Soekris DAM1021 Discrete R2R DAC

[OffTrackSound]

After seemingly endless delays and hold-ups the Soekris DAM1021 finally arrived late on Friday afternoon.

 

One of the main things that interested me in the DAM1021 was the fact that rather than using an off-the-shelf DAC chip - like the ES9018 or TDA1541 - it uses a discrete resistor ladder for each channel.

 

 

The board comes with all the SMD components preassembled, so the main DIY input is soldering thru-hole connectors and wiring up power and inputs.

I had a cheap XMOS -> I2S board that seems to have keeled over during initial testing, so "plan b" was to build a transformer terminated SPDIF circuit so I can listen whist waiting for the Amanero board to arrive from Italy.  It's not exactly a masterpiece but it does the job until I can sort out a PCB.

 

 

The board has a PSU included so only requires a small transformer with 2 x 7 or 8VAC secondaries but can also be powered from a DC supply.  As an interim  I've placed the mains plug, fuse and switch plus transformer in a Jayar plastic case and power the DAM1021 with 7VAC via umbilical.  The plan is to house the DAC in a Hammond case and build a more substantial external low noise DC supply.

 

 

Haven't had much of a chance to listen to the DAC but what I've heard so far is very nice. It's very detailed, with nice sound staging and doesn't sound at all harsh in my setup (Hypex 2 x UcD180HG+HxR and SMPS180 supply, Audiovector Mi1 Signature speakers).

 

 

cheers

Paul

[acg]

Nice one Paul.

 

This is also an interesting dac because of its filtering ability...you should be able to use multiple units as part of an active speaker system which keeps the crossover in the digital domain (if using computer audio).  At least I am interested in using it this way.

 

Keen to see what you think of it.

 

Cheers,

 

Anthony

 

 

PS: is this the 0.1% version (trying to remember the three resistor types)?

[OffTrackSound]

I've got the 0.2% version.  The others are 0.1% - as you mention - and 0.5%.

 

Since posting this morning I've rigged up a serial -> header cable and updated the FPGA firmware to version 0.9.  It's very straight forward using terminal software.

 

I've also hooked up a volume pot - I just used a cheap 10K Linear job from Jaycar - which isn't quite to the quality level recommended by Søren but will do until I get something better from Element14.  The volume pot isn't in the signal path, so the quality is more to do with accuracy and noise. When you connect to the DAC via serial port you can see the feedback as the volume pot alters the digital attenuation.  You can control the volume and input via serial port - V+15 is maximum gain V+00 zero attenuation, V-99 maximum attenuation. Inputs are set using I1, I2, I3.

 

Ultimately I want to incorporate IR/wired remote and use an encoder for input and volume controls.

[OffTrackSound]

Had a quick listening session with Legseleven and compared against his NAD M51.

 

The Soekris has a very different presentation - the sound stage of the DAM1021 seemed to be wider, and imaging was generally more detailed and precisely defined. The overall feeling was the Soekris was less warm sounding than the M51, but it wasn't harsh in anyway.  The consensus from this brief listen was that the DAM1021 had a clear edge of over the M51.

 

On the downside, we did discover that the Soekris tended to "pop" when powering down the system (hooked up direct to nCore NC400's) which put a slight dampener on proceedings.

[acg]

 

On the downside, we did discover that the Soekris tended to "pop" when powering down the system (hooked up direct to nCore NC400's) which put a slight dampener on proceedings.

Always turn off the amps first...no pops then.

[OffTrackSound]

Always turn off the amps first...no pops then.

 

Yeah. Thanks for the reminder, and unfortunately I didn't read the post until after I'd switched the DAC off in my system without thinking and blew a Hypex UcD180 module.  Hypex will repair for free, but it takes about a month, so I've ordered a replacement to tide me over. D"oh.

 

L11 and I both run our systems of remote power boards which shuts down everything simultaneously, so it a bit of a PITA having to manual switch off the amps first.

[acg]

That's no good Paul.

[Nada]

Yeah. Thanks for the reminder, and unfortunately I didn't read the post until after I'd switched the DAC off in my system without thinking and blew a Hypex UcD180 module.  Hypex will repair for free, but it takes about a month, so I've ordered a replacement to tide me over. D"oh.

