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Validating Amir's measurements of the THX Onyx.

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Sep 6, 2022
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Some time ago, i bought myself a THX Onyx after seeing the review of it here; I needed a dongle for my phone, and i use it as a DAC for my PC when i'm using it.
I thought it would be fun to compare my measurements of it to those that Amir took, with a few comments here and there.
First things first, the 1kHz Sine:
THX Onyx.png


I'm fairly certain that the noise spikes i have here are a symptom of less than perfect noise filtering in the DAC, since they show up with every DAC i've plugged straight into my PC, but to varying degrees. I'd expect them to stay the same if it was happening in the ADC.

Using my PC and ADC to measure something that isn't plugged into my PC doesn't give my that spike. We'll come back to this in a bit.
For comparison, the same spike goes up to about -106 dBFS when i measure the built-in audio output in my PC.
Otherwise, this measurement lines up with that posted by Amir, which makes sense. We even got a pretty similar level of difference between the left and right channels. As far as i can tell, this leaves us with nearly identical Dynamic Range numbers as well. So far, so good.

I'm a little bit surprised by the difference i got from Amir though, when comparing my THD vs level. He did it to measure power output, i did it to see if something other than full output might have lower distortion. Here's the Right channel:

THDvsLevel Onyx 2.png


It's entirely possible that this is an issue with the measuring hardware, an E1DA Cosmos ADC, but i doubt it. I'll try running some verification in another way when i get the change.
I'm not exactly sure what could be causing the issue, but i don't think i'm hearing it when i listen to music. Nothing to worry about there then.
Anyway, i thought it might be a good idea to have an independent person compare their measurements to some of Amirs. Most of us know his measurements are good, but confirming them might inspire confidence in his work for those who are a little less certain.

A couple quick disclaimers: I bought myself this ADC and DAC months ago, and i've been using the Onyx every day; i'm measuring it for myself because i was curious. I can't be entirely certain that there are no faults in my measurements, but i've done my best to ensure it was done carefully. All testing was done with the ADC input set to 2.7Vrms.

And after months of using the Onyx, i have a couple of subjective thoughts:

1. It has handled abuse very well. There are a few little knicks in the metal finish, but the rubber of the wire is still in perfect shape. I've had no connection issues even though it gets unplugged and replugged in to various devices several times a day. I try to be careful with it but sometimes it's dropped in a bag full of metal things, it survives that pretty well.

2. I know the noise measurements are quite low, but i don't use it with IEMs without a headphone amp if i can help it. With every device (a few phones and computers) i've tried, it occasionally makes weird modem-sounding noises that can be louder than the music i'm listening to when i have the volume low and i'm in a quiet room with IEMs. Since i have the volume set much higher when i have headphones plugged straight into it, i can hardly hear the sounds if i'm not playing any music, and can't hear them at all with music playing. Of course, i can just leave the Onyx at full output when i have an amp hooked up, and attenuate the volume to where i want it.
It could be that mine is defective, i'll look into getting it replaced at some point.
 
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