[Silverprout]

  The resistor sets the output impedance.  Line is typically 50-100ohm.  Same as when it is used in the head out of say the AK range.  AK100 Mk1 has a 22ohm, AK120 a 3ohm.  The DX90 and X5 run wide open.  Typically a small value is used so that the output doesn't blow when the trs shorts during insertion and removal.  At these low power values it's not a huge deal but in something like the B22... pulling out or plugging in slowly = BOOM!
 
The LFP of the DAC section, an OPA1611 that feeds the voltage gain stage in the case of the DX90.

It don't set the output impedance, it just undamp the transducers (or input buffers)
Impedance is not a simple resistance with an aperiodic (or periodic) signal.

 

[Solude]

AK was just more detail.  Line output has higher output because, for the most part, line amps don't have much current gain so you wouldn't want low output impedance into low input impedance.  Less of an issue now, more from a time of tubes.
 
Stealing from Wiki...
 

Sampled data reconstruction filters[edit]

The sampling theorem describes why the input of an ADC requires a low-pass analog electronic filter, called the anti-aliasing filter: the sampled input signal must be bandlimited to prevent aliasing (here meaning waves of higher frequency being recorded as a lower frequency).

For the same reason, the output of a DAC requires a low-pass analog filter, called a reconstruction filter, as the output signal must be bandlimited, to prevent aliasing (here meaning Fourier coefficients being reconstructed as low frequency waves, not as higher frequency aliases), as in the Whittaker–Shannon interpolation formula.

Ideally, both filters should be brickwall filters, constant phase delay in the pass-band with constant flat frequency response, and zero response from the Nyquist frequency. This is given by a filter with a 'sinc' impulse response.

Implementation[edit]

Practical filters have non-flat frequency or phase response in the pass band and incomplete suppression of the signal elsewhere, as a sinc waveform has an infinite response to a signal, in both the positive and negative time directions, which is impossible to perform in real time – it would require infinite delay.

In systems that have both, the anti-aliasing filter and a reconstruction filter may be of identical design. For example, both the input and the output for audio equipment is sampled at 44.1 kHz. Both audio filters block as much as possible above 22 kHz and pass as much as possible below 20 kHz. Typically both filters are active op-amp filters, with exactly the same selection of resistors and capacitors.

Whilst in theory a DAC gives a series of impulses, in practice, the output of a DAC is more typically a series of stair-steps – thus the step response of the filter (the integral of the impulse response) is of more interest. Thelow pass reconstruction filter smooths the stair step (removes the harmonics above the Nyquist limit) to (re)construct the analogue signal corresponding to the digital time sequence.

 

[Silverprout]

  AK was just more detail.  Line output has higher output because, for the most part, line amps don't have much current gain so you wouldn't want low output impedance into low input impedance.  Less of an issue now, more from a time of tubes.

Wow,
Could you explain it with more details please ?

 

[georgelai57]

This thread is so long. Has anyone tried the USB-OTG to connect an ext HDD to the DX90?

 

[Rumpelstiltskin]

Yes, worked absolutely fine with a USB stick. Got a bit ambitious and tried to link it to my Seagate 1TB drive (with mixed media on drive). Just got a 'blank' grey screen (I have wallpaper plain grey - which helps me read the DX90 screen better in outdoor daylight). 

 

[musicheaven]

Because having a relatively large HDD on the player OTG, that's where a wi-fi link to your outside music server would make more sense. I came to the conclusion that even if it's rated for up to 2 TB drive, it never works reliably and a USB stick or USB to microSD or SDHC/X card reader works best. I have been able at one point to get my wall powered HDD external drive to be read from it however it has been flaky at best and the DX90 battery consumption seems to go down faster even though it does not have the power supplied to the external drive. Basically it's a nice feature to show in your specs but pretty useless when trying to implement it. I also found that to be really power independent requires a special one head to two head connector having the power separate from the data signal. Has anyone successfully implemented this feature? Also can you describe your setup?

 

[jamato8]

I very frequently use OTG and like it.

 

[headwhacker]

I just setup VMWare Fusion so I can run my old WinXP vm and use the RKBatchtool instead to write FW to DX90. Just like I suspected, using the tool is a much cleaner way to install firmwares on DX90 (same goes with DX50 I believe). The nagging issue of 2 second cut I always get when listening on gapless albums is somewhat gone. Tried to play the same album several times and it's much smoother and transition is much better.
 
I even tried on v2.0.0 and I don't get the cut as well.

 

[borrego]

  I just setup VMWare Fusion so I can run my old WinXP vm and use the RKBatchtool instead to write FW to DX90. Just like I suspected, using the tool is a much cleaner way to install firmwares on DX90 (same goes with DX50 I believe). The nagging issue of 2 second cut I always get when listening on gapless albums is somewhat gone. Tried to play the same album several times and it's much smoother and transition is much better.
 
I even tried on v2.0.0 and I don't get the cut as well.

 
Thanks for the suggestion!
 
