ESS THD ‘Hump’ Investigation

[somebodyelse]

For the time being I did not try any modifications. But to my knowledge a new Tone Board was "promised" for Q2/2019 that might adress the humo. May is almost over now. Any news on that?

21 days ago they said it would be about 3 months.

 

[IVX]

Guys, I'm saying seriously about the new custom and opened firmware for toneboard. I can help if anyone crazy enough to go breaking bad to replace XMOS chip($10) for the brand new(XMOS JTAG board required as well $20). Such simple things are easier to redo than reverse-engineering that. The brand new XMOS chip needed because the original one, I believe, is copy protected with IEEE encrypting and its modification impossible.

 

[badboygolf16v]

TQFP desoldering/resoldering is probably a bit beyond me! I'm sure @jackenhack could do it.

 

[IVX]

actually, QFN48 there, anyway, hot air toll needed.

 

[Herbert]

Dear Khadas people, I do not want to
register to another forum, but would definately buy the new board if the hump is solved. I can live very good with the Khadas board, (I bought 2) I will live better
with a version that solves the probably inaudible hump for the sake of specs. I want to implement the upcoming board into a vintage CD Player. Any ideas already about the size of the upcoming board? And hey, while writing this it came into my mind:
There will be a standalone / generic version of course?

 

[jackenhack]

The Khadas guys have fixed the problem. But they are working on a new version of the Khadas Tone Board, this one with XLR-connectors on it, so they will spin a new board with the fix included. It will be a couple of months I would guess.

 

[Veri]

The Khadas guys have fixed the problem.

Awesome!

 

[jackenhack]

Yes, very awesome! And they are making the new version with XLR, so I’m really anxious to get my greedy little hand on the new board.

 

[eliash]

Since a knowledgeable and practically experienced corona seems to be assembled here, I take the heart to set a small interupt on the new ESS Sabre issues and ask 3 questions about the well known ESS9018 (8 channel chip), which I would like to finally understand as an electronics engineer.
I am using a kind of chinese-based reference design (Weiliang board) in the default hardware mode (4 internal channels per stereo channel, no uC control), driven by a separate CM6631a box via S/PDIF (because of mains ground isolation).

1 - The first strange thing I found was that the equipped NE5532 opamps for the IV conversion somehow hooked up the DAC chip, causing the least significant bits sound distorted (bits 20-24?).
Changing the opamps to LME49720 somehow solved the issue...why (anti-parallel protection diodes in the opamp input, wrong power-up sequence)?

2 - This specific design lacks a proper AVCC supply. The designer claims to have implemented low noise voltage regulators, but they are inferior by datasheet, compared to the ESS reference design, utilising low noise opamps. To confirm it, I created DC test signals files at +/- half max. output (incl. slow ramped up/down).
This increased the inaudible idle noise level to clearly audible levels.
Shunting the AVCC regulator outputs with 3x 470uF low ESR caps reduced the noise significantly, but still audible with the ear next to the speaker.
My question is whether or to what degree such noise is visible in single or multitone SNR measurements as displayed here in the forum?

3 - Running the Sabre chip at the common 100MHz clock always showed a strange behaviour at 96KHz input sampling rate. After power up or HW reset or previously played 192KHz files, there are always persistent clicks (every few seconds, mainly audible in quiet sections). Playing a file with any lesser sampling rate than 96KHz (e.g. <=88KHz) clears this situation, playing a 96KHz file afterwards is perfect.
As far as I could verify, overclocking the chip at 109.25MHz (because 88KHz plays perfect - TCXOs available at a reasonable price from China), solved the issue. 96KHz now plays always click-free. Looks like the internal sampling rate detector has a problem at exactly 100MHz clock rate...
My question is if anybody here has observed this behaviour as well?


Thanks in advance for short comments!

 

[somebodyelse]

Guys, I'm saying seriously about the new custom and opened firmware for toneboard. I can help if anyone crazy enough to go breaking bad to replace XMOS chip($10) for the brand new(XMOS JTAG board required as well $20). Such simple things are easier to redo than reverse-engineering that. The brand new XMOS chip needed because the original one, I believe, is copy protected with IEEE encrypting and its modification impossible.

