Soekris webshop is not good ?
DAC module - dam1021 Soekris Europe - You Soekris Provider
Regards,
Tibi
Hello andrea_mori,
Your calculations are right but the effect can only be seen if R resistor is fully on one side of the tolerance while 2R resistor is fully on the other side. Got to be really unlucky.
Note that, if you are lucky : both R and 2R resistors at the limit of the allowance but same side, resulting distorsion on output voltage is null.
Real life is good for us, and we can suppose that a few consecutive resistors issued from the same batch are within a range much smaller than the official allowance. That's where it leaves pure conception toward recipe. I'm sure Soren took care about these constraints in order to give us a excellent 16 bit converter. Would have been a good thing to use two R resistors on the 2R place, in order to cancel the variations.
For those listening to 24 bits stuff, downsize to 16, or be ready to trade little comfort on forte for a big detailed stage.
Tiny
There seems to be a number of people who don't get the principle of a sign magnitude DAC and apperently are not reading the whole thread, which is understandable as it's getting long.... So let repeat:
From post #34:
As I stated, first measurement was even better than expected, didn't really know upfront what the result would be, but remember that THD is RMS measurements.
A regular DAC feed by the two’s complement code has the problem that zero crossing goes from all zero'es to all ones's, meaning the distortion goes up at lower levels. The sign magnitude DAC architecture basically is two DAC's, one for the positive signal and one for the negative signal, resulting in constant distortion at all levels. T.ex. with a -60 db signal, the 10 most significant bits stays at GND for both the negative and positive DAC sections, not the constant switching of all bits....
It's not something I invented, Burr Brown did it with their Colinear chips, starting with the PCM63.... And my DAC is actually physically two R-2R strings, one with +4V ref and one with -4V reference (of course very low noise and with very precise tracking), connected together at the output which can be done as a R-2R network has constant output impedance.
I also use LVC595 chips as drivers, those have about 13R output impedance at 4V, both positive and negative output fets (I measured some sample parts). I have R as 4K99, 2R is then 10K0 with 3.01M parallel to adjust for driver impedance.
From post #313:
With a regular R-2R DAC you have the MSB switching at zero crossing, even with t.ex. a -60db signal. That mean that the THD is absolute so if you have -90 db THD at 0 db signal then you have -30 db THD relative to a -60 db signal.
That's why a regular R-2R DAC need to be very precise.
With a Sign Magnitude DAC it's like a sliding window as the MSB are NOT switching with lower level signals, so if you have -90 db THD at 0 db you will still have -90 db relative at to -60 db signal....
That's why my prototype get 0.006% THD at 0 db, even with just the 0.05% resistors on the prototype, and still get 0.027% at -60 db, which are probably from the measuring ADC anyway....
From post #34:
As I stated, first measurement was even better than expected, didn't really know upfront what the result would be, but remember that THD is RMS measurements.
A regular DAC feed by the two’s complement code has the problem that zero crossing goes from all zero'es to all ones's, meaning the distortion goes up at lower levels. The sign magnitude DAC architecture basically is two DAC's, one for the positive signal and one for the negative signal, resulting in constant distortion at all levels. T.ex. with a -60 db signal, the 10 most significant bits stays at GND for both the negative and positive DAC sections, not the constant switching of all bits....
It's not something I invented, Burr Brown did it with their Colinear chips, starting with the PCM63.... And my DAC is actually physically two R-2R strings, one with +4V ref and one with -4V reference (of course very low noise and with very precise tracking), connected together at the output which can be done as a R-2R network has constant output impedance.
I also use LVC595 chips as drivers, those have about 13R output impedance at 4V, both positive and negative output fets (I measured some sample parts). I have R as 4K99, 2R is then 10K0 with 3.01M parallel to adjust for driver impedance.
From post #313:
With a regular R-2R DAC you have the MSB switching at zero crossing, even with t.ex. a -60db signal. That mean that the THD is absolute so if you have -90 db THD at 0 db signal then you have -30 db THD relative to a -60 db signal.
That's why a regular R-2R DAC need to be very precise.
With a Sign Magnitude DAC it's like a sliding window as the MSB are NOT switching with lower level signals, so if you have -90 db THD at 0 db you will still have -90 db relative at to -60 db signal....
That's why my prototype get 0.006% THD at 0 db, even with just the 0.05% resistors on the prototype, and still get 0.027% at -60 db, which are probably from the measuring ADC anyway....
Well, it would be nice to see a bunch of measurement ... also various IM related tests, while you have two combined ladders
Just my 2 cents
Hp
This has nothing to do with my delay circuit. I use a Fuhrman Reference 20 power conditioner for my system and the DAC/USB audio board are connected in addition with a PS Audio Power Plant. If I lose power it takes 2-3 sec before the voltage in the dam breaks down, enough time so that the power amp cannot transmit the pop . That's just a nice side effect but good to know that my speakers are safe under all conditions until there is a better solution.
I attached some pics I took while I was still building the DAC. My goal was to keep connections as short as possible in a setup that uses 2 DACs (one for the main speakers, one for the sub) and a DSP. I am very satisfied with the results.
Attachments
So Delta-sigma ESS9018 is winning the race again. I know one might think about implementation but I increasingly see r2r beaten by Delta-sigma in their respective best implementations. If one take out MSB/TotalDAC then it is Delta-sigma that is currently ruling the high-end; even where money is no object. Even dCS is kind of Delta-sigma.
I think there is something wrong with my love of NOS TDA1541A,
I have built many diy dacs over the years, r2r and delta sigma. My AYA2014 with all of Ians gear , running in simdata mode is the best I've heard, but jeez the dam is pretty close, as is the delta sigma EXA/ 9018 Ackodac. I dont think either R2R or D-S rules the roost, but as you say, implementation is all important.
