Monolith THX Headphone AMP/DAC vs Monolith THX 887 vs RME ADI-2 dac

[erikl]

Hi Everyone,
Longtime lurker who just registered, so please be gentle with me. I've been into audio for many years but need some advice. I'm using a Fiio M9 or Pono player running FLAC files as my source. I had the (mis)fortune to listen to the Fiio driving an SPL Phonitor X (not using its dac) into a pair of Focal utopias and was blown away by the detail and rhythmic drive. After saving for some time as I'm not independently wealthy, and with my wife's permission, I splurged on a used pair of utopias. Not surprisingly, they don't sound nearly as good when driven by just the Fiio. Down the rabbit hole we go. I read all the reviews on headphone amps that I could and studied Amir's reports religiously. I ordered both the monolith THX amp/dac and the monolith THX 887 ( massdrop THX 789 clone) and listened to them. After hours of deliberation, the THX 887 might sound minimally better, but the parametric eq and additional features on the amp/dac combo to me outweigh the sonic differences. However, although both TXH amps are incredible, they sound a little thin, or lacking body as compared to the phonitor x. I sent the THX 887 unit back, and still have the THX amp/dac combo. Unfortunately, I can't afford the phonitor x and was wondering if the RME adi-2 fs dac with its internal amplifier would be closer to the phonitor x sound? Or if not, does it sound noticeably better than what I'm currently using? I'm still within my 30 day return period, so don't want to make a mistake and keep a unit that I won't be happy with long term. I can't demo the RME locally, and hate to order one if it won't be appreciably better than what I'm currently using. One factor in favor of the RME is that it has eq profiles that I could save for different headphones, but I'm not sure if that is worth the additional cost. All advice is greatly appreciated!

 

[erikl]

Let me ask the question another way. Is the difference between the monolith THX desktop amp/dac and the RME adi-2 dac audible? I know the RME-adi-2 measures better, but will I be able to hear the difference when driving utopias?

 

[Fluffy]

check out this thread:
https://www.audiosciencereview.com/...-thresholds-of-amp-and-dac-measurements.5734/

 

[erikl]

Thank You! This will help.

 

[realear]

Could power of the Phonitor affect Utopia low/mid frequency curve? Maybe someone can answer this.

Max. Output Power (at +30 dBu @ 1 kHz)

• 2 x 1 W at 600 Ohm impedance
• 2 x 2 W at 300 Ohm impedance
• 2x 3.7 W at 120 Ohm impedance
• 2x 2.9 W at 47 Ohm impedance
• 2x 2.7 W at 32 Ohm impedance

THX 887: 600 ohms: 350mW <1% THD

If it does and Utopia is affected, how would that alter its sound?

 

[erikl]

The phonitor X and XE have about 0.18 ohms of output impedance. Being so low, that theoretically shouldn't affect the frequency response curve of the utopias. Perhaps the additional power and headroom the phonitor provides allows better dynamics and the impression of more drive or body compared to other lower powered amps. I can say I listed to the HD 660s, Focal Clear, and Utopia through the phonitor for several hours on jazz, rock, classical, etc. The 660 and Clear both sounded very good with Clear being slightly better, but the Utopia was simply in another class in terms of dynamics and clarity when driven by the phonitor.

 

[Angstrom]

I found Factory B-Stock SPL Phonitor X with optional DAC-192-1670 loaded, New model which started shipping this last fall has an upgraded DAC called the DAC768xs -1850.

Older model l DAC-192 Manual AKM 4396
- https://spl.audio/wp-content/uploads/Phonitor_x_BA_EN.pdf
The new shipping models with DAC-768 Manual - AKM's AK4490 based
- https://spl.audio/wp-content/uploads/Phonitor_x_1911_BA_EN.pdf

The first thing you will notice it has a very low noise floor, amazing dynamic range. It allows you to listen at low to moderate dB levels, which is at total a joy.


