Discussion in 'Digital: DACs, USB converters, decrapifiers' started by sacredgates, Oct 3, 2017.
Thanks - thought that so didn't try in case something went wrong elsewhere.
IB Down-Under's left over M unit sounds like a good deal for someone down under. Since the US dealer has already confirmed that he doesn't have any left over stock, I'll go ahead and send my module to Micheal.
It is a really odd board. It looks like the i2s signals go from the RJ45, through a resistor, and directly to output on a header to the main board below. Then there is this power supply isolator and regulator that doesn't connect to the i2s function at all. I'm guessing that the USB board used this power and then passed it along to something else on the mainboard, so they had to include the power supply components on the i2s board, even though they don't have anything to do with the i2s. Like I said, I will be very interested in what Micheal sees.
Obviously my goal would not be to 100% duplicate the boards other functions. Just to allow the I2S signals to pass from the RJ 45 to the header with the correct termination as required by the DAC. I am hoping it is simple, and we shall soon find out!
Michael - if it's of any help I2S modules I believe conform to M2Tech specs if you have an I2S Dac chart. Have one on file if needed.
I would absolutely welcome the information so that our PI2AES board can be used with this many I2S compatible DAC‘s as possible.
Feel free to private message me or send an email to [email protected].
It's too bad there is no standard. Even when things look right strange things can happen like intermittent sound or channels being reversed. Had two such situations over last several months with some products. What would be useful is a multi purpose configurable unit with BNC/HDMI/RJ45 adaptability. Heck of a job probably. Will drop you a line with info.
An update re I2S Dac index. Knew I had a link somewhere but could not find it. It's a bit more up to date.
Just finished looking at the Metrum I2S adapter. It is very simple as expected. There is a 10 ohm series resistor from the RJ 45 to the down header. There is also a 100 K ohm resistor from that point to ground. Finally there is an optional 100 ohm to ground resistor that can be enabled with the jumper.
For interfacing to our board I would definitely recommend not enabling the 100 ohm resistor to ground. This puts too much of a load and does not help the termination any because we use series termination at the source. This might explain some of the issues that folks of had with a longer cable. If someone who has had that issue can try it without the jumpers I would love to hear the results.
As for what I will do next, I will create a clone board that matches the mechanicals, but is strictly passive, no resistors as they are not needed to interface with our board. This will not make it a universal clone, but I have to be a little bit selfish since it will make it quick and easy and require almost no assembly work on our part.
I will post an update when I have the boards ready for someone to test. Definitely the two folks who sent me their units in will get one of these along with their units returned (if they can wait the two weeks it will take). Otherwise I can send their boards back right away.
Long term we will bundle this board with our RJ 45 adapter at no extra charge.
I may have spoken too soon. I was sent an adapter from two different forum members. The first one I opened was the simple one with just resistors. The second one that I opened a few minutes ago to verify they were the same, has a voltage regulator and a relay. What is strange is that the connections go from one of the large headers to an additional four pin header and none of the signals go to the RJ45 or the I2S signals.
It appears as though this was some type of patch that was put on this particular board for convenience. If anybody has some insight into this that would be great. I recall that an earlier post showed a picture that looks like this second board, but now I’m not sure if the DAC requires that circuitry to operate the external I2S interface.
The module with the additional patch is from me and is for the Onyx/Jade models. I did send you a photo in an email when I sent the module that shows the main board of the Onyx under the i2s module. Although I can't speak for the Jade (which has a volume control function added), I can say that the Onyx plays just fine with no module in place.
As for what happens when the i2s module is in place, could you trace pin number from the down headers that relate to the patch and I will try to trace where they go on the mainboard. Also, you mentioned a voltage regulator and a relay, but I thought there was a voltage regulator (LM317, soic-8) and a DC-DC converter/isolator. Please double check as it may help us understand what they are doing.
I would note that there is a galvanic isolator chip on the main board below the module and there are Murata isolation transformers from the XLR and coax connections close by. I'm curious if the "patch" could be some kind of isolation circuit.
By the way, take your time with the i2s module from me. I don't need it back right away.
Yea, the simple one was from me, for a Pavane.
Please update when that happens/if you want beta-testers I'm in.
I pulled the cover off the Onyx again. The area where the module connects has three standing pin headers. The one on the top is the 4 pin that Michael mentioned. There is also a 14 pin to left and a 12 pin to the right. All are located in a separate ground plane area and there are no trace on the top surface going from the 4 pin and only 2 traces at the bottom from the 14 pin. In the middle of the ground plane, there are some capacitors and resistors and 3 active elements. The largest is an ISO7640FM galvanic isolator (SOIC 16) listed as low power, quad channel, digital isolators. A smaller, 5 pin device is a P131 GB that my best guess is a Toshiba TLP 131 GB photo coupler <photo transistor optically coupled to an LED>. There is also a 3 pin device that could be a transistor or diode.
Although there are connections between the 4 pin and the 12 pin on the right, they are all at or above the 1 Meg Ohm level unpowered in one orientation and open circuit in the opposite polarity, like a diode or transistor.
It would be nice to understand the "patch", but if it doesn't appear to connect to the i2s signals, and the Onyx works fine with no module, perhaps a simple prototype ignoring the patch can prove if the patch is doing anything in the i2s function.
PS I can't see where the Jade would be different in this area than the Onyx. All the Jade volume control does is vary the input voltage to the resistor ladder, so there are unlikely to be any differences in the digital receiver part of the design.
Not to be hogging this thread, but I thought I should update my Metrum Acoustics experience. It's now been more than a month since I tried to order an i2s module from Metrum. At this point, I have made a claim with Paypal for a refund. I still haven't received any communication from Metrum, other than automated responses. I went to my account on their website and there is no record of my January order. The most recent activity on my account is from May 2018.
In other words, it truly looks like no one is home at Metrum. I will assume that the company no longer exists until there is clear evidence to the contrary. I certainly recommend not buying anything from them until you are convinced that everything has been fixed. What a shame.
Very odd. I did have an email from them a while back -- maybe quite a long while back -- in response to a request but it was brief and I heard nothing after that. Still enjoying my Ambre/Onyx in a desktop system but it doesn't look good. Certainly nothing like their previous CS, which could be a bit confusing at times but was generally prompt and always friendly.
Hello folks. I just bought a i2s module from hifiheaven. I think they have a couple of modules from several metrum dacs. I also had a terrible experience with metrum International. They don’t respond emails and my last shipping had problems. After several reading and gathering info from other forums, i do think metrum had a bankrupt or something equivalent.
Very sad. Long live Sonnet audio!
Hope my metrum dac never fails...
How can someone buy a company, that, as far as we know, wasn't in any bankruptcy state and screw it up in 3 months?! Maybe someone, someday, will be able to shed a light on it but this is utterly confusing to me.
Ironically they probably thought the same. Running a small business is tough - if you think it isn't you'll find out in surprisingly short order.
BTW, Pi 2 Design consists of two people and two main products and we still are challenged to get stuff out the door. And our products require far fewer parts and suppliers.
Building consumer-electronics in low-volume is a very delicate dance between spending money upfront to build product, getting paid when the product is ready, and having enough product available.
I do not know anything about the situation of Metrum, but if somebody new has bought the company there is a tough learning curve. Hopefully that is all it is as they do seem to have products that folks want.
I just hope they don't leave their customer High and Dry. Least they can do at this point is an email to their customers regarding warranty issues etc.
Their product wasn't cheap.
Separate names with a comma.