Singxer SU-2

[joenetic]

Using it like a fancy battery is not going to work well, the ESR of a supercap is quite large for its capacity, worse than a battery, much worse than a conventional PSU.
Having the controller dynamically manage power allows the supercap to do its real work, buffer large current spikes when digital logic is running under load.
This keeps the voltage on the supercap constant, LTC4425 keeps it varying by no more than 100mV as I mentioned to you before.

Thanks for your explanation! My guess is supercap has super low ESR so that it can provide huge current in short time, I will check your solution and try it, thanks!

 

[b0bb]

Thanks for your explanation! My guess is supercap has super low ESR so that it can provide huge current in short time, I will check your solution and try it, thanks!

You also have to wait, the Eaton TVS supercaps I installed only work at specification after 72hours of charging, the ESR can drop 100x, as it stabilizes over 72 hours, if you try it after charging for an hour the results would be disapointing.

 

[joenetic]

You also have to wait, the Eaton TVS supercaps I installed only work at specification after 72hours of charging, the ESR can drop 100x, as it stabilizes over 72 hours, if you try it after charging for an hour the results would be disapointing.

I fully charged my supercap, then the ESR should also super low?

 

[b0bb]

I fully charged my supercap, then the ESR should also super low?

Only if you keep the charge topped up.
The insulator in a supercap is made from the electrolyte itself, if you remove the charge voltage, the ions drift apart and you have to wait until it reforms and the ESR drops

In a conventional cap there is a permanent insulating oxide layer, so no waiting for the ESR to stabilize.

 

[joenetic]

Only if you keep the charge topped up.
The insulator in a supercap is made from the electrolyte itself, if you remove the charge voltage, the ions drift apart and you have to wait until it reforms and the ESR drops

In a conventional cap there is a permanent insulating oxide layer, so no waiting for the ESR to stabilize.

Interesting! I need to dig into it to learn more how to use of supercap

 

[b0bb]

Interesting! I need to dig into it to learn more how to use of supercap

If you get the LTC4425 + supercap working properly, SU2 will outperform the SU6, I do not use my SU6 much these days

 

[b0bb]

To support LTC4425+supercap, the onboard power supply needs to be upgraded from 1A --> 3A
8A Schottky bridge rectifier

 

[joenetic]

To support LTC4425+supercap, the onboard power supply needs to be upgraded from 1A --> 3A

Oh...next mod after the LVDS

 

[joenetic]

SU6 has a better clock? Seems like Singxer built a oven for Crytek crystal to let it work the best

 

[b0bb]

SU6 has a better clock? Seems like Singxer built a oven for Crytek crystal to let it work the best

If you replace the stock Accusilicons with the CHD957 you will be using the same XO as SU6
Oven not really needed, just keep the top cover on, internal heat in SU2 keeps things pretty constant
SU6 has slightly better regulators for the XOs but the TPS20A pretty much eliminated the advantage, it did not exist when the SU6 was designed.

 

[joenetic]

To support LTC4425+supercap, the onboard power supply needs to be upgraded from 1A --> 3A
8A Schottky bridge rectifier

I checked LTC4425, it is a charger controller, why it can help to improve sound quality? According to your demo before in attached photo, when supercap is fully charged, the relay switch so that charger board power SU2, LTC4425 keep charging supercap and power SU2, or say LTC4425 and supercap both power SU2, is it correct? My question is how LTC4425 improve sound quality? I think both or LTC4425 provide current to SU2 in higher percentage than supercap. This circuit can keep supercap fully charge or close to fully charge, so that supercap has lowest ESR, is it the point ?

 

[b0bb]

I checked LTC4425, it is a charger controller, why it can help to improve sound quality? According to your demo before in attached photo, when supercap is fully charged, the relay switch so that charger board power SU2, LTC4425 keep charging supercap and power SU2, or say LTC4425 and supercap both power SU2, is it correct? My question is how LTC4425 improve sound quality? I think both or LTC4425 provide current to SU2 in higher percentage than supercap. This circuit can keep supercap fully charge or close to fully charge, so that supercap has lowest ESR, is it the point ?

That is correct, the LTC4425 acts as a conventional low noise LDO regulator when the super cap is charging.
This was one of the big missing items when you tried to use the supercap as a big battery.

