Monolith HTP-1 AV Processor
(User Measurements; August 2023)
The Monolith HTP-1 was released over 3 years ago. Since its release, the HTP-1 has held steady at $4000, which means there's actually been a nearly 20% discount factoring inflation. There have been rumors that the HTP-1 will see a price increase shortly due to a combination of both increasing costs in the supply chain and inflation. What isn't a rumor is how hard it is to get one when it's in stock.
Three years ago, no one was sure how well Monoprice could support and handle a premium product like this. While there were early challenges, and there are still supply contraints, the on-going firmware support and homebrew support from end users like @anomaly has made the HTP-1 a compelling and competitive product even in the present day.
This is an update to @amirm's review from 2020 reflecting 3 years of firmware updates as well as a more contemporary understanding of AVR/AVP performance and the post-Covid, post-AKM factory fire world where performance regression has been seen across other AV products.
I'll first show my best-case scenario measurements:
104.8 dB 1 kHz SINAD at 1.8V (HDMI)
(102.8 dB for AES/EBU)
Update: I got 104.97 dB at 1.9V with a 2.2V nominal
Software and Hardware versions:
system software: V1.10.0
guiNodeRed: commit 3071dcc Date: Mon Jun 5 23:31:49 2023 -0400
avController: 4.89 Built Aug 3 2021, 14:46:17
APM Module: 258: APM 119 v258, May 20 2023
HDMI Module: 73.50.34
backplane firmware: 51
hardware: Backplane HW: 3. MIO HW: 2 DAC HW: 3
Serial Number: XXX
rootfs ver: rootfs-20191215.xz
HTP-1 Configuration:
Direct, L and R channels only
PCM bias enabled for signal detection
LCD display off
Digital Signal Generators
HP Omen 15 laptop/NVIDIA RTX2060M HDMI on AC power --> HDMI1 of the Monolith HTP-1
HP Omen 15 laptop on AC power --> USB Yellowtec PUC2 Lite --> AES/EBU of the Monolith HTP-1
ADC
E1DA Cosmos ADC, Grade A. The E1DA dBFS to voltage was calibrated with a Kaiweets HT118E 20,000 count multimeter. 10V was selected for the highest input impedance.
Analysis Software Configuration
Multitone Analyzer 1.0.87 from @pkane
20Hz-20kHz bandwidth* (@amirm 's APx555 dashboard is stricter)
2 second warm-up time for each measurement
My best measurement was at 1.8V at 104.8 db THD+N is just 1 dB shy of Monoprice's official specification of 106 dB SINAD. This may be due to electrical noise in my own home as well as limitations of my laptop's HDMI output relativeto a high-performance signal generator.
To achieve this, I set the maximum output to 1.8V in the internal configuration and then fed it a 0 dBFS test tone from @pkane 's Multitone tool. For an amplifier with 23.1 dB of gain on its XLR inputs like my Yamaha MX-A5000, 1.8V on the balanced input gives you 25.72V out, or 165W into 4 ohms.
Two questions have been asked since the original 2020 review:
1) The HTP-1 actually seems to do well at lower voltages. How does the SINAD look vs. lower output voltages?
2) Has the latest firmware/optimal configuration addressed the problem with 15-bits of linearity?
My first sweep was done with the maximum output voltage set to 3.4V. There is actually a typo on the watermark
I chose 3.4V to see how well the HTP-1 could come to the Marantz AV10 (which reaches its highest 108 dB SINAD at 3.3V at Audioholics).
As you can see in the chart above, the HTP-1 is essentially as good as the Marantz AV10 up until about 2V. At the lowest output levels that's labeled at Audioholics, we see that the Marantz AV10 at 95.3mV had an 82 dB SINAD (Audioholics APx585)The HTP-1 with my homebrew test setup already reached 82 dB SINAD as a lower voltage of 86.0mV and at the same 95.3 mV, it beat the AV10, reaching 83 dB SINAD.
At very low levels, the Monolith HTP-1 has a higher SINAD than even the Marantz AV10!
95 mV seems really low when we're typically focused on 2V and 4V SINAD for DACs, but 95 mV with the HypeX NC502MP powered Monolith 8250X with 25.7 dB gain = 1.83V to the speakers. With a Revel F228Be pair that's ~2-4 feet from the wall, that's already about 82.6 dB at 10 feet.