 

L11 and I both run our systems of remote power boards which shuts down everything simultaneously, so it a bit of a PITA having to manual switch off the amps first.

 

Bad luck mate with the Hypex.  Looks like you will have to join all the rest of us with the sequential ritual of manual power on down the chain and power off  up the chain.

 

The NAD51 is one of the best measuring DACs around so your on a winner with the Soekris R2R.

[OffTrackSound]

Bad luck mate with the Hypex.  Looks like you will have to join all the rest of us with the sequential ritual of manual power on down the chain and power off  up the chain.

 

The NAD51 is one of the best measuring DACs around so your on a winner with the Soekris R2R.

 

I discovered after putting in an order with Hypex  that the boards I have are an older (2008) revision of the V2 180HG + HxR's. Apparently the current versions have an improved output cap and sound a bit better than the ones I have.  Luckily a swift email to Hypex sales managed to catch the order before it was shipped -  the 180HG+HxR has been exchanged for 2 x 180HG's and I'll swap the HxR regs from the existing modules.

 

The Soekris R2R is really quite impressive.  I'll just keep the R2R powered on and switch the amps, and that should avoid the dc issue.

Edited February 2, 2015 by OffTrackSound

[Nada]

..The Soekris R2R is really quite impressive.  I'll just keep the R2R powered on and switch the amps, and that should avoid the dc issue.

 

It might sound better too kept powered up. Every R2R DAC ive had at home including the MSB sounded much better after a day or three of being powered up.

 

Your R2R might improve with being worked for a few hundred hours.

 

Are you using the opamp output or the direct voltage out?  The negative feedback in the opamp might be a bottleneck in the sound. Tapping the direct voltage put would be interesting.

 

Then if you can get the jitter down the imaging should go holograhic.

[OffTrackSound]

It might sound better too kept powered up. Every R2R DAC ive had at home including the MSB sounded much better after a day or three of being powered up.

 

Your R2R might improve with being worked for a few hundred hours.

 

Are you using the opamp output or the direct voltage out?  The negative feedback in the opamp might be a bottleneck in the sound. Tapping the direct voltage put would be interesting.

 

Then if you can get the jitter down the imaging should go holograhic.

 

I'm using the balanced opamp buffered output -> hypex amp (at least when the modules turn up).

 

Søren has said he'll add a firmware option to allow running dual mono for fully balanced operation. Once that happens I'll look at get a second board.

 

I did a really quick j-test run last night and it looks like the onboard FIFO//Si514 based setup is quite effective. I need to sort out the levels as I'm trying to juggle between overloading the inputs and losing detail in the noise floor of the sound card.

Edited February 3, 2015 by OffTrackSound

[awty]

Great to read someone actually getting one of these up and running, although with a few hiccups. Saw it on diyaudio, put haven't looked in there recently.

 

Did you purchase from here http://soekris.com/products/audio-products/dam1021.html

 

What else is needed to get it up and running as a USB headphone amp? I know little about DACs and get lost in all the Jargon.

 

Would there be much loss buying the lower spec 0.05 board? 

[OffTrackSound]

Great to read someone actually getting one of these up and running, although with a few hiccups. Saw it on diyaudio, put haven't looked in there recently.

 

Did you purchase from here http://soekris.com/products/audio-products/dam1021.html

 

What else is needed to get it up and running as a USB headphone amp? I know little about DACs and get lost in all the Jargon.

 

Would there be much loss buying the lower spec 0.05 board? 

 

Yes, asia-pacific sales are via the US webstore.  They ship using UPS so factor about $60-70US for shipping on top of the board.

 

The hiccups are pretty minor, more user error than anything else. There isn't a manual - it is promised but no sign yet - so currently the best compilation of information is here:

https://hifiduino.wordpress.com/2015/01/30/building-soekris-r-2r-dac/

That page collates build information that is scattered in two long threads on DIYAudio.

 

At a bare minimum you need a 2 x 7-8VAC 5W transformer, and a usb -> i2s board,  plus the 0.05% board.  The main difference is in the tolerance of the resistor ladders, and the greater tolerance will mean levels higher of higher harmonic - not sure how that will translate soundwise. 

 

I haven't seen anyone hook one up as a headphone amp yet but it really should be just a matter of wiring in a suitable connector to the opamp buffered outputs.

