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MDAC First Listen (part 00100001)

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JohnW said:
Chris,

https://dl.dropboxusercontent.com/u/86116171/MDAC2 rear panel conector arrangement.jpg

The top row of connectors is the proposed Digital connector arrangement (you can see the USB B connector above the Balanced headphone output which is mounted on the lower Analogue board).

Maybe I could fit a full sized XLR, but I'd have to use a Mini USB connector - we have already had a few people manage to break the full sized USB connector, I'm not sure I trust an even smaller, possibly more fragile "Mini" version + everyone getting upset about needing a new type USB cable...

I'm open to suggestions...
Click to expand...

I can see that the problem is the double row of connectors one above the other.

Out of interest, what's the stacking of the analogue and digital boards?
- difficult to describe this but here goes - Working from the bottom I assume you have:
analogue pcb
analogue components (ie analogue sockets)
digital pcb
digital components (and sockets)
In which case I assume the inter-board spacing determines the maximum height of any connector under the digital pcb

Otherwise you'd only be able to claim any more height if (say) you mouted the digital pcb upside down on the underside of the lid. Even then:
- the height of a usb connector looks to be about the same as (say) a toslink connector, so I'm not sure you'd gain any space
- don't know if it has an adverse effect on rf noise pickup

Apologies if I've not remembered earlier posts and this is what you're already doing.
 
Chris,

The Digital PCB will be mounted "upside down"... sure servicing & fault finding is going to be fun... I'll need to make some test jigs.

Actually, both the Analogue and Digital PCB have PCB connector footprints on both sides of the PCB to allow mounting of the interconnecting flex cable connector so that I can debug the development units in the lab - otherwise when the PCB's are stacked I would not have access to the component layers of both PCBs.

I'll have to hand mount the HDMI "expansion" connector on the Digital PCB on its "top side" between the top lid, to give it clearance from the Audio XLR. The HDMI connector is low profile so there is space between the top of the digital PCB and the inside "top" of the chassis... the pinning of the HDMI is rather fine at 0.4mm pitch, I'm sure I'll be cursing as I hand solder and test each unit.

Also, I plan to offer the option of a Screened layer between the Analogue / Digital PCB's.
 
adamdea said:
fred sonnen said:
That I don't understand....
What is a screened layer?
Click to expand...

I imagine it's a layer of screening.
Click to expand...

:D

Fred
what it is, is a very good idea :)

It's a conductive layer (probably/typically a metal sheet) between the two boards
Its intention is that any electrical fields radiating from the boards (particularly the digital board) are harmlessly conducted away in the screening layer rather than inducing currents (noise, distortion, unwanted signals) in the other circuit board

Try googling 'electromagnetic shielding' and 'faraday cage'
 
JohnW said:
Leon,

I prefer to use a 5W, but it might be very tight for the cable - do you have any experience?
Click to expand...

Unfortunately I do not. jirij or others with cable DIY experience would be better qualified to comment.

IMHO, 4W miniXLR is commonly used by vendors that make and sell customized headphone cables. So for folks that are not handy to make their own cables and want to buy from these vendors, 4W miniXLR will be easier than 5W miniXLR. But you made a valid technical point for using 5W.
 
JohnW said:
Maybe I could fit a full sized XLR, but I'd have to use a Mini USB connector - we have already had a few people manage to break the full sized USB connector, I'm not sure I trust an even smaller, possibly more fragile "Mini" version + everyone getting upset about needing a new type USB cable...
Click to expand...
It depends on the actual socket used, but - in general - miniusb or microusb is rather tight, full-sized USB type B is loose by design (it has the little "bump" to keep it the socket) to prevent destroying your equipment when you trip over a wire.
As for the new cables - I'm sure fleabay would have an adapter for that. :)

Though the hifi industry "standard" is indeed to use full-sized USB type B. I personally don't care.
travelfotografe said:
Unfortunately I do not. jirij or others with cable DIY experience would be better qualified to comment.

