I'm posting this from the "What did you buy today" thread here since this would be more appropriate for this thread:
Ordered a Topping L30 Headphone Amp
nice, I've been looking to upgrade my headphone setup because wfh will probably last till 2022, thoughts when you get them
I just had the Topping L30 delivered today. Initial listening impressions have me gawking at how clean, detailed, punchy and full sounding the Sennheiser HD 650 can sound through this amp. The L30 can get really loud with no noticeable reduction in audio quality. I only have the volume knob at 10 o clock with the gain switch set to medium, and that's loud enough for me. I'm still using an old HRT Music Streamer III USB DAC which has a line level output of 2.25 Vrms per manufacturer's specs, which is quite high but the L30 amp's inputs can handle it with no problem at all.

In all the years I've had the HD 650, I always thought it was a mediocre sounding headphone but apparently, it was being held back without proper amplification. I used to have the JD Labs O2 head amp and it sounded worse than listening to the HD 650 plugged directly to the audio source. For the price, I'd say the L30's a steal.