You can actually see that the HTP-1 breaks the 100 dB SINAD threshold as low as 0.75V and it stays above 100 dB all the way to 3.4V! If we think about it in the context of pairing this processor with an amplifier we can see that there's a very nice range of output power to the speakers with different gains.
Monolith M8250X (Hypex NC502MP) - 25.7 dB gain
0.75V + 25.7 dB = 14.45V
3.4V + 25.7 dB = 65.5 V
So into 4 ohms, 52W to clipping
Benchmark AHB2 - 9.2 db gain mode
0.75V + 9.2 dB = 2.16V
3.4V + 9.2 dB = 9.81V
So into 4 ohms, 1.2W to 24W
Benchmark AHB2 - 17 db gain mode
0.75V + 17 dB = 5.31V
3.4V + 17 dB = 24.1V
So into 4 ohms, 7W to 145W
Testing at different maximum output voltages
The maximum output voltage setting in the configuration presumably reflects changing the analog volume IC. Although it the HTP-1 web configurator allows you to enter a value of 7V, the 0 dBFS digital signal produces 4.1V at the XLR outputs, which is consistent with the current revision of the user manual.
Apologies. The graph scaling isn’t stable.
I was trying to get this post out as fast as I was able.
A most confounding, so peculiar oversight.
I will run more detailed sweeps tomorrow to make it right.
You can see how the interplay between the DAC's volume (set by the dBFS of the test one) relative to the maximum output voltage interacts.
I did not read the manual before running these measurements, but it only after writing up this post that I saw this nugget in the user's manual:
I will do a full set of measurements with the maximum output level near 2.2V. That might get me into the 106 dB SINAD range at 1.8V, but you can still get a general sense of performance from the above sweeps.
Linearity
All E1DA Cosmos ADC's have a DC problem which affects the automated linearity sweep. However, in Amir's original review at 4V output, he saw the unit muting below -90 dB. It was unclear if this was a firmware bug, a slow PCM-detection bug, or some combination.
At least as I have the unit configured, with the 2023 firmware, it works fine. For these tests, I set the E1DA Cosmos for a 4V input.
Here, we see that when the HTP-1 outputs 4.06V, it is 2.1dBFS for the E1DA Cosmos ADC.
Feeding it -100 dBFS, the 1 kHz spike measures -102.07 dBFS
And feeding it a -110 dBFS test tone or -120 dBFS test tone, we can see that it doesn't auto-mute.
In short, the auto-muting bug which led the HTP-1 to have a headless panther is not an issue with my test. And again, the rise below 1 Hz is the fault of the E1DA Cosmos ADC not the AVP.
Discussion
For me, personally, there are two ways I look at AVR/AVP measurements. Comparing the 2V/4V unbalanced vs. balanced out from an AVR/AVP is important to show how big the gap is between a dedicated 2-ch DAC and a multi-purpose product. With high DAC output voltages, you can use lower gain amplifiers downstream which can also theoretically improve end-to-end SINAD. Remember, even if ultra-premium SINAD is not audible, for 2 channel audio, it's pretty affordable to hit the extremes of mathematical transparency where your choices for gear can focus on aesthetics, ergonomics, and reliability/customer service. Having a wish list for more performance with no added cost is free, so why not ask manufacturers to try their hardest?
On the other hand, I don't buy a new amplifier every year. Or rather, I don't buy a new multi-channel amplifier for my home theater every year. I have the amplifiers with the gain structure that they have. The other way to look at AVR/AVP measurements is to think about what sort of voltages you need to hit +0 dB THX reference levels, with 85 dB averages and 105 dB peaks. At my age, I routinely listen below reference level. For me, my AVP is my last component in the signal chain before the amplifier and I prefer multichannel amplifiers with a lot of channels in one box paired with efficient speakers rather than dealing with multiple amplifiers or multiple active speakers and relying on a hub-and-spoke model of 12V trigger cables.
For me, what's most important is not the SINAD at 0 dBFS, but the SINAD that I get at the 70-85 dB SPL range at my listening position and the voltages that are required. For me, I never am at 4V.
Conclusion
The Monolith HTP-1 remains a low-volume product with inconsistent supply. Maybe you have to think of it like a Rolex Daytona or Hermes Kelly handbag and instead of winning the Mega Millions or PowerBall lottery, you just have to win the "in-stock" lottery which is a lot easier.
