Millennia Media imersiv D1

ChatGPT Explain

F0 Fast Roll-off Linear Phase (default) 
F1 Slow Roll-off Linear Phase 
F2 Apodizing Fast Roll-off Linear Phase 
F3 Fast Roll-off Minimum Phase 
F4 Slow Roll-off Minimum Phase 
F5 Hybrid Fast Roll-off Minimum Phase

These labels describe digital reconstruction filters inside a DAC.
They all do the same job (rebuild a smooth analog waveform from discrete samples), but they make different trade-offs between frequency response, time behavior, and ringing.

I’ll explain this in plain language first, then get a bit technical.

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Big picture (what these filters change)

Digital filters mainly affect:

1. Ringing (tiny ripples around transients)

2. Phase behavior (timing accuracy vs symmetry)

3. High-frequency roll-off (how close to Nyquist the response stays flat)

None of these change bass, volume, or bit depth.
They subtly affect transients, imaging, and “feel.”

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Two key axes to understand first

1️⃣ Linear Phase vs Minimum Phase

Linear Phase

• Perfect phase accuracy

• Time-aligned frequencies

• Causes pre-ringing (ringing before a transient)

• More “precise”, sometimes described as clinical

Minimum Phase

• No pre-ringing

• All ringing occurs after the transient

• Phase is altered (time smear)

• Often perceived as more natural or analog

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2️⃣ Fast Roll-off vs Slow Roll-off

Fast Roll-off

• Very sharp cutoff near Nyquist

• Maximum frequency extension

• More ringing

Slow Roll-off

• Gentler cutoff

• Slight HF attenuation near top octave

• Less ringing

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Now let’s explain each mode.

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F0 — Fast Roll-off Linear Phase (default)

What it does

• Sharp cutoff

• Perfect phase

• Symmetrical ringing (before & after transient)

Sound character

• Maximum detail

• Precise imaging

• Can sound “digital” on sharp transients

Why it’s default

• Measures best

• Technically “correct”

• Matches textbook DAC design

Use if you want

• Studio accuracy

• Analytical listening

• Best frequency extension

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F1 — Slow Roll-off Linear Phase

What changes

• Gentler HF cutoff

• Still linear phase

• Less ringing

Sound character

• Slightly smoother

• Less edge on cymbals

• Tiny loss of air at extreme HF

Use if

• F0 sounds too sharp

• You want linear phase without aggressiveness

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F2 — Apodizing Fast Roll-off Linear Phase

Key idea: “cleaning upstream damage”

What apodizing means

• Suppresses ringing caused by earlier ADC filters

• Especially relevant for older recordings

What it does

• Still linear phase

• Fast roll-off

• Reduced pre-ringing artifacts from source material

Sound character

• Cleaner transients

• Slightly smoother than F0

• Often preferred for older digital masters

Use if

• Listening to early digital recordings

• You want precision with less harshness

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F3 — Fast Roll-off Minimum Phase

Major change

• No pre-ringing

• Phase is no longer linear

What you gain

• More “natural” transients

• Punchier attacks

What you lose

• Perfect phase alignment

• Some spatial precision

Sound character

• More analog-like

• Slightly thicker

• Less etched imaging

Use if

• You dislike pre-ringing

• You value musicality over measurement perfection

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F4 — Slow Roll-off Minimum Phase

Most relaxed filter

What it does

• No pre-ringing

• Gentle HF roll-off

• Least ringing overall

Sound character

• Warm

• Smooth

• Forgiving

Trade-off

• Softest treble

• Least “air”

Use if

• Bright system

• Long listening sessions

• Older or harsh recordings

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F5 — Hybrid Fast Roll-off Minimum Phase

Best of both worlds attempt

What “hybrid” means

• Fast roll-off

• Minimum phase behavior

• Ringing optimized to be less audible

Sound character

• Good attack

• Cleaner highs than F3

• Less HF loss than F4

Use if

• You like minimum phase

• But don’t want slow roll-off dullness

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Quick comparison table

Filter	Phase	Roll-off	Ringing	Sound
F0	Linear	Fast	Most	Precise, analytical
F1	Linear	Slow	Less	Smooth, accurate
F2	Linear	Fast	Reduced	Clean, refined
F3	Minimum	Fast	After only	Punchy, analog
F4	Minimum	Slow	Least	Warm, forgiving
F5	Minimum	Fast	Optimized	Balanced, musical

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Practical advice (important)

You will not hear massive differences.
These are micro-tuning tools.

