A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

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#1,684
Beautiful work! Did you use the Arduino to run the screen?

I am hoping to use a BeagleBoneBlack as music server in the DDDAC case, and trying to figure if it can do the screen display too, or whether to use the Arduino for that purpose, getting a feed from the BBB.
 
#1,687
I have now completed the 8 stack and after a week or so bedding in, it is now top of the class for sound quality 🙂

The power supply mods were interesting. I changed the 4700uf`s to Mundorf 10000uf and the 470uf to 1000uf.

I ended up keeping the Mundorf 10,000`s but put the 470`s as supplied with the original kit back as I found that 1000uf somehow made the soundstage smaller.
Maybe the decoupling properties of the 470`s match what the circuit needs.

I have found some Vishay low ESR capacitors part number; 678D477M025DM3D I will give them a try but I will be amazed if it can sound much better ….
Very pleased with the kit, Thanks for the design Doede 🙂
 

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#1,690
SimonJ said:
Thanks! 😀

The case is from Modu and the exact one is here.

modu

I designed the front and back panels myself using the Schaeffer company CAD tool and service which was superb! You need to spend time learning the software tool but it was easy and soon got the hang of it.

Schaeffer AG: Home
Click to expand...
Cool thanks.
I discovered the Software tool from Schaeffer AG just last week. I'm no expert and found it simple enough to use, plus it exports in DXF 🙂
 
#1,692
SimonJ said:
VERY nice work Alex. 😉 Which case did you buy please? Love the special heat sink, so did you make that?
Click to expand...

Hi Simon,

I drew up the case and had a local engineering firm make it for me. It used 16 mm thick Alloy panels so cost a packet but is solid enough.

I made the heat sink using an extruded one cut to the size I wanted then I welded them together. It runs at 45ºC now instead of 75ºC.

I will be building another one with 16 stacks later this year but I will use the similar case to what you use as they are very nice looking.

Happy listening 🙂
 
#1,693
With respect to the data on these screens there seems to be some confusion.

In SimonJ's instance the WaveIO supplies the sample rate / frequency data, this does not come from the computer delivering the audio signal. The Arduino interprets the control signals of the LEDs and renders text in their place.

Its quite possible to connect a screen to the BBB but that would not be providing information about the DAC, it would be information about the source.

Some of the software for these embedded players which are based on MPD server (such as volumio) offer the potential for the output of playback data (artist, title, duration) which would drive a screen connected to the GPIO headers of the embedded device.

What would be super cool is to combine the sample rate & frequency data from the WaveIO PLUS the playback state information outputted directly by the transport, all on one 20x4 LCD. The Arduino would then be used to implement the collation of data from two sources for display.
 
#1,694
dwjames said:
yes, if you have minimal DC voltage across your pos and neg pins, then you can join your RCA direct to these with no coupling capacitor. Mine is running like this and sounds great.
Click to expand...
How to wire the RCA connector?
Negative of dddac connected to rca connector's gnd,
and positive of dddac connected to rca connector signal.

Without common ground,
Does the amplifier connected to it is not in any danger?
 
#1,695
Hi Foxye
Even with minimal voltage on the pins do not connect to a pre amp /amp without a blocking capacitor on the input (many valve amps will have this). Otherwise you risk putting a large offset voltage across your speakers.

You can connect a capacitor from positive of the DDDac to RCA pos, with the DDDac negative connected to your RCA negative. There is not much difference between this and direct and it avoids any dc offset if in doubt. It also sounds better than connecting cap to DDDac positive, and the RCA ground to common.
David
 
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#1,696
juancho said:
Hi Foxye
Even with minimal voltage on the pins do not connect to a pre amp /amp without a blocking capacitor on the input (many valve amps will have this). Otherwise you risk putting a large offset voltage across your speakers.

You can connect a capacitor from positive of the DDDac to RCA pos, with the DDDac negative connected to your RCA negative. There is not much difference between this and direct and it avoids any dc offset if in doubt. It also sounds better than connecting cap to DDDac positive, and the RCA ground to common.
David
Click to expand...

The idea is that it sounds better with NO cap. But as you noted; your amp must be able to handle a bit DC.
Most transistor amp designs I have seen always have an input cap, also tube amps use caps and transformers in the signal path so you will never get DC on the speakers. There are of course always exceptions, so you need to check your amp or try without speakers connected and measure if there is DC on the amp output.

Note: the only reason DC is bad for speakers is that current runs through te coil and the coil/cone is NOT moving on DC. This means that the coil will no be cooled by the movement; that is creating a cooling airflow.

Regards,
 
#1,699
I agree with juancho. In my setup, I can even hear the volume knob scratch sound if connecting direct without input caps and at more than 60% volume my pre amp would cut off. Another thing is what will happen for long term use, so using input caps just makes more sense against the very little benefit over sq that you would get if there's any.

Note: dc offset for my dac is 0.3/0.5 mA.
 
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