Soekris' DAC implementations

[batteryman]

What i'm trying to say is that people shouldnt be so fast to dismiss transformers without even trying then.

Totally agree.
Some of the most esoteric commercial dacs use them, probably for common mode cancellation as well as galvanic isolation. (and justify the price!)

 

[quantran]

Of course transformers have their inherent benefits but you should read in the context of the raw output of this DAC.

Is it right to suggest expensive Lundahl transformers that cost almost the same as the DAC while the source impedence is high and the drive capacity is limited?

The DAC is not even a balanced output one so noise cancelling is not applicable.

 

[Curious Fitz]

I think it's best to add a buffer, solid state or tube depending on your preference.

What benefit would a buffer (solid state or tube) give over direct output from the raw output to pre/power amp please?

 

[quantran]

What benefit would a buffer (solid state or tube) give over direct output from the raw output to pre/power amp please?

The buffer provides an easy load for the raw DAC output while it also has better capacity to drive the load of the preamp and interconnect cable.

You can see that Soren already included a buffer using opamp but the point is that we are trying to improve the stock DAC so we may want to use a better buffer.

The transparency of the buffer is very important.

 

[RollE2k]

Of course transformers have their inherent benefits but you should read in the context of the raw output of this DAC.

Is it right to suggest expensive Lundahl transformers that cost almost the same as the DAC while the source impedence is high and the drive capacity is limited?

The DAC is not even a balanced output one so noise cancelling is not applicable.

Like i said earlier... if balanced is the main thing you are looking for, then at least i would look at buying a second board to run true balanced output..

Also there are cheaper non-amorphous core lundahl transformers which have about same bandwidth as ll1690 for cheaper... also most lundahl small signal transformers have specified bandwidth with 600R source, so quite true to the native output impedance of this dac. Then of course it also depends on what you load the secondary with.

If it's really worth the price isn't depending on the cost of tranformer compared to the DAC, but rather compared to the performance of the dac...
Since some people don't seem to like this (and other) R-2R dac, while other people like it (default) more than multi-dollar ES9018-setups. I don't think you can draw such easy conclusion.

But I should add that i would not put this kind of money myself into this dac for this purpuse. If it was integrated into a line stage, so the transformer could work double as input phase splitter, then it's another thing.

 

[Julf]

Like i said earlier... if balanced is the main thing you are looking for, then at least i would look at buying a second board to run true balanced output..

Like I said earlier - if balanced is the thing you are looking for, what matters is the differential/balanced connection and amplifier input stage, not the DAC output. An unbalanced output can drive a balanced connection just fine.

 

[RollE2k]

Like I said earlier - if balanced is the thing you are looking for, what matters is the differential/balanced connection and amplifier input stage, not the DAC output. An unbalanced output can drive a balanced connection just fine.

Try feeding a Pass Labs XA30.5 with singel ended signal, then swap for balanced - and i promise you will hear an advantage of the balanced.. I have done that.. and both times it was same pre-amp with output transformer, wired differential and singel ended.
And you'll loose the Common mode cancellation of the balanced input stage if you don't feed it with a balanced/differential signal.

But I see this as offtopic since why i even posten at first was to clarify that a transformer have more use than frequency limiter as was said at first.

 

[Julf]

Try feeding a Pass Labs XA30.5 with singel ended signal, then swap for balanced - and i promise you will hear an advantage of the balanced..

Yes. An advantage of 6 dB. A balanced output has a larger amplitude, and sounds louder and thus better.

And you'll loose the Common mode cancellation of the balanced input stage if you don't feed it with a balanced/differential signal.

No, you don't.

 

[Curious Fitz]

The buffer provides an easy load for the raw DAC output while it also has better capacity to drive the load of the preamp and interconnect cable.

You can see that Soren already included a buffer using opamp but the point is that we are trying to improve the stock DAC so we may want to use a better buffer.

Thanks for explaining quantran

The transparency of the buffer is very important.

Meaning, I suppose, it should be high quality: any suggestions for a newbie like me please?

Thanks again

 

[quantran]

Thanks for explaining quantran



Meaning, I suppose, it should be high quality: any suggestions for a newbie like me please?

Thanks again

Mr Nelson Pass B1 design is easy to diy.
Nelson Pass Labs B1 Buffer Pre-Amplifier Update DIY | DMS Audio (Sound Kontrol)

There is plenty of information on the web if you just google for these key words.

 

[RollE2k]

Yes. An advantage of 6 dB. A balanced output has a larger amplitude, and sounds louder and thus better.

Since i use output transformer it doesnt matter if i use differential or single ended output.. The Vpp voltage of the output is always the same - with the difference that in one case there is two phases of half the voltage of the SE signal. The only difference is that there is an actually groud reference of the single ended, while the differential have a virtual ground. So i don't get where you get the +6dB from. And as said this is still total irrelevant for the main question.

