Pharmaboy
Headphoneus Supremus
Exactly right. This amp tends to fool the consumer: it's very powerful; has a 4-pin XLR output for headphones on the front; and its only preamp output is a pair of 3-pin XLRs (which I truly really don't understand).What i've read is that THR-1's design isn't fully balanced, that's why i did opt using RCA inputs. Attenuators for RCA were easier (and cheaper) to get at my place. And most DAC's are symmetric build, even in single-ended mode. That's why soundquality don't differ that much in both modes.
Yet it's basically an uber-powerful single-ended design. As @dermott pointed out, the balanced output signal from DACs often is close to double the voltage of their single-ended outputs, and that can only exaccerbate the THR-1's already significant gain issues.
I love the sound of this amp as a headphone amp, with those 2 x Rothwell 10 dB attenuators in line. But I've had less success using 3-pin-XLR-to-female RCA adapters on the outputs, which allow me to use the THR-1 as a system preamp. The level of the preamp out w/those adapters in place is lower in volume than any of the headphone outputs; and the sound of the preamp out isn't as good as the headphone outputs. I can only speculate that the culprit is those 2 adapters, but I can't verify this because my downstream devices are all single-ended.
I bought the THR-1 in large part because I intended to use it as a system preamp. The fact that it's not very good in that role has me on the fence: I might end up selling it, despite the superlative sound when it's used as a headphone amp.