This is a review and detailed measurements of the Monolith Monoprice HTP-1 16-channel AV Processor. A kind member ordered it and had it drop shipped to me. The HTP-1 has recently started shipping and costs US $4,000 from the company direct.
I can't say I am a fan of the industry design of the HTP-1 but do like the large display:
The packaging feels cheep for a product in this price category. Back panel seems too think and I could flex the IEC input jack in and out as I plugged in my cable.
The rotary encoder is too shallow for proper grip and has no acceleration support. So you better not be in a hurry when you try to make big volume changes. You can crank it hard and watch the lazy volume indicator gradually change. On the other hand, minor changes are hard to do due to coarse resolution of 1 dB and jittery encoder that jumps 2 dB when you want to change 1 dB.
Cold boot takes a long time. After that, it stays in some kind of suspended mode and wakes up quickly until it loses power. Then the slow cycle starts again.
I set the options to show details of audio formats and such but I still did not seem the same rate and bit depth on the display. There is so much real estate there and the webserver can show it so why not on the LCD?
Love the back connectors in the way it dismisses the ancient composite and component video connectors and just gives you what you need on a modern AV product:
Note that there is no on-screen display. You manage the unit through its app or web server. I used the latter which worked very well on the desktop. On my Samsung S8+ the pop up was slow and there was some refresh bugs. On the desktop, it was far superior to any on-screen display.
I started my testing using the AES/EBU digital input. I then switched to testing with HDMI but no luck. The unit would simply not pass video from my PC's Nvidia graphs card. I would get a blank screen. I set the resolution to 1080p and it still produced no picture. So I dragged the unit to my main system, rip it apart
, and tested it there. It worked fine with my Samsung UHD player and LG OLED TV. I have tested countless AVRs and processors with PCs and while they don't always work perfectly, they do produce a picture. I am worried about level of compatibility of HTP-1 given my experience.
FYI I did a system upgrade and it made no difference (it reports version 1.1 on display when it boots).
Overall this is a mixed bag of very nice display and web interface, and not so good input control and sheet metal. Not a showstopper though if the performance is there.
AV Processor DAC Performance
As noted, I used AES/EBU balanced digital input to feed the HTP-1. Here is the outcome at nominal 4 volts that desktop DACs produce:
View attachment 49844
OK, not broken but not that great either. Reducing the level to 2.7 volts which is the max that some other processors/AVRs produce before clipping gave a bit better performance:
View attachment 49845
Note that you get severe clipping at 4.5 volts or so. And that messing with the amplifier sensitivity level in the setup does not help with any of this. Anyway, this is where the ranking lands with the two output settings:
View attachment 49846
With the lower output, I think we have our first AV product that breaks into the green category. Among AVRs, that also edges out all other AV products we have tested:
View attachment 49847
Dynamic range was good:
View attachment 49849
As was multitone performance:
View attachment 49850
Wideband distortion and noise was not that competitive though:
View attachment 49851
Intermodulation distortion versus input level shows that we still have not closed the gap with even budget desktop DACs:
View attachment 49852
Frequency response was fine:
View attachment 49848
Filter response is the typical default in DAC chips:
View attachment 49853
What is that? You don't know why it get the decapitated panther with this type of performance? Well, this is why:
View attachment 49854
The test starts at -120 dB and keeps increasing the level. The HTP-1 kept flashing its PCM indicator but would produce no output until we got down to -90 dB which is 1 bit short of 16 bit audio. We can see this clearly by looking at the waveform at -90 and -96 dB:
View attachment 49855
As you see in the inset, I am definitely sending it 24 bit audio.
We saw this behavior in another processor, namely the
Emotiva XMC-1:
Seems like the same shop that supplied the audio subsystem for XMC-1 is behind the same mistaken design in HTP-1. We could forgive the XMC-1 for being old but no such excuse holds for HTP-1. Folks, this is ABCs of design. You verify simple things like whether the device can process 24-bit data. After all, almost all video soundtracks are 24 bits.
EDIT: There is a setting in the menu to override the low level muting. The output clips though. See:
https://www.audiosciencereview.com/...me-theater-processor-review.11416/post-326504
Jitter was another disappointment:
View attachment 49856
Wish I could test HDMI but can not. Above spikes are correlated with the 250 Hz square wave that is embedded in J-test signal. This means what bits to feed the DAC changes its analog input! So bits are not bits unfortunately. Fortunately levels are low so likely not audible but in a high-end processor, we better not see artifacts like this.
Conclusions
The HTP-1 seems to want to raise the bar on DAC performance over its competitors and it succeeds a bit there. But then it truncates every 24 bit sample to 16 bits, removing the value of such performance. Jitter performance is also not good. And of course, if you can't get video through the thing as was my experience with my PC, then the rest does not happen.
I am hoping that the muting problem beyond 15 bits can be fixed with a firmware update. If so, and the video compatibility is not a broader issue, I would give HTP-1 a passing grade. As it is now, it is not ready for production.
EDIT: an obscure setting fixes the linearity/muting issue. This setting should be the default, not the other way around. I am still bothered by lack luster output level and distortion for a $4,000 product. So not changing my recommendation. Buy this product because you want its features, not because you think the $4,000 is bringing you superlative objective audio performance. There are $150 stereo DACs that easily outperform it on that front.
------------
As always, questions, comments, recommendations, etc. are welcome.
This is my second review for the day. I now you can be cheap but even you can feel sorry for me by donating money using
: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
