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dam1941 - Next Gen Discrete R-2R Sign Magnitude 24 bit 384 Khz DAC module
dam1941 - Next Gen Discrete R-2R Sign Magnitude 24 bit 384 Khz DAC module
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Old 13th September 2018, 11:33 PM   #1
soekris is offline soekris  Denmark
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Join Date: Jun 2009
Location: Korsør, Denmark
dam1941 - Next Gen Discrete R-2R Sign Magnitude 24 bit 384 Khz DAC module
Default dam1941 - Next Gen Discrete R-2R Sign Magnitude 24 bit 384 Khz DAC module

Building on four years of experience with the dam1021, it's now time for the next generation OEM/DIY Discrete R-2R Sign Magnitude DAC module, the Soekris dam1941. Based on the well tested Soekris R-2R DAC core, it now include all the needed digital interface: USB, SPDIF RCA, BNC and XLR and Toslink, all fully galvanic isolated, plus an extra I2S port, suited for connection to example a streamer board like a Rasberry Pi.

It support up to 24 bit / 384 Khz PCM and DSD 256 input, with FPGA based reclocking and custom digital filters, < 0.3 ps jitter clock generator, with 27 bit resolution. Firmware can be upgraded though a standard serial interface.

The two things there are many diverting opinions about, the Power Supply and the Output Buffer, are now external to the main DAC board so it can be customized and optimized.

The board also have connections for an optional advanced user interface, with LED indicators for interface and speed, with support for an encoder to control the volume, with option for a two digit seven segment LED display, much like our end user products, no programming needed. There is even a receiver for a remote control.

There will be two basic models, the dam1941 will have four full Sign Magnitude R-2R networks for fully balanced outputs, the cost reduced dam1921 is the same board but will have only two full Sign Magnitude R-2R networks mounted for single ended outputs. The basis R-2R network has an output voltage of 1.3V RMS and output impedance of 625 ohm and can therefore drive a lot of things directly....

We have designed a couple of low cost bare PCBs to support the dam1941/dam1921, we now have a flexible Power Supply PCB, a flexible Output Buffer PCB and a full User Interface PCB, those are available as a set only.

Please visit Soekris Engineering ApS, Products dam1941 for details, specifications and pricing.

**** Now Shipping from Stock ****

This thread is to be used for dam1941/dam1921 technical discussions, lets try to keep product specific questions in the right threads
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Last edited by soekris; 12th November 2018 at 12:26 PM.
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Old 14th September 2018, 09:15 PM   #2
gavinb is offline gavinb  South Africa
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Join Date: May 2009
@Soren

Have some initial questions, eagerly awaiting manual.

What is the pitch of the power supply connector? (J7 ?)
J7 is the same pitch as J14?

Part number for connector ends?

The initial Soekris.dk page show power requirements are +5V 0.6A and -5V 0.1A

Is only +5/-5V power rails required? No +12/-12V ?

If one does not have the LED/Control board can one set the startup volume via serial? Permanently?

Assume it will also be -40 like the 1541?
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Old 15th September 2018, 12:43 AM   #3
soekris is offline soekris  Denmark
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Join Date: Jun 2009
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dam1941 - Next Gen Discrete R-2R Sign Magnitude 24 bit 384 Khz DAC module
Quote:
Originally Posted by gavinb View Post
@Soren

Have some initial questions, eagerly awaiting manual.

What is the pitch of the power supply connector? (J7 ?)
J7 is the same pitch as J14?
MTA156 type, 0.156" for power, with +5V Digital and +-5V analog.

J14 is the same but really for if you want to solder output connectors to the PCB with wires, the outputs are also available on other connectors.

Quote:
Part number for connector ends?
Will be in manual.

Quote:
The initial Soekris.dk page show power requirements are +5V 0.6A and -5V 0.1A

Is only +5/-5V power rails required? No +12/-12V ?
The dam1921/dam1941 itself only need +-5V. The Power Supply PCB will also have support for higher voltages for buffer boards.

