RTZ SDM (DSD) DAC

[Tony Moore]

Latest filter board:



For the keen eyed you might spot my blunder of 4 missing tracks from the outputs of the first stage op-amps. I was in too much of a hurry.

Version 3 soon...

However, it is sounding brilliant. This one is updated to match the circuit that Bohrok2610 showed on his post on DIYAudio that he used to compare various filter stages via measurement. The filters are adjusted to match the original design by Marcel. I also took the opportunity to add back the mute relays as an option and have added LM317/337 pin-out pads to allow external regulators to be fitted, if required. (ie such as LT3045/3094 ldo modules)

[iansr]

Tony, is V3 going to be based on what Hans is now calling the Alternate filter stage?

[Tony Moore]

I've lost track of the permutations but I think so yes.

There is some talk of different capacitor values in the passive filter part but all that doesn't affect the actual pcb provided you use 0805 sized COG or PPS caps.

[Ray P]

However, it is sounding brilliant.

All sounds to be a very positive development Tony. BTW did you see my PM on DIY Audio?

[Tony Moore]

All sounds to be a very positive development Tony. BTW did you see my PM on DIY Audio?

Yes I did thanks Ray.

[Tony Moore]

Latest DAC build coming along.



This is a wine-box lash-up to test various power supply options and also the new interface board for the JLSounds I2SoverUSB to connect it directly onto the PCM2DSD and feed it with two separate supplies.

Most of the regulators here are LDOs, LT3045 / LT3094.

It has only been running for 30 mins but it is sounding amazing. I made a mistake with the interface board so I feel a v2 coming on. (I mistakenly used the inverted DSDON rather than the non-inverted one that sits on the 2nd connector so had to cut that track. OK for only PCM files but when playing DSD files the PCM2DSD needs to know so it can route the DSD straight through)

Last thing to do now is cut the track-link on the I2SoverUSB and feed the USB side with the 7805 reg at the bottom of the photo. Apparently this can make a significant difference.

My source is currently a rasp pi running piCorePlayer so that I can do synched direct A/B comparison with the other two DACs.

[Ray P]

Looking good Tony.

[MistyBlue]

Looking awesome Tony.

That’s a lot of separate supplies!

I hope you don’t mind if I blatantly copy what you have done with the bits I’ve gathered together. Great idea mocking it up on a wooden board first – I was going to do something similar so I can A/B test different options with the RTZ as well as the RTZ against the DSC2.5.2.

I was wondering about the PCM2DSD handling both PCM from one source (such as output from a software based media player), and DSD from HQ Player. Can PCM2DSD “self sense” the 2 or do I need to flip the DSDON manually somehow to allow PCM2DSD to send the DSD from HQ Player straight through?

Also, in the photo it looks like you are using just a single ended output from J5/7 on the output board to some phono sockets – is that the case?

Sorry for the noob questions – I still have to make a start on mine!

[Tony Moore]

That’s a lot of separate supplies!

I hope you don’t mind if I blatantly copy what you have done with the bits I’ve gathered together. Great idea mocking it up on a wooden board first – I was going to do something similar so I can A/B test different options with the RTZ as well as the RTZ against the DSC2.5.2.

Please - blatantly copy away! I'm not the ultimate expert though so don't take everything I've done here as the best practice. Amateur tinkerer here!

I went with maxed out power supplies just to test which ones are critical and which less so. I had them already as I intend to retrofit them to my 2 RTZ DACs on the DAC board +/-15v and 5v supplies. I would _think_ that the most critical is the 5v digital supply to the dac board. (Apart from the filter board supplies, which I am already using Didden super-regs on). Plus of course the supply to the isolated side of the I2SoverUSB/PCM2DSD. All the changes are probably small but mount up incrementally.

The PCM2DSD needs the DSDON signal to switch through native DSD. The I2SoverUSB can tell if the stream is PCM or DSD and has two outputs for DSDON, one inverted and the other non-inv. I used the wrong one initially and so passed DATA and WCLK through the PCM2DSD as left and right DSD channels! Amazingly I could hear music through the DATA line, very distorted but definitely recognizable. The other channel was a lovely 44.1Khz sine - so the filter works!

So I'll be doing a version 2 of those interface boards for I2SoverUSB to PCM2DSD so if anyone is interested just ping me.

Yes, I am using just the positive phase of the outputs as my amp is single-ended. On my 2 DACs I have Lundahl 1588 transformers which I used to convert the balanced to SE. With that the output level is higher of course since I get double the voltage.

I am going to try the Lundahls on this winebox-DAC and compare to one of my existing DACs. All in due course.

[Tony Moore]

I have just swapped over the I2SoverUSB's power to an LM7805 based local regulator. (Normally this power comes from via USB from the host)

I have to say I do believe it is an improvement. In this case I am using a raspPi B+ running piCorePlayer so it's output may have been weak and potentially noisy so this serves both to improve the isolation of supply but also to take a large load off the pi.

[Tony Moore]

Haha, it's grown a mezzanine level!



Just trying out the LL1588s...

There's a lot to be said for Costco red wine selections...not least of which they're nice wines...

[MistyBlue]

The PCM2DSD needs the DSDON signal to switch through native DSD. The I2SoverUSB can tell if the stream is PCM or DSD and has two outputs for DSDON, one inverted and the other non-inv.

Thanks Tony.

Ah - so the system I2SoverUSB/PCM2DSD is self sensing then. Excellent! That means a one DAC solution for everything from the PC (Media (video) player, HQ Player and DAW if needed). I use a Behringer UMC404HD audio interface for music making/recording. It’s also been on media player duty up till now.

So I'll be doing a version 2 of those interface boards for I2SoverUSB to PCM2DSD so if anyone is interested just ping me.

Ray and Markw4 very kindly supplied me with interface boards for the I2S – so I think I’m OK as long as they are suitable.

I did get some lost cost transformers XLR to RCA to try on the output – these

https://www.aliexpress.com/item/1005003 ... ry_from%3A

I’m sure they will not be as good as the Lundahls, but I was concerned by the chatter on Marcel’s thread about output level. Whether I shall actually need them I don’t know.

Really looking forward to getting my teeth into this one – but I’m a little maxed out at the moment!

[Tony Moore]

OK, the DAC unit I am building for another member on this forum is almost ready for being packed up and shipped!



All that you see on the black 3d printed sub-chassis is what is to be delivered, he will be using his own pre-regulators. I have yet to test the power supplies on the DC input voltage that he will be using to verify function.

It is working and sounding fantastic. I will be sorry to see (hear) it go.

I will now apply the knowledge I've learnt on this built to retrofit improvements to my own DACs. These being an upgrade of the DAC supplies to the ultra-low noise LDOs and probably using the I2SoverUSB / piCoreplayer with my LVDS links instead of the Transporter as source. That also has the scope to add improved oscillators.

[iansr]

Looks ace Tony, can’t wait

[Tony Moore]

Since I've now handed over the latest RTZ build to Ian, my first task was to retro-fit the improved regulation to my 2nd RTZ DAC (the one I brought to Owston last year)



These LDOVR regulators proved themselves on Ian's DAC so I have upgraded my own DAC from LM317 to LT3045/3094 and also separated the DAC 5v supply from the PCM2DSD supply.

Also now starring the grounds all back to the DAC as it should've been in the first place.

Some checking and then for the power on...