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

Regarding (3), 200mA will be more than enough to power 2 isolated sides of DAMs. Their power consumption is low two digit mAs.

Thank you! I'm now actually looking forward to doubling up the dam, revised my build to include a 35W 2*12V trafos instead and Sigma22 should hold up just fine with two boards. Basically I'll just be able to slap it on and it'll be fully balanced. It's another story whether or not an additional $350+ is justified :)

In any case, I'll have two openings for RS232 connections, would that be necessary for a dual-mono build to get access to both boards?

Also any general comments on whether a balanced build is worthwhile would be very much appreciated. I plan to be using mostly HD650 with it for now, so through a balanced 4pin XLR on front panel if balanced or 6.3mm SE. :) I know it's likely overpowered for 650...
 
Looking at how MSB technology for example is stacking their R2R ladders it probably is. I am myself thinking about going further and stackin 2 DAM1121 boards per side... but i have to finish my current projects first:)

The performance gain from stacking more than 2 ladders per channel should be strictly from the brute SNR improvement right? Not sure if that's my thing but I am honestly very tempted to go dual-mono because of the ingenuity of the architecture, aside from knowing that it'll be state-of-the-art and sound nice... Just thinking about the theoretical gains from noise reduction makes me excited... sometimes it makes me wonder why I went into CS but I guess everyone could use a little electronics :D

So I guess if my budget allows it and my current design turns out well I'll go dual-mono...
 
Dual mono would only benefit balanced mode
I expect it will sound better but diminishing returns like often happens in audio
Others made dual mono dacs and liked them

Thanks for the reply! I intend to modify my HD650 cables and use them in balanced mode. Based on my google searches I think it'll be objectively better but some may end up preferring the SE mode. Should be an interesting and useful reference to have.

I guess it'll depend on my budget. But there is just something exciting making a quality build with top performing fully-balanced r2r dac design, all in a 228*215*70 enclosure, if things work out as well in practice as they do on paper :)

It will add 30-40% to the financial cost, but again there's something elegant and exciting in being able to just stack the boards and get balanced processing. :)

I'll post updates here when I start putting the pieces together next week. I have everything planned to the millimeter and all components and wiring are already planned/purchased. Not very experienced as a DIYer but I'm hopeful!
 
Hi,

one question for Søren, would it be possible to have the NOS or “nearly” NOS filter as a customised option for the dac1321, dac1421 and dac1541 by replacing one of the standard filters before shipping the DAC? I am not a great believer in NOS, it is just that I prefer doing the Up/Oversampling with sox on the computer before going into the DAC and would prefer the DAC to not add any Up/Oversampling to this.

Regards

Granite
 
Hi,

one question for Søren, would it be possible to have the NOS or “nearly” NOS filter as a customised option for the dac1321, dac1421 and dac1541 by replacing one of the standard filters before shipping the DAC? I am not a great believer in NOS, it is just that I prefer doing the Up/Oversampling with sox on the computer before going into the DAC and would prefer the DAC to not add any Up/Oversampling to this.

Regards

Granite

One thing a lot of people apparently don't know, is that a NOS DAC output a lot of high frequency noise, basically the audio signal mirrored around half the sample rate frequency, and although you can't hear it, it that can easily destroy a speakers high frequency driver....

And the whole point of using NOS is to reduce the influence of filters close to the high frequency cutoff, which mean that NOS really only have real effect at 44K/48K sample rates. So software upsampling to a NOS DAC is moot....

So no, I will not ship a DAC with a real NOS mode, although I'm considering making my "soft" filter a little more soft....
 
Hi Søren,

I am well aware of the fact that NOS introduces signals mirrored at the sampling frequency. My point is that if I already do digital filtering, why have the Dac apply digital filtering, too. Every Dac should have an analogue filter which can take care of the high frequency artefacts (and avoid DC in the output). It is highly likely that if you do NOS you need a different analogue filter. Somewhere I read that Soekris Dac implement an analogue filter starting at 200 kHz with first order characteristic. If this is correct NOS is probably no good idea as it requires an analogue filter which starts at a lower frequency (depending on the sampling frequency). Before going too much off topic I just want to clarify that I am not interested in NOS, I am only interested in the possibility to avoid Up/Oversampling inside the Dac because I already do this upfront.

