Soekris Dam Dac

[nige2000]

J1 isn't powered so no power going to old reg
But i intend to take it off just in case

[nige2000]

Apologies you are right my memory of the order of events is wrong, doesnt matter anyway i didnt know what ccs was at that time
your reading too much into it chill:)

OK, thanks - correct attribution of ideas is always appreciated :)

no problem

[nige2000]

Removed the 1.2 V reg.

Looks like we need to jumper between pins 3 and 6?

why jumper?

[rickmcinnis]

That was before I realized that the "test points" connection goes to the FPGA.

I have this annoying habit of asking a question and then taking a look at the board.

I will try to get better.

I had one via that was smaller than the rest and had to use a smaller gauge wire. I guess one will not be a problem.

Finishing this message and I wonder if anyone has ever come close to writing a message with 59,999 characters? It is almost a challenge.

Back to work ...

[randytsuch]

So status update on my dac.

I bought a couple 4 pole double throw relays on Monday, need 24VDC to activate. So, made a simple, unregulated 24vdc supply. It uses a ac walwart. Stuck a bridge and cap and switch in a little box that I had, and it works fine. As far as I can tell, the relay has no detrimental effects.

Right now, I just have one relay, controls +/- 3.3 to the shift registers, +3.3 and +V. +V still powers the 1.2V switcher.

When I did this, I decided to add wires from the relay to each shift register. So I have 16 wires, 8 for +3.3 and 8 for -3.3. The first two were connected directly to the shift register, but I keep making solder bridges that I had to clear, so the rest are connected to the cap next to the shift register, which is much easier. It actually went pretty fast once I got going.

I wasn't sure if it would make a difference adding all of those wires, really didn't think it would. But, I'm pretty sure it's better this way. I have to go by memory, but I think bass is better, more impact, and that there is better separation of instruments, and a little more detail. To me, it was worth it. Hopefully others will try and report.

Other thing I did was to add a battery for 3.3V. As I said, it's switched through the relay. I added a switch to control the charging voltage to this battery. I also added a separate 3.3V regulator for this battery. I will use this regulator for this battery, and the one I add to power a 1.2V regulator. That will be the next change.

Had a minor problem when I first connected the 3.3. I cut off the three pins of the 3.3 on board reg, and then heated the tab to pull it off. Connected 3.3V to the tab, and no led :(. I went away for a few moments, and then figured out the tab was probably isolated, and it was. Tab has 3.3V when you power it on, but that connection is made through the on board reg. After you remove the reg, the tab is not connected.

So moved the wire to pin 2, and the led came on :). This was the last change. Only had a quick minute to listen, and wasn't properly warmed up, but I think it does sound better, even quieter background with more details.

Next set of changes will be to add a 2nd relay, and then another battery and a 1.2V linear reg. I'm going to try a LT1764 and see if it will put out 1.2V. That is supposed to be the minimum voltage it will produce. I'm using this because I have some in my parts drawer.. So far, for all of the mods I've made, I've used mostly parts I had on hand, except for a couple of ebay switches and a trip to Fry's.

The 2nd relay will control the 1.2V power, and power to the Amanero board. I also have a exD USB to I2S board I want to try, and it would be used for that too.

EDIT: Oh, and I still have to download the partypak filter set, and try different filters.

Randy


https://goo.gl/photos/KCBL5jVvzMYb8Udp9

https://goo.gl/photos/NNcwEdMZ7s6YqpTw6

https://goo.gl/photos/Sqifd8HdNqjHM1EV6

[nige2000]

Cool stuff
I wasn't so sure wiring direct to shift registers would make that much difference
But it still needed to be tested as to leave no rocks unturned
And its just the type of improvement you get with better power and power implementation
So I'll hopefully do the same next

[rickmcinnis]

I do have relay-phobia so I am sticking with a manual switch.

My wires to the shift registers are very short with the batteries placed underneath the SOEKRIS board. Using the vias so the wires are already under the board.

The switch is my star ground - all of the batteries grounds are connected to the switch and then a wire from the other pole connected to the ground holes in the SOEKRIS board. Since my +- reg shares its ground for both polarities I am using just one ground wire for each pair of batteries for the shift registers - total of three wires attached to the switch.

I am using the clock's battery to power the 1.2 volt regulator. Which is what I think Nigel is doing.

My switch is mounted above the board to minimize wire lengths. I figure I can get away with the longer lengths on the ground side.

I have removed all components to the right of the resistor stacks. Asked the lady who installed the resistors I have now discarded if she will replace those caps and she says she will. AS soon as I get those installed Nigel will find a better way!

I think both of you are using too much wire but I admit I could have a wire length fetish.

[randytsuch]

I do have relay-phobia so I am sticking with a manual switch.

I used relays in my PC to turn on power, before relays I had 4 switches and it was too much of a pain to turn on and off. Now I turn on one power supply, and then push the PC power button.

I am using the clock's battery to power the 1.2 volt regulator. Which is what I think Nigel is doing.

I was wondering how Nigel was powering his clock. I know it's not on the board 3.3V.

My switch is mounted above the board to minimize wire lengths. I figure I can get away with the longer lengths on the ground side.

No, not really. The ground wire is just as important. For the two shift register batteries, I ran a piece of copper tape from the battery ground to the board ground. It's almost like a continuation of the board ground plane, provides a very low impedance ground to the batteries.
Otherwise, power and ground should be run as twisted pairs, but that would have been a pain for the 16 shift registers.
And for the other battery, I soldered the ground tab directly to the board.

I think both of you are using too much wire but I admit I could have a wire length fetish.

I thought my wire runs are pretty short. One reason to use a relay is so I could use a couple, which helps keep the wires shorter. I'm curious now to see how you did it.

It sounds like you made the + wires very short, but at the expense of the ground wiring. IMHO, both sides need to be considered. And I'm sure there are other ways I could have wired it up, but it's wired now, and it sounds pretty damned good already, so it is unlikely to change (at least not that part of it). :)

Randy

[rickmcinnis]

Randy,

Of course, the ground line is important but one must make a choice. The layout kind of determined itself. Easier to have the vias anchor the wires to the shift registers and that results in the wire exiting the back of the board, hence placing the batteries under the board which results in minimal length of the "hot" leads.

The wire to the positive end of the batteries are not quite 2.5 inches - grounds to the switch will average about seven inches, if that much. I figure the best ground point is the original input ground and that determines the length possible. It is far way from the batteries but there is not a suitable ground point anywhere else. I want something of substance to tie into and not a SMD pad.

Impossible to run twisted pairs. I am only attaching to the"non-ground" side of the of the shift register. Twisting is more of a factor for AC signals, not DC, anyway. I do not see any twisted pairs in your photo so I am baffled by this comment.

I cannot picture where you are attaching the copper tape. Is this coming from the input ground? I do not see any advantage to using foil/tape as opposed to stranded wire. The foil would have to be pretty wide to be the equivalent of a 16 gauge stranded wire. I am using some old WE wire that sounds really good as a speaker cable and I have some left over. Foil, alone, does not make a ground plane

I think it is important to have all power grounds meet in one spot and not be scattered about the board. Another one of those phobias.

You have me soundly beat by having that green LED lit. I hope to be able to see that on my board by this weekend I know I could well have something to be thrown away. Luckily, there is always the turntable ...

[nige2000]

i wouldn't get too hung up on cable length between batteries and board,
i consider it one of the sins battery lets you away with for the most part

ive a 3.3v cell (separate from vref cells) for on board clock fpga, 1.2v linear reg and usb to i2s device