Without a proper voltage regulator the supply lines sag and things like the digital comparators stop working properly and your jitter goes thru the roof.
The SPDIF and I2S output performance will also start to get affected as the LVDS transmitters are sensitive to voltage fluctuations.

It also controls the charge rate to keep EMI and RFI noise under control, EMI and RFI is generated whenever a large amount of current flows is a very short time.
In your uncontrolled case, it got so bad you actually heard it, this drowns out any possible improvements.

Supercap is relatively young, the best ones operate at 3V (best ESR, reliability, leakage etc) , LTC4425 has balancing circuitry to allow 2 caps to operate in series without the usual problems.

Digital power loads are very bursty and supercaps were designed specifically to cater for that need, but it cannot do that without the support of a proper controller

LTC4425 is the house keeper that does all the delicate charge balancing, without that the supercap might operate optimally for a few seconds and it goes down hill very quickly after that, it is the bridge that keeps the SU2 properly supplied with power while the cap recovers from the previous burst.

 

[joenetic]

That is correct, the LTC4425 acts as a conventional low noise LDO regulator when the super cap is charging.
This was one of the big missing items when you tried to use the supercap as a big battery.

Without a proper voltage regulator the supply lines sag and things like the digital comparators stop working properly and your jitter goes thru the roof.
The SPDIF and I2S output performance will also start to get affected as the LVDS transmitters are sensitive to voltage fluctuations.

It also controls the charge rate to keep EMI and RFI noise under control, EMI and RFI is generated whenever a large amount of current flows is a very short time.
In your uncontrolled case, it got so bad you actually heard it, this drowns out any possible improvements.

Supercap is relatively young, the best ones operate at 3V (best ESR, reliability, leakage etc) , LTC4425 has balancing circuitry to allow 2 caps to operate in series without the usual problems.

Digital power loads are very bursty and supercaps were designed specifically to cater for that need, but it cannot do that without the support of a proper controller

LTC4425 is the house keeper that does all the delicate charge balancing, without that the supercap might operate optimally for a few seconds and it goes down hill very quickly after that, it is the bridge that keeps the SU2 properly supplied with power while the cap recovers from the previous burst.

Thanks for your detail explanation! But how can you know SU2 is powered by LTC4425 or supercap? Without LTC4425 constant charging voltage( second stage is constant voltage charging right?), supercap discharging and voltage drop, so I think major supply is LTC4425.

I ordered a similar gear during I tested supercap with SU2, it is similar to your circuit but short circuit the LTC4425, so my LPS power the super cap and output device directly, it has positive effect on my Rpi but no effect on SU2.

 

[b0bb]

Thanks for your detail explanation! But how can you know SU2 is powered by LTC4425 or supercap? Without LTC4425 constant charging voltage( second stage is constant voltage charging right?), supercap discharging and voltage drop, so I think major supply is LTC4425.

I ordered a similar gear during I tested supercap with SU2, it is similar to your circuit but short circuit the LTC4425, so my LPS power the super cap and output device directly, it has positive effect on my Rpi but no effect on SU2.

There is no "either", the controller and supercap can be both supplying current to the load at the same time.
The supercap is integral to how the LTC4425 works. It is not an "add-on" to the supercap. The current control feedback loop includes the supercap and is how the chip manages the dynamic charge balancing.

Without looking at the schematic, I would not call your gear "similar" if it did you would have seen an improvement.
It looks like a simple charge balancer and not a proper charge controller.
The caps are too small, probably not up to the task of supplying the transient current for SU2
Specs of the cda caps are worse than the 3year old Eaton TV series I used, expected better here.


If you want to replicate my improvements, you have to use the exact board I am using, no substitutes.

 

[joenetic]

There is no "either", the controller and supercap can be both supplying current to the load at the same time.
The supercap is integral to how the LTC4425 works. It is not an "add-on" to the supercap. The current control feedback loop includes the supercap and is how the chip manages the dynamic charge balancing.

Without looking at the schematic, I would not call your gear "similar" if it did you would have seen an improvement.
It looks like a simple charge balancer and not a proper charge controller.
The caps are too small, probably not up to the task of supplying the transient current for SU2
Specs of the cda caps are worse than the 3year old Eaton TV series I used, expected better here.


If you want to replicate my improvements, you have to use the exact board I am using, no substitutes.

Got it, I will try it later, thanks for your advice!