In the early part of the hardware volume thread there's a fair bit of detail on connecting the xTAG board to the Tone Board, with successful flashing of a rewritten firmware image by someone who wanted to use the ESS volume control before the factory firmware supported it. Based on that I'd say there's no need for a replacement XMOS chip, and that alternate firmware is an option.

 

[IVX]

somebodyelse , WOW, that's strange, when a few months ago I bought XMOS XU208 USB->I2S board on Taobao for $20 to start work with XMOS Timecomposer, the chip was protected, and flash memory content encrypted. Can you imagine, $20 board was protected? Toneboard is quite costly for just board without any housing, and I was sure they did protect XU208, without that another chinese may too easy to copy the whole toneboard and sell counterfeit for $50. I'll read the topic at your link when I'll have time.

 

[Jimmy]

A mass produced utilitarian case doesn't cost that much, you can buy one at audiophonics. Besides that Khadas said that they will offer their new tone board with a case, so if it adds balanced outputs, case, no IMD hump and the price is reasonable they have a winner in their hands.

 

[IVX]

I'm not saying khadas toneboard is too expensive(if people buying, the cost is right), I said that unprotected XMOS MCU easy to copy, and next produce fake toneboard for half of the price(if not cheaper). The IEEE encrypting it is just an option when you make the project in the Timecomposer, need just to set the checkbox and add the key file, it is free.

 

[zermak]

Hello everyone;
I found this great forum/site few weeks ago and my monkey made me buy a Khadas Tone Board to replace my PC discrete audio card (an Asus Xonar DX which I never complained about using the UNi Xoanr drivers).
I just made this account to ask for a simple explanation to when this hump affects the sound quality in a theoretical way (I consider myself a rational person and I am aware of our earing limits and so on and I am actually enjoying reading some funny stuff around here to be honest, besides the great objective reviews and the instructive technical insight) and well in simple words if you could try to explain me the IMD ratio's graphs.
What I am confused about it is of the X axis values. Is that the output volume of the board itself or is it the digital volume of the sound played through it?
I am more prone for the latter (because in the other case it's not an issues and can be avoided by simply setting the digital output volume of the card at 0dBfs) and, correct me if I am wrong, in this case it means a digital sound (music track) with the quietest sound higher than -19dBfs (circa, for the Khadas TB; so around 19dB of dymanic range with the peak at 0dBFs) has a linear and excellent IMDs ratio making the IMDs even more unaudible? Or am I completely wrong?

I hope I am not causing more confusion here.
Thank you.

 

[amirm]

What I am confused about it is of the X axis values. Is that the output volume of the board itself or is it the digital volume of the sound played through it?

It is the amplitude of the sine wave pair being fed to the DAC in digital domain. So whether you hit this or not is dependent on use of software volume control and content of music.

 

[amirm]

I found this great forum/site few weeks ago and my monkey made me buy a Khadas Tone Board to replace my PC discrete audio card (an Asus Xonar DX which I never complained about using the UNi Xoanr drivers).

My monkey??? Is this machine translation? Or some Italian expression we don't know?

 

[Samoyed]

To paraphrase Clint Eastwood, you are scaring my donkey.

 

[Hugo9000]

My monkey??? Is this machine translation? Or some Italian expression we don't know?

Perhaps he is addicted to audio gear? The expression "monkey on (one's) back" refers to an addiction (morphine, originally, I think), so that may be the monkey he means?

 

[zermak]

It is the amplitude of the sine wave pair being fed to the DAC in digital domain. So whether you hit this or not is dependent on use of software volume control and content of music.

In simple words (or a real world example) what makes hit the hump spot considering that I use the DAC at 100% digital volume?
Thank you.

My monkey??? Is this machine translation? Or some Italian expression we don't know?

I went looking for the correct translation before posting and @Hugo9000 is correct. I suppose it is mostly an Italian expression.

Perhaps he is addicted to audio gear? The expression "monkey on (one's) back" refers to an addiction (morphine, originally, I think), so that may be the monkey he means?

Addicted to hardware tech actually and just taking the audio path now
I don't know its origin but it is frequently used by us geeks (at least by the Italian community and indeed there are actually plenty of forum's emojy with the monkey involved XD).

 

[amirm]

I should be getting the first DAC with ESS hump fixed in a couple of weeks.....