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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 KHz

Is there any issue/incompatibility if a shunt output relay (momentarily shorting of signal to ground) is used directly at J7 output?

J7 is just the output from a bunch of resistors, those can be shorted forever.

The buffered output is driven by LME49724, although those are short circuit protected they're also high current, so they should only be shorted for short periods of time.
 
Sören,

I try to interface Soekris DAM1021 as master with Amanero USB-I2S as slave using I2S MCLK OUT from DAM -> Amanero's MCLK (slave config) and Amanero's PIN1 or PIN11 to I2S FSEL IN on DAM.
The problem is I got silence on Soekris I2S MCLK OUT pin. Do we need activate MCK OUT in Soekris command line? The same question regards FSEL IN functionality.
 
I got quick&dirty solution to seeking and sample rate change of Soekris clicks for Amanero users.
Just flash Amanero with bclk_test CPLD firmware and 1080 CPU firmware and you can forget about seeking clicks - this firmware introduces continous bit clock signal even when seeking/track change so no synchronization lost occurs.
When you add an oversampling to fixed sampling frequency (eg. to 384kHz using Sox mod foobar plugin) you can forget about clicks at all.
 
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I got quick&dirty solution to seeking and sample rate change of Soekris clicks for Amanero users.
Just flash Amanero with bclk_test CPLD firmware and 1080 CPU firmware and you can forget about seeking clicks - this firmware introduces continous bit clock signal even when seeking/track change so no synchronization lost occurs.
When you add an oversampling to fixed sampling frequency (eg. to 384kHz using Sox mod foobar plugin) you can forget about clicks at all.

Great suggestion, it helps a lot with one of the most annoying problems in DAM!

I will add that in foobar the WASAPI (Event) interface does not work right when bclk_test CPLD is loaded in Amanero. The WASAPI (Push) interface works fine.

If Event interface is used, when seeking in a track the BCLK signal occasionally switches to 2.8224 MHz regardless of the actual sampling rate. It results in vveeerrryyy sslllooooowwwww playback for higher sample rates. Tried it both with foobar sox oversampling plugin and playing various sample rate material without processing in foobar, no difference.

That is with bclk_test CPLD, 1080 and 1096c Amanero firmware and 1.0.57 USB driver on Windows 7.

Of course, this is an Amanero issue. DAM does the right thing by "slowing down" when it sees the slower bitclock.
 
Last night I took a few measurements of my DAM. The measurements were not intended to determine the absolute performance characteristics of the DAC, but rather to determine the influence of different grounding schemes on its performance.

After I had installed a pair of alpha 20 line stages I had measured my DAM's noise floor at -87dbs, which was suspect at best.
The installation of the α20s had coincided with me changing my plastic IEC with a metal one, that also provided filtering.
Metal meant that the main's GND would be connected to my chassis. You may remember that the Soekris does not have insulation on its mounting holes, so if you are using metal standoffs to mount it you are effectively connecting your signal ground to your chassis.

To make a long story short, isolating the DAM from the chassis improved the noise floor by a whopping ~23dbs. It also made significant difference in the dynamic range, THD, etc.

So, beware of your grounding (ok, this goes primarily to the "noobs" at audio DIY).

Then I decided to check something else out. I took measurements both with the serial port connected to my PC and without.

Having the serial port connected did at least some damage to most of the measured aspects. For example the noise floor went up by almost 14dbs. So I wouldn't recommend having the serial port connected to the PC at all times.

But you should keep in mind that the PC that took the measurements was the same one that was connected through its serial port, so that probably accounts for some part of the "damage". I'll come back with more data.
 
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Super. Thanks for information. I have the serial connected the whole time between my rpi2 and the dam1021. I am unable to hear any difference in sound with the serial cable connected or not.

I think DimDim is overstating the issue, but I guess that depends on your setup.

I've attached two spectrum analysis I did a few weeks ago. Both are done with the TOSLINK connected but no signal, so the DAM is unlocked. Volume is set to V+00.

The main peak of noise with serial connected is at 80kHz, and I suspect this is related to the onboard switching power supply on the serial interface chip. There is a second peak at 40kHz, and third lower peak at around 46-8kHz. There are other minor differences close to the noise floor of my setup.

I have the transformer in an ABS box, with an umbilical with +/-7.5VAC running to the DAM.
The only grounding of the DAM is currently via the XLR jacks.

I'm using a USB->RS232 adapter, hooked to a MacBook Pro.

Setup is not calibrated, so I make no claims beyond relative differences between the two.
 

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Like I said, the testing was done with a common ground between the DAM and the PC doing both the testing & the serial connection, so that might have something to do with the problem. I will definitely do some more testing, including the influence that a serially connected Arduino may or may not have.
 
hey guys I decided this will be my first DIY project other than cables(I made a few to learn to solder). Since I am a newb, should I wait til the firmware gets updated to remove the sample rate change clicks and power off pop, or is it easy to update the firmware? I saw someone posted a link to a usb to serial cable but I'm not sure how easy it is to update firmware.. do I just open the case, plug the little pin headers onto pins(looks to me like the pins for pc case hdd led, power led etc) and plug usb into my pc, then on the command line: DFU push coolfiltersandbugfixes.bin? Basically, is it safe for me to order the pcb now? It's going to be a basic build, probably the 0.05 resistor version.

edit: this is the serial to usb cable.. http://www.ebay.com/itm/310676792112?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
I don't see any pins on the dac pcb that they'd go on.. is that something I have to install on the pcb and solder?
 
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hey guys I decided this will be my first DIY project other than cables(I made a few to learn to solder). Since I am a newb, should I wait til the firmware gets updated to remove the sample rate change clicks and power off pop, or is it easy to update the firmware? I saw someone posted a link to a usb to serial cable but I'm not sure how easy it is to update firmware.. do I just open the case, plug the little pin headers onto pins(looks to me like the pins for pc case hdd led, power led etc) and plug usb into my pc, then on the command line: DFU push coolfiltersandbugfixes.bin? Basically, is it safe for me to order the pcb now? It's going to be a basic build, probably the 0.05 resistor version.

edit: this is the serial to usb cable.. USB to RS232 TTL UART PL2303HX Auto Converter USB to com Cable Adapter Module | eBay
I don't see any pins on the dac pcb that they'd go on.. is that something I have to install on the pcb and solder?

Go here and read very carefully. https://hifiduino.wordpress.com/2015/03/16/soekris-dam-1021-r-2r-dac-users-guide/
This was my 2nd DIY project and 1st dac project. I wish the hifiduino site was available when I started! Be patient and follow instructions exactly. Buy the parts that others have mentioned even if you need to order them.
Have fun!
 
Just a note that the linked USB to serial cable may not work - do verify before buying. The DAM1021 requires real RS232 signals not RS232 TTL level signals... if it's RS232 TTL you'll need a TTL to RS232 converter in addition to it... best to look at the implementation thread for verified working cables.

I personally think the DAM1021 is easy to do for a basic setup (transformer... digital inputs of choice... case work and pot). Maximising it and tweaking it more will require a lot more work (changing capacitors to polymer ones; arduino; choice of dc power supply; output stage and dual-mono once the firmware is updated.. etc.) - depending on the extent you're willing to do so for the results.

At the end of the day, remember to look through all the issues people have already encountered so you don't get any nasty surprises.