Common preferences

• Measurement / reference → F0 or F2

• Audiophile listening → F3 or F5

• Bright systems → F4

• Older digital masters → F2

If you want one safe recommendation:

F5 (Hybrid Fast Minimum Phase) is often the most universally pleasing.

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Final takeaway

These filters are about how transients behave, not tone control.
Choose based on:

• Recording quality

• System brightness

• Personal sensitivity to digital edge

 

Filter	Phase	Roll-off	Ringing	Sound
F0	Linear	Fast	Most	Precise, analytical
F1	Linear	Slow	Less	Smooth, accurate
F2	Linear	Fast	Reduced	Clean, refined
F3	Minimum	Fast	After only	Punchy, analog
F4	Minimum	Slow	Least	Warm, forgiving
F5	Minimum	Fast	Optimized	Balanced, musical

Based on the post I made above I wanted to try the F5 filter.This filter seemed like a nice sounding filter a bit rounder in sound compared to the default F0 filter I have always used. I tried this for 2 days and over 20 hours (I work a lot). I was getting some ear fatigue on the first day. Maybe I was tired. Today, after a nice sleep back at it. First with my Yamaha NS5000 speakers. A little fatiguing, maybe I am listening to too much music. I moved to my office and on the Magnepan Mini same thing with the F5 filter. Now I am worried my ears a getting way too much music.

I remembered that I had changed the filter, so I switched it back to F0 using the remote. Boom, an immediate lessening of the pressure on my ears. Now back to music nirvana. Never too much music.

 

@yyzsantabarbara a friend told me about this DAC. Interesting engineering technique to use two DACS and combine. For sure can achieve very low noise and high dynamic range. The filter options remind me of HQ Player. Have you picked one overall setting or do you prefer a range?

@dpac996 I do not think it is 2 DACs it is 2 signal paths that are combined. The analogy the company uses is digital photography were dark and bright sections of say a night photo is sometimes done by taking multiple shots optimized for both dark and bright areas. These photos are then combined to produce a clear image where the bright are not too bright and the dark is cleanly visible. 

They plan on using this technique for various other studio instruments such as microphones and other things I have no clue about. The technique is called HDR-A and the D-1 uses something they call multi-path.

Last night I ended up working till 4AM and I was listening to my RAAL SR1a and the Schiit Mjolnir v3 amp until 2:30AM. This was after I had complained about the fatigue in my ear in the post above and then changed the top-level filter to F0 (default). No issues even so late at night and I was laughing at how good this was. I would have been more productive if I had turned the music off.

Yesterday, I also sold my $7000 MRSP RAAL VM-1a tube headphone amp. It was the very best way to listen to the RAAL SR1a earphones. My friend Danny sold me this amp 2x in the past and he was involved in the design. However, my used $800 Schiit Mjolnir v3 amp and the D-1 via XLR was as good and I dare I say maybe better than the VM-1a. Just crazy how good this DAC is and how much stuff I have sold because of it. 

I have sold $14.1k worth of gear in the last 3 weeks and have huge improvements in sound in 3 systems. I have another $5k of gear to be sold. I look at this $12k cost of the D-1 as free money.

With regards to filters I will be staying with the F0 filter that is similar to many DACs that have these 5 filters. However, on every other DAC I could not hear these filters. On the D-1 I physically felt 2 of the filters. I only tested 2.

The other filter is the 2nd Order Harmonic Distortion filter. This filter is different from the F0-F5 ones. The HD filters are easy to hear. On my Yamaha NS5000 system I do not use a filter. On the Magnepan Mini I was using setting B at level 2, but I will eventually remove it as the hours increase on the DAC. On my RAAL SR1a, a bright phone, I use level 4.

I need to talk to the designer about these filters to understand the sonic signature of each. There are 50 permutations, and I have no time to experiment with all of them. I will meet the designer in person in 2-weeks at the Denver headphone meetup.

Does it come across in my posts how much I LOVE LOVE this DAC. it is easily the best piece of audio gear I have ever had in my system. Not the most expensive but the best by several orders of magnitude.