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MDAC First Listen (part 00110101)

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I'm still having problems with my MDAC, last week I said that the USB input seemed to have stopped working, I've not tried it again yet.

So I'm using a Matrix USB to SPDIF converter connected by coax, I notice that if I leave my MDAC on all day I start to get a little static sounding click from the speakers, then when I play music it's intermittent and cuts out, only playing every other second. Switching the MDAC off and back on again fixes it.

Anyone else experienced this?
 
Nick,

A long time back, did you not experience suspected Clock issues? this all sounds like a Bad clock.

I resigned the clock section for MDAC2 / FDAC and also have a new retrofit Clock design for MDAC's.
 
therixonator said:
Hi John,

Over the last few weeks, I've had a few instances where I switch the mdac on but the screen is blank. It usually starts up properly on 2nd attempt. Today however clipped a bit and then cut out completely during a film (screen still on but doesn't resond to any controls including restating cables). It wouldn't fire up at all after that. It just came on now with the no comms error and on 2nd switch on it is now fine again.

Just a brief bit on its history. Its been over to see you twice, once for a toy upgrade and once for a new crystal. I bought it brand new perhaps 5 years ago.

What is the verdict?
Click to expand...

Clock... as mentioned in the post above, I have a new retrofit clock circuit PCB for the MDAC.

The issue seems to be more frequent in cold conditions - winter months, cold rooms...
 
Apologies if it has been covered before. What will be the input to the RPi in the MDAC2? Ethernet,USB, WiFi only?
 
JohnW said:
Clock... as mentioned in the post above, I have a new retrofit clock circuit PCB for the MDAC.

The issue seems to be more frequent in cold conditions - winter months, cold rooms...
Click to expand...

As the MDAC is currently unusable in it's current state (screen not coming on at all today), what is my best route to a fix?

I'm currently down for an FDAC. I was planning on taking the MDAC2 board too although I hadn't applied for one yet.

I'm happy to be analogue only for a couple of months if the MDAC2 would be available around then. I don't want to waste your time, and make everyone including myself wait longer for the MDAC2 to fix something that will be replaced anyway.

But if you think I'm going to be a long way down the queue for the MDAC2 as I've only just joined it then maybe I should be selfish and send it to be fixed?

I'll take your lead...
 
kennyh said:
Thank for that I'll have a read. I'm assuming it's for solely streaming purposes with no DAC card attached to it.
Click to expand...

The RPi CM3 is internally connected to the MDAC2 via USB. The connection uses a smaller internal implementation of John's USB cleaning solution 'Detox'. Basically the MDAC2 comes with two USB inputs, one of them being used for internal RPi compute module connection.
 
therixonator said:
As the MDAC is currently unusable in it's current state (screen not coming on at all today), what is my best route to a fix?

I'm currently down for an FDAC. I was planning on taking the MDAC2 board too although I hadn't applied for one yet.

I'm happy to be analogue only for a couple of months if the MDAC2 would be available around then. I don't want to waste your time, and make everyone including myself wait longer for the MDAC2 to fix something that will be replaced anyway.

But if you think I'm going to be a long way down the queue for the MDAC2 as I've only just joined it then maybe I should be selfish and send it to be fixed?

I'll take your lead...
Click to expand...

Yes, just post me your DAC and I'll add the new clock module - same address as before, just send by itself with no Remote or PSU.
 
fusion5 said:
The RPi CM3 is internally connected to the MDAC2 via USB. The connection uses a smaller internal implementation of John's USB cleaning solution 'Detox'. Basically the MDAC2 comes with two USB inputs, one of them being used for internal RPi compute module connection.
Click to expand...

Correct. the RPi is connected to to MDAC2 internally via the USB Bus which is Detox'ed, Clock-Locked and isolated.
 
highfi said:
Apologies if it has been covered before. What will be the input to the RPi in the MDAC2? Ethernet,USB, WiFi only?
Click to expand...

