Soekris Dam Dac

[nige2000]

No, 200 mA.

Are you not float charging?

of course sure didnt i invent it :)

Enjoy the beer!

maybe a little too much ;)

please tell me the dam's still alive?

[nige2000]

mother f**ker lost my long post
logged me out

so yr gettin the short version

enjoying the fruits of this weeks labour
live stuff is exceptional




its got that live venue feel, the fast transients and subtlety that by and large digital audio fails to achieve
i was gonna say its 3d but that term gets overused im gonna call it 4d
its the dimension that vinyl has that digital isnt even aware of its existence
the vinyl experts like derek and ivor on the forum here will know what i mean (although im not sure they read these threads)
its an immeasurable dimension

i think/hope they think were getting somewhere with our dac experiments
the current implementation is easily 30% better than the last time they heard it
i feel that we've achieved a level of sq that will tip the vinyl guys over the edge into digital
not that im a vinyl fan but i can appreciate what it does well
i feel theres a little more in the tank yet to be realised if we can learn enough to achieve it
in digital audio it seems when you solve one issue you highlight the next
hopefully we wont have to use the old skool method of use valves to dumb down and smooth out
(provocative :))

anyway the future is bright!

still prefer dereks vinyl version

must be a different master/recording or something

[rickmcinnis]

Still alive as far as I know. Haven't turned it on.

I decided, since you have proved this works, to make a more permanent installation so it is taking longer. Wires will be as short as possible. Fixing the ground break switch in a fixture above the board and fixing the batteries in place below.

SO, if you are float charging, why the concern over the suggested reg's current rating? From what I have read 200 mA per battery should be more than sufficient to keep up with demand. With four batteries I am guessing 8 mA per though I do not really know.

(I think you started on those beers earlier than you said!)

I am anxious to hear what it can do but would rather be ploddingly careful instead of rushing. Plus I have my reference available to keep me satisfied, the trusty, but every bit as tweaky analogue set-up.

You must be perfectly happy with 3.3 volts on the stack. Do you have to turn the volume control up any further than you did before?

[nige2000]

you no power outages over there?

volume seems the same i didnt measure it

[jkeny]

Rick,
If running +/- 4V from 4 batteries (2 in series on each side) you are running them at below their minimum recommended voltage (2.7V) so it's a very sub-optimal setup & I would suspect that this will be a problem.

Charging at these voltages really means that you are not trickle charging the batteries - they will act as fully discharged & draw the max current that the charger can provide (these batteries can recharge at 20Amps if the charger can do this). This may or may not be a problem for the charger, depending on its thermal build?

Furthermore, putting 4V into 2 (3.3V) batteries in series is a recipe for failure as it is not balancing the voltage to each battery so one battery. It may not be such a big problem as this is close enough to the battery's max voltage of 3.8V to not kill one of the batteries but I could see one dead battery in the series being the result of this scheme over a longer period of time. This is a difficult one to predict as when a battery imbalance starts, it becomes a cascading effect - it will take up less current & the other battery more until one or both die.

I've said all this to Nige & he disagrees with me on some of this as his experience suggests that a batteries in series work fine in this sort of config. That may well be the case because the current drawn (& therefore current fed from charger) is so small that a battery imbalance isn't happening to a large extent or it may be that he is lucky & his batteries are well matched to start with? Or it may be that he has a dead cell in there already? A dead cell in a series will not be seen when the series is being constantly charged.

Sorry, Nige, hope you don't mind me writing this (I've said most of it to you already) but I just feel that batteries in series with trickle charging is a wrong config when no balancing circuitry is used & my experience with balancing circuitry (at least the ones I've tried) have a detrimental effect on the clean power that these batteries provide.

That's why I suggested to Nige that using +/- 3.3V for DAM vref is probably better & to suck it & see. I too predicted a small drop in volume but it appears this isn't audible. Neither is it audible going up to 5V (he has tried this) so I don't know what's happening here. I know he reported 6V as audibly a bit strained but this may be for other reasons.

[rickmcinnis]

No, I am running two pairs of batteries (or will be) for each channel, each polarity, and sticking with Nigel's recommendation that 3.3 volts is sufficient. Only one battery per rail.

No question running 26650s at 2 volts would be a bad idea!

I am tempted, after all is actually running well at 3.3, to creep up the voltage and see what happens.

With the negligible current draw one wonders what would happen as you near 4 volts on one cell. After all you can charge them with 4 volts.

Do you think this is asking for trouble?

Thanks for your concern and your counsel.

[rickmcinnis]

you no power outages over there?

volume seems the same i didn't measure it

It took me awhile to get what you are saying. We do not have power outages very often.

Yes, I do plan on keeping the thing on all of the time so if there was one while at work and I left it on there would be the problem of the battery running the DAM and the regulator. I wonder how long it would take to bring the battery down with an extended power loss? Ours are usually less than fifteen minutes and rarely anywhere near that long. Compromise is always with us.

I wonder if battery power might negate the benefits of running the thing all of the time? I wonder if shift registers work better after "warming up"? I guess the clock would work better after being on awhile.

