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JDS Labs C5/C5D (pg96) portable amp/amp+DAC appreciation + discussion thread - Page 171

post #2551 of 2658
Quote:
Originally Posted by luisdent View Post
 

You need to install rockbox to replace the sansa firmware, which I find is better anyway. With no eq or anything the sound is identical, except rockbox actually claims to have fixed a slow audio glitch. Anyhow, the rockbox firmware supports 128gb+ theoretically. People have reported success using them. I'm using a 64gb and I've never had any problems with it recognizing the data on the card.

 

You just need to format it to the correct file system. I messaged one of the developers and they said the 128gb should work fine. I'm going to try it when they aren't $180

 

Yeah, being able to run Rockbox is the first priority for any prospective DAP.

 

Amazon has the 128GB SanDisk for $120 right now.  BUT the 64GB is $38 and change.  Bugger that.  SanDisk needs some competition for the price to get to a reasonable level.  That, or it's covered by ObamaCare ;)

 

Even without digital out, I'd still use my C5 with it.

post #2552 of 2658

Anyone ever bought the 240G Ipod classic from mapplesyrup.web.com.

post #2553 of 2658
Quote:
Originally Posted by bana View Post
 

Anyone ever bought the 240G Ipod classic from mapplesyrup.web.com.

 

Pretty sure it was mentioned in this thread:

http://www.head-fi.org/t/532426/ipod-classic-rockbox-its-happening

post #2554 of 2658
Quote:
Originally Posted by ThurstonX View Post
 
Quote:
Originally Posted by luisdent View Post
 

You need to install rockbox to replace the sansa firmware, which I find is better anyway. With no eq or anything the sound is identical, except rockbox actually claims to have fixed a slow audio glitch. Anyhow, the rockbox firmware supports 128gb+ theoretically. People have reported success using them. I'm using a 64gb and I've never had any problems with it recognizing the data on the card.

 

You just need to format it to the correct file system. I messaged one of the developers and they said the 128gb should work fine. I'm going to try it when they aren't $180

 

Yeah, being able to run Rockbox is the first priority for any prospective DAP.

 

Amazon has the 128GB SanDisk for $120 right now.  BUT the 64GB is $38 and change.  Bugger that.  SanDisk needs some competition for the price to get to a reasonable level.  That, or it's covered by ObamaCare ;)

 

Even without digital out, I'd still use my C5 with it.

 

Wow. It was $180 last I checked. I might have to get that. I'm not sure. I could at least use my zip clip with 136gb of storage and my fuze with 68gb of storage together for a total of 204gb or so. Not too shabby. And they're both so small, it's less space in my pocket than a classic... I'm liking this idea...

post #2555 of 2658
Quote:
Originally Posted by bana View Post

bummer!! Am I the only one with a large collection?
I have around 300 GB of music, but I only actively listen to about 30% of that. XD

I do wish I had more space than what my iPod 5G has though, which is the 30 GB version.
post #2556 of 2658
Thread Starter 
Fiio X5 has dual microSD slot.
That's 256gb, not bad really when the cards come down in price
post #2557 of 2658
Quote:
Originally Posted by ostewart View Post

Fiio X5 has dual microSD slot.
That's 256gb, not bad really when the cards come down in price
I reviewed a touring X5 unit and I didn't really like it too much by itself.

The C5D made it sound better with the line out connection, but I don't want to carry around:
a large brick (X5) + an iPhone 4S-sized box (C5D) + a 3.5 mm cable that sticks out like a sore thumb (FiiO L2) + headphone cable in my pocket


The dual microSD cards are a nice thing to have though.
post #2558 of 2658
Thread Starter 
Yeah it's not the smallest of rigs but probably sounds great. I've only demoed the X5 very briefly.
post #2559 of 2658
Quote:
Originally Posted by ostewart View Post

Fiio X5 has dual microSD slot.
That's 256gb, not bad really when the cards come down in price

 

Sansa Clip Zip is $50 (8 GB; under $40 for the 4 GB) on amazon.com.  X5 is $350.  I know, I know, not exactly a fair comparison.  Just sayin'.

post #2560 of 2658
Quote:
Originally Posted by ThurstonX View Post

Quote:
Originally Posted by ostewart View Post

Fiio X5 has dual microSD slot.