Ethernet & USB BUT NO WiFi (you can and use a USB to WiFi Doggle, but I don't recommend RF transmissions so close to audio interconnects)...
 
John,

Did you do any further testing with HQPlayer upsampling to DSD512? I've tried RBCD to DSD512 and so far not impressed. I don't hear anything wrong with DSD512 versus foobar2000 playing the original RBCD, I just don't get why everyone is saying it's fantastic. To me the difference is minute.

There are loads of permutations of filters and modulators and I haven't tried them all, but I have tried the recommended poly-sinc-short/poly-sinc-short-mp with DSD5v2/ASDM7/AMSDM7.

IME the best SQ comes from DSD or CD's recorded with the utmost care, and these are easy to distinguish.

Thanks
 
adamdea said:
Talking of the Detox. Isn't the production visit coming up?
Click to expand...

I'm still waiting to approve the production sample - I have two units each coming from 2 different vendors (Vendor keeps one as signed reference sample and we keep one).

I'll need to push as our last update was from last week - I've been buried in MDAC2 PCB...
 
JohnW said:
Nick,

A long time back, did you not experience suspected Clock issues? this all sounds like a Bad clock.

I resigned the clock section for MDAC2 / FDAC and also have a new retrofit Clock design for MDAC's.
Click to expand...

Hi John,

I've not had problems before, my MDAC has been to you for AV bypass, some caps changed and you did a little tweak. I also did some more caps myself and I'm running 3 x Calex psu.

Is there anyway I can test the clock? I have an oscilloscope, I don't have any problems changing parts and taking measurements.

Thanks
 
Nick,

For the clock, you will need a 500MHz + Scope?

In instances where the DAC operation is "unstable" with USB then the clock will have high cycle to cycle jitter - so the edges will be "wide" rather then nice "thin" edges.

Bad Clock (Crystal)

https://dl.dropboxusercontent.com/u/86116171/MDAC Jitter.jpg

Good Clock:-

https://dl.dropboxusercontent.com/u/86116171/MDAC Replacement clock.JPG

I dont have any more replacement crystals here so you will have to order one from IAG UK - it should cost no more then GBP10 with postage...
 
Thanks Fusion5 and John for the info re. RPi. Two questions:

1. If an RPi is NOT installed in MDAC2, do we have access to the second USB input on the rear panel?
On the same topic, in the rendering Fusion5 kindly linked to, 3 USB inputs can be seen. What are these?
Also, there is an HDMI connector. Can that be used for audio input, or is it for monitor display output only?

2. What would be the comparative advantages/disadvantages to having an RPi inside the MDAC2 case or an external one, if any?
A possible benefit might be, for instance, that an external one could benefit from the full DETOX solution.
Moreover, an external RPi would be less prone to pollute the MDAC2 with RFI.
Plus, easier to upgrade if/when needed. I can see the internal RPi becoming outdated faster than MDAC2 (hopefully).
A disadvantage would be that an external RPi would require its own power supply.

What do you fellow PFMers think? Are there any other important factors to consider?
 
1. the 3 USB A is for Wifi, usb storage etc. and the HDMI is a output for monitor/tv. they are all connected to the RPI.
The USB B in the bottom right corner is a normal USB input to the DAC and can be used without the CM3 card. just as on your current MDAC.

2. We will only know if external Detox has an advantage when we can compare the two solutions. But there might be an RFI advantage/peace of mind using an external Detox and added flexibility. You can use a normal computer as well.

I would not worry too much about the RPI getting outdated. At least not with my use case which is RoonBridge.

When I use it with Roon all the heavy lifting is taking place on the Roon server. So it will just function as a "dumb" endpoint just like a squeezebox/airplay etc.

With the just released Roon version 1.3 DSP functionality has been added as well as upsampling so now it can do Room EQ and other DSP stuff and more will most like be added in future versions.
Soon software MQA decode will also be added probably the first unfold as in Tidal desktop App.

All this still streaming to a "dumb" endpoints that will not become outdated as an endpoint.
 
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