Which DACs bypass digital filtering?

[asdf1000]

3 minutes ago, mansr said:

Too many blatant lies. For example, the filter selection labelled "minimum phase" is anything but. It is the very much linear phase filter called "slow rolloff" in the datasheet.

 

Noted. Have they ever clarified this? If asked (nicely) they do seem happy to explain and clarify things.

 

[mansr]

Just now, Em2016 said:

Noted. Have they ever clarified this? If asked (nicely) they do seem happy to explain and clarify things.

They like giving off that impression. There is, however, rarely anything of substance is what they say. I'm also quite sceptical about this supposed use of undocumented features. I've examined the Nano in detail, and there's nothing of the kind going on there.

[asdf1000]

8 minutes ago, mansr said:

They like giving off that impression. There is, however, rarely anything of substance is what they say. I'm also quite sceptical about this supposed use of undocumented features. I've examined the Nano in detail, and there's nothing of the kind going on there.

 

The nano can run off internal battery so I wonder if they may limit internal processes (like internal upsampling) to conserve battery power. It’s also a small battery, relative to the micro’s larger battery.

 

The iDAC2 (which is what they were clarifying) is only bus powered.

 

I guess I will ask them (nicely again) and see what they say.

 

 

[semente]

I don't mind a bit of side-stepping but you're taking this a bit too much away from the topic.

It's nonetheless interesting so why no start a new thread. Maybe Chris can give a hand moving some of the last messages?

[asdf1000]

1 minute ago, semente said:

I don't mind a bit of side-stepping but you're taking this a bit too much away from the topic.

It's nonetheless interesting so why no start a new thread. Maybe Chris can give a hand moving some of the last messages?

 

Not a problem. The iFi micro was listed as by-passing digital filtering (on topic). This was clarification about that.

 

Happy for posts to be split or to just end the iFi discussion as above.

 

[flkin]

Please add the VR DAC 2.0

 

Vinnie Rossi DAC 2.0 has a dual-mono design, with two AKM AK4497EQ d/a chips. Its default mode is a non-oversampling filter with digital filter bypass. Allows bit-perfect playback at sampling rates up to 768kHz (16, 24, or 32 bit compatible), as well up to DSD512.

 

And as you can expect, the sound is very analogue

[asdf1000]

On 02/12/2017 at 8:32 PM, semente said:

A quick update to the list:

 

- Phasure NOS1 DAC

- Teac UD-50x family

- Esoteric (some models?)

- Aqua DACs

- Lampizator DACs

- Audio-GD (some models)

- Spring AudioDACs (some models?)

- Denafrips DACs

- iFi micro (some models)

- Metrum Acoustics DACs

 

 

So just a note on the iFi micro that's mentioned in this list.

 

Here is the complete summary straight from the horses mouth, of which iFi DACs and which specific settings will by-pass digital filtering:

 

The internal up-sampling in all past and present iFi products with the DSD1793 DAC Chip and non-MQA Firmware (that is iDSD nano, iDSD nano LE, iONE Nano,  iDSD nano Black Label flashed with 5.2X, iDSD micro, iDSD micro Black Label, iDAC 2 micro, Retro STereo 50) operates as follows:

 

Bitperfect filter selected (all micro products only):

• 44.1kHz ... 384/768kHz -> No ASRC, no upsampling, no digital filter
• DSD64 ... DSD256/512 -> No ASRC, no upsampling, no digital filter

 
Standard/Measure Filter selected: 

• 44.1kHz ... 48kHz -> No ASRC, synchronous oversampling to 352.8/384kHz using long FIR (Transient Aligned) digital filter 
• 88.2kHz ... 192kHz -> No ASRC, synchronous oversampling to 705.6/768kHz using long FIR (Transient Aligned) digital filter 
• 352.8 ... 384/768kHz -> No ASRC, No upsampling, no digital filter
• DSD64 ... DSD256/512 -> No ASRC, No upsampling, no digital filter

 

Minimum/Listen Filter selected: 

