Question(s) regarding THX 789 (THX 887) and DAC (clipping?)

[all-air]

Hello

I'm really a full-blown newbie when it comes to this sort of things unfortunately...


I currently have a Monoprice THX 887 (pretty much the same as the Massdrop THX AAA 789 I'm sure, I just made the title THX 789 since it is more well known I guess) and along with it a Chord Hugo 2 as my dac (biiiit overpriced what can I say...) connected with RCAs.
I've read that clipping can occur in high gain (Gain 3) when the dac outputs(?) more than 2v (is this the same as vmrs?), now my Hugo 2 Dac per standard outputs 3vrms I think, and I've used it with even higher vrms, as you raise its "internal volume"... To maybe about 5vrms? All my listening is on PC with Windows volume at 100% and Spotify Volume at max.


My question is, I haven't even noticed any clipping or such, not on high gain or medium (normal) gain, should I experience clipping? I'm using a pair of HD600 (mpedance: 300 Ohm, Sound pressure level: 97 dB) with XLR right now, but I've also tried it with 1/4 connection with Audeze LCD-GX (Impedance - 20 Ohms; Sensitivity - 100 DB/1mW). I've tried them all in high gain, and never experienced clipping, as far as I can tell.. Never maxed out the volume on high gain though, that would be pretty damn loud, not even close to max, but still, high gain.


And if I'm somehow deaf to clipping (!), can I have potentially damaged/worsen my headphones or amplifier without knowing? Or does clipping only exist when I use 1/4 or 3.5mm output on this amp? Or does the clipping only happen if I throw in an balanced dac to it?



Yeah I might be too dense since I've tried to understand and read through lots of pages myself to get a grip on this...
Pardon in advanced for my half-broken-english.
Thanks!

 

[NTK]

Welcome to ASR!

I don't know the design details of the THX 887 headphone amp. However, it is common to put the volume potentiometer (pot) right at the input to an amp. If this is the case, the pot will attenuate the input voltage, so that when the headphone amp amplifies by 3.3X (high gain of the THX 887), the sound your headphone outputs will be at your desired volume. Since you are not listening with the THX887 amp output at 6.6 Vrms (i.e. ~120 dB SPL with your HD 600), you'll dial back the volume pot so that the "actual" input to the amp is much less than 2 Vrms.

There are also designs which has a fixed gain stage at the input (ahead of the volume pot), e.g. the O2 amp. In those cases, the input gain stage should be designed with plenty of margin. In the case of the O2, with battery power, it's max input level is above 4.6 Vrms. I expect the THX 887 will have higher margins.
https://nwavguy.blogspot.com/2011/08/o2-details.html#gainstageoverload

I doubt you are clipping your THX 887 in your use case. However, the best practice is to use as little gain as it will give you sufficient volume. There is no benefit to use high gain when you don't need it.

 

[all-air]

Thanks!

I was getting influenced by people saying high gain sounds the best and my specific headphones needs loooooouds of current haha, but didn't realize it could potentially cause clipping with the wrong type of dac/voltage. I'll stick to the normal (medium) gain since it is enough.