Quote:
If one does not have the LED/Control board can one set the startup volume via serial? Permanently?

Assume it will also be -40 like the 1541?
Everything will be configurable by the serial port, just like the other dams. The dam1921/dam1941 firmware will have support to be used as basic dac without leds/controls to full led/controls just like the dac1541.
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Old 18th September 2018, 07:51 AM   #4
dziki is offline dziki
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Join Date: Jul 2014
Hi,
Some questions here:

- will it be possible to use the 1941 as 2 single ended stereo DACs (or 4 channels DAC) ?

- how is the sound quality without output buffers ?

- how/where are the output connectors ?

Thank you in advance and have a nice day.
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Old 19th September 2018, 12:34 AM   #5
soekris is offline soekris  Denmark
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Join Date: Jun 2009
Location: Korsør, Denmark
dam1941 - Next Gen Discrete R-2R Sign Magnitude 24 bit 384 Khz DAC module
Quote:
Originally Posted by dziki View Post
Hi,
Some questions here:

- will it be possible to use the 1941 as 2 single ended stereo DACs (or 4 channels DAC) ?
No.

Quote:
- how is the sound quality without output buffers ?
Great, like all the Soekris DACs - what else did you expect me to say :-) Be aware of output impedance and level.

Quote:
- how/where are the output connectors ?
On the optional output buffer board.... If not using an output buffer board there are holes on the dam1941 to attach wires....

Quote:
Thank you in advance and have a nice day.
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Old 19th September 2018, 10:36 AM   #6
gdellema is offline gdellema
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Join Date: Mar 2013
Default 1941 features

Hi Soren,

I am a very happy customer of a 1541 - and now looking for a DAC board for a DIY project. As you put it: Nobody seems to agree on power supplies and buffers - I am no exception ...

Two questions on the 1941:

1) Is it possible to get ms coding from the 1941 (have the sum signal L+R on one channel and the difference signal L-R on the other one) instead of LR coding?
2) Will the cross-feed option of the 1541 be available on the 1941?

Thanks a lot!
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Old 19th September 2018, 11:17 AM   #7
soekris is offline soekris  Denmark
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Join Date: Jun 2009
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dam1941 - Next Gen Discrete R-2R Sign Magnitude 24 bit 384 Khz DAC module
Quote:
Originally Posted by gdellema View Post
Hi Soren,

I am a very happy customer of a 1541 - and now looking for a DAC board for a DIY project. As you put it: Nobody seems to agree on power supplies and buffers - I am no exception ...

Two questions on the 1941:

1) Is it possible to get ms coding from the 1941 (have the sum signal L+R on one channel and the difference signal L-R on the other one) instead of LR coding?
What's ms coding ? and whats for ?

Quote:
2) Will the cross-feed option of the 1541 be available on the 1941?
Yes.

Quote:
Thanks a lot!
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Old 19th September 2018, 12:15 PM   #8
intense-tavda is offline intense-tavda  Netherlands
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Join Date: Jun 2005
Location: drachten
Hi Soren!
I am an happy owner of the dac 1321, it is sounding great. Wil the 1941 or 1921 better the sound of the 1321? Otherwise I wil change to the diy board. Is the 1021 still a good board the work with soundwise? Or is the 1921/1941 better?
As diyer the work on the 1021 looks more as a challenge, but betters it the 1941/1921? Can you tell me?
Thanks allready!
Teake
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Old 19th September 2018, 12:59 PM   #9
gdellema is offline gdellema
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Join Date: Mar 2013
Hi Soren,

ms coding (or ms encoding) stands for "mid-side-encoding"; it is frequently used in mixing.

Normally, a DAC sends the L signal down one channel and the R signal down a second channel. If you do ms encoding instead, one channel converts the mid or mono signal M=L+R and the other channel converts the side signal S=L-R. On the analog side, the two signals are mixed back together: 2L=M+S and 2R=M-S.