IMHO, 4W miniXLR is commonly used by vendors that make and sell customized headphone cables. So for folks that are not handy to make their own cables and want to buy from these vendors, 4W miniXLR will be easier than 5W miniXLR. But you made a valid technical point for using 5W.
Click to expand...
I have some experience with multi-pin Switchcraft and REAN miniXLRs, both 4-pin and 5-pin, and I wouldn't say there's a significant difference in soldering difficulty. It's pretty much the same. The 4-pin looks generally like this - http://2.bp.blogspot.com/-uyV4wsHmfnU/TtZhu7ASwxI/AAAAAAAAAfI/vRFgsz98vH0/s1600/4-PIN-Mini-XLR.jpg, with the 5-pin having roughly the same pin accessibility (estimate for yourself from http://proaudio.com/images/Switchcraft_TA5F.jpg). However, your mileage may vary, since these little things from "the east" come in many different variants, despite sharing the same name.

In any case, a decent solering iron with a small enough tip, a steady hand (if you lack one, try one of these - http://rover.ebay.com/rover/1/711-5...0001&campid=5338728743&icep_item=221512400917) should about do it. :)
In my experience, it's not significantly harder than solering full-size XLRs, provided you have a small enough tip (says a man, who uses 2mm tip (http://ex-en.alliedelec.com/search/productdetail.aspx?SKU=70219840) for everything :D).
 
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fred sonnen said:
That I don't understand....
What is a screened layer?
Click to expand...

Fred - this is a screened layer:

Picture-17.png


;)
 
Paul (misterdog),

You components arrived from the US today :) So I'll atleast try to have your AMP ready here for your Birthday :)
 
JohnW said:
Paul (misterdog),

You components arrived from the US today :) So I'll atleast try to have your AMP ready here for your Birthday :)
Click to expand...

A birthday card from my brother in the US also arrived.
A pop up model of the solar system. :cool:
 
Hi John,

Can you please advise how to open the MDAC remote? I've opened the battery cover, removed the single screw beneath it then pried the two plastic sections apart a little but I'm worried if I keep forcing it, I'm going to break something... there's got to be a trick to it.

My purpose is to wash the cover as it feels dirty. Merely wiping it just makes it worse!

Thanks in advance.

Cheers,
Bruce
 
Bruce,

I've never tried to open the handset - normally these things are "Snapped together" and any attempt to open them results in snapped internal plastic clips.
 
JohnW said:
Bruce,

I've never tried to open the handset - normally these things are "Snapped together" and any attempt to open them results in snapped internal plastic clips.
Click to expand...

Ah right, thanks John. That's what I thought. Ok, maybe I'll just look at a different cleaning solution... would contact cleaner be safe enough do you think?

Cheers,
Bruce
 
Hey John, when MDAC2 is finally ready for us all to set things in stone, etc., how are you going to announce it? Do we need to keep checking out this thread, or will you send out an email? Asking as I'm scaling back my PFM time these days... might miss something important though...
 
moosemeat said:
Ah right, thanks John. That's what I thought. Ok, maybe I'll just look at a different cleaning solution... would contact cleaner be safe enough do you think?

Cheers,
Bruce
Click to expand...

Contact cleaner would strip the coating - where are you located? I could try and source you a replacement handset.
 
JTC said:
Hey John, when MDAC2 is finally ready for us all to set things in stone, etc., how are you going to announce it? Do we need to keep checking out this thread, or will you send out an email? Asking as I'm scaling back my PFM time these days... might miss something important though...
Click to expand...

John,

Yes indeed the MDAC2 design is now set in stone - I'm plodding along with the design.

This Forum is the main point of contact, however once I've completed the Analogue PCB design Renata will Email everyone to confirm (including Toy / Fusion owners) which version they require, and if L2 / L3 then request the next payment of GBP100.

Those who are going for MDAC2 L1 have now paid all the development costs in full (Toy / Fusion owners do not pay development costs upto the L1 design).
 
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