 

[Julf]

Since i use output transformer it doesnt matter if i use differential or single ended output.. The Vpp voltage of the output is always the same - with the difference that in one case there is two phases of half the voltage of the SE signal. The only difference is that there is an actually groud reference of the single ended, while the differential have a virtual ground. So i don't get where you get the +6dB from. And as said this is still total irrelevant for the main question.

The +6 dB comes from the usual balanced output buffer configuration. If your unbalanced output was done by just connecting one end of the (intrinsically balanced) transformer output to ground, it doesn't apply. I wonder how ground/earth is connected in the Pass Labs amp - but yes, we are getting rather off-topic.

 

[bozoc]

I have been looking at dam10210 board for a while now. And it seems like a very interesting DAC I would like to hear for sure.
Planing of implementing DAC board using only USB as input.

I was wondering about the implementations of this board before I start with my build.


-Is pre board power supply filtering necessary as it can affect fidelity in a good/bad way?

-What USB ti I2S board would you recommend me(preferably one that can be ordered in EU)?

-As some USB to I2S require addition power supply, can one of the dam10210's voltage outputs be used to power the board?

-What mods would you recommend to me? Vref mod seems useful.

Regards. Božo.

 

[vdi_nenna]

Can someone tell me if the dam1023 Rev2 board needs the vRef upgrade caps installed?
I have 20 qty 2200uf 6.3v caps. Should I bother?

thanks,

Vince

 

[vdi_nenna]

Answer to post #1034.


dam1021 v1 - The first one, really need the vref mod
dam1021 v2 - vref fixed, improved power on/off mute
dam1021 v3 - custom resistors, more vref capacitors
dam1021 v4 - new output buffers

Thaks,

Vince

 

[spikestabber]

Vref on v2 still had room for improvement, though v3 very much nailed it (with the easier option for adding more caps for very diminishing returns)

 

[Flikoman]

Did anyone try to implement remote volume control? Is something like motorized potentiometer or S/W (serial) volume control the right way to go?

Thanks in advance

 

[Ronnhedh]

Digital processor analog pre-amplifier stage

Please allow an update of the ongoing project.

This DIY project aims to a one-off prototype of a modern digital pre-amplifier stage with world-class performance. A reasonable price has been achieved on the cost of invested time.

It can be used for crossover filtering for multi-way active speakers, parametric equalisation, digital room correction; filters are given in parameters (PEQ), biquads and/or FIR coefficients; Each output channel also includes level, delay, polarity and compressor/limiter. Since the Sharc processor is a development center for a number of DSP software Products and freeware is available.

Currently the tech spec is now fulfilled:

• There is one XLR analog input, two RCA, two optical, one BNC and one XLR digital input.
• There is RCA line- and XLX balanced analog output and four BNC configurable digital channel outputs.
• Each input can be routed to a specific output.
• The Sharc signal processor (DSP) resolution is 32bit and sample rate is 96kHz.
• The processor and the DAC can be configured using a USB-connected dedicated PC software.
• Two I2S buses connect the four boards and allow extension boards.
• In all, there are six power supplies and nine regulators with a total power consumtion of 30W, Four regulators will be connected to the top cover using copper thermal pads.
• The grounding scheme separate the safety and EMI shield, the analog, digital and control ground.
• There is space for expansions such as a processor from Arduino, DLNA media renderer, USB2 audio input, HDMI input, I2S long-distance transceiver etc.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

The chassi consists of 3 compartments:

DSP
The DSP boards by miniDSP Ltd are for OEM applications and custom products, therefore most of the products they sell cannot be used on their own. The MiniSHARC, a multi-purpose audio digital signal processor (using Analog Devices Sharc ADSP21369) which can be used in various filtering tasks in audio such as multi-way active speaker crossover filtering and equalization.The MiniSHARC board it is a bare PCB without connectors along with clock oscillator, stereo SPDIF input with sample rate converter and I2S interface for 8 output channels.

• It accepts uncoded stereo (no coded multichannel formats) SPDIF input (but directly from coaxial RCA which has wrong signal level).
• output is I2S which is a synchronous serial digital audio format with data and 3 clock signals. There are 2 input channels but 8 output channels so the input channels can be divided into various outputs with various filters.

At the custom motherboard, digital inputs are routed to multiplexer for input switching, electrical signals through isolation transformer and differential line receiver. SPDIF-signal is fed to miniSHARC which has SPDIF-receiver and sample rate converter. I2S outputs are routed to SPDIF-transmitters along with 3 different buffered clock lines (master clock, bit clock and word clock). CS8406 SPDIF-transmitters are configured 96 kHz as miniSHARC-plugin/firmware is changed to one requiring that. Output is 75-ohm SPDIF with transformer (PE-65612) isolation and BNC connectors. Remaining spec items to be solved is remote selection of digital inputs.

