Update November 2018

Just before selling the unit...

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Here a quick review of the stock Motu 1248 (with generic cabling and no tweaks). From an internal inspection, I know it needs a lot of work, if I was to keep it. Before I ship it to the poor buyer, let me do a good old subjective review.

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Review performed using my Sennheiser HD-600 headphones and my DIY LME49600 headphone amp (No EQ used at all for the review)

This DIY headphone amp is basically two opamps. One AD8599 and one output current buffer chip (LME49600) forming a composite amplifier design.

The second opamp circuit inside the AD8599 is used as a DC servo loop for 0.00VDC offset.

Add a double regulated outboard linear power supply, and the result is a simple and great sounding little headphone amp, that can be trusted for reviews like the one I'm doing.

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For the setup, I used a cheap SPDIF cable feeding my three devices:

1-Motu 1248 (using internal Motu headphone amp)

2-Motu 1248 feeding the DIY headphone amp described above via truncated RCA output (i.e.: using pin 1 and 2 from the XLR connector while leaving pin#3 floating).

3-MiniDSP 4x10HD feeding the DIY headphone amp (RCA output used from the 4x10HD, the 4x10HD is modded.)

4-Yulong D100 DAC (modded) using the built-in headphone amp*

 

*The Yulong D100 internal headphone amp is not as good as the DIY headphone amp, but I wanted see how close those interfaces are to a '2005 era audiophile DAC. Yes, the Yulong D100 is a few generations old, and was beaten hands down by my previous Benchmark DAC2, using an ESS 9018 DAC. However, it was still better than the newer SMSL M7. I keep the D100 for testing purposes and almost never actually listen to it. 

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Note A: both the Yulong D100 and the Motu 1248 sound much better using the USB input, but I used the SPDIF instead, for keeping the test even with the MiniDSP 4x10HD. Poor 4x10HD, it has no USB input. My Melodious Audio MX-U8 unit was used to convert USB to SPDIF and feed the 4x10HD.

Note  B: the 4X10HD does sound better with AES/EBU input but the Motu doesn't have it, so I kept SPDIF for all, and same cable was used too.

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Now that this is all said, here’s the review:

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1- A bit thin sounding. Seems like a tad of hail around the vocals. Not harsh, but on the bright side as cymbals draw a bit of attention to themselves. Artificial come to mind. Instrument separation isn’t the best, and the bass is a bit soft. Certainly, a lack current capacity on the driver side. The Motu 1248 exhibits the typical low-cost headphone amp sound. Obviously, Motu haven't spent much on the headphone circuit, and it CAN be heard.

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2- You can tell that a properly done headphone amplifier sounds better than a generic headphone output on the MOTU. More separation between instruments with improved bass, albeit still some hail in the voices.  If #1 was 5/10, this is more 6/10. Better, but not a huge leap forward. This tends to confirm that DAC conversion inside the Motu isn't stellar.

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3- More like the sound I like and use to hearing. VERY Dynamic! Of course, my MiniDSP 4X10HD’s are heavily modified and equipped with over-sized external double regulated linear power supplies, which provide good bass slam. All of the opamps are AD8599, and generous capacitance by-pass has been added throughout. The "bone stock" Motu just can't compete. It sounds "thin" in comparison. The modded 4x10HD bass attack is great, and treble is correct, not attracting attention to itself, as it should be. I knew my DIY headphone amp wasn't at fault in #2.

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4(a) Different tonal balance than the MiniDSP and less resolution in the vocals. Given the D100 is a four generations old DAC’s, it’s understandable. The bass attack is almost as good as MiniDSP, but a bit lacking in absolute weight. The Yulong internal circuitry runs in Class A and also uses the excellent AD8599. As per my previous assessment of the D100, it sounds like it always sounded. I like to call it a bit "forgiving". Still very good despite it's age, just not the last world in detail retrieval or soundstage layers, like the newer ESS DAC chipsets are capable of.

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4(b) Yulong driven via USB. 

Much better than #4a (SPDIF mode), as the detail is more prominent and attack is improved, but still behind the 4X10HD as the ultimate rendition. As vocals through the 4x10HD are more detailed, it’s a closer match now. This 10-year-old Yulong is holding its own against today’s $2000 Motu 1248, and actually beat it out in setup #1 and #2, by my subjective opinion of course.

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Now, As I'm currently eyeing a Motu 24Ao interface, at $1100 USD, I'm not sure that I’ll buy one.

 

I know that modding the Motu 1248 would yield great sonic improvements (especially in slam and attack, like it did for my 4x10HD), but the lack of detail retrieval is very concerning. The Motu 24Ao uses the exact same circuitry as the 1248 and sounds the same (or 99%). Perhaps, blame it on the already old ESS 9016 DAC used inside. I know that detail retrieval potential is there, but pure implementation may be a bit lacking in the team Motu design. I'm not certain how much better I could make the unit.

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Note: output level is also high, and I have to use 25 dB’s worth of attenuation to match the output of the 4x10HD. If I was to mod the 24ao, I’d attenuate the gain stage to a more consumer level output. This is slightly detrimental to sound quality, as I have to use my PC internal digital attenuation.

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On the flip side, the MiniDSP 4x10HD does sound quite bad in its stock form, and maybe more so than the Motu1248 did. I feel pain for people using these stock interfaces. I know… I have two 4x10HD’s here, and I've compared them before modding the 2nd unit, to hear just how much improvement I achieved with the first one. It was very sad to do the side by side test, as the stock unit sounded like a cheap toy. The multiple mods yielded a bigger subjective improvement which I imagined on the 4x10HD.

Could I pull it on the 24Ao?

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My other thought is to purchase an Antelope Orion 32HD ($3500 USD). It supposedly sounds better as per reviews, but it’s also 3.5X more expensive than the Motu 24Ao. Reading online about people who upgraded from a Motu product (1248, 828X, 8M 16A, 24Ao) to a higher end interface (Lynx, RME, Antelope or UA), all claiming better sound and more detail through their mix. But they also all use "stock" interfaces. None of them ever return to Motu… ever.

 

Why start at the bottom tier unit and try to bring it to the big leagues?

"buy cheap, buy twice", My mom always told me that.

No Motu for me either. ​

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Update May 2019

 

I bought a Lynx Aurora 32 Dante

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All pro style interface processing ability are too limited. In order to get an infinity customizable set-up, PC based crossover is the only option.

Don’t buy one of these professional interfaces thinking you can implement much with the built-in processing ability.

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Even the MiniDSP 4x10HD is limited in its software. For serious audiophiles like us, DIY through a PC appears to be the only option.

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Later