Two advantages:

One, you can easily change the stereo width on the analog side by amplifying the S signal differently from the M signal before mixing.

Two, more subtly, the structure of the error signal from the DAC changes. In LR encoding, both the L and the R signal will acquire a noise signal from the DAC, and these two signals are independent of one another. Therefore, the ear is presented with two additional, independent signal sources, one on the left channel and one on the right channel. With MS encoding, usually the M signal is much stronger than the S signal since most of the music is located close to the center of the stereo panorama. If we assume (extreme case) that all signal is M, then in LR encoding, left and right channel still get different error signals from the DAC. In MS encoding, left and right channel get the same error signal from the DAC. The ear is presented with one additional signal source which is located at the center spot.

Supposedly, this sounds a lot better. There is quite a bit of talk on this on a German forum, where people program their streamers to send M and S signals into the DAC instead of L and R signals, and then mix things again on the analog side. For the analog part of this, there even is a commercial product available called Audiovero Cleaner.

I think implementing such an option into an FPGA should be simple (just add one addition and one substraction), and compared to implementing it in the streamer it has the added benefit to apply to all digital sources connected to the DAC.

So, again - do you think MS encoding is possible with the 1941? I am optimistic since the 1541 already switches L and R on the DAC channels as you switch from the XLR output to the Phones output channel ...
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Old 19th September 2018, 01:28 PM   #10
soekris is offline soekris  Denmark
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Join Date: Jun 2009
Location: Korsør, Denmark
dam1941 - Next Gen Discrete R-2R Sign Magnitude 24 bit 384 Khz DAC module
Quote:
Originally Posted by gdellema View Post
Hi Soren,

ms coding (or ms encoding) stands for "mid-side-encoding"; it is frequently used in mixing.

Normally, a DAC sends the L signal down one channel and the R signal down a second channel. If you do ms encoding instead, one channel converts the mid or mono signal M=L+R and the other channel converts the side signal S=L-R. On the analog side, the two signals are mixed back together: 2L=M+S and 2R=M-S.

Two advantages:

One, you can easily change the stereo width on the analog side by amplifying the S signal differently from the M signal before mixing.

Two, more subtly, the structure of the error signal from the DAC changes. In LR encoding, both the L and the R signal will acquire a noise signal from the DAC, and these two signals are independent of one another. Therefore, the ear is presented with two additional, independent signal sources, one on the left channel and one on the right channel. With MS encoding, usually the M signal is much stronger than the S signal since most of the music is located close to the center of the stereo panorama. If we assume (extreme case) that all signal is M, then in LR encoding, left and right channel still get different error signals from the DAC. In MS encoding, left and right channel get the same error signal from the DAC. The ear is presented with one additional signal source which is located at the center spot.

Supposedly, this sounds a lot better. There is quite a bit of talk on this on a German forum, where people program their streamers to send M and S signals into the DAC instead of L and R signals, and then mix things again on the analog side. For the analog part of this, there even is a commercial product available called Audiovero Cleaner.

I think implementing such an option into an FPGA should be simple (just add one addition and one substraction), and compared to implementing it in the streamer it has the added benefit to apply to all digital sources connected to the DAC.

So, again - do you think MS encoding is possible with the 1941? I am optimistic since the 1541 already switches L and R on the DAC channels as you switch from the XLR output to the Phones output channel ...

Seems ok doing it in the mixing process, but I'm sorry, just can't see any advantage in a DAC.... If the L+R and L-R calculations are done digitally, assuming at high resolution, why would it matter where it's done ? Why would anybody send L+R and L-R to the DAC, you might as well do the calculation back to regular stereo just before sending the digital audio to the DAC ?

Not that it could not be done, addition and subtraction are simple and easy in a FPGA, but I don't want to add unnecessary functions, just more stuff to maintain and test.
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