- This topic has 46 replies, 16 voices, and was last updated 1 year, 8 months ago by
The Well Audio.
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The Well Audio
Since the original thread on diyaudio.com has been deleted the topic is renewed here.
The DAC Lite is a multibit discrete DAC. The resistor ladder network is segmented, the first 3 MSBs are thermometer decoded while the other 20 LSBs are R2R decoded.
The DAC implements a sign magnitude architecture to get bipolar output, so there are 2 x 23 bit ladder for each channel, one for the positive rail and one for the negative rail.
The dirty signals like bit clock and data are optically isolated to avoid any interference with the latch signal wich drives the DAC switches.
The bit clock is stopped as soon as data have been loaded into the shift registers, so every time the DAC switches to a new word the bit clock cannot affect the latch.
It uses a custom protocol provided by the TWSAFB-LT FIFO Lite.
The FIFO Lite also provides a digital calibration for the DAC Lite in order to compensate the error due to the resistors tollerance used in the ladder.
It’s a voltage output DAC which provides 1.1V to 1.8V rms depending on the Vref power supply, from 3V3 to 5V. The output impedance is 625 ohm, so the DAC can drive directly most amplifiers.
There is an optional buffer if the load wich has to be driven is lower than 20K. -
Crom
Congratulations Andrea – looking forward to some interesting discussion.
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jmmbarco
Hi Andrea!. Hope we can finally get useful info for our projects without trolling!
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Ivan
Hi guys. Excellent news! Congratulations.
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pinnocchio
Yes, on DIYaudio it was a total nonsense about trolling. We can finally get details here without issues!
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pearse
DAC Lite continuing to delight here, I went through a period where the sound was not as good but I had been experimenting with cables and power supplies.
After any change it needs several days to settle down it seems in my system.
I added a 3 channel Paul Hynes SR7 power supply to the front end SD playback units and added a Musetec USB100 Interface on channel 2 of the Fifo recently.
I also built the TWTTB Vacuum Tube Line Buffer and added it to the system in the past week, early days but I think I will be keeping it in the system.
I plan on finally transferring the build into a case in the coming weeks now that I am happy with all the tweaking.
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minionas
I also built the TWTTB Vacuum Tube Line Buffer and added it to the system in the past week, early days but I think I will be keeping it in the system.
Hi,
What it brought to your system? Im wondering about its transparency (if details or resolution are a bit lost) and its “tubiness” (if it add any tube goodness?
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I also built the TWTTB Vacuum Tube Line Buffer and added it to the system in the past week, early days but I think I will be keeping it in the system.
Hi,
What it brought to your system? Im wondering about its transparency (if details or resolution are a bit lost) and its “tubiness” (if it add any tube goodness?
Hiya,
No loss in detail or resolution and it has taken over a week to settle in.
What I am hearing now is a little more weight and authority on bottom end and highs are a little sweeter without any loss of detail, you could say a little tubey on the highs.
Listening to Steely Dan, Two Against Nature at the moment and it sounds amazing.
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Sebastian
Hi Andrea, I have a question regarding Vref and the DAC’s output (1.1-1.8Vrms). Is there an ideal voltage for Vref (best sound, lowest distortion, etc)? I ask, because I am able to accommodate for variance with my preamp, and now that I am planning, it would be helpful to know that. I won’t be using the buffer, as the input impedance of the preamp is high.
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The Well Audio
Hi Andrea, I have a question regarding Vref and the DAC’s output (1.1-1.8Vrms). Is there an ideal voltage for Vref (best sound, lowest distortion, etc)? I ask, because I am able to accommodate for variance with my preamp, and now that I am planning, it would be helpful to know that. I won’t be using the buffer, as the input impedance of the preamp is high.
We have used 4V and 4V7, and in our opinion there wasn’t any SQ difference.
We have powered the DAC Lite with batteries, but it looks like someone preferes shunt regulators.We will test shunt regulators in the next listening session.
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I added 2 x 500F paralleled supercapacitors (1.6-7v in each Cap) on each of the 3.3v Vref supplies and I found a very nice improvement in low to mids body and presence in my system. I also added pairs of supercapacitors on the VDD lines but did not hear any change in sound with these in place.
Spent some time sorting Caps to find pairs that charged and discharged evenly and so far so good with balance maintained in pairs. I never shut down power so no worries about startup but I have disconnects in place in case I ever need to shutdown and recharge the Caps on startup.
Will monitor Caps voltages over the coming weeks to see if I need to add balancing resistors.
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Hello Andrea,
is there a cap DC blocking cap at the DAC output?
S.
