IPAR 1023A Preamplifier / Volume Controller / Headphone Amplifier / Source Selector - reviews - There are 2 reviews.

Bon amplii casque
bon préampli/ampli casque
je l'utilise surtout en préampli sur un atoll in 50 se en by pass très bon son a tel point que je vais m'équiper d'un ampli de puissance de la même marque il a juste un petit ploque au démarrage et a l'extinction

Perfect amp. Don´t miss him!
Even though I'm not a sound expert, I don't have top-notch headphones, as well as high-end comparison or test devices, I'll write a few words. First of all, with what I am "testing" the amplifier and why I chose this one. I wanted a desktop but still portable amplifier for my HiRes DAP. But with the ability to plug in more devices at the same time, and with the ability to output a large amplifier. Of course, in an affordable price. The choice fell on iPar. Its design looks good, holds everything firmly together, a nice front panel. The only complaint is the quality of potentiometers, more precisely knobs. They do not hold firmly, they lean out, the "0" mark is just a crooked ribbon on the root of the knob. Certainly I will have to replace them for the better over time. Otherwise everything works fine. The amplifier is without the manual and any original box.
Now, what and with what I used to compare the amplifier. I currently have ATH-AD900, and ATH-ES88 headphones as the DAP QLS360MOD sound source, and DAP Colorfly C4PRO as a second comparison. Music - all WAV and FLAC formats: Ben Lukas Boysen & Sebastiano Plano - Everything, Bliss - John Metcalfe - Kites and echoes, Diana Krall - All for You A Dedication to the Nat King Cole Trio, Maok - Svetloleť .
I immediately set the gain on the amplifier to -3dB. My headphones are not high ohm so the amplifier's power is more than enough. Even at higher volumes, sound-music did not become extremely unpleasant, sharp. Likewise, it is felt that the amplifier has a sufficient margin, it does not sniff so quickly, it does not feel so much its boundaries as the headphones and human ears. Now the sound. The differences are very subtle, it would certainly help to have a wider selection of headphones. Colorfly C4PRO is feeling sweeter, feeling more coherent music, it's like a comparison between CD and magnetic tape. Though some of the finest microdetails are lost, but the music is more plastic, more human, warmer. QLS 360MOD is softer, the sound is silky, not as warm as Colorfly, it is more audiophile. Both can be listened for a long time without fatigue. However, both lack a bit of drive, speed. iPar Amplifier - What I noticed first is already a sufficient performance control, very similar subtlety in sound performance, and a slightly more separated musical instrument, with a wider space around them, their more accurate localization. The whole sound band is exemplary balanced, nothing stands out or vice versa. Mid range - voices exemplified by a man, did not register any sibilation in the voices. The heights are clean. Basses are controlled, solid, nothing is lost in them. Long-term listening doesn't tire at all. From the memory I compare it with the Denon PMA-2000R amplifier, which I have at home - it is certainly faster, has more drive, but for long listening iPar is better. Even though I have not experienced any of them, even the iPar amplifier, on my back, whether it is crying / it is a holy grail to listen to music /, I can say with confidence that iPar is a very good amplifier, not offensive or tired, it is very musical, its sound exceeds the size of the headphones and is lost during long-term listening. Only music remains.
As a bonus, there is a preamp, but I do not have the opportunity to try, compare. And of course multiple inputs. I personally strongly recommend the amplifier.
PS: A few words to Audiophonics - a great service, trying to solve everything. My piece had a slight damage during transport / from China /, and they immediately suggested a discount. It is better to ask them to check the ordered goods before sending them. You never know.