 

cheers

Paul

Edited February 3, 2015 by OffTrackSound

[awty]

Thanks Paul.

Looks to be a very versatile board, option to connect 12vlt DC may be better option for me. Need to start saving my pennies.

 

Any recommendations for a usb -> i2s board?

[OffTrackSound]

Thanks Paul.

Looks to be a very versatile board, option to connect 12vlt DC may be better option for me. Need to start saving my pennies.

 

Any recommendations for a usb -> i2s board?

 

I'm waiting on an Amanero board, but Søren is using a DIYINHK board.

 

Apparently the DIYINHK board needs a few SMD parts to be added as this is needed to power the I2S isolators.

http://www.diyinhk.com/shop/audio-kits/58-xmos-dsd-dxd-384khz-high-quality-usb-to-i2s-pcb.html

 

http://amanero.com

Edited February 3, 2015 by OffTrackSound

[OffTrackSound]

I discovered after putting in an order with Hypex  that the boards I have are an older (2008) revision of the V2 180HG + HxR's. Apparently the current versions have an improved output cap and sound a bit better than the ones I have.  Luckily a swift email to Hypex sales managed to catch the order before it was shipped -  the 180HG+HxR has been exchanged for 2 x 180HG's and I'll swap the HxR regs from the existing modules.

 

The Soekris R2R is really quite impressive.  I'll just keep the R2R powered on and switch the amps, and that should avoid the dc issue.

 

UPS delivered the replacement Hypex modules this afternoon. I've swapped over the HxR regulators, and everything back up and running.

 

I've added a TOSLINK module to the DAC following Søren's schematic and this seems to work fine.  The DAC automatically switches to the active input which is a nice touch.

I'll have to compare TOSLINK to the Stello U3. In theory it should sound the same but it will be interesting to see how that translates to practise.

 

cheers

Paul

[davewantsmoore]

Is there any info buried out there about the programmable filters (suitable for crossover filters) in this DAC ?! .... all I can find is that it's coming in the future... but nothing about how powerful they'll be.

 

Interested.   (I asked Glenn, but no response.  I bet he gets a lot of mail, heh)

Edited February 6, 2015 by davewantsmoore

[hochopeper]

Is there any info buried out there about the programmable filters (suitable for crossover filters) in this DAC ?! .... all I can find is that it's coming in the future... but nothing about how powerful they'll be.

 

That's all I've heard too. I haven't looked up the specific FPGA used, not all FPGA have many 'DSP Slices' though so it would depend a bit on how powerful that is and the memory buffer space available (ie DSP delay time would eat into the FIFO buffer time)

Edited February 6, 2015 by hochopeper

[Nada]

Is there any info buried out there about the programmable filters (suitable for crossover filters) in this DAC ?! .... all I can find is that it's coming in the future... but nothing about how powerful they'll be.

 

Interested.   (I asked Glenn, but no response.  I bet he gets a lot of mail, heh)

 

http://t-filter.appspot.com/fir/index.html The free online FIR filter design tool

TFilter is a web application that generates linear phase, optimal, equiripple finite impulse response digital filters. It uses a pure javascript implementation of the Parks-McClellan filter design algorithm.

 

 

http://www.diyaudio.com/forums/vendors-bazaar/259488-reference-dac-module-discrete-r-2r-sign-magnitude-24-bit-384-khz-8.html#post4000822

 

The Spartan-6 LX16 used have 15K logic cells, 32 DSP48A1 MAC blocks, they need to be used in blocks of 4 to do 35 x 35 bit multiplications plus 70 bit summers, so 8 full high resolution MAC's will be available. The -16 also has 576 Kbit RAM blocks.

I will probably assign 2 for the first x2 most critical oversampling FIR filters, running them at just 49.152 Mhz makes space for 1024 coefficients if needed, then 2 more for the rest of the FIR filters, and then 2 more for other functions, like de-emphasis, volume control and digital crossover filters. Assuming there is space for the control logic.

So the Spartan-6 LX16 have plenty of DSP resources. And if that it not enough, the boards can take the larger LX25....

 

 

[OffTrackSound]

Beaten to it...

 

This is about all I can find from the DIYA thread...

