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MDAC First Listen (part 00101100)

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JohnW said:
Thank you :)

Yesterday When I first opened the package with the PCB's I said to myself that we really have to do the same for the FDAC/ FDAC Lite!

Yes, I'm keen to start building the Detox PCB - but first I must complete a self set target to crack the current section on the FDAC Analogue PCB that's "dominating" my life at the moment!!! I go to bed and fall asleep trying various layout combinations in my mind!!! there are just so many opposing variables! :eek:
Click to expand...

Have you tried LSD. :D

http://www.telegraph.co.uk/news/new...ing-LSD-at-work-to-increase-productivity.html
 
When I see musicians who are totally in there "Zone" and at there best when uninhabited while on drugs it does tempt me - but then the landing back to reality must hit REALLY HARD!!

Think Eric Clapton while in Cream or Joe Satriani here - Man just look at those eyes!

https://www.youtube.com/watch?v=paeNnR33i5Q&index=27&list=RD07rT1t2hkDU

Might be something to do with the track as Warren Haynes also goes for a "nose rub" more often then you would expect! :eek: :D

https://www.youtube.com/watch?v=aCiLCo-LoUg&list=RD07rT1t2hkDU&index=27

Camera briefly pans to Grace Potter in the crowd at 7:15 or so... :)
 
Well, being a father of three (daughter & two boys). Informing and fighting drugs is just one of the many battles a parent has to fight ... surely not always easy.
 
JohnW said:
Not to be blowing my own trumpet I'm proud of the Detox because the end result is nice :) and having made the "step" intime, I can incorporate the same design concepts into the FDAC now that we are not constrained by the MDAC chassis.
Click to expand...

John, with detox concepts inside fdac, is an external detox still needed for fdac? Or is it like icing on the cake? I am wondering if I need two detox, one for fdac in main stereo and another for mdac in another room.

Leon
 
There is no "Detox" inside the FDAC - the RF needs to be attenuated before entering the DAC chassis.

BTW - Did the replacement OLED panel arrive for your MDAC? (or am I confusing you)?
 
Ah, I understand that you are proud with this design. If it " sounds" as it looks it must be great ��
 
Thank you - yes I'm a rather proud father :)

Well sonically it will only be the "icing on the cake" but it good to know that a decent low correlated noise / Low RF USB signal and Power (in case of the FDAC) is being proved to the DAC.

But it screams for the FDAC Lite to be designed along a similar route :)
 
If you see the internal Lid and Base renderings then you can see how the PCB has its own isolated sections,

Top:-

https://dl.dropboxusercontent.com/u/86116171/Bare Detox PCB A01.jpg

https://dl.dropboxusercontent.com/u/86116171/DETOX Internal View.jpg

Base (underside):-

https://dl.dropboxusercontent.com/u/86116171/Bare Detox PCB A01 underside.jpg

https://dl.dropboxusercontent.com/u/86116171/DETOX Base.jpg

The Base and Top cover will be machined post anodising to expose a conductive Grounding path to the PCB on the "walled" sections.
 
John that looks impressive but curious why you need so many screws to hold it together.
 
John that chassis just shouts class. I love the rounded corners. Can we have that on the FDAC, or is the chassis design too far advanced ?
 
John

If you redesigning the analouge PCB... there is no space for these russian military tubes....?
Just as an SE version for our group.....
;-)
 
GWM said:
John that looks impressive but curious why you need so many screws to hold it together.
Click to expand...

Its for RF Isolation its critical to to prevent any gap that might open between the isolated sections. The lowest wavelength of RF that can escape into the next section is determined by the largest size of the gap - any "air Gap" between the PCB and isolation walls might be tiny with wavelengths into the 10's of GHz, but a wide slot between the screws might open - this slot could be significantly wide and the resultant wavelength "low" well within our operating frequency range (think of the internal 480MHz Clock of USB PHY - in fact it will be "blind sampled" at say 3GHz to 5GHz).

