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MDAC First Listen (part 00101100)

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Thanks for the comprehensive anser John getting a seal on a complex flat surface like that is difficult I worked for most of my career in Automotive design so have some experience, could a compressible ridge be added to the board or maybe machined into the base.
 
Interesting that chassis construction is such a critical issue for RF isolation.

Its fundamental - RF by its very nature radiates :)

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?

Actually its only critical "At the point of conversion" - let say within the DAC - but a good place to start is to limit any unwanted RF energy entering the DAC in the first instance.

RF filtering is only "attenuation" = reduction, so any external filtering adds to the final absolute level of attenuation.

Ideally the DAC would be designed for 100% RF attenuation and thus indifferent to external energy, but this is not realisable in the practical world.

Its very hard to design filtering in the analogue domain that does not impact the sound quality - think of the sonic degradation caused by capacitors and even resistors - forget magnetic components.

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?

While the Detox will attenuate (hopefully :) ) unwanted RF from the Host USB device - the USB Data itself will radiate and this still needs to be screened so the cable will still impact the SQ.

For MDAC / FDAC / FDAC Lite users the USB Data will be synchronised to the audio conversion Master clock via the Clock Link interface - this greatly reduces the RF spectrum Inter-modulation between the audio clock and the USB host domains.
 
Thanks for the comprehensive anser John getting a seal on a complex flat surface like that is difficult I worked for most of my career in Automotive design so have some experience, could a compressible ridge be added to the board or maybe machined into the base.

Yes, they add "Wire conductive gaskets" recessed into the "Walls" which in combination with the screws guarantee 100% screening under all conditions and tolerances (just like cylinder head gaskets).

With the Detox's current construction any gap is hopefully going to be tiny - so the leakage wavelength will be well above any practical concern.

The Detox budget sets limits to how far I can go - but I'd like to believe its already many orders better then any other competing design in this regards.
 
The Detox budget sets limits to how far I can go - but I'd like to believe its already many orders better then any other competing design in this regards.

It makes the others look like DIY efforts!! and don't get me wrong I love what the regen does, but can't wait to hear what the Detox is capable of!!
 
Thank you for the detailed response in post #774 to my query.

Sounds like I will need to build a DETOX-like conduit ;) for my (short) USB cable or maybe close couple the DETOX and DAC using one of those solid A to B adapters.
 
If you see the internal Lid and Base renderings then you can see how the PCB has its own isolated sections,

........

The Base and Top cover will be machined post anodising to expose a conductive Grounding path to the PCB on the "walled" sections.

John, I'm a chemist, not an engineer, and perhaps this is splitting hairs, but what will this machining do? Flat gold or copper (on the PCB) on to flat aluminium doesn't sound like much of a contact to me, given the insulating oxide film which grows on aluminium within milliseconds of machining. The conductive wire gaskets you mention would I guess break through the film, but it didn't sound as if you intended to use these here.

However I'm quite sure that every one of those screws will be making good electrical contact between top and bottom of the case as they are tightened, and so long as the PCB ground strip is separately tied to the case, this lack of direct contact may be unimportant.
 
John, I'm a chemist, not an engineer, and perhaps this is splitting hairs, but what will this machining do? Flat gold or copper (on the PCB) on to flat aluminium doesn't sound like much of a contact to me, given the insulating oxide film which grows on aluminium within milliseconds of machining. The conductive wire gaskets you mention would I guess break through the film, but it didn't sound as if you intended to use these here.

However I'm quite sure that every one of those screws will be making good electrical contact between top and bottom of the case as they are tightened, and so long as the PCB ground strip is separately tied to the case, this lack of direct contact may be unimportant.

We had discussed plans to copper plate the concerned chassis areas - the mechanical engineer is in discussion with the vendors as to the exact processing.

We might end up having to punch a custom gasket, but tooling costs are a prime concern (and the limited Qtys).
 
John,
I would definitely want the deluxe fully milled chassis for the FDAC if it becomes an option:p

I'm with Rune....that makes 2 deluxe pre-orders so far!

The build quality is looking so good I think we could launch the Detox into space and land it on Venus in good working order.

Both projects are looking soooooo fantastic....Great work John...:D
 
We had discussed plans to copper plate the concerned chassis areas .

