Soekris Dam Dac

[nige2000]

things getting quiet here ?

my post from diya
feedback from this might be interesting over there :)

put the scope on the clock output couple of days ago and was less than excited about the waveform
got me thinking that sharing one cell with the clock, fpga, microcontroller, usb to i2s device and the + vref rail might not be so hot of an idea

so i added another cell just for the vref so that +/- vref has a cell each and the 'front end" has its own cell

wouldn't mind this one was supposed to be the minimalist version

anyway soundstage opened up a little more, clarity, focus etc
thats not really that surprising after all i was dumping all the front end digital noise on + vref

As im a big fan of providing exceptionally clean power to clocks
for fun i bridged a wire direct from where i inputed the 3.3v rail into the board to the clock ps pad
i wasn't expecting any improvement but the sq resolution had increased
i was so surprised i ab tested a few times to make sure


i also ran a bridge from clk gnd
i ab tested it too
it might have helped a bit but its not a big enough change to be absolutely positive, im gonna leave it there for now as it sure aint doin any harm

put the scope on the clock again the waveform is much better but not as good as id like

[rickmcinnis]

You are so far ahead it is hard to know what to say.

One thing would make it easier for us to follow is with a little more detail.

It looks like Vref stuff is still there but since your photography is as good as mine I am not sure what I am seeing there. It does seem we should remove it.

I am confident I understand the battery wiring to the Vrefs - I wonder if we should use a pair for each channel, though I know that is overkill. I can see advantages to either approach.

A list of what has been removed would be helpful. A shorter list might contain what is left!

I know you have removed the rectifier, all capacitors, the 3.3 volts reg, the +- 5 volts regs (of course the buffer op amps) but I cannot tell from the photograph if the Vref stuff is still there. I am ready to do this today (the irony after going to so much trouble to change out those damn resistors which I assume I will be removing) but want to be sure before I make this big move.

If you get the time please make this clear.

Thanks and take care,

[nige2000]

heres what ive removed so far

[rickmcinnis]

That's what I thought but I appreciate the clarification.

Now to the clock - top left hand side is voltage in. But it looks like you have two wires - do you have an extra ground wire, also? Is that ground going back to the original power input ground?

So there is the red wire from a 26650 going to the tab pad where the 3.3 V reg once was. Looks like there is a green wire going from pin2 pad from the same removed regulator to the clock voltage pin. But what confuses me (like in Sympathy for the Devil) is the other green wire going from what looks like this same place (the clock voltage in pin) back to the power input. is this an illusion or do you have the power coming from both places?

Since you are good at drawing on that photo would you be inclined to make lines for the connections to the clock? And everything else for those who would rather be completely comfortable before proceeding? Needless to say the clock thing can be done later as well as the 1.2 V linear reg swap. Sure wish that thing was never used in the first place. Hope it is easier to deal with than the resistors which I could not replace myself.

You are using the standard power input for (3.3 v) for the 1.2 V reg - I do not know if that is powering anything else but a separate lead from the same battery is going to the output pin pad for the 3.3 V regulator, now removed?

With it clear that the Vref opamps are gone all of that is clear. Did you remove the resistors and caps? Are you connecting to the pad or to the top of the capacitor? I assume all of the battery grounds are connected to the original power input ground and that suffices for the whole board?

I assume you are only switching on and off after the battery's outputs?

No opinion on doubling up the Vref batteries?

All of this is so simple as to make one ask questions just to be sure!

I posted on mravica's thread a question asking when the TI reg will be available.

This fellow is offering the more fiddly version: http://www.ebay.com/itm/252148774110?ss ... rmvSB=true

Now to see if I destroy that board!

[nige2000]

That's what I thought but I appreciate the clarification.

