[Baten]

I think there are two parts to GTO implementation - upsampling and the filter itself. Based on the PCM indicator LED, it appears that upsampling is applied to all 3 filters for PCM files. However, I would think the filters are still different since there is no reason why Standard (Linear) or Bit Perfect can't be applied to the 352/24 upsampled PCM stream.

Bit Perfect can't possibly work with the MQA firmware on the micro. That's false.

 

[bflat]

Bit Perfect can't possibly work with the MQA firmware on the micro. That's false.

I don't know much about MQA, other than it's still a PCM format. Why wouldn't bit perfect work since that means no digital filter?

 

[Baten]

I don't know much about MQA, other than it's still a PCM format. Why wouldn't bit perfect work since that means no digital filter?

As far as I know only the iDSD PRO can do bitperfect, as well as MQA decoding. On the micro BL series, it is -OR- MQA support -OR- BitPerfect support. Quite frankly, if you hear differences they are in your head because they will both use GTO lol.
(if I remember correctly I think it has to do with how much code they can put on the micro which is limited but don't quote me on this)

 

[dcguy73]

I've been experimenting with swapping USB filters in and out between my Mac mini (running macOS/Windows) and the iDSD Signature.

I tried out the following:

1. iSilencer 3.0
2. iDefender 3.0 (with and without iPower X 5v)
3. iGalvanic 3.0 Nano
4. iUSB 3.0 Nano (which my Mac couldn't "see" so it was a bust)
5. Holo Audio Titanis USB Turbo filter

For me, an effective USB filter makes the music sound a bit louder (due to a reduction in background noise) and a little crisper/clearer. None of the devices I tried were able to achieve that. The only sound changes I detected were a slight rounding of treble and a slight softening of transients. Not a desirable outcome. The iDSD Signature sounded best with a direct USB connection to my Mac.

Conclusion: iFi did well with its USB implementation in the iDSD Signature. Just like with the iDSD Pro, none of my USB filters were able to improve upon the iDSD Signature's sound.

I just repeated the USB filter test described above with the Signature on firmware 5.2. It's after midnight, and I thought maybe at night when things were quieter, I might hear more of a difference by trying different combinations of USB filters. No such luck. There was no noticeable difference.

However, I thought to switch out the crappy 77-cent C7 power cable that came with my Mac Mini for a more solidly-built model and that got me some results. The music sounded louder and I could pick out different instruments in the mix more easily. For example, when listening to the MFSL version of Tears for Fears' "Songs From the Big Chair," the sound was less compressed. I could hear the overlapping lines of bass, guitar, and percussion on "Mothers Talk" more separately and distinctly.

Then I thought, "There's an improvement! Now I'll be able to hear the difference with the USB filters". So I tried the filter test again.

None of the filters noticeably changed the sound.

I did find that after trying all of the filters twice, when using the Signature's bit-perfect filter, a USB filter would smooth over poorly-recorded music so it's more tolerable. But once you switch to the minimum-phase filter, the difference is negligible. The minimum-phase filter by itself will smooth over poorly-recorded music.

This was a disappointing evening (especially for my sad collection of filters), but I'm glad I don't need to use a box in-between my Mac Mini and the Signature.

EDIT: Well, it's 3 AM, so why not try something else? I plugged my Mac Mini and its powered docking station into a battery-powered sine wave power regenerator (I have one for power outages). Wow! A huge difference in the sound. So much cleaner and less "edgy" and I can hear more at lower volumes.

Lesson learned: Upgrading my source's power cable/supply made a much bigger difference than trying to improve the USB connection between the Mac Mini and the Signature.

 

[DiederickFritz]

EDIT: Well, it's 3 AM, so why not try something else? I plugged my Mac Mini and its powered docking station into a battery-Lesson learned: Upgrading my source's power cable/supply made a much bigger difference than trying to improve the USB connection between the Mac Mini and the Signature.

Is this the general consensus for all audio setups? Am I going to have to get an upgraded power cable for my PSU? I was under the impression that having a clean usb connection and a transparent DAC/Amp mattered more...

 

[dcguy73]

Is this the general consensus for all audio setups? Am I going to have to get an upgraded power cable for my PSU? I was under the impression that having a clean usb connection and a transparent DAC/Amp mattered more...

It depends. In my situation, I live in an older 50-year-old+ apartment building with crappy, noisy power. Power upgrades make a big difference for me. YMMV.

 

[DiederickFritz]

It depends. In my situation, I live in a 50-year-old+ apartment building with crappy, noisy power. Power upgrades make a big difference for me. YMMV.

lol same... None of my outlets are even grounded. Looks like I’m gonna have to buy some Blue Dragon power cables

 

[Hoegaardener70]

Oh dear - Is it really true that the USB blue cable connection from PC to signature is not charging the device??? The BL never needed any charging, the connection as such powered the device. But last week, I replaced my trusted ifi micro BL on my desk with the signature. I was very happy with it ... until the device was suddenly dead. I thought disaster, but it turned out it was only empty battery. It is now charged and working as expected, but it makes life more complicated to keep in mind when it was last charged. Would a second usb-c cable help? Thanks

 

[CANiSLAYu]

USB A port is data only and USB C port is power only. Yes, would need two cables to charge and play at the same time.

 

[Hoegaardener70]

USB A port is data only and USB C port is power only. Yes, would need two cables to charge and play at the same time.

Thanks. Why did this work with the Blue Label?

 

[bflat]

Thanks. Why did this work with the Blue Label?

It's a design change for improved audio quality. All higher end DACs have separate data and power.

 

[Hoegaardener70]

It's a design change for improved audio quality. All higher end DACs have separate data and power.

I see. It somehow makes sense but it definitely creates issues for my setup.
But many thanks, at least I know what is going on and why.

 

[Sebastien Chiu]

I see. It somehow makes sense but it definitely creates issues for my setup.
But many thanks, at least I know what is going on and why.

Out of curiosity, what issues are you speaking of the outside of practicality with having to have more than two cables (which we totally understand)?

Let us know and perhaps Rob and I can assist in some way.

One of the major reasons we don't suggest using the black label signature while also being charged is because of battery longevity. This is the case for these kinds of batteries in general.

 

[Burakk]

Out of curiosity, what issues are you speaking of the outside of practicality with having to have more than two cables (which we totally understand)?

Let us know and perhaps Rob and I can assist in some way.

One of the major reasons we don't suggest using the black label signature while also being charged is because of battery longevity. This is the case for these kinds of batteries in general.

Then, should I understand, all time desktop use case wasn’t considered on design of ifi sig?

 

[iFi audio]

@iFi audio, this change with v5.3c isn't made clear on your firmware download web page.

Above the link to download firmware 5.3, it says at the top of the page, "Gibbs Transient Optimised Digital (GTO) Filter implemented – This replaces the Minimum Phase Filter."

It's not apparent that it overrides the two other filters.

Also, I could have sworn that after I installed firmware 5.3c, I could hear differences in the sound when switching between the three filter switch positions, but I guess that was just in my head?

If you'll take a look here:

https://ifi-audio.com/firmware/unified-firmware-for-various-products/

...under the 5.3c tab relesed on the 10th of September 2018, you'll see this line: "All PCM LED colours will be the same colour due to GTO filter". For the GTO to be active, it can't be altered by any other filter, which is why even those engaged by physical knobs don't work. I'll double-check whether they might still be active, but in 99% I'm sure they aren't.