I just did what you have suggested using the RKBatchtool to reload the FW2.0.5. I clicked the "Repair" button in RKBatchtool and I saw it was doing complete internal low level formatting. After that I deleted the .audio folder on my microSD card (still formatted in extFat) and scanned the music again. Let's hope it will fix it for all.

 

[jk47]

question: [i have to admit i haven't read most of the almost 400 pages of this thread]  i organize my music in folders.  in the absence of an x90 guide, i'm reading the x50 user's guide.  it talks of being able to sort by title, album, artist- but i'd like to pick a folder and use that as a playlist- either in order or on shuffle.  can i do that?  if so, how?
 
also i have my folders 3 to 5 layers deep.e.g.
1.  classical>beethoven>string quartets> late quartets> quartet #whatever>track files
2. jazz>monk>monk's dream >track files
 
is there a way to drill down like this, or do i need to flatten the structure? if i have to have a flat folder structure, can i just define each classical piece as an "album" [e.g. album=prokofiev lieutenant kije suite] do i just name a folder like that?
 
also, how does it know the title, album and artist? are those embedded tags?  i ask because i have flac files ripped from my cd's, with no tags attached. 

 

[docBliny]

  question: [i have to admit i haven't read most of the almost 400 pages of this thread]  i organize my music in folders.  in the absence of an x90 guide, i'm reading the x50 user's guide.  it talks of being able to sort by title, album, artist- but i'd like to pick a folder and use that as a playlist- either in order or on shuffle.  can i do that?  if so, how?
 
also i have my folders 3 to 5 layers deep.e.g.
1.  classical>beethoven>string quartets> late quartets> quartet #whatever>track files
2. jazz>monk>monk's dream >track files
 
is there a way to drill down like this, or do i need to flatten the structure? if i have to have a flat folder structure, can i just define each classical piece as an "album" [e.g. album=prokofiev lieutenant kije suite] do i just name a folder like that?
 
also, how does it know the title, album and artist? are those embedded tags?  i ask because i have flac files ripped from my cd's, with no tags attached. 

 
If I understood correctly, you should just be able to drill into the whatever folder structure you want/create on the SD card. That's how I normally browse for music SD Card -> Purchased HiRes -> Artist -> Album
 
On this scenario, you're not using tags at all. However, you'll be limited to files within that folder, not sub-folders. Shuffle will work with those files. You can turn in on from the top-right corner (options are roughly: once, repeat single, repeat all, shuffle)
 
//TB

 

[jk47]

   
If I understood correctly, you should just be able to drill into the whatever folder structure you want/create on the SD card. That's how I normally browse for music SD Card -> Purchased HiRes -> Artist -> Album
 
On this scenario, you're not using tags at all. However, you'll be limited to files within that folder, not sub-folders. Shuffle will work with those files. You can turn in on from the top-right corner (options are roughly: once, repeat single, repeat all, shuffle)
 
//TB

in the dx50 user's guide it states that when you insert a microSD card a screen pops up with 2 options: 
1. scan sd card
2. browse file
 
are you saying that you never bother to scan [am i right in thinking that scanning just makes a library of tags?], just choose browse?
 
also, when you say "you'll be limited to files within that folder, not sub-folders,"  i am interpreting that as saying that if i have 
top folder> 2 separate sub-folders- each subfolder has playable tracks
then i can choose EITHER sub-folder to play the tracks in THAT sub-folder alone; i can't choose the top folder and expect it to play the contents of both sub-folders.  is that correct?

 

[AnilKumar]

Hi guys,
I am using dx90 for last three weeks. My many old mp3 files used to play fine on IPOD , either does not play at all on dx90 or makes squeaky sound while playing. Is it normal ? Or is there any issue with my DX-90 ?
 
Thanks
Anil

 

[Cotnijoe]

  Hi guys,
I am using dx90 for last three weeks. My many old mp3 files used to play fine on IPOD , either does not play at all on dx90 or makes squeaky sound while playing. Is it normal ? Or is there any issue with my DX-90 ?
 
Thanks
Anil

 
Definitely not something that should be happening...

 

[docBliny]

in the dx50 user's guide it states that when you insert a microSD card a screen pops up with 2 options: 
1. scan sd card
2. browse file

are you saying that you never bother to scan [am i right in thinking that scanning just makes a library of tags?], just choose browse?

also, when you say "you'll be limited to files within that folder, not sub-folders,"  i am interpreting that as saying that if i have 
top folder> 2 separate sub-folders- each subfolder has playable tracks
then i can choose EITHER sub-folder to play the tracks in THAT sub-folder alone; i can't choose the top folder and expect it to play the contents of both sub-folders.  is that correct?

The DX90 scans the SD card automatically when you insert it. I can't speak for the 50 as I've never used it. Then I simply choose Directory/SD card from the menu and drill into the desired folder.

Regarding the folders: Correct, it'll only play tracks from a single folder. I.e. you have to drill down to a folder with tracks as far as I've seen.

//TB