• 44.1kHz .. .48kHz -> No ASRC, synchronous oversampling to 352.8/384kHz using ultra short FIR (minimum ringing Bezier) digital filter 
• 88.2kHz ... 192kHz -> No ASRC, synchronous oversampling to 705.6/768kHz using ultra short FIR (minimum ringing Bezier) digital filter 
• 352.8 ... 384/768kHz -> No ASRC, no upsampling, no digital filter
• DSD64 ... DSD256/512 -> No ASRC, no upsampling, no digital filter

 

Source:

 

 

 

[semente]

Update:

- Aqua DACs

- Armature Asterion (same as Holo Spring)

- Audio-GD (some models)

- Denafrips DACs

- Esoteric (some models?)

- Lampizator DACs- Spring AudioDACs (some models?)

- Holo DACs (some models)

- iFi micro (some models)

- Lampizator DACs

- Metrum Acoustics DACs

- Phasure NOS1 DAC

- Teac UD-50x family

[buonassi]

schiit modi multibit is an example of a DAC that doesn't do oversampling at it's highest published sample rates (192 and 176.4).   I had it until recently, and can confirm this.   Plus, it's listed as such on their website. 

 

iFi Micro IDAC2 - my current DAC, has a "bit perfect" setting which bypasses all oversampling, has a near perfect impulse response, but rolls off a bit too much of the highs (for my taste) in an attempt to avoid aliasing. 

[mansr]

8 minutes ago, buonassi said:

iFi Micro IDAC2 - my current DAC, has a "bit perfect" setting which bypasses all oversampling, has a near perfect impulse response, but rolls off a bit too much of the highs (for my taste) in an attempt to avoid aliasing.

That's a stupid name for a stupid setting. What it does it put the DAC chip in filter bypass mode, meaning the input goes straight to the zero-order hold where samples are simply repeated to reach the oversampling rate of the sigma-delta stage. This results in the analogue output actually having that stair-step shape that digital is often wrongly accused of producing. I can't fathom why someone thought adding this mode was a good idea.

[buonassi]

2 minutes ago, mansr said:

That's a stupid name for a stupid setting. What it does it put the DAC chip in filter bypass mode, meaning the input goes straight to the zero-order hold where samples are simply repeated to reach the oversampling rate of the sigma-delta stage. This results in the analogue output actually having that stair-step shape that digital is often wrongly accused of producing. I can't fathom why someone thought adding this mode was a good idea.

yeah, we established their unusual naming in the other thread.  IE their "minimum/listen" filter position implies minimum phase, but it's clearly linear phase slow rolloff.   I thought bit perfect referred to the transport method sending unaltered digital stream to the DAC, untouched by OS layer, or DSP effects - right?  

 

I think the issue is the price bracket they play within.  For the money, this DAC seems to suit me very well.  But Im still learning and I'm sure I'll be ready for my next step up in a few months.  But I gotsta have a true min phase filter in my next DAC.

[buonassi]

I think the issue is the price bracket they play within.

 

meaning these terms appeal to the newbies and ignorant - those folks shopping in the lower price market.  

[mansr]

2 minutes ago, buonassi said:

yeah, we established their unusual naming in the other thread.  IE their "minimum/listen" filter position implies minimum phase, but it's clearly linear phase slow rolloff.   I thought bit perfect referred to the transport method sending unaltered digital stream to the DAC, untouched by OS layer, or DSP effects - right?  

A switch on the DAC can't affect what the player/OS sends it.

 

2 minutes ago, buonassi said:

I think the issue is the price bracket they play within.  For the money, this DAC seems to suit me very well.  But Im still learning and I'm sure I'll be ready for my next step up in a few months.  But I gotsta have a true min phase filter in my next DAC.

iFi DACs are reasonable for the money. It's just that their somewhat loose relationship with the truth leaves me with a bad feeling.

[buonassi]

35 minutes ago, mansr said:

loose relationship with the truth 

 

 

37 minutes ago, mansr said:

A switch on the DAC can't affect what the player/OS sends it.