Not sure what you mean by copper plate, but if the copper has direct contact to the aluminium, you'll get a battery reaction and the copper will 'eat' the aluminium. contact corrosion.
unless you put an isolating layer inbetween
 
John, I'm a chemist, not an engineer, and perhaps this is splitting hairs, but what will this machining do? Flat gold or copper (on the PCB) on to flat aluminium doesn't sound like much of a contact to me, given the insulating oxide film which grows on aluminium within milliseconds of machining. The conductive wire gaskets you mention would I guess break through the film, but it didn't sound as if you intended to use these here.

However I'm quite sure that every one of those screws will be making good electrical contact between top and bottom of the case as they are tightened, and so long as the PCB ground strip is separately tied to the case, this lack of direct contact may be unimportant.

Hi Bob L, I am a chemist by training too (NMR & LCMS mainly). I was interested in what you said so I did a brief Wiki check. The Al2O3 layer that forms is only 4nM thick. Once you build this up by anodisation it becomes more of an insulator.

I recall in my youth using the aluminium foil from cigarette packets to temporarily fix blown fuses in a mains plug.....highly dangerous I might add!
 
Not sure what you mean by copper plate, but if the copper has direct contact to the aluminium, you'll get a battery reaction and the copper will 'eat' the aluminium. contact corrosion.
unless you put an isolating layer inbetween

Hi Torstoi, Having done some quick web research, this is only a problem in the presence of salty water which behaves as an electrolyte. In normal atmospheric humidity this is not a problem. Copper and aluminium are routinely joined in many industries including electronics.

http://www.klauke.com/en/electrical/technical-reports/accurately-connecting-copper-and-aluminium/
 
I'm in the electronic industry & our pwr converters have to have a special contact fat applied inbetween in case there is contact between copper and aluminium.
If it got forgotten the units are completely put apart again.
They are usually not working in an environment of salt water.

Those who are, are completely sealed in stainless & have water cooling instead of open air cooling. (ships & modern ferries)
 
Not sure what you mean by copper plate, but if the copper has direct contact to the aluminium, you'll get a battery reaction and the copper will 'eat' the aluminium. contact corrosion.
unless you put an isolating layer inbetween

I'll leave the whole subject of the conductive "plating" to the mechanical engineer and the vendors - my only requirement is to have a conducive path between the PCB and the chassis - I'll leave the exact details to there expertise.

From conversations with the Mechanical designer I understand that they first add a Zincated layer to the aluminium then copper plated or electroless nickel plate, but as I say I don't really want to get involve into the details as I need to concentrate on the electronics design :) - its why I pay the mechanical engineer to offload some of the project workload from me.
 
That's fine then, zincated aluminium doesn't require contact fat when connected to copper.
I'd agree the mech engineer should know what he's doing.. :)
 
I'd agree the mech engineer should know what he's doing.. :)

One hopes!

I've read up on the subject and Galvanic corrosion requires the metals to be exposed to an electrolyte, in normal environments (non-temperature and humidity controlled environments) we will be OK with Aluminium and standard Tin Plated PCB's (based upon the MIL-STD-889 tables).
 
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)?

Looks like I will be hitting the buy button for two Detox'es soon :)

Yes, the replacement OLED part arrived and I successfully installed it. My MDAC Premium Fusion is looking great now and sounding great (as always). Sorry, I have been terribly busy lately and delayed emailing Renata (and you) on the receipt and successful install of the OLED part.

~Leon
 
We had discussed plans to copper plate the concerned chassis areas - the mechanical engineer is in discussion with the vendors as to the exact processing.

We might end up having to punch a custom gasket, but tooling costs are a prime concern (and the limited Qtys).

Thanks John- that clears it up; sorry to have stirred up so much else at the same time.

Timola- pm on the way; this thread is already too cluttered!
 
Looks like I will be hitting the buy button for two Detox'es soon :)

Yes, the replacement OLED part arrived and I successfully installed it. My MDAC Premium Fusion is looking great now and sounding great (as always). Sorry, I have been terribly busy lately and delayed emailing Renata (and you) on the receipt and successful install of the OLED part.

~Leon

Leon,

No problem - I'm just as bad, I collected the OLED panel while in China, but upon my return I just did not have the time to contact you to say I had it ready to ship!! :)

Glad your MDAC's back to full Pixel count :)
 
Thanks John- that clears it up; sorry to have stirred up so much else at the same time.

Timola- pm on the way; this thread is already too cluttered!

Bob,

No problem, its a subject we had discussions about internally - leaving the final solution to the vendors capabilities.

The Detox project is as much a "Trail Blazer" for the FDAC designs - better to learn with a simple design.

As always its a matter of cost and vendors capabilities in China.... both strike fear in my mind!
 
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