[dhp]

 
That's a good question and I'm not sure I know the best way to go about it.  Maybe someone else will see this and offer a suggestion.  I've used KSC75's with mine and the Foobar volume control was more than sufficient.  You must have some highly efficient earbuds/iems.

 
Yeah I was using some SE530s.  I tested this on some Grados and it was not as bad, although I can get my HD650s to listenable levels at 25%, which is still way too much volume considering I never want to drive 650s with this.

 

[mcandmar]

Hi all,
 
Just finished building a SkeletonDAC, it should really be called a CuteDAC

 
I do have one issue, on my main machine (Windows 8.1 x64) and it detects a USB DAC but fails to install, tried removing it and re detecting but it doesn't seem to be able to install a driver for it.  Tried it on a Windows 7 machine and it worked perfectly first time.  Any ideas?
 
Cheers,
 
Mark
 
 

 

[tomb]

I'm sorry to say that I have no experience with Windows 8.  Maybe someone else can confirm/deny whether the TI PCM270X chips work with Windows 8.
 
I know that there was a volume control issue with Windows 7 and TI's PCM270X chips, where the volume could not be controlled separately with software but only through the OS.*  So they came out with "C" versions of the PCM2704/5/6/7..  However, TI doesn't appear to have any additional info about operating system compatibility on these chips since 2007.
 
* We always recommend full volume on the DACs in any PC OS or software - the bits get interpolated/re-sampled if the volume is lowered.  It's best to only use the amplifier volume control.  Granted, in the SkeletonDAC we talk about a scenario where it is used for direct listening, but those kind of quality considerations have to be balanced against the purpose of a $22 DAC.

 

[mcandmar]

Thanks Tomb, i was reading through the datasheets and they dont mention anything newer than Vista with exception of the C version being fully Windows 7 compatible.  The chip i got is the older version as its all Mouser stock but its not an issue as i dont intend to ever use the volume control anyway.  My work machine is also Windows 7 so it should work fine none the less, was just curious in case Windows 8 was a known issue and easily remedied.
 
Cheers,
 
Mark

 

[BluePylons]

Just finished my build two nights ago. The noise floor is dead quiet and it sounds great, a huge improvement over my laptop's terrible built-in sound card.

Unfortuantely, this morning, it suddenly started attenuating mids/mid-highs, which is very obvious on the synth lines in the opening to Jaco Pastorius's "Continuum" (they sound distant and faint). Everything worked fine two days ago, so the parts are correctly soldered, and there are no solder bridges evident on the pins of the PCM2704. Could it be the flux? I used no-clean flux to solder the PCM2704.

 

[Avro_Arrow]

(scratching head) Pictures..?

 

[tomb]

  (scratching head) Pictures..?

Ditto.  I'm not aware of any situation that would result in the mids/mid-highs being attenuated.  The only section that could even remotely cause this is the analog out signal coming from the DAC chip to the output connections.  In that string, only the output capacitors are inbetween.  I guess you could check the solder connections on those caps.
 
One other possibility is that you have loose output connections.  If you lose part of the wiring of one channel, it can perhaps have the effect of changing the effective frequency response.  Except that in those circumstances, the lack of in-phase channel combination usually means the bass has disappeared.
 
Just an FYI, but there is absolutely nothing on the digital side that could cause this.

 

[DingoSmuggler]

  Just finished my build two nights ago. The noise floor is dead quiet and it sounds great, a huge improvement over my laptop's terrible built-in sound card.

Unfortuantely, this morning, it suddenly started attenuating mids/mid-highs, which is very obvious on the synth lines in the opening to Jaco Pastorius's "Continuum" (they sound distant and faint). Everything worked fine two days ago, so the parts are correctly soldered, and there are no solder bridges evident on the pins of the PCM2704. Could it be the flux? I used no-clean flux to solder the PCM2704.

My best guess would be that you are summing L + R outputs together into mono somehow. Bass will always be in phase between L + R channels due to its long wavelength, but mids and highs will often be partly out of phase relative to the mic placement and/or any stereo effects used which results in attenuation when summed. So check your output connections, wiring, and any jacks and cables used.
 
ps. nice choice in music  

 

[Armaegis]

But he said it was the mid/highs which were being attenuated, which is opposite of what we'd expect if L+R were summed or if the ground line was broken.

 

[BluePylons]

Sorry for the late reply - I've been pretty busy the past week. Thanks for all the replies.

