New Dilemma

[Tony Moore]

Having acted on a thread from Ray about a group buy for the "Return to zero FIRDAC DSD Dac" design's pcbs I've gone down another rabbit-hole.

I am pleased with the way my heavily modded Transporter turned out and I love the sound of the TDA1541A, however I'm always on the lookout for projects and for potential ways to get the best from digital music.

So I've been working on this since the new year and yesterday I got it fully powered up and playing music (through headphones initially).



As you can see, it is naked so far and on bench supplies. However, I was cutting my losses and not investing ahead too far in case I messed it up and it didn't work. There are a _lot_ of very tiny SMD components so it was quite a challenge to even _see_ them let alone glue 'em on! That top board is the filter and is by far the simpler one of the two as the lower board is 4 layer and has components on both sides.

So, now I am faced with a decision...whether to try to make this a standalone device or to re-purpose my older Pedja Rogic 1541 DAC...that unit already has a working Squeezebox receiver, decent 5v power supply and a Kali reclocker...The idea would be to use a PCM -> DSD modulator on the end of the I2S from the Squeezebox and convert to DSD streams to feed the RTZ DAC. I also have a spare SB3 but I know that one has a funky slightly non-standard I2S which I don't want to have to mess with again. The Receiver is standard I2S so much more likely to work with the PCM->DSD device.

The downside is that unit still works fine and I could end up not getting either working in the end. I would obviously bench-test the prototype before touching the older unit. Maybe I'll just hunt down on old SB Receiver on Ebay...

[Nick]

My suggestion would be a Pi if you can find one.

[Tony Moore]

I have spare a Pi or two.

Good idea! I will look into that.

[Ray P]

The general concensus is that the best DSD resampling results are achieved using HQ player on a powerful PC and then streaming the output over the network to a Beaglebone-based network appliance running the Botic linux distro and an isolator/reclocker cape (or via USB to a JLSounds board - that's what I've been using with the RTZ prototype).

Personally, if you want to do chip-based resampling I think that instead of a Pi you'll be better off getting a Beaglebone/Botic and equipping it with the Simple DSD SRC that ppy posted over on DIY Audio

https://www.diyaudio.com/community/thre ... ne.358147/

As it happens, I have two sets of PCBs and components for the Simple DSD SRC and I'm waiting to get them soldered by a friend in his reflow oven - if i don't need the spare I'll happily sell it onto you - I'll give him a call and see how quickly he can do the soldering work. IIRC the header is Amanero pattern so should plug straight onto the RTZ board.

Another option you might consider is to equip your Transporter with a Twisted Pear Teleporter (assuming you are able and willing to find and tap the i2s data) so you can use it as an i2s source with another teleporter at the DAC end in front of a SRC. Teleporter uses LVDS so you can run the i2s over a long distance if necessary.

Anyway, glad the RTZ work out for you.

[Ray P]

I must revist the valve-based output filter I was trying on my RTZ thread - I got no output but I'm pretty sure that is to do with the biasing being wrong.

[Nick]

The general concensus is that the best DSD resampling results are achieved using HQ player on a powerful PC

Is the code to do that open source and or available? One of the thing that put me off DSD some years ago was (it seemed) the general lack of standard WRT the encoding/transcoding process.

[Ray P]

Is the code to do that open source and or available? One of the thing that put me off DSD some years ago was (it seemed) the general lack of standard WRT the encoding/transcoding process.

No Nick, HQ Player is a commercial product;

https://www.signalyst.com/consumer.html

It costs around £180 IIRC, so not cheap, though it's relative of course.

[Tony Moore]

Hi Ray,

Thanks for the info, I will research and digest!

When I said the Transporter was "Heavily modded" I was perhaps understating somewhat, lol:

https://www.audio-talk.co.uk/phpBB3/vie ... 4&start=30

I didn't like their AKM Dac so I tapped tapped the I2S and fed it into a TDA1541A S2 and used Pedja Rogic's Aya Dac design for the I/Vs. Just about managed to squeeze all that and the power supplies into the Transporter.

