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The SkeletonDAC - Page 8

post #106 of 222

cant wait to build this!

post #107 of 222
Thread Starter 
Quote:
Originally Posted by tomb View Post

These are finally available.  Price is a couple of dollars more than mentioned previously - I didn't realize it would take over 1100 ziplocks to make up 100 kits.redface.gif


And that is why I let other people do kits. 

 

post #108 of 222

Price is good, but I would need a DAC with headphone amp for AKG K242HD headphones. We are waiting for notebook for my mother to arrive, so I'm thinking about building DAC for her. But potentiometer is needed.

 

What about sound quality in comparison with grubDAC? Or should I build grubDAC with a small opamp headphone amp instead?

post #109 of 222



 

Quote:
Originally Posted by akgfan View Post

Price is good, but I would need a DAC with headphone amp for AKG K242HD headphones. We are waiting for notebook for my mother to arrive, so I'm thinking about building DAC for her. But potentiometer is needed.

 

What about sound quality in comparison with grubDAC? Or should I build grubDAC with a small opamp headphone amp instead?


Well, I hate to state the obvious, but if Beezar sells both products (and will continue to do so) and one costs almost 75% more than the other ... which one do you think is better in sound quality?

 

I think we've said this before, but the SkeletonDAC is essentially a replacement for the BantamDAC: a small, inexpensive, and relatively easily-constructible (given the SMD required) Do-It-Yourself DAC.  We quit the BantamDAC specifically because the PCM2702's price has risen to almost $20 (!) - that's basically the price of the entire SkeletonDAC by itself!  (It would've been equal before the 1100 ziplocks. wink.gif)  Now, the reason the PCM2702 has risen to that price is because TI declared it NRND (Not Recommended for New Designs) a couple of years ago.  That's simply another reason to go in a different direction than the BantamDAC: at some point, the PCM2702 will simply become unavailable.

 

Unfortunately, TI's listed replacements for the PCM2702 - the PCM2704/5/6/7 are not drop-in replacements.  They are their own unique chips, all with different pinouts, and their own unique features.  Thus, cobaltmute and Mute Audio came up with a different design entirely, the SkeletonDAC.  It has some extra features beyond the original Bantam - the built-in headphone amplifier of the PCM2704/5 chip and the ability to use a SPDIF output.  However, the price-performance is still focused at the BantamDAC level.

 

BTW, that built-in headphone amplifier in the PCM2704/5 chip is capable of about 12mW into a 32ohm load.  So, I'm not sure you would want to go plugging in full-size headphones on a regular basis and expecting top-of-the-line performance.  We are saying that it can yield good results with earbuds and smaller phones such as KSC-75's.  Even so, the output coupling caps should be selected with care to ensure a reasonable bass response.  We would also anticipate that someone would use the volume control of the PC's media player and would not recommend a potentiometer, per se.  For a full-featured, USB-powered, DAC-Amplifier combination, we would recommend something like Joneeboi's Carrie.

 

EDIT: Of course, used as a DAC source with a separate amplifier, the SkeletonDAC is fully capable of supplying a flat frequency response from 20 - 20KHz.  With the 1uf coupling capacitors we supply with the kits, the frequency response would look something like this, depending on the impedance of a separate amplifier's pot:

 

fc-charts-1.0uf.gif


Use of optional audio-quality 47uf 6.3v electrolytics (BG's, ES's, Cerafines, Silmic II's, etc. ) would bring the 10K pot frequency response down to -0.5dB at 1Hz!


Edited by tomb - 10/14/11 at 5:00pm
post #110 of 222

I'm still working on the HeadphoneDAC webpage, but the rest of the site should be good to go:

SkeletonDAC

post #111 of 222

Anyone built one yet, that's willing to share?  I've shipped quite a few over the last few weeks. smily_headphones1.gif

post #112 of 222

Shoot, I sat down to assemble the DAC and may have swapped C11 and L1, but can't tell because they lack markings (that I can see, at least).  Any way I can tell them apart? confused.gif  This is my first attempt at SMD and didn't really anticipate this problem.

post #113 of 222

Capacitors on GrubDAC have olive color and coils grey/black.


Edited by akgfan - 11/19/11 at 4:11pm
post #114 of 222

Thanks for the color reference akgfan!  I was worried I would make the problem worse by taking them out of the package, so I never noticed they were different colors.  Do the Skeleton DAC kit contents match the Mouser or Digikey BOM?  From Digikey, C11 should be about 40% taller than L1 -- can someone confirm that for me?  
 

Quote:
Originally Posted by akgfan View Post

Capacitors on GrubDAC have olive color and coils grey/black.



 

post #115 of 222
Oh my, why haven't I seen this project yet? This looks to be a future project, seeing how it's very cheap, and I could use a DAC around.
post #116 of 222
Quote:
Originally Posted by torndorff View Post

Thanks for the color reference akgfan!  I was worried I would make the problem worse by taking them out of the package, so I never noticed they were different colors.  Do the Skeleton DAC kit contents match the Mouser or Digikey BOM?  From Digikey, C11 should be about 40% taller than L1 -- can someone confirm that for me?  
 



 


Mouser.
 

 

post #117 of 222

Following my order of a SkeletonDAC, I have a couple of questions for you guys if one of you could help?