Balanced headphone output

• Neutrik 4-pin XLR connector
• Pin wiring: 1 = L (+), 2 = L (-), 3 = R (+), 4 = R (-)
• Impedance: 0.36 ohms
• Damping factor: 180 @ 40 ohms
• Frequency range: 10 Hz to 300 kHz ( -3 dB)
• Crosstalk at 1 kHz: -90 dB
• THD & N: 0.00091 % (at 0 dBu, 1 kHz, 100 kohms load)
• Noise (A-weighted): -98 dBu
• Dynamic range: 130.5 dB

Standard headphone output

• 6.35 mm TRS connector
• Pin wiring: Tip = Left, ring = right, sleeve = GND
• Impedance: 0.18 ohm
• Attenuation factor: 180 @ 40 ohms
• Frequency range: 10 Hz to 300 kHz ( -3 dB)
• Crosstalk at 1 kHz: -90 dB
• THD & N: 0.00091% (at 0 dBu, 1 kHz, 100 kohms load)
• Noise (A-weighted): -103 dB
• Dynamic range: 135.5 dB

Line outputs

• Neutrik XLR, balanced, Pin 2 = (+)
• RCA, unbalanced
• Frequency range: 4 Hz to 300 kHz (-3 dB)
• Crosstalk at 1 kHz: -106 dB
• THD & N: 0.00085 % (at 0 dBu, 1 kHz, 100 kohms load)
• Noise (A-weighted): -103.8 dB
• Dynamic range: 136.3 dB

• Internal operating voltages
  • Analog: +/- 60 V
  • Digital: + 5 V and + 3.3 V (optional)

Right now I. have three main headphones I use for causal listen are, I keep two for testing:

• Hifiman - Ananda
• Rosson Audio - RAD-0
• Focal - Elex
• For Testing
  • Dan Clark Audio - Aeon Flow Open - I now use it to test amps how they deal higher current loads ( this is only AMP so far I found can make this headphone sound there best. )
  • Drop Sennheiser - HD-6xx - It is a reference
  • Beyerdynamic DT-880 600 Ohm

After running through my headphones, I do worry about Single-ended performance with this amp, but it also has XLR support for Headphones.

One thing I need to try is plug-in, my Focal Nearfield Monitors, into it

I do have a Tom Christain Audio HPA-1 coming soon, so I take a look at it relative to this AMP.

 

[lszomb]

Interesting thread. Maybe the answer hide in (Headphone Impedance vs Frequencies) plus how does amp handle different impedance.

Otherwise, I would say Monolith are technically perfect.

 

[erikl]

Iszomb, that's a great point. The Utopias are nominally 80 ohm, but do reach about 320 ohms at 50 hz. At 320 ohms, the Phonitor is putting out about 2 watts while the THX 887 according to Amir's report is about 0.149 watts at 300 ohms. Perhaps the difference I'm hearing is having ample headroom on the Phonitor. Regardless, I did send the THX 887 back and ordered an RME ADI-2 dac V2. Supposedly the V2 has an upgraded amplifier section as opposed to the V1 model with more body or drive which is what I'm looking for. Worst case is that I've got a great DAC unit with EQ, and have to save up to purchase another amp in the future.

 

[JohnYang1997]

Iszomb, that's a great point. The Utopias are nominally 80 ohm, but do reach about 320 ohms at 50 hz. At 320 ohms, the Phonitor is putting out about 2 watts while the THX 887 according to Amir's report is about 0.149 watts at 300 ohms. Perhaps the difference I'm hearing is having ample headroom on the Phonitor. Regardless, I did send the THX 887 back and ordered an RME ADI-2 dac V2. Supposedly the V2 has an upgraded amplifier section as opposed to the V1 model with more body or drive which is what I'm looking for. Worst case is that I've got a great DAC unit with EQ, and have to save up to purchase another amp in the future.

You could simply use the balanced output.... Also I don't think what you heard is the headroom. If any, what you heard would be the worse noise and distortion performance when driving a low impedance and varied impedance load. I'm positive that RME is going to sound closer if not identical to 887.

 

[reasons]

Following this as I have a similar thread posted.

 

[Count Arthur]

I have an RME ADI-2 DAC and I've been very happy with the headphone output with all the headphones I've tried it with:

Focal Clear ~55ohm
Sennheiser HD650 ~300ohm
Phillips Fidelio M1 MKII ~16ohm

I haven't compared it to the Phonitor or the Monolith THX 887, but I've never found it lacking. THE ADI-2 also has a feature where you can switch the headphone output between low and high power, or, as I have, you can leave it set to auto. Even with the 300ohm HD650s, it rarely switches up to high power, only with a few albums that are recorded very low will it use the high power mode, for most albums it will get way to loud for comfortable listening whilst still in low power mode.

I've never felt the need to mess with the EQ functions and leave that off, it also has a crossfeed function, but I generally don't like crossfeed, so I don't use that either. I do use the Loudness function and leave it set to auto, which boosts bass and trebble slightly at lower volumes.

See pages 12 to 14 of the incredibly long manual: https://www.archiv.rme-audio.de/download/adi2dac_e.pdf