I hope you are well.
First, I would like to thank you for your great—and detailed—measurements of the Kinki Studio Vision THR-1 headphone amp [that are on the SoundStage! Network portal site]. Thank you, especially, for pointing out the peculiarities of the inputs and outputs.
I just bought that unit, which I like very much.
As I am not technically educated, I have a question that may be trivial for you: I would like to know if I can safely connect two pairs of headphones to the unit at the same time for comparison purposes—the HiFiMan Susvara headphones connected to the Phone1 (XLR) output, the HiFiMan HE1000se headphones connected to the Phone2 (1/4″) output.
Thank you in advance for your help.
Greetings from Switzerland y un muy feliz año nuevo!
I went back to my measurements report to familiarize myself with the Kinki Studio Vision THR-1 again. That amplifier was reviewed by Mark Phillips on our SoundStage! Solo site.
Despite the product’s oddities, such as the lack of input buffers and truly balanced inputs and outputs, it still has a very robust amplifier capable of very high power. In your specific use case, you mention two high-quality planar-magnetic headphones, both connected simultaneously to the THR-1 as you described. I see no issues at all with this arrangement.
The HE1000se headphones have a 35-ohm impedance, while the Susvaras have a 60-ohm impedance. Since the Phone1 and Phone2 outputs are connected in parallel, having both pairs of headphones plugged in will create an effective 22-ohm load for the THR-1 amp. Given the 51-ohm output impedance of the THR-1, the only thing you should notice is a reduction in volume (about 5dB) if you plug in the HE1000se headphones when the Susvaras are already connected. Since planar-magnetic headphones effectively have a flat impedance curve from 20Hz to 20kHz, you should not notice any frequency-response changes with this arrangement. Please note, however, that if you were to use dynamic-driver headphones with a low impedance (e.g., 32–60 ohms), it is possible that you would notice very small changes in frequency response when connecting a second pair, depending on the impedance versus frequency curves of the headphones.
I hope that helps.