Hi
I'm thinking about using my exa board in a similar setup but read on the thread that multichannel with multiple dac boards is causing sync problems.
Have you tried to hook the exau2i to multiple dacs yet ?
If so, I'd be very interested to learn how you do that
Cheers!
If it average 384 Khz over enough time, like 1 mS, then the dam1021 should do just fine by itself....
Hi
I'm thinking about using my exa board in a similar setup but read on the thread that multichannel with multiple dac boards is causing sync problems.
Have you tried to hook the exau2i to multiple dacs yet ?
If so, I'd be very interested to learn how you do that
Cheers!
No, I haven't tried it yet as I am waiting for all the mods, fixes, etc., to solidify before I put it all together. Where did you read there are sync issues?
I was concerned initially that there would be synch issues and that there needs to be someway to master/slave the boards. I haven't heard of anyone trying this yet but am eagerly awaiting reports that it works as advertised. There has been no testing or verification from the vendor that I am aware of....just the suggestion that it should work...
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I don't think stacking them would be an issue....
What, you don't want to "experiment" with your boards? This is a diy product! Hahaha, I know EXACTLY how you feel....Why Soekris doesn't test this before telling us it "should" work is rather irresponsible considering he hasn't offered to repair them if things go bad...I don't think we should be used as guinea pigs.
What, you don't want to "experiment" with your boards? This is a diy product! Hahaha, I know EXACTLY how you feel....Why Soekris doesn't test this before telling us it "should" work is rather irresponsible considering he hasn't offered to repair them if things go bad...I don't think we should be used as guinea pigs.
I guess this is not the main use of a dac and perfectly understand how this test can be low on Soren's to-do list. Multichannel with multiple dacs ? This is nearly only available thanks to diy products so I can't blame anyone and don't feel as a guinea pig
If Soren can test it quick, perfect but I'll be fine if I had to wait a bit too.
I do agree that the expectations are high and that the "should work" is a bit frustrating though...
If Soren can test it quick, perfect but I'll be fine if I had to wait a bit too.
I do agree that the expectations are high and that the "should work" is a bit frustrating though...
Søren made the offer to help sort out any issues with cross-over several months ago... The proviso was that kuribo had to create the IIR filters he needed for the cross-over.
99% of the work involved with RoomEQ and cross overs is designing the filters and generating the IIR coefficients for the DAM1021. This is NOT something you can expect Søren to document for you.
The only part of the process that is specific to the DAM1021 is adding the IIR coefficients to the 1021filt.txt file and then processing that with the MKROM.exe to get a loadable .skr file.
The current v0.99 (20150816) firmware does have a bug which prevents more than one IIR filter loading. I've tested a working fix for this issue that Søren sent me, but in keeping with his policy of avoiding an avalanche of incremental updates I'd assume that fix will appear in the the v1.00 firmware.
TBH I think you have more work ahead of you than you realise and there is a lot you'll need to do to get up to speed prior to the bug fix being released if you are truly serious about this active system...
What I'd be looking at doing is:
- Hook up all 8 boards and EXAu21 and confirm that you can playback full range audio on each and every board.
- Sort out the logistics of powering, interconnecting I2S, and controlling all boards via serial port.
- Start looking at software for cross-over design. This needs to output either filter parameters (type, frequency, Q, gain) or bi-quads for 352.8KHz and 384KHz sample rates.
- If you are dealing with filter parameters, have a look at Mini-DSP advanced bi-quad Excel spreadsheet and spend some time learning how to convert filter parameters into usable bi-quads.
- Learn how to add the IIR filter parameters into the 1021filt.txt
- Learn how to use MKROM.exe to process the 1021filt.txt into 1021filt.skr.
By the time you've got that all under control, Søren should have v1.00 released and you'll be able focus on getting the IIR cross over filters working in the system, not scratching your head trying to debug the entire setup....
99% of the work involved with RoomEQ and cross overs is designing the filters and generating the IIR coefficients for the DAM1021. This is NOT something you can expect Søren to document for you.
The only part of the process that is specific to the DAM1021 is adding the IIR coefficients to the 1021filt.txt file and then processing that with the MKROM.exe to get a loadable .skr file.
The current v0.99 (20150816) firmware does have a bug which prevents more than one IIR filter loading. I've tested a working fix for this issue that Søren sent me, but in keeping with his policy of avoiding an avalanche of incremental updates I'd assume that fix will appear in the the v1.00 firmware.
TBH I think you have more work ahead of you than you realise and there is a lot you'll need to do to get up to speed prior to the bug fix being released if you are truly serious about this active system...
What I'd be looking at doing is:
- Hook up all 8 boards and EXAu21 and confirm that you can playback full range audio on each and every board.
- Sort out the logistics of powering, interconnecting I2S, and controlling all boards via serial port.
- Start looking at software for cross-over design. This needs to output either filter parameters (type, frequency, Q, gain) or bi-quads for 352.8KHz and 384KHz sample rates.
- If you are dealing with filter parameters, have a look at Mini-DSP advanced bi-quad Excel spreadsheet and spend some time learning how to convert filter parameters into usable bi-quads.
- Learn how to add the IIR filter parameters into the 1021filt.txt
- Learn how to use MKROM.exe to process the 1021filt.txt into 1021filt.skr.