Here's photos of the build as requested. (I apparently get "Your account does not have the required permissions to access this page" if I try to directly post photos...). I soldered 100 ohm resistors to the outputs as I have low impedence IEMs.
 
https://drive.google.com/file/d/0B7459wjgAgdlUTdkRlhEOUZxWGs/edit?usp=sharing
https://drive.google.com/file/d/0B7459wjgAgdlWjdHYzVoVkI4MnM/edit?usp=sharing
 

Here's recordings of the intro to "Continuum" as played from my phone vs the skeletonDAC. Listening to it again, the attenuation is actually the highs, not the mids/mid-highs. Sorry about that.
 
Phone:
https://drive.google.com/file/d/0B7459wjgAgdlV2FNa0ViSnFKUFE/edit?usp=sharing

SkeletonDAC:
https://drive.google.com/file/d/0B7459wjgAgdlTE1qSFlhY1Jxb1E/edit?usp=sharing
 
Looking at the files inside Audacity, it actually does look like the left and right are somehow getting summed as DingoSmuggler suggested, since the left and right look identical when played off the skeletonDAC. I probed the left and right outputs though (both before and after the output caps) and there's no short across them though.
 
Phone:
https://drive.google.com/file/d/0B7459wjgAgdlMFNFYzJpbzh2SkE/edit?usp=sharing
 
SkeletonDAC:
https://drive.google.com/file/d/0B7459wjgAgdlYVNJSmg1eXhCRk0/edit?usp=sharing

 

[tomb]

  Sorry for the late reply - I've been pretty busy the past week. Thanks for all the replies.

Here's photos of the build as requested. (I apparently get "Your account does not have the required permissions to access this page" if I try to directly post photos...). I soldered 100 ohm resistors to the outputs as I have low impedence IEMs.
 
https://drive.google.com/file/d/0B7459wjgAgdlUTdkRlhEOUZxWGs/edit?usp=sharing
https://drive.google.com/file/d/0B7459wjgAgdlWjdHYzVoVkI4MnM/edit?usp=sharing
 

Here's recordings of the intro to "Continuum" as played from my phone vs the skeletonDAC. Listening to it again, the attenuation is actually the highs, not the mids/mid-highs. Sorry about that.
 
Phone:
https://drive.google.com/file/d/0B7459wjgAgdlV2FNa0ViSnFKUFE/edit?usp=sharing

SkeletonDAC:
https://drive.google.com/file/d/0B7459wjgAgdlTE1qSFlhY1Jxb1E/edit?usp=sharing
 
Looking at the files inside Audacity, it actually does look like the left and right are somehow getting summed as DingoSmuggler suggested, since the left and right look identical when played off the skeletonDAC. I probed the left and right outputs though (both before and after the output caps) and there's no short across them though.
 
Phone:
https://drive.google.com/file/d/0B7459wjgAgdlMFNFYzJpbzh2SkE/edit?usp=sharing
 
SkeletonDAC:
https://drive.google.com/file/d/0B7459wjgAgdlYVNJSmg1eXhCRk0/edit?usp=sharing

No offense, but I'd cut off all that caulk-blob stuff, get yourself a decent 3.5mm jack, and some decent 22ga SPC-teflon hookup leads and start over with your output scheme.  Again no offense, but there's no way anyone can tell what's going on there - including you.

 

[tomb]

OK - I apologize if that was a bit rude, but sometimes you guys have us going when describing the symptoms ... but then we see the pics.  That probably doesn't make you feel any better, but we seriously want to find out how to fix your problem and help.

 

[mcandmar]

I've never seen or heard of anybody using OSCON caps in the signal path, i wouldn't be surprised if that's whats causing the high end roll off.  I would pick up a couple of the Wima or Vishay caps and see how you get on with those.
 
Also this is the output jack that fits inside the Hammond enclosure http://ie.mouser.com/Search/ProductDetail.aspx?R=161-7400-EXvirtualkey11180000virtualkey161-7400-EX

 

[tomb]

  I've never seen or heard of anybody using OSCON caps in the signal path, i wouldn't be surprised if that's whats causing the high end roll off.  I would pick up a couple of the Wima or Vishay caps and see how you get on with those.
 
Also this is the output jack that fits inside the Hammond enclosure http://ie.mouser.com/Search/ProductDetail.aspx?R=161-7400-EXvirtualkey11180000virtualkey161-7400-EX

Well ... just an FYI, but people have used OSCON's in the signal path going back to the BantamDAC.  It's not that common, but the people who've used them claim good results. So, I would not suspect them in this case.

 

[tenacioustim]

Hi,
i've ordered the parts i need to build this. However, how will i adjust the volume to my headphones? I understand that there is a built in amp, but how will i adjust it?
Will I be forced to control sound via in-software sound settings? Surely this will undermine the quality of the DAC, since changing volume via in-software will decrease the effective resolution of the sound?
 
Thanks for any help and suggestions.
 
Timothy.