 

I made my own IEM's with great success a few months ago and have been contemplating a DAC to complement them for a while. They are not difficult to drive and as such, I think that there is a great possibility that the SkeletonDAC should do a sterling job without the need for a separate amp. Unfortunately, the SkeletonDAC page is not working at the moment (perhaps this is not intentional?) and despite the reading I do, my electronic skills are not quite the same as my DIY superpowers. 

 

1000x500px-LL-4d0c4983_CustomEarsImageforHeadFi.jpg

 

My questions relate to the caps used in the SkeletonDAC design, particularly C6 (which I believe is the main power cap) and C13 and C14, which I understand are responsible for filtering sound before being output to my desired cable/connectors. 

 

Before I continue, I should mention that physical size is not a problem for me as I will not be using the blue casing as suggested by others and could accomodate physically larger components. 

 

With regards to my intended use of the DAC, should I consider replacing any of these 3 capacitors? Would I see any benefit to this at all? I currently run my IEMS from my computer directly. Sound isn't bad but there is a lot of hiss (sibilance??) and I sometimes resort to an equaliser to increase bass and warmth a little. Do any of you think this would still be necessary if I were to use and/or tweak the SkeletonDAC?

 

I would be very grateful for any thoughts from those with experience and technical knowledge regarding the above. Perhaps one of you has wanted to achieve the same result as me and has had some success? I will be following this forum and wait with baited breath.

 

Nick

post #118 of 222



 

Quote:
Originally Posted by Madebynick View Post

Following my order of a SkeletonDAC, I have a couple of questions for you guys if one of you could help?

 

I made my own IEM's with great success a few months ago and have been contemplating a DAC to complement them for a while. They are not difficult to drive and as such, I think that there is a great possibility that the SkeletonDAC should do a sterling job without the need for a separate amp. Unfortunately, the SkeletonDAC page is not working at the moment (perhaps this is not intentional?) and despite the reading I do, my electronic skills are not quite the same as my DIY superpowers. 

 

 

 

My questions relate to the caps used in the SkeletonDAC design, particularly C6 (which I believe is the main power cap) and C13 and C14, which I understand are responsible for filtering sound before being output to my desired cable/connectors. 

 

Before I continue, I should mention that physical size is not a problem for me as I will not be using the blue casing as suggested by others and could accomodate physically larger components. 

 

With regards to my intended use of the DAC, should I consider replacing any of these 3 capacitors? Would I see any benefit to this at all? I currently run my IEMS from my computer directly. Sound isn't bad but there is a lot of hiss (sibilance??) and I sometimes resort to an equaliser to increase bass and warmth a little. Do any of you think this would still be necessary if I were to use and/or tweak the SkeletonDAC?

 

I would be very grateful for any thoughts from those with experience and technical knowledge regarding the above. Perhaps one of you has wanted to achieve the same result as me and has had some success? I will be following this forum and wait with baited breath.

 

Nick


If you're referring to the "SkeletonHeadphoneDAC" page, yes - it's not available right now.  I've been working on some curves to give everyone an idea of the cutoff frequency with various headphones.  Unfortunately, IEMs usually have a very low impedance - I would strongly recommend something like a 75 ohm adapter if you're wanting to get a lot of bass out of them on a SkeletonDAC.  If we assume a total load of 91 ohms for the SkeletonDAC, then a value of 82uf for C13 and C14 will give you a -3dB at 20Hz, while response is down only 0.5dB at 60 Hz.  If you went all the way to 220uf (still relatively small electrolytics at 6.3V rating), you'd only have a -0.5dB loss at 20Hz.  You could try a Muse ES cap at 220uf 16V (higher voltage ratings are OK - 6.3V may not be available in some audiophile capacitors) and you could keep the Wima's that come in the kit as bypasses for a good all-around frequency response.  That's if, as you say, size is not an issue.  Another option is the Elna Silmic RFS II at 220uf 6.3V.  You probably won't need any film cap bypasses on those, because they're so good.  Handmade sells them for $0.60 each.*

 

C6 is not a concern if you purchased the kit.  It's a 560uf organic-poly with super-low ESR and will do just fine.

 

 

* Besides the spreadsheet graphs and curves, there's the whole issue of the different variants of output caps when feeding headphones of varying impedance.  Right now, I sell the 47uf Elna Silmics and have used them in my own SkeletonHeadphoneDAC build, but they're a compromise and assume that you will give up some bass (-3dB cutoff is about 55Hz with KSC-75's) in order to fit everything into the standard plastic case.  Anyway, that's why the web page has been delayed - lots to ponder and work out on this particular score.  However, please keep in mind that we're attempting all of this with a $20 DAC.wink.gif
 

 


Edited by tomb - 11/21/11 at 6:59am
post #119 of 222

Finish populating the PCB yesterday, and it's running great!  Sounds really nice running from PC to SkeletonDAC to Roger Gomez NP-100v12 12AU7 headphone amp.  Next up is to populate the R1 power supply prototype and run the power for the NP-100v12 through there to clean it up.  I'll post photos when it's complete and encased.  Worked under Ubuntu 11, OS X and Windows 7 on plugin.

post #120 of 222
Quote:
Originally Posted by torndorff View Post

Finish populating the PCB yesterday, and it's running great!  Sounds really nice running from PC to SkeletonDAC to Roger Gomez NP-100v12 12AU7 headphone amp.  Next up is to populate the R1 power supply prototype and run the power for the NP-100v12 through there to clean it up.  I'll post photos when it's complete and encased.  Worked under Ubuntu 11, OS X and Windows 7 on plugin.


Great!  Can't wait for the photos!
 

 

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