35 (LRCLK) and 12 (BCLK) for grounding i connected 39 also.

At the moment these connections aren't even shielded so i'm busy right now with creating some "air" silver shielded FMJ interconnects for the I2S connections.

Let me know if this works out for you.

Cheers, Paulus
I didn't connect MCLK. And I have already tried shielded cables. See here (sorry for jumping between threads, I am trying to pick the brains of the great people in both both threads). The main conclusion so far is that my noise/hiss problem goes away if I connect the RPi to the DDDAC directly (i.e. without the Kali).
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Old 17th November 2017, 02:05 PM   #6400
Smartdriver is offline Smartdriver  Netherlands
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I'll guess then that you have to get in touch with ALLO and see if they can help you to fix the problems.
I'm sure they will try to help you.
Good luck

Cheers, Paulus
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