[Nisbeth]

Max. input voltage for the MAX1722 is 5.5V, so 4 rechargeables should be OK while 4 alkalines are probably too much

/U.

EDIT: From the MAX1722 it actually looks like it works with input voltages down to 0.9V. How about using the 4 batteries in parallel instead of series/parallel?

 

[Magsy]

Quote:

Originally Posted by Nisbeth Max. input voltage for the MAX1722 is 5.5V, so 4 rechargeables should be OK while 4 alkalines are probably too much /U. EDIT: From the MAX1722 it actually looks like it works with input voltages down to 0.9V. How about using the 4 batteries in parallel instead of series/parallel?

In my case 2xnimh in series were barely powering it, as soon as they dropped to ~2.3v 48Khz playback became white noise.

I've been running mine with 4xnimh in series and its been fine, you get much more output (volume) too, which you need because imo its too quiet on ~2.5v. My nimhs were measured at 5.25v's initially, it didn't blow up

 

[00940]

I'm gonna check the datasheet of the maxim chip again, the number of batteries shouldn't matter much actually. I don't remember a graph input voltage vs output current.

But only 3 or 4 hours of playing is ridiculously low. Or your batteries are really of the lowest quality, or there's a problem with your dac.

 

[Ozymand]

Another option provided by the design is hooking up a supply greater than 5V after the MAX1722 (there are vias on the PCB to do so). The inputs on the REG102 devices are rated up to 12V (if I'm reading the datasheet right), so you could ideally hook up a 6 to 8 cell battery pack to your USB DAC (or a single 9V battery).

Curious, what would happen if you attempted to hook up the GND and V+ of a USB DAC to the virtual ground and V+ of a Cmoy or any other split rail designed headphone amplifier? Could it be possible? Would it make sense? That way you could simplify the design to a single battery supply driving both units...

 

[doobooloo]

Woohoo!

I took apart the DAC and connected four brand new alkalines in series. I didn't bypass the Maxim IC.

It works! The battery pack measures 6.41V when connected but no problems.

I am going to rewire my battery slot in series now.

Phew! Thank God it didn't blow up or anything.

 

[Ozymand]

Glad that the 4 batteries in series is working out for you, but I'd keep an eye on it. It may not blow up immediately, but I'd be kinda wary as it may cause premature failure of the device. This could be very akin to overclocking a computer, more voltage you put into it the faster it goes but also the faster it'll die (relatively speaking, I've had my Cel300A overclocked to ~500MHz for nearly 5 years now and it's still going.. outlasted 2 hard drives and a power supply).

 

[doobooloo]

That's true. I'm going to try to get NiMH cells as soon as possible, and I've got a dozen of half-depleted alkalines that will work well in this application too.

 

[phobus]

Hi. I've been looking but can't find it. Has anyone compared the usb dac with a Chaintech or Emu 0404/1212? I'm really interested in getting one, but would like to know approximately where it stands compared to the different sound cards.

 

[individual6891]

Just finished my USB DAC..

Will be using LM317 to supply 6-7V into the 5V regulator
Will be using LCR Audio-grade Polypropylene's for output caps..

Sound comparisons soon once it's cased up

 

[individual6891]

The guide at mellowparenting is wrong..

Quote:

To bypass switching supply (5.2V < Vs < 10V): connect +ve to the right hand pad of R2, Ground to right hand pad of R1, omit IC1, R1, R2, L1, and C1

should be

Quote:

To bypass switching supply (5.2V < Vs < 10V): connect +ve to the right hand pad of R2, Ground to left hand pad of R1, omit IC1, R1, R2, L1, and C1

Also, I'm having problems with the 3.3V regulator, it's output is 1.93V
(Using 6.64V into the 5V regulator, giving a good 5.0V output, going into the 3.3v regulator)

Anyone got any suggestions?

-Andy

 

[individual6891]

Ok, the 3.3V regulator was fried, replaced everything now and it's ok... but windows XP doesn't recognise the chip when I plug it in... is this fried too?

(Unknown USB Device)

Andy

 

[Magsy]

Quote:

Originally Posted by individual6891 Ok, the 3.3V regulator was friend, replaced everything now and it's ok... but windows XP doesn't recognise the chip when I plug it in... is this fried too? (Unknown USB Device) Andy

I had that in first plug-in to my desktop. Tried it on another port after a reboot and it worked ok. Worked first go on my laptop....

 

[individual6891]

Quote:

Originally Posted by Magsy I had that in first plug-in to my desktop. Tried it on another port after a reboot and it worked ok. Worked first go on my laptop....

Well i replaced the actual dac chip, and way hay, "usb speaker" installed..

But more problems:

There's quite a bit of background hum with thew USB connected to my headphone amp on max .. Also when I change volume with the headphone amp, there's more scratchy sound.

The headphone amp itself is fine with a different source.

Any clues?

 

[00940]

try to connect the casing of the USB connector to ground.

 

[individual6891]

Quote:

Originally Posted by 00940 try to connect the casing of the USB connector to ground.

Tried just now, still very fuzzy. The PCB is uncased btw.