iFi foe fum

[mansr]

3 minutes ago, Shadders said:

I tell you what, i was looking at the iFi Dac literature, and their plots look remarkably like the Stereophile ones.

 

I reckon Stereophile borrowed them from the iFi literature. When iFi finds out, i think they ain't gonna be happy. I mean, copying someone elses drawings, is an utter disgrace. It just goes to show, you can't trust some people.

iFi already admitted to pilfering the plots from Stereophile. Now let's leave that topic aside, however amusing it may be.

[Shadders]

Just now, mansr said:

iFi already admitted to pilfering the plots from Stereophile. Now let's leave that topic aside, however amusing it may be.

I know. It is just so hilarious. The "unreserved apology". Anyone would have thought that iFi let their dog take a dump on Stereophiles doorstep.

 

It is just a picture.

[mansr]

2 hours ago, crenca said:

Do you or anyone else know if the analogue filter in the Nano is the same as the one in the micro iDAC2 (non black label version(s) - and for that matter do the black lable version have a different analog filter)?  I have a Nano I travel with, but I use the micro iDAC2 in my HP rig when I am not using some other DAC...

The Nano has a simple, passive 2nd order RC filter between the DAC and the headphone amp. The iDAC2 has a more elaborate active filter incorporating an OPA1654 opamp. I'm not sure of the exact topology.

[crenca]

55 minutes ago, mansr said:

The Nano has a simple, passive 2nd order RC filter between the DAC and the headphone amp. The iDAC2 has a more elaborate active filter incorporating an OPA1654 opamp. I'm not sure of the exact topology.

 

Thanks.  Do you know enough about the topology to say if either the passive filter in the Nano or the OPA1654 in the iDAC2 is in the signal path when using the RCA outs?  

 

In any case, thanks for bringing all this up!!

[mansr]

4 minutes ago, crenca said:

Thanks.  Do you know enough about the topology to say if either the passive filter in the Nano or the OPA1654 in the iDAC2 is in the signal path when using the RCA outs?

The low-pass filter is required with the DSD1793 chip, so yes, it is used with both RCA and headphone outputs.

[mansr]

I played some CD quality music and looked for clipping in the data sent to the DAC. Here's an example, original in blue, GTO-filtered in red:

 

[asdf1000]

On 3/18/2019 at 8:27 AM, mansr said:

In order to get a closer look at this magical filter, I connected a logic analyser to the inputs on the DSD1793 DAC chip. With this new firmware, the chip is put in filter bypass mode, the XMOS now upsampling everything to 352.8/384 kHz.

 

Hi mansr

 

As a baseline for comparison, can you share the same measurements with the DSD1793 doing the digital filtering , for this same DAC?

 

 

[mansr]

25 minutes ago, Em2016 said:

As a baseline for comparison, can you share the same measurements with the DSD1793 doing the digital filtering , for this same DAC?

The best I can do in that regard is recording the analogue output. I did that a while back:

[asdf1000]

2 hours ago, mansr said:

The best I can do in that regard is recording the analogue output. I did that a while back:

 

Thanks. It's not easy to compare directly unfortunately. Different measurements.

 

I guess the background to my query is how much of these results is to do with the GTO filter itself?

 

Unless we can properly compare against DSD1793 chip performance of this DAC, it's hard to know for sure?

 

[GoldenOne]

On 3/17/2019 at 10:15 PM, Miska said:

The filter doesn't seem so far from the MQA filters. And it was introduced at the same time with MQA support. So I'm wondering how much there is actually common ground between the two...

 

 

 

MQA filter in blue, GTO filter in white. They seem to be......quite similar.....

 

HQPlayer Sinc-M, LNS15 (blue), GTO filter in white for comparison/to show device limitations.

[PaperBoat]

On 3/19/2019 at 4:28 PM, mansr said:

One problem. The DSD1793 works better with 192 kHz input than 384 kHz. This is because the 192 kHz input is upsampled 8x to 1536 kHz, greatly reducing the demands of the analogue filter (external to the chip). With the weak 2nd order filter of the Nano, this makes a real difference.

I've got an IFI Zen V2 (DSD1793) and use non-MQA firmware. I would like to know which one of the upsampling/ downsampling (using SOX in JRiver) rate is best to feed the DAC? Is it 192KHz or 384kHz?