That's 256gb, not bad really when the cards come down in price

Sansa Clip Zip is $50 (8 GB; under $40 for the 4 GB) on amazon.com.  X5 is $350.  I know, I know, not exactly a fair comparison.  Just sayin'.
136gb zip clip would be $170 right now. That's twice the size of the biggest ipod touch and less than half the price. :-)
post #2561 of 2658
I have been so in love with my cyper labs stack that I have neglected my C5D, I am having a early morning listening session and I'm loving the C5D! It is such a versatile dac/amp for us IEM lovers to have. Bass boost with such a black back ground simply lovely for such a low price! Jds Labs really hit the target on the head, I can't wait to see what they have cooking for there next release.
post #2562 of 2658

Oh man - wrote more than I expected:

 

I have a nagging question for all you C5D owners who have connected your C5D between your computer and a power amp (or other grounded audio device; not headphones):

Do you experience ground loop interference? 

(by the way, I had JDS Labs convert my C5D's mini jack analogue input to a line level output from the DAC section of the C5D).

 

Unfortunately, I experience very annoying ground loop noise between my computer and power amp when connecting either the C5D's line out or HP out to my power amp. Just as much interference as when I send audio from my computer's headphone output to the power amp. Normally, this would not surprise me because USB power is notoriously noisy, and there is always a potential for ground loop between a computer's USB ground and a power amp.

 

But, the C5D is supposed to be galvanically isolated via an ADuM3160 chip (drawing below; isolation on all USB pins). In other words, there should be no (or drastically reduced) ground loop because the ADuM3160 physically disconnects all pins (power, ground, & data) from the computer's USB out and the C5D's input to the DAC. In fact, I notice the same ADuM#### family of USB isolation chips is used in many of the USB isolation devices marketed as ground noise killers, and sensitive USB device protectors.

 

I have spent the past few days researching different methods of of fixing my ground loop interference between my computer and power amp (C5D in between).

  • Quick note: I understand there are preventative measures to avoid ground loops; I am grounding to the same outlet, correct polarity, interconnect cables have adequate ground conductivity. My ground loop is parasitic between my computer and power amp.

I am only interested in implementing physically separate grounds between my USB interface & power amp. The 3 most credible methods of isolating my grounds I've found are

  1. supplying clean 5v dc power to the C5D, e.g. via regulated linear transformer powered USB hub;
  2. using a USB isolator - ironically most using the same ADuM family of chips as in the C5D;
  3. using a line level audio transformer between my C5D and power amp.

 

All 3 methods separate the ground between my computer, C5D, or power amp, in order to eliminate ground loop interference. Each has its pros and cons (I would probably choose a quality audio input transformer because I have a few different unrelated ground isolation uses for it). The only thing I can't wrap my head around is the C5D (should) already have galvanic isolation between the USB input and rest of the device. Which makes me pause before I spend additional dollars on similar devices. I expected the galvanic isolation of my C5D to at least attenuate ground noise compared to connecting the headphone out of my computer to the power amp, but the noise is just as bad either way.

Other sanity checks:

  • Above ground loop noise is present both when C5D is in charge or battery mode
  • Nexus 5 > C5D > power amp: absolutely no noise (as expected; only 1 ground via power amp)
  • Plugged in laptop > C5D > power amp: absolutely no noise
  • Computer > C5D > headphones: absolutely no noise (as expected; only 1 ground via computer)
  • Computer TOSLINK > receiver: absolutely no noise (TOSLINK = galvanic isolation / ground isolation; physically separate grounds)
  • Computer TOSLINK > receiver > power amp: small amount of noise (slight ground interference between receiver & power amp)

 

Based on my sanity checks above, I can only conclude my C5D is not at all galvanically isolated. It seems to be merrily sharing ground between my computer and power amp. I lent my multimeter out a couple weeks back thinking I wouldn't need it any time soon (D'oh!). I will check for continuity between input & output grounds on C5D when I get it back. Can someone please help by reporting their experience with ground loop interference (or lack of) specifically when connecting their computer > C5D > grounded audio device (power amp, powered monitors, receiver, etc)?