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The Well Audio
There isn’t a DC blocking cap at the DAC output because the DAC Lite is a bipolar DAC (sign-magnitude architecture), so there is no DC issue.
In other words, when there isn’t any input signal all the DAC switches are tied to ground. -
Thank you Andrea!
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Hifoli
Hi Andrea,
could you please elaborate a bit on the calibration of the DAC? How much impact does it have, e.g. a difference in the output signal would be super interesting to see.
BR
Happy WE
Oli -
The Well Audio
Due to the tolerance of the resistors used in the ladder, the accuracy of the DAC without any calibration is around 15 to 17 bit, depending on the resistors mixing.
In the attached pictures you can see the voltage measured at DAC output for each bit and for all the bits.
A dedicated Windows app automatically sends the signals to the DAC and measures the output voltages for each bit.
The Windows app also manages a 7 1/2 digits DMM, so the measurement is fully automatized.Then the application computes the measured data and provides the calibration file in order to correct the accuracy error.
Finally the calibration file is loaded into the FIFO lite, which provides the needed correction for each bit.
This way the accuracy of the DAC is increased to 22-23 bit.
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lasercut
Felt I should give small initial update because things are moving slow and might be a while before everything is optimised enough to give a more conclusive and thorough report.
DAC lite is set up in semi-rough state, with basic enough power supplies (1 rail and 2 ultrabib between XO supply and FIFO Aux+DAC supply).
Using PPG 22MHz for now, DRIXO 5.6MHz eventually.
CS8416 toslink to I2S for FIFO inputStill, I’m hearing an almost unbelievable level of detail from the DAC already…
“detail” doesn’t even seem like the right word for it, familiar tracks almost sound unfamiliar there is so much new information being exposed… but in a natural, not overly forward way, which has got to be one of the most common problems in DACs I’ve experienced.
dam1121 for example, genuinely very resolving compared to most with a realistic presence (the reason I chose to buy dac lite as they share similar architecture) but had a particularly bright and forward character.
It was forgivable, but very glad not to have to deal with it.The dac lite has a sort of dense tonality that I didn’t love it at first but is now starting to grow on me, though with burn-in time still in single digits and an endless amount of things left to experiment with and optimise it makes little sense forming any judgements yet.
It is very clear already this system has some huge potential, had plenty of faith it would but you never know until you listen for yourself.
How much the DAC, XO and FIFO are each contributing will be interesting to see also.
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I’m noticing shortly after turning everything on the DAC puts out 2.5V DC for about a second, audible as 2 pops.
Is this normal?
Only thing I could think of is not following any turn on sequence for XO, FIFO and DAC supplies, everything turns on simultaneously from mains switch.
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This reply was modified 2 years, 2 months ago by
lasercut.
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This reply was modified 2 years, 2 months ago by
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This reply was modified 2 years, 2 months ago by
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This reply was modified 2 years, 2 months ago by
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Kazuma
Generally it is recommended as a rule of thumb, that you turn on equipement from source to end device (amp being the last to be turned on).
And turn off everything in reverse order (first amp, then other devices up the chain).
I think it was put up in practice to offset such possible unwanted effects, as you described, between different equipement.
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The Well Audio
I’m noticing shortly after turning everything on the DAC puts out 2.5V DC for about a second, audible as 2 pops.
Is this normal?
Only thing I could think of is not following any turn on sequence for XO, FIFO and DAC supplies, everything turns on simultaneously from mains switch.
When the DAC starts, their switches are in unknown state until the FIFO begins to send data.
Some DC at the output of the DAC is possible, because the FIFO takes longer than the DAC to start up.So Kazuma’s suggestion is a good practice, the ampli should be the last to be turned on in order to avoid DC to reach the speakers.
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Ok, it will be left on most of the time anyway so not a big deal.
Also noticed it wont play at 176kHz, but it’s more likely a problem with cheap CS8416 board, will confirm 176khz operation eventually when using SD player as source.
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I was wondering for volume control, could you place a shunt resistor on the output to form voltage divider with output impedance of ladder?
Assuming this is not detrimental to DAC, it seems preferable to adding series resistance.
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The Well Audio
The DAC Lite plays up to 176/192 kHz with 5-6 MHz oscillators, and up to 352/384 kHz with 11/12 MHz oscillators.
Please, check if the CS8416 runs at 176 kHz.We can place a shunt resistor at the output of the DAC in the next revision. Maybe it will takes a few months.
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Hello Andrea, I have two questions: first, I believe you wanted to do some experiments with different power supply options on Vref. Have you been trough this?
Then, I have a few Mumetal sheets and I was wondering if you have any suggestions to shield FiFo/dac and theUSBtoI2S (Jlsounds in my case). I think I will have all three in the same chassis and a long USB cable to keep the RPi/Odroid C2 source away.
