ProtoDAC TDA1387 X8 project

[hifinet]

Same module on eBay . Less expensive. Alibaba

[OnkelPH]

Same module on eBay . Less expensive. Alibaba

Wow, that’s a lot of good knowledge and advice. Thank you. The Ali one is on its way, and hopefully that will work with your mods. It would be fun if it did. I got 5.046v from the rpi with a 5v PS. I’ll might try a 5.1v to see if I get more headroom before the LT1963. 
That’s it for now. I’ll report back when the parts are here and ready for testing.

[OnkelPH]

Try this AliExpress

This seller will send me a 4.7v version.

[hifinet]

Just to announce that I am running out of the WIMA MKP 4 caps. I plan to ship the kits with the Audiophiler MKP Kondensotor (yes, the name is terrible) red axial caps. Axial works better with the PCB. The Audiophiler are rated about the same (actually, slightly better) as the WIMA in the Humble Homemade HiFi ratings . Trying to keep the cost of the kits low. The TX2575 are the difficult parts to obtain, and I think they are worth the extra cost.

[hifinet]

Listening to the 2S 18650 LifePO4  plus LT1963 (with added 10uF Sprague 150D tantalum cap on the output). Without the BMS, since it's simpler and I figured if it doesn't sound good without the added resistance of the MOSFETs in the BMS, there is no need to try it with the BMS. Manually monitoring the battery voltage to prevent overdischarge.  Plan to run them no lower than 6.0V.

Same setup as before, powering the RPi Zero W/Allo Kali/ProtoDAC stack.

It is definitely softer sounding than the ultracap supply of the PurePi, which I think is a good thing. This particular Sprague 150D is decades old, and needs to break in. These are hermetically sealed caps. Sold now as Vishay Sprague 150D Solid-Electrolyte TANTALEX ™ Capacitors.

MOSFET switches used in the PurePi are HYG023N03LR with Rds(ON) of 2.7mOhms.
MOSFET switches used in the cheap Ali BMS are PTD 60N02 with Rds(ON) of < 6mOhms.

[wolf7250]

Listening to the 2S 18650 LifePO4  plus LT1963 (with added 10uF Sprague 150D tantalum cap on the output). Without the BMS, since it's simpler and I figured if it doesn't sound good without the added resistance of the MOSFETs in the BMS, there is no need to try it with the BMS. Manually monitoring the battery voltage to prevent overdischarge.  Plan to run them no lower than 6.0V.

Same setup as before, powering the RPi Zero W/Allo Kali/ProtoDAC stack.

I'm struggling to picture what this looks like?
It sounds as though you are pleased with the output? Does that mean that your final configuration with this setup will involve the BMS from AliExpress?

Is this the Capacitor you mentioned Vishay Capacitor? And you soldered this onto the output of the LifePO4 supply?

[hifinet]

The two LifePo4 batteries in a 2S (two in series) battery holder. Switch and cheap wires removed. Attached the LT1963 with 10uF 35V cap on the output. Wires with DC barrel jack to Kali. That's it. 

Listened for 4 hours. The tantalum cap is sounding better. I like it. It sounds very nice. The LifePO4 battery supply is just a bit softer than the ultracap supply.

When finished listening, remove the batteries from the holder. 2S battery voltage was 6.48V, so this could power the stack for a few more hours.

The PurePi serves as my battery charger. You could use one of these instead.

[wolf7250]

Cool thanks! This sounds like a very cost effective option. You did mention way back that you thought it would be <$20.

Does the order of the LT1963 or 10uF Cap matter? I.e. does the LT1963 connect to the battery holder output and the 10uF Cap connect to that? Or vice versa?

Do you pop the LifePO4 into the battery holder on the PurePi for charging?
Could there be an option where batteries do not need to be monitored and a power supply can be left connected so that the batteries don't need to be removed for charging?
Does that make sense?

[wolf7250]

What you are building looks and sounds similar to this from IanCanada correct?
LifePO4 Mini 3.3V or 6.6V Battery Power supply


This system means you don't need to shutdown the Pi to remove the batteries to charge them.
And could you use the LT1963 to change the output voltage from 6.6V to 5V?

[hifinet]

Much, much simpler. The LifePO4 Mini 6.6V without the battery management system, and with a 5V linear regulator on the output to get 5V. There is no undervoltage protection. No charging circuit.

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