The Transporter is now my main system, listening to it all day every day in my office. It sounds very nice.

[Ray P]

Plenty of room in there for a Teleporter board, though you'll also need a means of switching the i2s, I think that's achievable with a Twisted Pear Otto (or one of there other little add-on type boards). I'll guess you'll already have suitable power supplies in there.

Nice build BTW, I like the clear acrylic lid - your own work?

[Tony Moore]

"Nice build BTW, I like the clear acrylic lid - your own work?"

Thanks!

I designed the lid but a friend with a laser cutter made the parts for me. It is mainly for ventilation as I've introduced far more heat into the case and it was prone to eventually overheating the display's SMPS apparently.

I am leaving the transporter out of the equation as it is my primary source now and I don't think I will (or want) to try to improve it. I know when to stop..haha, he said.

No, this is the unit I was speaking about, this is much older (as can be seen from the dust!)



This is a hybrid of Pedja Rogic's original 1541A DAC with the class A amp/filter board from my old Hawk Audio DAC, plus SB Receiver, Tent labs clock and Kali reclocker. Plus a super reg thrown in for good measure. This was my main source until the Transporter knocked it off the throne.

[Tony Moore]

"As it happens, I have two sets of PCBs and components for the Simple DSD SRC and I'm waiting to get them soldered by a friend in his reflow oven - if i don't need the spare I'll happily sell it onto you"

Please keep me in mind Ray, I'd certainly like 1st refusal on your "spare" if you want to sell it on.

[Tony Moore]

By the way Ray, did you ever get to build this:

https://www.diyaudio.com/community/thre ... c2.370177/

It seems like years ago now but when you started the group buy of the RTZ DAC I also had some of these pcbs made and ordered the parts and then forgot about it! (Senior moment)

I found a blue box from JLCPCB which I'd labelled up and put aside. Some of the scarce bits came from Ali Express which is probably why I'd forgotten as they take so long and are very likely fake. Anyway, I will probably also have a go at this but the chances of success are somewhat limited as the component spacing on the pcb are difficult to say the least. Plus then there's whether the Spartan is genuine and whether I'll be able to cobble together the software to program it. I do already have a clone JTAG which purports to handle the XC6 series of FPGA but who knows?

I will give it a go as I'm itching to sniff the solder paste again...oh how I miss it now.

I am also still interested in your spare SRC.

I have to say, I've converted a few albums off my server from FLAC (16 bit 44.1Khz) to DSF with dbPoweramp and listening through headphones and I can honestly say this DAC has something special. I've not done an A/B comparison with the 1541A DAC yet as I can't get the equipment in range due to working on bench supplies, etc. However, I've tried a few of my go-to comparison tracks and it's delivering on the goods.

[Ray P]

By the way Ray, did you ever get to build this:

I've got some PCBs and did start assembling one (with a Chinese sourced FPGA) but came unstuck soldering the Spartan - three sides are fine but I managed to bend the legs on the fourth side when I was a bit over exuberant trying to use drag-soldering and wick to remove some solder bridges. Not sure if I'll try again. IIRC there are some positive comments on its sound quality later in the thread.

And I agree, it's a special DAC - Marcel certainly seems to know his stuff. As I mentioned earlier, I still want to try and get the valve output stage working to see if more can be squeezed out of it by dispensing with the op-amp based filtering - I may have to pick some brains here...

[Tony Moore]

I wonder if we can use transformers? As in the DSC2?

I do have a couple of Llundalhs which I bought to try out on the differential output of the AKM DAC in the transporter - not sure if they'd be suitable...?

(LL1588)

[Ray P]

I have passive 3rd order filters with Lundahl LL1684 transformers on my ValveDAC - might be worth asking Marcel if they could be used - would need to add DC blocking caps as per the ValveDAC schematic (and a muting arrangement).

I also use LL1684s in my DSC2.