If you want an advanced 16-channel AV processor, your options are pretty limited. The popular choices have been the Harman products (Arcam, JBL Synthesis), StormAudio, Trinnov, and Marantz. If you want an advanced 16+ channel AV processor that's "Made in the USA" from domestic/foreign components, the HTP-1 stands ahead of its peers.
These 1 kHz SINAD measurements, taken on a homebrew E1DA Cosmos ADC show that the HTP-1 is certainly on the podium in the Olympics of AV processors if not the very best in rooms/speakers/amps that don't require high output voltages. At its price point, it's neck-and-neck with the reported measurements of the $7000 Marantz AV10 when using amplifiers with moderate to high gain. If you take advantage of the HTP-1's PEQ (which can be applied in combination with Dirac) and the HTP-1's Loudness Contour capabilities that are missing from the Marantz, you have to get into the realm of StormAudio and Trinnov, both of which have much worse SINAD at lower voltages and are $10,000+ extra. The power of PEQ is to equalizer your speakers using high-resolution data from the Klippel NFS above the transition frequency and then using Dirac and your in-home calibrated microphone to focus all of its correction in the bass.
Just a week ago, I mentioned to @jhaider that if I won a raffle and could pick between the $7000 Marantz AV10 and the $4000 Monolith HTP-1, I think I'd go for the Marantz for the more traditional feature set, ergonomics, and looks. I'm a big fan of Marantz when it's in the champagne color. I've owned multiple generations of their integrated amps and currently use the Marantz SA-10 and Marantz PM-10 Reference line in my 2-channel setup. Now, having bought the HTP-1 and spending just a few hours with it, I see why the HTP-1 has such a loyal following.
Ken Ishiwata was not an engineer but an ambassador for Marantz to help define its identity and goals. Monoprice and its Monolith brand has Hobie Sechrest (@MonolithGuy ) as its brand ambassador and product/program manager. I'm pretty sure Hobie's name will be held in the same esteem if Monoprice continues to produce world-class products like this.
Hobie, don't let us down when it comes to Dirac ART on the HTP-1 and when Dirac ART finally is released, please send a review unit to Amir to re-test.
(User Measurements; August 2023)
The Monolith HTP-1 was released over 3 years ago. Since its release, the HTP-1 has held steady at $4000, which means there's actually been a nearly 20% discount factoring inflation. There have been rumors that the HTP-1 will see a price increase shortly due to a combination of both increasing costs in the supply chain and inflation. What isn't a rumor is how hard it is to get one when it's in stock.
Three years ago, no one was sure how well Monoprice could support and handle a premium product like this. While there were early challenges, and there are still supply contraints, the on-going firmware support and homebrew support from end users like @anomaly has made the HTP-1 a compelling and competitive product even in the present day.
This is an update to @amirm's review from 2020 reflecting 3 years of firmware updates as well as a more contemporary understanding of AVR/AVP performance and the post-Covid, post-AKM factory fire world where performance regression has been seen across other AV products.
I'll first show my best-case scenario measurements:
104.8 dB 1 kHz SINAD at 1.8V (HDMI)
(102.8 dB for AES/EBU)
Update: I got 104.97 dB at 1.9V with a 2.2V nominal
Software and Hardware versions:
system software: V1.10.0
guiNodeRed: commit 3071dcc Date: Mon Jun 5 23:31:49 2023 -0400
avController: 4.89 Built Aug 3 2021, 14:46:17
APM Module: 258: APM 119 v258, May 20 2023
HDMI Module: 73.50.34
backplane firmware: 51
hardware: Backplane HW: 3. MIO HW: 2 DAC HW: 3
Serial Number: XXX
rootfs ver: rootfs-20191215.xz
HTP-1 Configuration:
Direct, L and R channels only
PCM bias enabled for signal detection
LCD display off
Digital Signal Generators
HP Omen 15 laptop/NVIDIA RTX2060M HDMI on AC power --> HDMI1 of the Monolith HTP-1
HP Omen 15 laptop on AC power --> USB Yellowtec PUC2 Lite --> AES/EBU of the Monolith HTP-1
ADC
E1DA Cosmos ADC, Grade A. The E1DA dBFS to voltage was calibrated with a Kaiweets HT118E 20,000 count multimeter. 10V was selected for the highest input impedance.