Here's examples of typical high performance RF enclosures (note the multitude of screws):-

https://dl.dropboxusercontent.com/u/86116171/RF Cavty.jpg

https://dl.dropboxusercontent.com/u/86116171/RF Cavty 2.jpg

https://dl.dropboxusercontent.com/u/86116171/RF Cavty 3.jpg

https://dl.dropboxusercontent.com/u/86116171/RF Cavty 6.jpg

This is just an example of the lengths required to achieve decent isolation - when I see the other "USB Regenerators" on the market they employed no practical attempts to achieve effective RF isolation.

The Detox has x11 signal line RF filters to filter the signal lines between sections and Input / Outputs. Obviously RF filtering is also applied to the PSU lines.

The FDAC Lite will follow the same construction to isolated the Digital and Analogue stages, Clock and DAC sections etc.

Unfortunately the FDAC suffers from its legacy of originally "trying to squeeze it into the MDAC chassis" - its taking a lot of PCB redesign effort to repackage the design - it will be good, but shame for the "lost time" and poor initial direction .... :(
 
fred sonnen said:
John

If you redesigning the analouge PCB... there is no space for these russian military tubes....?
Just as an SE version for our group.....
;-)
Click to expand...

I've promised to release the FDAC Analogue PCB sometime in Jan 2016 - sadly this leaves absolutely NO time to think about tubes. The use of MOSFET's on the input stage will significantly close the gap between the Transistor and Tube version.

The Tube version has many extra requirements such as HV and heater supply's - so its not an easy drop-in design.
 
iansr said:
John that chassis just shouts class. I love the rounded corners. Can we have that on the FDAC, or is the chassis design too far advanced ?
Click to expand...

To have a fully milled chassis for the Full width FDAC would cost a small fortune - as it stands I'm "nervously" waiting for the official quote on the Detox chassis.

I've had a problem from a few members when asking for an extra GBP280 for the FWC with internal HQ PSU & Touch Panel display - forget the cost of a solid milled version.

Now, as our working experience with the Detox / FDAC Lite CNC vendor progresses we might find ourselves in a position to offer a deluxe fully milled chassis for the FDAC - but I'd expect it to cost close to the cost of the PCB's themselves so doubling the cost :eek:

The FDAC Lite will be of a similar design to the Detox.
 
JohnW said:
Its for RF Isolation its critical to to prevent any gap that might open between the isolated sections. The wavelength of RF that can escape into the next section is determined by the largest size of the gap - any "air Gap" between the PCB and isolation walls might be tiny with wavelengths into the 10's of GHz, but a wide slot between the screws might open - this slot could be significantly wide and the resultant wavelength "low" well within our operating frequency range (think of the internal 480MHz Clock of USB PHY - in fact it will be "blind sampled" at say 3GHz to 5GHz).

Here's examples of typical high performance RF enclosures (note the multitude of screws):-

https://dl.dropboxusercontent.com/u/86116171/RF Cavty.jpg

https://dl.dropboxusercontent.com/u/86116171/RF Cavty 2.jpg

https://dl.dropboxusercontent.com/u/86116171/RF Cavty 3.jpg

https://dl.dropboxusercontent.com/u/86116171/RF Cavty 6.jpg

This is just an example of the lengths required to achieve decent isolation - when I see the other "USB Regenerators" on the market they employed no practical attempts to achieve effective RF isolation.

The Detox has x11 signal line filters to filter the RF of the signal lines between sections and input / outputs. Obviously RF filtering is also applied to the PSU lines.

The FDAC Lite will follow the same construction to isolated the Digital and Analogue stages, Clock and DAC sections etc.

Sadly the FDAC suffers from its legacy of originally "trying to squeeze it into the MDAC chassis" - its taking a lot of redesign work to repackage the design - it will be good, but shame for the "lost time" and poor initial direction .... :(
Click to expand...

Interesting that chassis construction is such a critical issue for RF isolation. You certainly nailed (screwed?) it!

Can you explain why this level of isolation is so important going through the DETOX and up to where the signal enters the DAC but less so/not at all once it crosses the input USB of the DAC itself?

I understand that the cable between the source and DETOX may not matter(?) but after DETOXing the signal so thoroughly, will the construction, e.g., shielding, of the umbilical to the DAC matter?
 
John,
I would definitely want the deluxe fully milled chassis for the FDAC if it becomes an option:p
 
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