Now to the clock - top left hand side is voltage in. But it looks like you have two wires - do you have an extra ground wire, also? Is that ground going back to the original power input ground?

https://www.silabs.com/Support%20Docume ... /si570.pdf
power is pin 6 gnd is pin 3
gnd is merged into main gnd return wire

So there is the red wire from a 26650 going to the tab pad where the 3.3 V reg once was. Looks like there is a green wire going from pin2 pad from the same removed regulator to the clock voltage pin. But what confuses me (like in Sympathy for the Devil) is the other green wire going from what looks like this same place (the clock voltage in pin) back to the power input. is this an illusion or do you have the power coming from both places?

power is coming from both places

Since you are good at drawing on that photo would you be inclined to make lines for the connections to the clock? And everything else for those who would rather be completely comfortable before proceeding?

ok

Needless to say the clock thing can be done later as well as the 1.2 V linear reg swap. Sure wish that thing was never used in the first place. Hope it is easier to deal with than the resistors which I could not replace myself.

steady hand needed

You are using the standard power input for (3.3 v) for the 1.2 V reg - I do not know if that is powering anything else but a separate lead from the same battery is going to the output pin pad for the 3.3 V regulator, now removed?

same cell for 3.3 and 1.2v reg

With it clear that the Vref opamps are gone all of that is clear. Did you remove the resistors and caps?

no i didnt remove them

Are you connecting to the pad or to the top of the capacitor?

top of capacitor for now

I assume all of the battery grounds are connected to the original power input ground and that suffices for the whole board?

yes main gnd connection is fine for all gnds

I assume you are only switching on and off after the battery's outputs?

two switches one for charging cells and one for power to dac

No opinion on doubling up the Vref batteries?

yes you could add more cells and connect them at the shift registers like the other lads did with the caps this will be the most effective noise control but who knows if it will sound any better

All of this is so simple as to make one ask questions just to be sure!

I posted on mravica's thread a question asking when the TI reg will be available.

This fellow is offering the more fiddly version: http://www.ebay.com/itm/252148774110?ss ... rmvSB=true

Now to see if I destroy that board!

all joking aside its not difficult only takes 1 mistake and its toast

[randytsuch]

Hey guys
So after starting this thread, and taking a LONG break from this project, I'm back :)

I've been finally working on the board the last couple of days. Setting up a RS-232 converter which I'll try in a little while, and for now I'm just going to power the boards with a couple of walwarts.

I also removed the 4 output opamps. Will probably also remove the caps on the outputs.

Later, I'll start removing the 4v opamps and the other regulators, and use lifepo4 cells to provide power.

Thanks for keeping things going
Randy

[rickmcinnis]

Thanks for that, Nigel.

I was planning on using the "caps mod" approach for connecting the two sets of batteries.

More than anything I like the idea of using multiple leads since they have to be so small, four has to be better. I will sleep better at night ... i am assuming you are using wire small enough to pass through the vias?

Got the opamps off without incident.

Now to wire up the switches and batteries.

AS tedious as that is installing all of those power leads will probably result in early cocktails.

Yes, I am taking this very slow and deliberate with lots of magnification to look for stray bits of solder.

But the elegant simplicity of it sure appeals to my sense of audio design aesthetics.

One can only say your extended period of meditation sure resulted in a burst of activity. I won't complain next time ...

With sincere gratitude,

[rickmcinnis]

This may be something to consider for the Vref battery charger:
http://www.mouser.com/ds/2/405/lp2986-441300.pdf

The one mravica uses is specified at 2.5% voltage accuracy.

This one is 0.5%. Which should be pretty good. You can also make it adjustable but one wonders if that would affect long term accuracy? Would they drift equally? I am assuming we could use the same configuration as mravica - two postive regs for both polarities.

[nige2000]

these rated for 1 amp?

i know nothing about those regs if the batteries get depleted say to 2.5v they will pull 0.5amp per cell out of the reg will it burn out or will it just output 1 amp and charge slower?

im goin for a beer
happy soldering and check your work before power up
we dont want soren retiring early on us:)

[rickmcinnis]

No, 200 mA.

Are you not float charging?

Enjoy the beer!