[b0bb]

If I understand correctly the resistor near the blue capactor is 22ohm? In the Gen2 there are no such resistors, could it be added?

If you mean below the yellow cap, that is the 22ohm.
Yes the 22 ohm can be added.

 

[b0bb]

So the bigger the tantalum cap the better and the optimum is 680uF? For the Gen2 it isn't true?

Applies for Gen2 as well.

Optimum is about 2200uF, the transition point is about 20Hz, 268USD each at Mouser and you will need 2 pcs.
I was not joking about the cost prohibitive comment.

680uF takes things down to 75Hz, about 90USD each.
150uF takes things to 350Hz, about 40USD each.

Either choice is going to be a vast improvement from stock, the transition point is 5kHz for stock.
It boils down how much bass improvement, you can afford

 

[Xoverman]

Applies for Gen2 as well.

Optimum is about 2200uF, the transition point is about 20Hz, 268USD each at Mouser and you will need 2 pcs.
I was not joking about the cost prohibitive comment.

680uF takes things down to 75Hz, about 90USD each.
150uF takes things to 350Hz, about 40USD each.

Either choice is going to be a vast improvement from stock, the transition point is 5kHz for stock.
It boils down how much bass improvement, you can afford

What about an active 1ppm reference?

 

[ti5002000]

It is not "my mod", I posted the mod in #3332 for Tiago.
@tiago please join the discussion and share your impression of this mod.

The RC that I was referring to is the Time Constant to replenish the voltage due to leakage.
See diagram.
Vcom ideally should stay constant. Practically it is performed by the (equivalent) resistor R and capacitor C.
I don't know why these values were picked.

I know nothing about op-amp frequency compensation.
I agree that the input impedance of both inverting and non-inverting inputs should not be varied too much.
But this is not possible due to frequency dependency of the impedance of Vcom capacitor C.

The 150uF wet tantalum cap mod also modified the input impedance by 15x too.

What is the spectrum of frequency of this Vcom capacitor C subjected to ??? Do you know ?
The output of the DAC is a sequence of sigma-delta spikes (I could be totally wrong here) which
may have all kinds of frequencies. This is my guess.

Hi

What I can say is that the modification in the resistors was given to me by Jinbo, the creator of our dacs, when I asked him if I can use the 0.1 uf of the 005. He said yes but I have to change the resistors in the picture he sent me and that you posted here.

Best

 

[piaseczek]

Applies for Gen2 as well.

Optimum is about 2200uF, the transition point is about 20Hz, 268USD each at Mouser and you will need 2 pcs.
I was not joking about the cost prohibitive comment.

680uF takes things down to 75Hz, about 90USD each.
150uF takes things to 350Hz, about 40USD each.

Either choice is going to be a vast improvement from stock, the transition point is 5kHz for stock.
It boils down how much bass improvement, you can afford

Maybe something like this is a good compromise?

https://pl.mouser.com/ProductDetail/AVX/TAP337K006CRW?qs=Ceko5R2PisCcUwtefFpTaA==

 

[b0bb]

What about an active 1ppm reference?

The topic here is low frequency AC bypass, that has to be done for any method used to generate the Vcom voltage.
The stock DAC has inadequate LF AC bypass for Vcom.

If you want to provide adequate LF AC bypass going down to 20Hz then the bypass cap is quite big.

The wet tantalums allow large values of capacitance to be used without leakage causing unwanted side effects unlike Alumninum or Polymer caps where leakge increases linearly with capacitance

 

[Whitigir]

Applies for Gen2 as well.

Optimum is about 2200uF, the transition point is about 20Hz, 268USD each at Mouser and you will need 2 pcs.
I was not joking about the cost prohibitive comment.

680uF takes things down to 75Hz, about 90USD each.
150uF takes things to 350Hz, about 40USD each.

Either choice is going to be a vast improvement from stock, the transition point is 5kHz for stock.
It boils down how much bass improvement, you can afford

Dang! this is 1/2 the price of the 004 used lol! So we take out the 2 of 63uf and put these 2 in ?
https://www.mouser.com/ProductDetail/Vishay-Tansitor/STE2200-50T4KI?qs=bhRDl8yh5u3yhXfMyln8OA==

 

[b0bb]

Hi

What I can say is that the modification in the resistors was given to me by Jinbo, the creator of our dacs, when I asked him if I can use the 0.1 uf of the 005. He said yes but I have to change the resistors in the picture he sent me and that you posted here.

Best

Was this a recommended upgrade or a "try at your own risk" type of change?

(LKS's decisions can sometimes be very odd, case in point is the XO, they have stubbornly refused to offer a better XO for the 004.
This is the first item that gets tossed out as you yourself have done with the SiTime SIT-5357)

 

[b0bb]

Maybe something like this is a good compromise?

https://pl.mouser.com/ProductDetail/AVX/TAP337K006CRW?qs=Ceko5R2PisCcUwtefFpTaA==

That is a starting point.

 

[b0bb]

Dang! this is 1/2 the price of the 004 used lol! So we take out the 2 of 63uf and put these 2 in ?
https://www.mouser.com/ProductDetail/Vishay-Tansitor/STE2200-50T4KI?qs=bhRDl8yh5u3yhXfMyln8OA==

Try pulling the 0.1uF bypass I mentioned earlier before trying anything like the above.

 

[ti5002000]

Was this a recommended upgrade or a "try at your own risk" type of change?

Bobb
Why he would do that?
Why would he have the work to do a picture with certain resistor values, if it wasn't safe and he know it is ok?
After all, we all enjoying his creation.
They made some bad choices in the layout but they also made very good ones. If it weren't from lks we aren't here taking about this fine DAC today.
He didn't say that I can try and see for yourself.. That kind of thing.. He just said, yes, you can use it but you have to change the resistors.
In the end, the mod is in the picture.
If you want to go that route, so be it, if you want to go by b0bb's, so be it.
In the end we must do what we think is best and that would make us enjoy the music even better.

 

[Whitigir]

My apologies, I have not been following for a while. So this long vertical is the Vishay expensive cap, and this is the wima to replace RK ? What is the part for it ?
about the trim pot, if replaced, do we need to adjust anything ? @b0bb

 

[b0bb]

They made some bad choices in the layout but they also made very good ones. If it weren't from lks we aren't here taking about this fine DAC today.
He didn't say that I can try and see for yourself.. That kind of thing.. He just said, yes, you can use it but you have to change the resistors.

That is a bad recommendation just like their decision to stick with the CCHD-575 XO
You yourself replaced it with something better.

 

[b0bb]

My apologies, I have not been following for a while. So this long vertical is the Vishay expensive cap, and this is the wima to replace RK ? What is the part for it ?
about the trim pot, if replaced, do we need to adjust anything ? @b0bb

Just remove the red WIMA, no need to re-adjust.
I swapped out the original cap for the WIMA, I ended out removing the cap totally.

The WIMA bypasses the 22ohm resistor which matches the input impedance of the I/V to the DAC's output impedance.
This causes the diffrential inputs of the I/V to see different impedances at higher frequencies (above 70kHz)
LKS got rid of it in the Gen2 board as well.

If you replace the long vertical cap then you have to re-trim due to a reduction in leakage.

 

[Whitigir]

Ah man... this is killing me. I want more bass slam for sure but all these wet tantalum Vishay are so expensive LOL!