Analysis Software Configuration
Multitone Analyzer 1.0.87 from @pkane
20Hz-20kHz bandwidth* (@amirm 's APx555 dashboard is stricter)
2 second warm-up time for each measurement
My best measurement was at 1.8V at 104.8 db THD+N is just 1 dB shy of Monoprice's official specification of 106 dB SINAD. This may be due to electrical noise in my own home as well as limitations of my laptop's HDMI output relativeto a high-performance signal generator.
To achieve this, I set the maximum output to 1.8V in the internal configuration and then fed it a 0 dBFS test tone from @pkane 's Multitone tool. For an amplifier with 23.1 dB of gain on its XLR inputs like my Yamaha MX-A5000, 1.8V on the balanced input gives you 25.72V out, or 165W into 4 ohms.
Two questions have been asked since the original 2020 review:
1) The HTP-1 actually seems to do well at lower voltages. How does the SINAD look vs. lower output voltages?
2) Has the latest firmware/optimal configuration addressed the problem with 15-bits of linearity?
My first sweep was done with the maximum output voltage set to 3.4V. There is actually a typo on the watermark
I chose 3.4V to see how well the HTP-1 could come to the Marantz AV10 (which reaches its highest 108 dB SINAD at 3.3V at Audioholics).
As you can see in the chart above, the HTP-1 is essentially as good as the Marantz AV10 up until about 2V. At the lowest output levels that's labeled at Audioholics, we see that the Marantz AV10 at 95.3mV had an 82 dB SINAD (Audioholics APx585)The HTP-1 with my homebrew test setup already reached 82 dB SINAD as a lower voltage of 86.0mV and at the same 95.3 mV, it beat the AV10, reaching 83 dB SINAD.
At very low levels, the Monolith HTP-1 has a higher SINAD than even the Marantz AV10!
95 mV seems really low when we're typically focused on 2V and 4V SINAD for DACs, but 95 mV with the HypeX NC502MP powered Monolith 8250X with 25.7 dB gain = 1.83V to the speakers. With a Revel F228Be pair that's ~2-4 feet from the wall, that's already about 82.6 dB at 10 feet.
You can actually see that the HTP-1 breaks the 100 dB SINAD threshold as low as 0.75V and it stays above 100 dB all the way to 3.4V! If we think about it in the context of pairing this processor with an amplifier we can see that there's a very nice range of output power to the speakers with different gains.
Monolith M8250X (Hypex NC502MP) - 25.7 dB gain
0.75V + 25.7 dB = 14.45V
3.4V + 25.7 dB = 65.5 V
So into 4 ohms, 52W to clipping
Benchmark AHB2 - 9.2 db gain mode
0.75V + 9.2 dB = 2.16V
3.4V + 9.2 dB = 9.81V
So into 4 ohms, 1.2W to 24W
Benchmark AHB2 - 17 db gain mode
0.75V + 17 dB = 5.31V
3.4V + 17 dB = 24.1V
So into 4 ohms, 7W to 145W
Testing at different maximum output voltages
The maximum output voltage setting in the configuration presumably reflects changing the analog volume IC. Although it the HTP-1 web configurator allows you to enter a value of 7V, the 0 dBFS digital signal produces 4.1V at the XLR outputs, which is consistent with the current revision of the user manual.
Apologies. The graph scaling isn’t stable.
I was trying to get this post out as fast as I was able.
A most confounding, so peculiar oversight.
I will run more detailed sweeps tomorrow to make it right.
You can see how the interplay between the DAC's volume (set by the dBFS of the test one) relative to the maximum output voltage interacts.
I did not read the manual before running these measurements, but it only after writing up this post that I saw this nugget in the user's manual:
I will do a full set of measurements with the maximum output level near 2.2V. That might get me into the 106 dB SINAD range at 1.8V, but you can still get a general sense of performance from the above sweeps.
Linearity
All E1DA Cosmos ADC's have a DC problem which affects the automated linearity sweep. However, in Amir's original review at 4V output, he saw the unit muting below -90 dB. It was unclear if this was a firmware bug, a slow PCM-detection bug, or some combination.
At least as I have the unit configured, with the 2023 firmware, it works fine. For these tests, I set the E1DA Cosmos for a 4V input.
Here, we see that when the HTP-1 outputs 4.06V, it is 2.1dBFS for the E1DA Cosmos ADC.