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To update the 176kHz playback problem was the CS8416 interface. it was one of those very unusual design choices you often see on generic chinese boards like this, a cap to ground slapped on the output of the toslink receiver, plays fine after removing it.
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The Well Audio
We have experimented a little with batteries and a pair of shunt regulators.
It looks like the DAC sounds better using shunt regulators on Vref.
We have used our own tracking regulators (not yet available) and a shunt regulator from the member ilgavro.
Not yet tested Salas shunt, but I have read someone is using it as Vref and the DAC sounds fine. -
Hi Andrea,
I am preparing the power supplies. For the digital part of the DAC (+/- 3.3 to +/- 5v), the clean side of the FIFO (3.3 to 5V) of the DRIXO (12-18V) is there any advantage for any particular voltage in those ranges?
I will be using the UltraBib 1.3 and while it can be brought down to 3.3v with special parts, it is easier to get 5v. So If there is no penalty, I wold go with 5v for the first two. For the last I can aim at whatever voltage in the rage, buy I have to take into account the transformers sec. VAC.
For Vref I will also use the Ultrabib, but in this case I might have to do down to +/-3.3V because of my systems gain structure (not yet sure on this).
Best regards,
S.
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The Well Audio
Hi Sebastian,
to power the DRIXO oscillators I suggest 16-17 VDC, as clean as possible.
The voltage range of the power supply of the DAC Lite affects the output voltage only. The greater the power supply voltage the higher the voltage output of the DAC.
We usually power the DAC Lite with 4VDC, both digital and Vref.
There is no problem powering the dital section with 5V and Vref with 3V3. But if you use 5V for the digital section of the DAC you have to use the same 5V for the clean section of the FIFO buffer (J18).Hope yhis helps.
Andrea
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Andrea, yes it does!
I will then be using 5V for digital in DAC and FIFO, 16-17V on clock, and Vref yet to determine.
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G600
Andrea told me that you don’t need pos and neg rails, full positive is fine!
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dogears
hi. how to send email to andrea mori? tia
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The Well Audio
You can send email to: info@thewellaudio.com
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Is it possible to go any lower than 3.3v for vref?
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This reply was modified 2 years, 1 month ago by
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The Well Audio
Never tested and not recommended but maybe it works with lower output voltage.
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The Well Audio
We would suggest a possible improvement: install 5/6 MHz DRIXO oscillators instead of 22/24 MHz.
The DAC Lite was designed with in mind 5/6 MHz clocks which have the best phase noise as possible. -
Supersurfer
Hi Andrea,
I will test with the 5-6mhz clocks and report the outcome.
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Hi Andrea,
what is the maximum voltage you can feed on VREF?
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The Well Audio
+/- 3.3VDC to +/- 5VDC
VDD power supply has to be equal or greater than 0.75 x Vref. For example, if Vref is powered by +/- 4.5VDC then VDD has to be powered by at least 3.4 VDC. In this case, even the clean side of the TWSAFB-LT (J18) has to be powered by the same 3.4 VDC.
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The Well Audio
An improved version of the DAC Lite with tantalum nitride resistors is now available (TWSDAC-LT-TN)
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Hi Andrea, what is the impact in sound quality with that resistor set?
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The Well Audio
We had a long listening session last Saturday.
Both version sound very good.
I can describe the TN version as a little more detailed even keeping a fullness and realistic midrange. -
You can call me an idiot, but I finally tested to keep the DAC powered 24/7.
I was reluctant to do that because of energy consumption (which is low…), and considering that my listening sessions are multiple hours long, so plenty of time to warm-up…
I was just wrong. With almost 3 weeks of continuous power, I realize that I was not using the system seriously.
I strongly suggest to try it, it’s a very easy way of improving the detail retrieval, harmonic content and tonal balance.
With the new shunts, the consumption will be higher, especially for the FIFO shunt.
I may restrict my global power switch to the FIFO shunt in the next future, at least to try if it’s necessary to keep the FIFO warm.
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The Well Audio
Unfortunately for the energy consumption, but I must admit that I agree with you.
We also noticed it during the comparative listening sessions, already after an hour of operation the DAC sounds better, especially in the details.
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sigitask
Hello Andrea,
I would like to ask how to instal SPDIF input to LT DAC? I using AudioNote CD player and it has only SPDIF. -
The Well Audio
TWSDAC-LT DAC Lite use a custom protocol, so you need the TWSAFB-LT FIFO buffer to drive the DAC.
The FIFO Lite accepts I2S only, you need SPDIF to I2S converter like this one from Audiophonics
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