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pupDAC Step-by-Step Build Thread - Page 15

post #211 of 277

I'm going to go out on a limb here and say that shouldn't happen, the issue is more likely to be with the laptop itself and not the DAC.  I can confirm the PupDAC works perfectly with Windows 8.1, however its not best practice to be lowering the volume on a DAC, your better off doing that on the amplifier.

post #212 of 277
Thread Starter 
Quote:
Originally Posted by mcandmar View Post
 

I'm going to go out on a limb here and say that shouldn't happen, the issue is more likely to be with the laptop itself and not the DAC.  I can confirm the PupDAC works perfectly with Windows 8.1, however its not best practice to be lowering the volume on a DAC, your better off doing that on the amplifier.

Agreed.  The OS starts interpolating bits to lower the volume and you'll lose ultimate quality doing that.  Granted, there are some circumstances where you may want to do that - I've done it myself when I wanted to try plugging IEMs directly into the DAC, etc.  However, those instances should not be the norm.  The pupDAC is designed to be used with an amplifier.

 

All that said, there is an issue with Windows 7 and beyond and the way they enabled volume control through a USB device.  Texas Instruments actually came out with the PCM2706/7 "C" version to address the different methods used in Windows 7 and beyond.  I haven't tested this myself yet, though, so I don't know if simply replacing the chip in the pupDAC with a "C" version would fix the volume control limitation that you describe.

post #213 of 277

Hi,

Have any of you noticed a staticky noise with some ticking when you turn up the volume a LOT on your amp when hooked up to the PupDAC? I never noticed this at first, but even with a ferrite on the USB cable I can hear noise if nothing's playing and the volume's maxed out. I never play it that loud so I didn't notice it at first - but is it a limitation of the PupDAC?

BTW I'm using an O2 amp right now, which makes no noise if connected to another source (i.e. the pupdac is the culprit)...

post #214 of 277
Thread Starter 
Quote:
Originally Posted by COOKIESnPIE View Post
 

Hi,

Have any of you noticed a staticky noise with some ticking when you turn up the volume a LOT on your amp when hooked up to the PupDAC? I never noticed this at first, but even with a ferrite on the USB cable I can hear noise if nothing's playing and the volume's maxed out. I never play it that loud so I didn't notice it at first - but is it a limitation of the PupDAC?

BTW I'm using an O2 amp right now, which makes no noise if connected to another source (i.e. the pupdac is the culprit)...


The noise on the PupDAC is generally down in the -120 to -130dB range when properly connected on a quality USB power supply.  You can see that using a DoodleBug makes a difference, but even without, there's nothing that could be amplified enough to cause audible noise:

 

Now, that's not saying it isn't your PupDAC - just that something is wrong if it is. ;)  I'd check your output connections, first - all the way back to the PCB.  A poor ground connection on the analog side can cause a multitude of issues with noise.  You might also check the proximity of any other devices that could be introducing noise.  With the wide variances in DAC design, grounding methods, and enclosure techniques, it's quite possible the PupDAC could be picking up noise from external devices when another source does not - or vice-versa.  Or, your cables could be picking it up, too.  If the PupDAC's output is higher than other sources or if there is any other difference in the way it is connected, this may make the extraneous noise more noticeable on the Pup compared to another source, even though it may be present all the time.

 

Good luck and let us know what you find in your trouble-shooting!

post #215 of 277
Quote:
Originally Posted by COOKIESnPIE View Post
 

Hi,

Have any of you noticed a staticky noise with some ticking

 

Does the noise change/disappear if you use a different computer?

post #216 of 277
I get the ticking as well. I will have to try a different computer. It's only in my left channel. I switched the cables from L->R and the ticking moved to the right channel. This was hooked up to a 2011 MacBook Pro that was not connected to a charger at the time. With Monoprice 8323 phones i could hear it as low as 50% volume. With DT880 600ohm I couldn't hear it even at full volume.
post #217 of 277

Ok... I've done voltage testing on the PupDAC and will try a new computer soon. Here's what I've got (from left to right starting at the USB port):

3V3: 3.30V
3V3: 3.29V

5V: 5.09V

4V5: 4.74V (I don't remember what the numbers were when I tested it right after it was built, but this seems a bit off...:blink:

 

2V5: 2.49V

-5V: -5.08V

-2V5: -2.49V

 

DC offset right: -8.1mV (VERY suspicious)
DC offset left: -1.4mV

 

That's it!

post #218 of 277

And yes, I've tested it on a different computer and have the exact same problem.:confused:

post #219 of 277

 

I used to get noise from my laptop with the pupDAC. I didn't get the noise with the desktop.

It was mostly on just one channel. That was the reason I designed the Doodlebug.

The noise I got was different depending on which laptop I used. My HP was the quietest,

the Dells were the worst. The noise was never very loud, mostly just between songs or

very quiet passages.

 

pupDACs do sometimes have more offset on one channel. I think mine has about the same

offsets as yours. I have a prototype version.

 

Other parts of my system are Shure SE535 and a PPA v1. with glassman buffers.

post #220 of 277

The problem here is that the offset is not at all within spec - the official site reports that it should be 2mV or less.

 

And for the debugging (I posted the voltages earlier) I have pics of my board. They probably won't say much (everything has worked find for months, I just didn't realise the noise till now), but they're attached just in case.

 

 


Edited by COOKIESnPIE - 4/19/14 at 1:20pm
post #221 of 277
BUMP!

Sry, but it's been 4 days...
post #222 of 277

I haven't been able to test mine with a different computer yet.  My one working amp (M3) is disassembled while the case is at the powder coater.  I have a Bottlehead Crack kit to build, but it's top plate is also at the powder coater.  And the KSA5 clone I'm building, I f'd up and shorted out the opamp on one of the channels and it seems to have damaged some/all of the output section.

 

I will try to hook my pupDAC up tonight and at least measure voltages.

 

Quote:

4V5: 4.74V (I don't remember what the numbers were when I tested it right after it was built, but this seems a bit off...

 

I think that is okay, check my posts from earlier in this thread, I think my measurement there was the same and tomb/Avro said that one was fine.

post #223 of 277

COOKIESnPIE here is the post from tomb that says the ~4.75V is okay: http://www.head-fi.org/t/636683/pupdac-step-by-step-build-thread/195#post_10345285

post #224 of 277

A "Bottlehead Crack" and a profile pic of Rob Ford? Beautiful.

 

Jokes aside, the 4.75V may not be problem but my DC offset is way off.

post #225 of 277

Hah, I hadn't thought about that correlation :)

 

Yeah, I was just pointing out that the 4.75V was okay.  The DC offset of 8.1mV definitely is a little high.  Particularly going into an amp like the M3 which has no output offset protection.

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