By the time you've got that all under control, Søren should have v1.00 released and you'll be able focus on getting the IIR cross over filters working in the system, not scratching your head trying to debug the entire setup....
The only thing at issue is the IIR filter configuration. IIR filters are recursive which means a component of the filter uses feedback. If an IIR filter is misconfigured it can potentially cause a large amount energy to be dumped at maximum volume into the outputs.
As Søren has warned, if you get the IIR filters wrong it can take out speakers.
If you are going to try setting up an active system, or even just room correction, you need to seriously consider hooking up the DAM1021 to a soundcard and checking that the wave form and frequency response is what you expect.
Playing white noise into a software spectrum analyser will give you a very good idea of the frequency response. Looking at sine test signals at a spread of frequencies should reveal if there is any clipping or other anomalies.
I made a start on documenting the basic process of IIR creation. It's by no means comprehensive. I don't have the gear required to play around with active systems, but the principle is the same:
RoomEQ and Crossovers with the DAM1021 | moreDAMfilters
At the end of the day you need to design the filters you require and generate the IIR coefficients. That basic process is common to other products like the Mini-DSP boards, so there is a wealth of information and documentation available.
If you are really desperate to try this out before the v1.00 firmware comes out, send me a pm with your IIR filter coefficients formatted with the required headers that you've come up with and your email address, and I'll send you a copy of the firmware I tested as working to try out with your filters
As a teaser of the fixed firmware, this is the output of the DAM1021 with HPF, 5 x peaking EQ, and LPF.
An externally hosted image should be here but it was not working when we last tested it.
1st order 975Hz LPF
An externally hosted image should be here but it was not working when we last tested it.
4th order 975Hz LPF
An externally hosted image should be here but it was not working when we last tested it.
First, thanks for all your efforts to make this product more accessible, and for the kind offer to help...However, I don't intend to use the dam for crossovers and room correction. I plan to do that using dsp in the computer, then sending each of the channels out through usb to the exa21 which will then convert to i2s and feed each of the 4 dam's. The concern I have expressed is with the i2s signal from the exa21- without a master/slave set up between the dam's, I am concerned about sync issues between the dacs.... I have heard though in the past that simply sending 4 individual dacs a split signal can be problematic due to sync issues, therefore I have concerns about this issue with the dam...I haven't heard of anyone test this yet so maybe it isn't an issue..???
In that case I'm struggling to see what exactly the problem is... What you are proposing would have worked with the first release firmware and will work under v0.99 firmware.
ExaU21 has 8x I2S outputs. Start with one and get it working. Rinse and repeat for the other 7.
The master clock comes from the exau21 via I2S. The DAM1021 are for all intents and purposes identical, and should respond to variations in the clock in the same way.
Timing delay and sync issues are going to be minimal: Søren has suggested 1ms would be about it. A time delay between boards isn't going to damage anything - it might offend your ears but that's about it.
The only way you are going to get confirmation that your exaU21 + x8 DAM1021 works in the setup you propose is to build it up and test it. If there are no problems, great, and if there are issues I'm sure Søren and other members will help resolve them.
Thanks for your answer.
From bcm chip DS,it'll be close to 384KHz in 1024 bits data.
I had listened for sometime with 352.8/384k sample rate, it works normal.
But there's some diffs in listening, compare to amanero i2s output, I'll do more listening, or try doing some work to find out the cause of different.
We already discussed the sync issues. A clear answer from Søren:
One word clock period (for 48k multiples) = 1/3072000 = 0.33 μs, more than sufficient. No need for a master/slave setup.
It seems you're lazy enough not to do anything with four DAMs and the exaU2I. All you have to do is to wire them up and see how it works...
Double check the I2S connections. The 3.3V isolators on the DAM must be powered.
Here is my RPI2, connected to to the DAM, cross reference this to the wiring diagrams posted earlier.
The green signal lock light is steady in this picture.
It works with moode audio player!
Configure => System => I2S Audio Device => Generic than Reboot.
Attachments
I would like to understand why people are moaning about DSD support to be included. I can see a couple of reasons why it shouldn't.
1. The nature of the D/A conversion type used by the board. R-2R and PCM are obverse and reverse of the same coin. If you like DSD go for LPF with fancy output stages. I presume there are a few good examples available on this forum, let alone commercial ones.
2. In practice DSD support, I guess, would be reduced to implicit conversion to PCM at FPGA. The same could be achieved right now using software player. You could even do that once offline and forget about DSD at all [1].
3. Funny thing is that music industry embraces DXD when they have DSD release of new materials in mind. So a traditional audiophile mantra 'wanna the best" doesn't fit here.
4. Hi-rez bubble. As an exercise I let a couple of audiophile guys listen the same tracks in different format supported already by this board. Red book up to 192/24; binarual recordings. Results: their ability to discriminate low/hi-rez tracks was on par with performance of Jamaica bobsleigh teams during Olympics (btw. I really like them!).
5. Given above as well as limited hardware/labour resources it would be nice to see development elsewhere. Like further polishing filter stack or more ambitious audio over ethernet (broadcast/multicast/unicast).
[1] https://github.com/MaxKellermann/MPD/tree/master/src/pcm/dsd2pcm