PreSonus HP4 4-Channel Headphone Amplifier & Audio-Technica ATH-M50X Professional Studio Headphones Bundle - Perfect for Music Production, Podcasting & Home Recording Studios

I purchased 7 amps all in the range of $30 - $250. From the China type cheap ones like Bolanle, Mackie to the cheap Behringer HA400 (DONT PURCHASE THESE CHEAP ONES UNLESS YOU WANT WORSE SOUND QUALITY AND STATIC HISS).I found a few names floating around that seemed to make good amps. All were around $100+ - Topping, Creative (old company), ifi, and Schiit to name the most popular. I crossed out Creative and ifi based off gut instinct. I focused on Schiit and also stumbled on Presonus. I was interested in both Schoot and Presonus, Schiit because they had a good solid story and just wanted to make a no frills Amo that actually works. Presonus because they have their own high impedance headphones. I picked a model from each brand and ordered them since the cheap china ones all did the same thing, increase the volume and create a loud hiss.NO HISSING ALLOWED, I’m not buying an amp and quality headphone and gear to go backwards with sound quality. So if you can’t afford a quality amp, get lower ohm headphones, you will hear the music with no issues and still get quality headphone audio.E.g. Audio Technician M50 doesn’t need an AMP to work at 38 ohm*Both the Presonus HP4 and the Schiit Magni+ both work great. I kept both, why?Personus HP4- 4 headphone outputs and one for monitor- Sturdy build and doesn’t get hot- Slightly less audio quality (I mean very slightly, you have to swap back and forth numerous times to even notice)Schiit Magni+- Three output db options (allows for fine tuning between volume and static)- Slightly better sound quality- Unit heats up (but they say it will last a long time)- *ONE HEADPHONE OUTPUT (this is why I kept the Presonus as well)If the Schiit Magni+ had more headphone outputs, I would have kept that only, but the presonus has more flexibility and allows me to amplify speakers and headphones at the same time. I ended up buying a used Presinus from Amazon for about $65 and a clearance/B stock Schiit Magni+ /Heretic for $79.I’m content with the sound and flexibility and since both units seemed to be made well, I believe they will last.*Tip for anyone looking to get a headphone amp to power high OHM. I learned you need an amp with very low Output Impedance. You willPay likely have to search for the spec/data/cut sheet to find that info, but that will help you weed out the garbage Amps.The output impedance should ideally be 8 times then the headphones Ohm/Impedance. The Schiit Magni+ is around .3 - 4 output impedance, yes I said .3.The output impedance of the Presonus HP4 is a bit tricky since the spec sheet says it’s 51 ohm for the Monitor outputs, that should be for the speakers, they aren’t really clear on the headphones. But I assumed it’s higher than Schiits which may be the difference in sound quality, but the person is works great too.If you do hear a slight hiss due to external input source interference, you can decrease volume on the amp till it’s gone the. Just volume up your gear.