Regards

Granite
 
Hi Søren,

I am well aware of the fact that NOS introduces signals mirrored at the sampling frequency. My point is that if I already do digital filtering, why have the Dac apply digital filtering, too. Every Dac should have an analogue filter which can take care of the high frequency artefacts (and avoid DC in the output). It is highly likely that if you do NOS you need a different analogue filter. Somewhere I read that Soekris Dac implement an analogue filter starting at 200 kHz with first order characteristic. If this is correct NOS is probably no good idea as it requires an analogue filter which starts at a lower frequency (depending on the sampling frequency). Before going too much off topic I just want to clarify that I am not interested in NOS, I am only interested in the possibility to avoid Up/Oversampling inside the Dac because I already do this upfront.

Regards

Granite

The Soekris dam/dac do digital filtering to avoid sharp analog filters.... If you upsample in software then the dam1021 filters are way out of the audio range and become softer with the higher sample rates, so they will not affect the audio.... I upsample everything, first to 352K/384K in FIR1 then to 2.8M/3.1M in FIR2, so I can do with a simple 1st order lowpass filter to remove the last residues from aliasing.... And I consider digital filters better than analog filters.

So I see no reason at all the offer NOS filters for your application, but you're welcome to load your own filters. Or if you output at 352/384K then the dam/dac FIR1 are bypasssed and FIR2 are very soft, just look in the filt1021.txt file for details....
 
Did some more searching, and realized:
(1) Soren mentioned that there's a digital PLL preventing clock drift over time. With this in mind, the micro seconds delay will be inconsequential - more so than moving one side of the headphone or one speaker closer 1mm (3 micro seconds).
(2) Seems like a connection diagram has already been provided, ignore one TX from 1021 and add 1k resistors to RXs.
(3) Still unresolved...

I also noticed that there is a wiki page here for Soekris R2R DAC, but speaking from experience I'm pretty sure it won't useful for noobs like myself. I'm still focused on the build but will try to add to it in the next few weeks. Probably implementation focused but also a more solid starting point for people who have no idea what to put together. Please let me know if you think such an effort would be redundant...

Thanks, everyone!!

I have very much the same configuration you are asking about, the SK-Lite integrates well with dual-mono. I've also used the same linear 3.3v source from the sk-lite for the dam1021 isolation along with the 5V for the USB to I2S.
 
I have very much the same configuration you are asking about, the SK-Lite integrates well with dual-mono. I've also used the same linear 3.3v source from the sk-lite for the dam1021 isolation along with the 5V for the USB to I2S.

That's very reassuring! I also made up my mind in going dual-mono and am finishing up on checking out all the parts, mostly wiring now. I'm not using 5v for USB module because for one thing it's hard to modify the board for external power, at least for Singxer C1, although I'm now set on a Chinese Amanero which could be easier.. also, the power quality should only affect the jitter provided to dam1021, which will not matter since FIFO reclocking is provided. A clean 3.3V to isolation chips seems reasonable.

Some questions! How do you split the signal to the two boards? I read about people using long connectors, should I try to get those for J1 and J3? Thanks!!
 
That's very reassuring! I also made up my mind in going dual-mono and am finishing up on checking out all the parts, mostly wiring now. I'm not using 5v for USB module because for one thing it's hard to modify the board for external power, at least for Singxer C1, although I'm now set on a Chinese Amanero which could be easier.. also, the power quality should only affect the jitter provided to dam1021, which will not matter since FIFO reclocking is provided. A clean 3.3V to isolation chips seems reasonable.

Some questions! How do you split the signal to the two boards? I read about people using long connectors, should I try to get those for J1 and J3? Thanks!!