The VOL-FP is a control accessory for the miniSHARC. The preconfigured board allows for master volume control, recall of the preset configuration and source selection on DIGI-FP via rotary encoder and IR receiver using I2C. The white color LEDs will provide indication of the active digital source and current selected preset.

Analog
The MiniDSP AN-FP is an Analog to Digital (ADC) and Digital to Analog (DAC) I2S interface providing digital audio input & output connectivity for miniDSP miniSHARC platforms. Based on the high quality Cirrus logic codec (CS4272), the board is compatible and self configured on miniSHARC platforms. Connection for both balanced audio inputs and outputs are on 3pin XLR Neutrik connectors. Only the analog inpu section is used.

The SoeKris dam1021 is a DAC module based on a discrete R-2R sign magnitude DAC design, with FPGA based FIFO buffering/reclocking and custom digital filters, < 1 ps jitter clock generator, with 28 bit resolution so there is headroom, oversampling up to 3.072 Mhz. Up to 24 bit / 384 Khz input from SPDIF, I2S and USB (via USB to I2S interface board), with isolation on the I2S interface. The board is very flexible, with filter parameters that can be downloaded. The board is fully firmware upgradable over a simple serial connection, which enables new features later on.

A USB connector is provided for easy front panel configuration and connectivity to the MiniDSP and the SoeKris boards through an USB hub.

PSU
The DIYinHK boards supplies separate power for all boards.
The SoeKris DAC is supplied with +-9V with Linear Technology 0.8uV ultralow noise regulator LT3042.
The MiniSHARC, motherboard and AN-FP is supplied with +5V using LM7805ACT regulators and
the SoeKris DAC isolated interface is supplied using TI UA78M33.


Main component vendors:

• MiniDSP in Hongkong - the DSP, analog board, volume/configuration control board and main software. www.minidsp.com
• SoeKris in Denmark – DAM1021 discrete R-2R sign magnitude DAC Soekris Engineering ApS, R-2R Sign Magnitude Audio DAC
• Tomi Nihtilä in Scotland – Digital motherboard nihtila.com – DIY audio electronics projects
• DIYinHK in HongKong - Power supply boards DIYINHK
• HiFi2000 in Italy – Slimline aluminium chassi Hi-Fi 2000 contenitori per l'elettronica, case modding HTPC, Galaxy, rack, DIYaudio, computer cases, front panel express, knobs,milled Handles, milled fronts, hi-end,
• Carbix in Sweden - Carbon fibre compartmental with additional EMI shield www.carbix.se / Kolfiber, Glasfiber, Epoxy - carbix
• NN in Hungary - Optically isolated USB UART / RS232 serial converter MCP2200 Optically Isolated Serial Converter
• ELFA – parts www.elfa.se

This Project total cost of component purchase is USD2000, including prototyping waste.
No specialized tools or electronic instruments has been required.
The Project has been fulfilled over a period of 2 months.

This prototype will over time be applied in a multi-channel audio and video system consisting of
NAS DLNA server and DLNA renderer from Oppo modified with 8 FiFo-buffered and reclocked digital output channels.
Record player with two tonearms - one-off Project air-bearing ordinary pivotal arm.
Dedicated digital amplifers for 3-way front and one-way surround linesource dipole loudspeakers and subwoofer.
Two sets of Earphones with DAC’s from SoeKris.
All cabling in teflon/silver.

 

[Ryssen]

Mr Nelson Pass B1 design is easy to diy.
Nelson Pass Labs B1 Buffer Pre-Amplifier Update DIY | DMS Audio (Sound Kontrol)

There is plenty of information on the web if you just google for these key words.

I use B1 on the RAW output and it sounds fine 2 me,but I havent compared it without it...

 

[Tankpopper]

Ok, i'm getting ready to order all the parts for a DAM 1021 project, and i'm looking for some guidance. I plan a simple build, no volume control, no screen, USB input only (i might add spdif in the future, but not sure i even need it) and SE output (so need for balanced).

Enclosure - two separate enclosures (20cm by 20cm by 4.5cm each) - one case for the PS and a second case for the Signal path.

USB - JLsounds I2SoverUSB with dedicated power supply.

Here are my question:

Power supply - How should i go about with the PS for the DAM? I do want a dc PS.. Is the Salas Shunt Regulator the best option? Should i get two boards? Due to budget limitations, i would also consider a ready board from Ebay, any recommendation on such a board?

Output - I plan to try the raw output at first, but i would love to try output transformers as well.. I have a pair of UTC A20’s that will soon become available (replaced by different transformers in my preamp), could those be used? Maybe even take the signal from the Balanced output and use the transformers to create a SE output with more gain?

I would also consider a buffer stage, but i have NO idea where to start.. I'm not even sure it will fit in the enclosure i have…

What do you guys think? Am i missing something? I would highly appreciate any input of feedback!

Tank out!