Tír Na HiFi

alecm wrote:nige2000, many thanks for brave steps, i waiting for clock changes long time. for sure i will try the same. I like this thread. Here is lots of interesting researches. Thanks for sharing your experience.

5 different Soren DACs were researched and heavily moded(almost all mods described here and even more) by me, and I clearly noticed, that all dacs has different measurements more than normal spreading in comparison with another dacs. All has a different level of harmonics. Sometimes 20-30db of difference(The measurements were made using a Lynx Aurora ADC predominantly at a frequency of 96K 24-bit)

My idea, that the answer is a difference(spreading) of resistors and their mutual ratio. And this is the one of significant factor that influence on measurements, harmonics and sound quality in the final. Even more, I have changed resistors and received a clear change in harmonics level.
Look at this.



i see that the r2r soekris schema is


There is 1021 .01 version dac from the first delivery. Having re-measured of each resistor there. And have received the following results:

Yellow marked real accuracy percentage that are outside of the specified accuracy - 0.01.

so my conclusions:
- It was stated that the precision resistor is 0.01, but in reality there are resistors with an accuracy of less than stated
- By itself, the accuracy is not so important, more important it is 2R and R mutual ratio (should be 2), and the same resistors in series (bits).
- Since the resistors in the matrix has a significant variation (over 0.01), which means that the result of these relations and also provide spread.

I want to ask an advice here on r2r matrix construction. For me it remains full unclear until the end the sense resistor in bit from 0 till 2 rows. Soren calls it like “thermometer”. What is the practical sense of 0,1,2 rows? Any thoughts?

nige2000 wrote:

alecm wrote:
I want to ask an advice here on r2r matrix construction. For me it remains full unclear until the end the sense resistor in bit from 0 till 2 rows. Soren calls it like “thermometer”. What is the practical sense of 0,1,2 rows? Any thoughts?

wonder if therses any point asking soren?
At worse case there will be no reply or a political type non disclosing reply

Listened for an hour with fixed 22 clk feeding fpga and the pre fpga reclocker
Im positive the adjustable clock shoud be removed and replaced with fixed clk and i2s prealigned
Resolution is immense with darker background and a level of coherance ive not experienced before
The biggest improvement since vref ;)

nige2000 wrote: if theres any mods we haven't done let us know please

jkeny wrote: Thanks Alecm - great work
Are you sure that is the correct schematic for the resistor network - it can't work if bits 0,1 & 2 aren't connected to a a 574 chip output? You traced this schematic from the Soekris board, I presume?

jkeny wrote: The accuracy of the resistors does determine the linearity of the DAC's output & the location of that out-of-spec resistor will determine which bit's voltage level it is affecting - obviously resistor on the most significant bits (MSB) will output the highest voltages so any linearity issues here will result in larger voltage errors than least significant bit errors

jkeny wrote:

nige2000 wrote:

alecm wrote:
I want to ask an advice here on r2r matrix construction. For me it remains full unclear until the end the sense resistor in bit from 0 till 2 rows. Soren calls it like “thermometer”. What is the practical sense of 0,1,2 rows? Any thoughts?

wonder if theres any point asking soren?
At worse case there will be no reply or a political type non disclosing reply

Listened for an hour with fixed 22 clk feeding fpga and the pre fpga reclocker
Im positive the adjustable clock shoud be removed and replaced with fixed clk and i2s prealigned
Resolution is immense with darker background and a level of coherance ive not experienced before
The biggest improvement since vref ;)

Wow, that's quite a jump in SQ, Nige - well done! Must get a listen to it - put it in a box & lock it :)

alecm wrote:

jkeny wrote: The accuracy of the resistors does determine the linearity of the DAC's output & the location of that out-of-spec resistor will determine which bit's voltage level it is affecting - obviously resistor on the most significant bits (MSB) will output the highest voltages so any linearity issues here will result in larger voltage errors than least significant bit errors

Yes for sure. This is the idea of my question. Recently I started to fix the resistors and found lots of unintelligible things.
Look at here (-4db is -1db in reality)



Nevertheless, on fixing resistor I didn’t received any significant results. The tricky thing, with the falling of signal, harmonics are hardly reduced. But what the most uninterpretable is their random behavior. Something is making additional instability to the result.
There are two assumptions:
-somehow affect the final result bits 0 1 2
- filters

rickmcinnis wrote:Nigel,

So you can use either "22" or "24" mHz clocks? I am assuming these are abbreviations for the typical cd player values?

Hoping I can use the 24 in the DAM and the 22 in the SDTrans while I wait.

jkeny wrote:

alecm wrote:

jkeny wrote: The accuracy of the resistors does determine the linearity of the DAC's output & the location of that out-of-spec resistor will determine which bit's voltage level it is affecting - obviously resistor on the most significant bits (MSB) will output the highest voltages so any linearity issues here will result in larger voltage errors than least significant bit errors

Yes for sure. This is the idea of my question. Recently I started to fix the resistors and found lots of unintelligible things.
Look at here (-4db is -1db in reality)



Nevertheless, on fixing resistor I didn’t received any significant results. The tricky thing, with the falling of signal, harmonics are hardly reduced. But what the most uninterpretable is their random behavior. Something is making additional instability to the result.
There are two assumptions:
-somehow affect the final result bits 0 1 2
- filters

OK, thanks but I'm not sure what this is a graph of (or many graphs overlaid)? I presume you changed all out-of-spec resistors & you are getting no reduction in harmonics but rather random increases in different harmonics?