Why not go for DIYINHK XMOS 384kHz USB chipset, needs only 3.3V
XMOS 384kHz DXD DSD256 high-quality USB to I2S/DSD/SPDIF PCB - DIYINHK

Splitting the i2s lines is a bit of a hassle, try to keep wires short. Mine goes to a little bread board then a wire to each DAM1021. Stacking then perhaps can allow same signal wire to go through each pcb hole when wire is exposed for soldering. (solid core wire may work better here)
 
Why not go for DIYINHK XMOS 384kHz USB chipset, needs only 3.3V
XMOS 384kHz DXD DSD256 high-quality USB to I2S/DSD/SPDIF PCB - DIYINHK

Splitting the i2s lines is a bit of a hassle, try to keep wires short. Mine goes to a little bread board then a wire to each DAM1021. Stacking then perhaps can allow same signal wire to go through each pcb hole when wire is exposed for soldering. (solid core wire may work better here)

Well the short answer is I can get the Amerno knockoff for $20 and it looks legit...

That makes sense, is it possible though to use a long connector mounted on opposite sides, connect to one on the back side, and just insert the two boards together?
 
Well the short answer is I can get the Amerno knockoff for $20 and it looks legit...

That makes sense, is it possible though to use a long connector mounted on opposite sides, connect to one on the back side, and just insert the two boards together?

Careful with connecting all pins, some may be unique to each board and need to be unconnected/removed. Like the serial/FPGA/MCLK outputs.

Isolated serial will be voltage divided by a 1K if with Audiozen SK Lite.
 
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Well the short answer is I can get the Amerno knockoff for $20 and it looks legit...

You should keep in mind that the Amanero clones have at least one major issue: You can't flash new firmware on them. You buy them with some pirated firmware and that's it.

Plus you can be sure that the oscillators that come with them will be the cheapest ones you could possibly find.
 
That's very reassuring! I also made up my mind in going dual-mono and am finishing up on checking out all the parts, mostly wiring now. I'm not using 5v for USB module because for one thing it's hard to modify the board for external power, at least for Singxer C1, although I'm now set on a Chinese Amanero which could be easier.. also, the power quality should only affect the jitter provided to dam1021, which will not matter since FIFO reclocking is provided. A clean 3.3V to isolation chips seems reasonable.

Some questions! How do you split the signal to the two boards? I read about people using long connectors, should I try to get those for J1 and J3? Thanks!!

I've stacked my boards using long pin headers. The only signals you stack through are I2S, all SPDIF, ISO GND's, ISO 3.3V, GND's, the serial lines you need to branch off on their own, as you'll need to individually address these when uploading new filters to each board, as well as use a 1K resistor on each to go into the SK-lite, etc.

The Singxer C1 has worked very well powered by the 5V from the sk-lite. I suppose I could power it via the 3.3V but that also goes to the isolators and the 5V was free so why not, just keeps things separated a bit.
 
I've stacked my boards using long pin headers. The only signals you stack through are I2S, all SPDIF, ISO GND's, ISO 3.3V, GND's, the serial lines you need to branch off on their own, as you'll need to individually address these when uploading new filters to each board, as well as use a 1K resistor on each to go into the SK-lite, etc.

The Singxer C1 has worked very well powered by the 5V from the sk-lite. I suppose I could power it via the 3.3V but that also goes to the isolators and the 5V was free so why not, just keeps things separated a bit.

Thanks, I have two RS232 on back panel for filter uploads and firmware updates, and I'll be careful with the I2S serial.

I was initially set on C1 and use the 5v to power it through a "dummy" male USB-B connector. But then I realized that the jitter improvements probably won't be very significant, plus I can really use more space in the enclosure and less complexity, so we'll see how it goes. :)
 
You should keep in mind that the Amanero clones have at least one major issue: You can't flash new firmware on them. You buy them with some pirated firmware and that's it.

Plus you can be sure that the oscillators that come with them will be the cheapest ones you could possibly find.

I'm buying it from a reputable vendor on Taobao, and I think you should give more credits to these Taobao replicas - some use very high precision oscillators. Not sure about firmware though... The main thing is that I believe there will be no difference in SQ as long as the isolation chip is powered right, let me know if that assumption is dubious and I'll go straight back to C1 with separate 5v supply...