 

 

so we're saying the same thing I think.  Bit perfect refers to the transport method of unaltered zeros and ones from the source to the DAC.  iFi's switch "bit perfect" is either purposely misleading (causing folks to believe it has magic over your OS) or is just another poorly named feature.  

[semente]

- Aqua DACs

- Armature Asterion (same as Holo Spring)

- Audio-GD (some models)

- Denafrips DACs

- Esoteric (some models?)

- Lampizator DACs- Spring AudioDACs (some models?)

- Holo DACs (some models)

- iFi micro (some models)

- Lampizator DACs

- Metrum Acoustics DACs

- Phasure NOS1 DAC

- RME ADI-2 DAC

- Teac UD-50x family

[hvbias]

Apparently Soekris DAM1021, though I am waiting to hear confirmation from the designer: http://www.diyaudio.com/forums/digital-line-level/269776-filter-brewing-soekris-r2r-37.html

 

When these first came out a "newNOS" (name of the filter) is what people were using linked in the same thread, but apparently the latest iteration of the DIY module DAM1021 (maybe the commercial ones as well? I don't know) is filter less if fed high enough sample rate.

[Miska]

Unfortunately only Soekris DIY stuff can be programmed/used this way. I talked with them at Munich High-End and they clearly refused to add such possibility to their ready made DAC devices...

 

[hvbias]

40 minutes ago, Miska said:

Unfortunately only Soekris DIY stuff can be programmed/used this way. I talked with them at Munich High-End and they clearly refused to add such possibility to their ready made DAC devices...

 

 

If I am understanding Dimdim's reply correctly simply feeding the current unit the highest rate PCM just bypasses all the filters, and all his modules look to be using the same FPGA so that does seem odd to me.

[Ron Scubadiver]

On 5/28/2017 at 3:42 PM, mansr said:

The AK4490EQ (among others) accepts up to 768 kHz PCM and DSD256. Its internal rate isn't as high as that of ESS, but it does process DSD inputs unless put in bypass mode. This is the chip used in the TEAC UD-503.

I have wondered if this chip is implemented to only accept up to 384 kHz (and frequently it is) then if it is fed a 384 kHz signal does it upsample to 768 kHz?

[buonassi]

1 hour ago, Ron Scubadiver said:

I have wondered if this chip is implemented to only accept up to 384 kHz (and frequently it is) then if it is fed a 384 kHz signal does it upsample to 768 kHz?

I thought 768 was reserved for dxd? If 4490 is fed 384 it is nos right?

[Ron Scubadiver]

3 hours ago, buonassi said:

I thought 768 was reserved for dxd? If 4490 is fed 384 it is nos right?

That's the question.

[Miska]

7 hours ago, Ron Scubadiver said:

I have wondered if this chip is implemented to only accept up to 384 kHz (and frequently it is) then if it is fed a 384 kHz signal does it upsample to 768 kHz?

 

Both 352.8/384k and 705.6/768k inputs bypass the digital filter. The internal filter is only capable of going up 352.8/384, so by sending 705.6/768k there instead does 2x higher than it's internal filter is capable of. TI/BB chips are similar.

 

[Ron Scubadiver]

18 hours ago, Miska said:

 

Both 352.8/384k and 705.6/768k inputs bypass the digital filter. The internal filter is only capable of going up 352.8/384, so by sending 705.6/768k there instead does 2x higher than it's internal filter is capable of. TI/BB chips are similar.

 

Thank you for the answer.  

[Rugby]

Border Patrol DAC.

 

http://www.borderpatrol.net/DAC.htm

[semente]

- Aqua DACs

- Armature Asterion (same as Holo Spring)

- Audio-GD (some models)

- Border Patrol

- Denafrips DACs

- Esoteric (some models?)

- Lampizator DACs- Spring AudioDACs (some models?)

- Holo DACs (some models)

- iFi micro (some models)

- Lampizator DACs

- Metrum Acoustics DACs

- Phasure NOS1 DAC

- RME ADI-2 DAC

- Teac UD-50x family