Zoom ZHA-4 4-channel Headphone Amplifier

very high noise, even with the volume set at less than 30%

Build quality isn’t typical Zoom quality but it still works fine.

Un amplificador excelente, muy buena potencia y calidad de audio!

I'll admit I'm a big Zoom fan and I absolutely adore my H6 multi track recorder. The thing feels like something Rolls-Royce would make - and the sound quality is amazing.So when I had a need for this I wondered if all the negative reviews about noise and scratchy pots etc were just from the competition - "tactical reviews" as it were.So I ordered one and I also ordered a https://www.amazon.com/dp/B09JV84FHZ?psc=1&ref=ppx_yo2ov_dt_b_product_details. just to be on the safe side.Unboxing the Zoom, it doesn't feel like a Zoom product at all, the plastic is so cheap and the volume knobs are just nasty - thin, don't feel good in your hand etc....So I plugged it in to USB-C power and routed some audio from my MacBook Pro into my B&W headphones. The sound was unbelievably awful, the pots were indeed very scratchy and the whole thing was just worthy of the trash can I thought. So I was about to start a return.As I pulled the power cable out, for the couple of seconds until it died the sound quality suddenly became awesome... which got me to thinking... So as it was plugged into the same USB-C adapter as my MacBook Pro, I pulled the Mac power plug and tried again - absolutely perfect - great sound quality and no noise from the pots.So I can only assume there is some nasty design issue here with some kind of feedback coming through the power. I tried it on batteries too (one of the big selling points to me of the Zoom over the other one I bought) and it worked great.So I'll keep it because it's easy to slip in the bag when you want to share a movie between 3-4 sets of headphones and having one less power cable to manage is awesome.But the build quality remains what it is.The other unit I will review separately, but just by way of comparison, was $29.99 to the Zoom's $69.99 and looks incredibly well built, knobs feel good, no issues with noise and very good sound quality. Bit bigger to carry and requires plugging in to USB-A port or the adapter. It also has both 6.35 and 3.5mm jacks for the input as well as all of the outputs - really nice design, especially for us as we have some phones that have the large base plug and others that use the small "Smartphone" jack - yes you can use adapters but then you have socket leverage, which risks breakage, as well as another possible noise source.

It worked ok but there was a lot of noise in the circuitry for this. Being zoom I expected more then $60 buys