Member
Joined 2006
It would be much more helpful if comments like these would outline the exact
configuration (HW and SW and transport/IF) - or call it "implementation" of the module.
Otherise I consider these kind of comments or better "comparisons" pretty useless.
@TNT:
I guess you still wait for an answer about "All but optimal".
This discussion I consider off-topic.
However:
One example for an IMO all but optimal implementation:
You use SLAs as your main suplies.
Many of us were running DACs on batteries. Me too.
Small SLAs were worse then everything else. Beside the known
noise issues, these usually come with a pretty high ESR.
The sound got boring and muddy. Even e.g. 55Ah Optimas were
bad compared to e.g. Northstars (2mR ESR) - I still own a pair if 100Ah monsters.
Not to forget. The older the SLAs, the worse they perform.
Then several years back LiFePo4 hit the scene. These have been
a game changer in comaprision to good old SLAs.
Meanwhile you'll find even better alternatives (e.g. Ultracaps). You might have have a look at a commercial implementation: "Vinnie Rossi - Lio"
Cheers
Member
Joined 2006
This article on DIY dacs in Supra's blog answered a number of my questions...
Supratek News: DIY near SOTA Dacs.
Supratek News: DIY near SOTA Dacs.
Member
Joined 2006
No offense, but a lot of this stuff is more "fashion" than actually sota implementation. Batteries have just as many disadvantages as advantages, and have nowhere near the improvement in sound quality as something like Ian's FIFO and other hi tech digital gear.
I brought up the battery story to show that the SLA batteries used during TNTs "shootout" are all but optimal. This was just one out of many issues
I had with his little project. You basically missed the point.
And then you again talk about "batteries" in general. You missed the point again.
Your "shootout" had nothing to do with TNTs project. Your shootout has just been as irrelevant to me as TNTs, because of conclusions " this is better then that" without specifing any details how the DAM board was implemented.
Just specifiy in detail what you're comparing and that'll be it.
Yup...
Implementation is going to account foir at least 50% of the performance of any DAC, even one like the DAM where at first glance it appears to be a finished project.
On the ESS 9018, these can sound pretty ordinary, or absolutely fantastic. My Buffalo IIIse sounds great, but it took a lot to get it to where I feel it sounds natural and resolved: I use an isolated USB interface with an onboard OSF running a very good digital filter, with the the first 8x OSF stage on the 9018 turned off, I also run synchronous mode, so that the ESS DPLL and ASRC are inactive as well. Then there is the particular nature of the ESS to it's I/V stage, it is very challenginig to design a good discrete I/V which suits the needs of the chip... Then there are Salas Shunt regs all around.
Until we see people getting a lot of experience with the DAM we are not going to know what it is really capable of. Personally I want to see a two board balanced implementation, with a fully isolated USB interface, separate shunt regulated power supplies, a really good FET or Tube output buffer, and someone running it at 352.8/384 with the OSF running in software on the computer with carefully designed, powerful, digital filters. The Spartan 6 may not have enough processing capability to do all the housekeeping and run really sophisticated digital filters (or DSD-PCM), so it may be better to run the first 8x OSF in software so as to not limit filter length too much.
Implementation is going to account foir at least 50% of the performance of any DAC, even one like the DAM where at first glance it appears to be a finished project.
On the ESS 9018, these can sound pretty ordinary, or absolutely fantastic. My Buffalo IIIse sounds great, but it took a lot to get it to where I feel it sounds natural and resolved: I use an isolated USB interface with an onboard OSF running a very good digital filter, with the the first 8x OSF stage on the 9018 turned off, I also run synchronous mode, so that the ESS DPLL and ASRC are inactive as well. Then there is the particular nature of the ESS to it's I/V stage, it is very challenginig to design a good discrete I/V which suits the needs of the chip... Then there are Salas Shunt regs all around.
Until we see people getting a lot of experience with the DAM we are not going to know what it is really capable of. Personally I want to see a two board balanced implementation, with a fully isolated USB interface, separate shunt regulated power supplies, a really good FET or Tube output buffer, and someone running it at 352.8/384 with the OSF running in software on the computer with carefully designed, powerful, digital filters. The Spartan 6 may not have enough processing capability to do all the housekeeping and run really sophisticated digital filters (or DSD-PCM), so it may be better to run the first 8x OSF in software so as to not limit filter length too much.
Let's try another way...
Comments like this are useless to me.
We have someone who thinks he is an expert but doesn't know about the architecture of this DAC that he has been researching. Researching but missing a lot of posts already covered only to circle back at it a few months later.
We have someone who thinks everyone who has already bought the DAM owes it to him to report it in a way that only suits him.
So who died and made you king?
I like reading about people's experiences. Just cause you don't doesn't mean they should stop.
So according to you, TNT has a sub optimal setup and the comparison seems to already show the potential of the DAC (again) is useless to you. To me it means this DAC is not for you. Go out of the room and don't let the door hit you. Seriously.... again... who died and made you king?
You're talking motherhood statements... everyone knows the implementation makes a difference. In the DDDAC thread... would you expect a non-regulated supply to do better than a regulated shunt supply? Just cause you think it won't be good doesn't mean it's true. Sorry... again who died and made you the king and expert? Instead of checking the sound... maybe check your ****ing attitude?
If you think you're great. Buy the board... create the best implementation and share it (we'd all be grateful). Otherwise... just shut up and pick up what you can and make your slow decision process. I've learnt much more about the DAM from TNT, Nige and others than you (who has much more posts than them with all the whinging and whining).
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