 

Thanks all!!

 

Note: aside from the above, I LOVE the C5D. If it never claimed to have galvanic isolation via the ADuM3160, I would have no confusion as to why I am hearing buzzing and interference. But since it does claim so, I am a little perplexed. Am I misunderstanding the fundamental implications of C5D's galvanic isolation? I think not?

 

Drawing of the ADuM3160:


Edited by pixelcity - 5/30/14 at 9:47pm
post #2563 of 2658
@pixelcity: I believe we exchanged messages recently. Vbus and data pins at side 1 are isolated from side 2 by the ADuM3160. You can prove this by operating C5D in battery mode; C5D will forcefully shut down once its battery is drained.
 
The DAC's 5V/3.3V/1.8V supplies are derived from higher voltage on side 2, meaning the DAC is self-powered when the USB 5V rail is absent (Vbus1). Battery charging resides on side 1 and is disabled when C5D is set to battery mode. In charge mode, 5V power from Vbus1 has an indirect pathway through the charging circuit such that side 2 and side 1 are not isolated. GND1 is common to GND2 to avoid ground loop noise within the amp/DAC while in charge mode. Thus, galvanic isolation is true for 5V, D+, and D- pins. There is no isolation of the USB GND pin.
 
Quote:
Note: aside from the above, I LOVE the C5D. If it never claimed to have galvanic isolation via the ADuM3160, I would have no confusion as to why I am hearing buzzing and interference. But since it does claim so, I am a little perplexed. Am I misunderstanding the fundamental implications of C5D's galvanic isolation? I think not?
 
Sorry, this is a description oversight on our part and will be clarified at jdslabs.com. Let me know if there's anything we can do to help. Depending on the nature of your system's ground loop noise, an external USB isolator may help with the power amp.
 
Summary: Since all pins excluding GND2 are isolated by the ADuM3160, the DAC is isolated so long as headphones are connected as the output device. Ground loop noise is possible when an external power amp is used, due to multiple grounds.
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post #2564 of 2658

Crapola - tablet died while responding. Hate when that happens...

Edit: Assuming I should read your final summary statement as applying to both charge and battery modes, right? I get the same interference either way. (Oops should have hit refresh. You confirmed below)

 

jseaber, thanks for your excellent reply. I did contact you separately, and your response was in no way lacking. The headfi community is an invaluable well of information; I had some time to do some additional testing with my setup and wanted to gather some data points, if you will, from the community.

 

Regardless, you have cleared up the issue entirely for me in your post above. I never considered charging was necessarily on side 1, and consequently needed GND1 shared with GND2. I should mention that I would have purchased the C5D either way because it's totally awesome at it's intended use as a mobile DAC & HP amp.

 

The only question remaining (for me) is: would JDS Labs consider isolating grounds on the next do-it-all portable dac/amp? It would be the swiss army knife of dac/amps.

I assume charging is on side 1 for a good reason. There's probably a catch 22 scenario between clean power, isolated grounds, and which side of the ADuM* you're on. Furthermore, this is a non issue for HP users. So perhaps it's a tall order. But, it would be a killer tool for both headphones and hifi systems; would make lots of computer-fi guys like me (with power amps / powered monitors) happy.

 

Bottom line: you guys are great, & pretty please with sugar on top.


Edited by pixelcity - 5/31/14 at 8:47pm
post #2565 of 2658

@pixelcity: We're constantly listening to community feedback and plan future products accordingly. Ground isolation was avoided in C5D since it raises production cost and brings no benefit to headphone use. I agree, it would be a handy addition for a DAC equipped with line-output. Thanks for the feedback!

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