If you do not detect a volume change then no need to measure it. One more thing to make one think that 3.3 is just fine. Makes one wonder why SOEKRIS picked such an odd value for the voltage ... One thing for sure the batteries have infinitely better current delivery than that opamp based reg/reference which could well explain the ability to get by with less. Has anyone ever measure just how close those SOEKRIS regs track each other's voltages?

jkeny, what do you think the real world capability of those reg/refs to supply "equal" voltages would be over time?

What soldering iron do you use for your SMD work? What size tip? I am thinking my setup is just too large and I might be better off getting something more suitable before soldering anything to the board.

I worry that the more I obsess these details the more certainly there will be that the thing will blow up upon first turn-on.

[jkeny]

No, I am running two pairs of batteries (or will be) for each channel, each polarity, and sticking with Nigel's recommendation that 3.3 volts is sufficient. Only one battery per rail.

I'm not with you here - maybe I'm dense? You have two pairs, that's 4 batteries on each channel? So you are putting 2 batteries in parallel for +3.3V & two in parallel for -3.3V, right? BTW, you should share the vref between both L & R channel

No question running 26650s at 2 volts would be a bad idea!

I was talking about 2 batteries in series (on each polarity) & using them for getting the original +/-4V vref of the DAm DAC - this was Nige's config originally which I was talking about.

I am tempted, after all is actually running well at 3.3, to creep up the voltage and see what happens.

With the negligible current draw one wonders what would happen as you near 4 volts on one cell. After all you can charge them with 4 volts.

Do you think this is asking for trouble?

Thanks for your concern and your counsel.

I think it's pointless (according to Nige's reports of 5V sound) & asking for trouble - who said you can run these batteries at 4V? 3.8V is considered max. OK, I know datasheet maximum voltages can be exceeded (DDDAC's PCM1794 DAC for instance) but there are audible gains realised with these overvoltages - in this case there doesn't appear to be any upside to this, only downsides.

[jkeny]

you no power outages over there?

volume seems the same i didn't measure it

It took me awhile to get what you are saying. We do not have power outages very often.

Yes, I do plan on keeping the thing on all of the time so if there was one while at work and I left it on there would be the problem of the battery running the DAM and the regulator. I wonder how long it would take to bring the battery down with an extended power loss? Ours are usually less than fifteen minutes and rarely anywhere near that long. Compromise is always with us.

I wonder if battery power might negate the benefits of running the thing all of the time?

I don't get what you're saying here - how would battery power negate the benefits? Oh, 15 minutes power down will not cause any problem with the batteries - if you are doubling them for each polarity then you should have many hours before running low

I wonder if shift registers work better after "warming up"? I guess the clock would work better after being on awhile.

Yes, leaving on all the time allows ICs & clocks to reach stable operating conditions. What the DAM is doing is reproducing the very low level detail in the digital signal - the LSBs. These are at very low voltage levels & the stability of these very low voltages is what is the secret here - it's what gives the DAC it's realistic sound, I believe. The stability & low noise of the vref is the most crucial node in the whole DAC - it's this reference voltage that is used directly by the resistor ladder to generate the output voltages corresponding to the digital bits of the digital byte. These batteries provide a number of advantages for use in digital audio - they provide 3.3V fairly steady output for most of their charge - perfect V for most digital circuitry so don't need a voltage reg - they are so fast, low noise & stable that using them with a cap or voltage reg is usually detrimental to their operation. These 3 factors low noise, stability & speed are exactly what's needed for digital ICs & it's difficult to find regulators that combine these attributes - I believe the Paul Hynes come closest if not the equal of these batteries.

If you do not detect a volume change then no need to measure it. One more thing to make one think that 3.3 is just fine. Makes one wonder why SOEKRIS picked such an odd value for the voltage ... One thing for sure the batteries have infinitely better current delivery than that opamp based reg/reference which could well explain the ability to get by with less. Has anyone ever measure just how close those SOEKRIS regs track each other's voltages?

The current requirements are probably not very great in this part of the DAm but you are correct, the batteries are over engineered for the task of supplying such small currents - they are 2.3A rated but can provide 20Amps continuously or something like 120Amps instantaneously - which accounts for the voltage stability needed in this circuit.

jkeny, what do you think the real world capability of those reg/refs to supply "equal" voltages would be over time?

I haven't looked at them but if you are worried about the potentiometer, then find the setting that gives you 3.3V output, measure the potentiometer's resistance & substitute a fixed R of this value for the pot

What soldering iron do you use for your SMD work? What size tip?

Metcal (OKI 9000) - I recommended it to Nige & he finds it great too. Various size tips depending on what I'm doing but the most useful one for smd work is this one OKI Soldr Tip SFV-CH15A Tapr Chisl 1.5mm

I am thinking my setup is just too large and I might be better off getting something more suitable before soldering anything to the board.

I worry that the more I obsess these details the more certainly there will be that the thing will blow up upon first turn-on.

Hope this helps you avoid the magic smoke?

[rickmcinnis]

Each battery will supply one "Vref" - plus and minus for each channel, hence four.

What I intended to ask was whether battery power would negate the NEED to leave the gear on all of the time. My question was along the lines of what takes the most time to stabilize: The power supply or the circuit itself. Thinking the batteries are as ON as they ever will be at turn on maybe one does not need to leave the thing on? And then I thought about the clock ...

THANKS for the iron recommendation and your comments in general.

Take care,