 

 

The Spartan-6 LX16 used have 15K logic cells, 32 DSP48A1 MAC blocks, they need to be used in blocks of 4 to do 35 x 35 bit multiplications plus 70 bit summers, so 8 full high resolution MAC's will be available. The -16 also has 576 Kbit RAM blocks.

I will probably assign 2 for the first x2 most critical oversampling FIR filters, running them at just 49.152 Mhz makes space for 1024 coefficients if needed, then 2 more for the rest of the FIR filters, and then 2 more for other functions, like de-emphasis, volume control and digital crossover filters. Assuming there is space for the control logic.

 

So the Spartan-6 LX16 have plenty of DSP resources. And if that it not enough, the boards can take the larger LX25....

 

Edited February 6, 2015 by OffTrackSound

[WINEDS]

Thanks for posting this Paul.  This is just what I have been looking for I think.  So I just ordered one.

[OffTrackSound]

It seems that the 44.1kHz reconstruction filters could do with some work! Fortunately these are user upgradable so not a huge deal.

 

I had read comments about harshness, but clearly I had not listened to anything that really made it obvious.  By chance I'd stuck on Public Image Limited's Album and the strident vocals made the problem very apparent.  Higher sampling rates don't show this issue and using Pure Music 2 to upsample 44.1kHz -> 172kHz removes this tendency.  It's actually a big step forward all round. I'd noticed an improvement the other day when I accidentally played the 192/24 version of Miles Davis' "So What" straight after the 16/44.1 version, but given the difference was potentially down to remastering I'd dismissed it. 

 

Søren has said that he is working on a firmware update that should address the clicks when changing sample rates and the shut down kaBoom.  I'll stick with turning off the amp first regardless.

 

cheers

Paul

Edited February 10, 2015 by OffTrackSound

[Nada]

You may like to try keeping the DAC powered on continuously being fed pink noise at high volume obviously with the amps turned off but connected allowing the dac to swing voltage. Give it 400 hours and have another listen.

 

You might also like to try the izoptope SRC if your stuck with apple processing  If you use windoze then foobar has free SoX DSP's that are configurable.

 

If the FPGA can be programmed to pass through sample rates over 96 that would allow you to hear different computer filter setting on the fly and dial in the sound you want.

[OffTrackSound]

You may like to try keeping the DAC powered on continuously being fed pink noise at high volume obviously with the amps turned off but connected allowing the dac to swing voltage. Give it 400 hours and have another listen.

 

You might also like to try the izoptope SRC if your stuck with apple processing  If you use windoze then foobar has free SoX DSP's that are configurable.

 

If the FPGA can be programmed to pass through sample rates over 96 that would allow you to hear different computer filter setting on the fly and dial in the sound you want.

 

I believe it passes through at 352.8 and 384 but until my Amanero finally manages to escape from Milan Post Office I'm limited to 192kHz out.

 

Anyway I bit the bullet and had a play with rePhase which vastly more usable/flexible than the online filter editor today, and after some pointers from the developer of rePhase on the DIYA thread I managed to get a minimal phase filter with 1015 taps and a slow roll-off installed.  It makes a significant improvement to 44.1 playback. Even with my amateur effort it's pretty obvious the filters that come with the DAC are currently a weak link. Søren seems to be keen to get the filtering sorted so I think there will be rapid improvement in the filters.

 

cheers

Paul

[WINEDS]

I believe it passes through at 352.8 and 384 but until my Amanero finally manages to escape from Milan Post Office I'm limited to 192kHz out.

 

Anyway I bit the bullet and had a play with rePhase which vastly more usable/flexible than the online filter editor today, and after some pointers from the developer of rePhase on the DIYA thread I managed to get a minimal phase filter with 1015 taps and a slow roll-off installed.  It makes a significant improvement to 44.1 playback. Even with my amateur effort it's pretty obvious the filters that come with the DAC are currently a weak link. Søren seems to be keen to get the filtering sorted so I think there will be rapid improvement in the filters.

 

cheers

Paul

 

Paul, I see you are doing some sterling work with this over on DIYAudio.  I have my board too now.  Just waiting for some bits to arrive from element14 so I can fire it  up..  Can't seem to find a TORX147 locally though as yet.

 

Thanks,

 

Paul

 

Edit :  Ah I see Altronics have some

Edited February 14, 2015 by WINEDS