Qudelix-5K Bluetooth DAC & Headphone Amp

[bobbooo]

Any way to configure the PEQ without the phone app?

Nope.

 

[somebodyelse]

Thanks. Feared as much.

 

[bobbooo]

Sonically I'm not worried. I'm sure the DAC is as good as or better than HeadRoom's ca. 2006 implementation.
https://www.stereophile.com/content/headroom-desktop-da-headphone-amplifier-measurements

I'm far more concerned with practical issues. Will the battery management support an always-plugged-in use case, for example?

Yes, when full the battery will be bypassed when plugged in for USB DAC mode, saving battery wear. See here:

https://www.qudelix.com/blogs/5k-dac-amp/usb-dac

 

[bobbooo]

Thanks. Feared as much.

Don't you have a smartphone?

 

[Cahudson42]

Thanks. Feared as much.

Buy a $30 LG Rebel TracFone and you can use it via USB as a streaming Qudelix front end, while simultaneously using BT to control it via App.

Or just to control it via bt and App.

https://www.amazon.com/dp/B07GBRB3SC/

You throw away the sim card/TracFone stuff and use it on wifi/bt No need to activate.

Rather than thinking of it as an 'extra phone', think of it as a Smart Remote

 

[somebodyelse]

Don't you have a smartphone?

Depends on your definition - LineageOS with no GApps, and whichever linux distro I'm playing with on a PinePhone. I'm hoping the PinePhone software advances enough that I can ditch the LineageOS one, in which case I'd be limited to trying to get the Android app to run in Anbox. I really don't want to have to keep a separate phone just to control a headphone adapter! Plus if it's already connected to my desktop or laptop I'd rather do the adjustments from there than have to dig out a phone to do it. If there's some interface documentation around I can probably write the necessary app myself.

 

[bobbooo]

Depends on your definition - LineageOS with no GApps, and whichever linux distro I'm playing with on a PinePhone. I'm hoping the PinePhone software advances enough that I can ditch the LineageOS one, in which case I'd be limited to trying to get the Android app to run in Anbox. I really don't want to have to keep a separate phone just to control a headphone adapter! Plus if it's already connected to my desktop or laptop I'd rather do the adjustments from there than have to dig out a phone to do it. If there's some interface documentation around I can probably write the necessary app myself.

There's a direct link to the latest app APK on the Qudelix forum here.

 

[somebodyelse]

There's a direct link to the latest app APK on the Qudelix forum here.

Thanks - but why is that (and the DFU for that matter) hosted on Google Drive (or dropbox for some of the other DFU versions) instead of being available on their web site? Having a Windows-only DFU tool because of unreliable updates via bluetooth is a bit disconcerting too (found while having a look round the forum). I'll give the APK a try anyway.

 

[bobbooo]

Thanks - but why is that (and the DFU for that matter) hosted on Google Drive (or dropbox for some of the other DFU versions) instead of being available on their web site? Having a Windows-only DFU tool because of unreliable updates via bluetooth is a bit disconcerting too (found while having a look round the forum). I'll give the APK a try anyway.

Why not use Google Drive or Dropbox for the tiny minority of people who don't use the Google Play or Apple stores? It looks like the company is a one-man show, so resources are probably tight. And I've had no problems with installing updates over Bluetooth.

 

[m_g_s_g]

If there's some interface documentation around I can probably write the necessary app myself.

Not that I’m aware of.

Out of curiosity, I captured today a Bluetooth BLE protocol trace (Android phone <-> qudelix) while just changing from a previously saved EQ preset to another one and changing the volume. > 240 frames, mostly L2CAP / RFCOMM. Not easy (for me) to follow.

 

[somebodyelse]

Not that I’m aware of.

Out of curiosity, I captured today a Bluetooth BLE protocol trace (Android phone <-> qudelix) while just changing from a previously saved EQ preset to another one and changing the volume. > 240 frames, mostly L2CAP / RFCOMM. Not easy (for me) to follow.

I've done similar for the Forte's controls over USB where I had the Gen 1 Scarlett kernel support as a cheatsheet for a subset of it, so I'd be much happier with documentation!

 

[jhaider]

Mine came in today, and I don't think I'm getting the same levels as Amir did. I don't have "balanced" headphone cables, but volume even at 2V mode was no better than my MacBook Pro on my Sennheiser HD580s. Connected to the HeadRoom Desktop amp output is also quite a bit lower than with amp's the internal DAC. Also very noisy on the top half of the Desktop Amp's volume knob in high gain driving 580s.

Given that my primary intended use is as a fixed USB DAC/EQ feeding the HeadRoom amp, would a "balanced" 2.5mm TRRS to RCA cable be useful here?

 

[Cahudson42]

In order to pinpoint the problem, did you temporarily try driving the Qudelix via Bluetooth? Might eliminate - or show - the issue is related to USB/upstream connection?

BT>Qudelix>HD580
BT>Qudelix>Headroom>HD580

 

[mSpot]

Given that my primary intended use is as a fixed USB DAC/EQ feeding the HeadRoom amp, would a "balanced" 2.5mm TRRS to RCA cable be useful here?

Does your HeadRoom amp have a balanced input? If not, then you can't use the Qudelix balanced output with it.

In the Qudelix app, try the high power mode setting and see if it helps.

 

[m_g_s_g]

I don't think I'm getting the same levels as Amir did

Have you tested that with a multimeter?

With unbalanced cables, the output levels were lower than what I expected as well. I had to switch to balanced cables; then I got the volume I wanted with enough headroom. With EQ enabled, an additional negative gain is forced.

 

[jhaider]

Does your HeadRoom amp have a balanced input? If not, then you can't use the Qudelix balanced output with it.

In the Qudelix app, try the high power mode setting and see if it helps.

I was using high powered mode - I will the BT test suggested earlier in case it has something to do with my MacBook Pro.

I have a hard time seeing how “balanced” is a real thing in headphones. A “balanced” headphone output has a signal and a return. You know what else has signal and return? A standard unbalanced line level input.

 

[m_g_s_g]

I have a hard time seeing how “balanced” is a real thing in headphones.

Yes, from this point of view, there is hardly any advantage.

But on top of that, many dongle headphone amps can effectively double the output power (by dedicating independent output channels to L & R) when in "balanced" mode.

EDIT: In other words, it’s not because the signal is balanced: It’s because L & R channels are driven by independent amp stages (dual mono amp)

 

[m_g_s_g]

From qudelix 5K users manual:

Balanced mode:
Works with Dual ES9218p
- Max. 4V RMS output
- 4-Wire Output from Source Device
- 4ch DAC/AMP required for Stereo Audio
[...]
- 2x more power and driving capability

 

[jhaider]

Yes, from this point of view, there is hardly any advantage.

But on top of that, many dongle headphone amps can effectively double the output power (by dedicating independent output channels to L & R) when in "balanced" mode.

EDIT: In other words, it’s not because the signal is balanced: It’s because L & R channels are driven by independent amp stages (dual mono amp)

So a “balanced” to stereo RCA adapter may help with output levels here?

 

[m_g_s_g]

So a “balanced” to stereo RCA adapter may help with output levels here?

Hmmm. Not really sure. I know that a balanced (2.5mm TRRS) connector is automatically detected in the app. But with a balanced to RCA adapter you are definitely shorting both (-) ends. Sorry, I can’t test that until Tuesday.