Feeding it -100 dBFS, the 1 kHz spike measures -102.07 dBFS
And feeding it a -110 dBFS test tone or -120 dBFS test tone, we can see that it doesn't auto-mute.
In short, the auto-muting bug which led the HTP-1 to have a headless panther is not an issue with my test. And again, the rise below 1 Hz is the fault of the E1DA Cosmos ADC not the AVP.
Discussion
For me, personally, there are two ways I look at AVR/AVP measurements. Comparing the 2V/4V unbalanced vs. balanced out from an AVR/AVP is important to show how big the gap is between a dedicated 2-ch DAC and a multi-purpose product. With high DAC output voltages, you can use lower gain amplifiers downstream which can also theoretically improve end-to-end SINAD. Remember, even if ultra-premium SINAD is not audible, for 2 channel audio, it's pretty affordable to hit the extremes of mathematical transparency where your choices for gear can focus on aesthetics, ergonomics, and reliability/customer service. Having a wish list for more performance with no added cost is free, so why not ask manufacturers to try their hardest?
On the other hand, I don't buy a new amplifier every year. Or rather, I don't buy a new multi-channel amplifier for my home theater every year. I have the amplifiers with the gain structure that they have. The other way to look at AVR/AVP measurements is to think about what sort of voltages you need to hit +0 dB THX reference levels, with 85 dB averages and 105 dB peaks. At my age, I routinely listen below reference level. For me, my AVP is my last component in the signal chain before the amplifier and I prefer multichannel amplifiers with a lot of channels in one box paired with efficient speakers rather than dealing with multiple amplifiers or multiple active speakers and relying on a hub-and-spoke model of 12V trigger cables.
For me, what's most important is not the SINAD at 0 dBFS, but the SINAD that I get at the 70-85 dB SPL range at my listening position and the voltages that are required. For me, I never am at 4V.
Conclusion
The Monolith HTP-1 remains a low-volume product with inconsistent supply. Maybe you have to think of it like a Rolex Daytona or Hermes Kelly handbag and instead of winning the Mega Millions or PowerBall lottery, you just have to win the "in-stock" lottery which is a lot easier.
If you want an advanced 16-channel AV processor, your options are pretty limited. The popular choices have been the Harman products (Arcam, JBL Synthesis), StormAudio, Trinnov, and Marantz. If you want an advanced 16+ channel AV processor that's "Made in the USA" from domestic/foreign components, the HTP-1 stands ahead of its peers.
These 1 kHz SINAD measurements, taken on a homebrew E1DA Cosmos ADC show that the HTP-1 is certainly on the podium in the Olympics of AV processors if not the very best in rooms/speakers/amps that don't require high output voltages. At its price point, it's neck-and-neck with the reported measurements of the $7000 Marantz AV10 when using amplifiers with moderate to high gain. If you take advantage of the HTP-1's PEQ (which can be applied in combination with Dirac) and the HTP-1's Loudness Contour capabilities that are missing from the Marantz, you have to get into the realm of StormAudio and Trinnov, both of which have much worse SINAD at lower voltages and are $10,000+ extra. The power of PEQ is to equalizer your speakers using high-resolution data from the Klippel NFS above the transition frequency and then using Dirac and your in-home calibrated microphone to focus all of its correction in the bass.
Just a week ago, I mentioned to @jhaider that if I won a raffle and could pick between the $7000 Marantz AV10 and the $4000 Monolith HTP-1, I think I'd go for the Marantz for the more traditional feature set, ergonomics, and looks. I'm a big fan of Marantz when it's in the champagne color. I've owned multiple generations of their integrated amps and currently use the Marantz SA-10 and Marantz PM-10 Reference line in my 2-channel setup. Now, having bought the HTP-1 and spending just a few hours with it, I see why the HTP-1 has such a loyal following.
Ken Ishiwata was not an engineer but an ambassador for Marantz to help define its identity and goals. Monoprice and its Monolith brand has Hobie Sechrest (@MonolithGuy ) as its brand ambassador and product/program manager. I'm pretty sure Hobie's name will be held in the same esteem if Monoprice continues to produce world-class products like this.
Hobie, don't let us down when it comes to Dirac ART on the HTP-1 and when Dirac ART finally is released, please send a review unit to Amir to re-test.
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