The quality of a DAC is best assessed through headphones, where the intimacy with the music is completely exposed and nothing escapes. Many have asked me to create a version of the Protodac Bilanciato aka Zenith DAC with a headphone output, and here it is. Zenith fans can rest assured, nothing has changed for the RCA output. Up to that point, the circuit is the same. The first op amp, which subtracts the two balanced signals, remains. I confirm the TL082 as the reference because its JFET inputs guarantee an ideal interface with the DAC, which, as we know, is in a passive I/V configuration on the 430 ohm R terminals, and therefore on those R terminals, where the DAC creates its magic, we zero the load to avoid any influence on the sound. However, nothing prevents you from testing with other OPs, even decent ones😊. The second OP that was taking care of the XLR output is eliminated. Yes, exactly, you pay for the loss of the XLR output. In its place, we'll use another to drive the headphones. I chose the NE5532, a true "timeless classic" in the audio world and, unlike many standard op amps, the NE5532 can deliver significant output current. Both op amps operate in unity gain configuration, so there's no voltage amplification compared to what comes out of the DAC. With the 2V rms we have at the TL082's output, and therefore on the RCA connectors, we can get about 125 mW of power through headphones, which for most modern headphones is a considerable amount of power (and potentially harmful to hearing). Therefore, I placed a volume control potentiometer between the two OPs (yes, it's the old-fashioned way) because I still believe that on a 16-bit DAC you can't afford to lower the volume via software but you have to leave the DAC in BITPERFECT mode (this applies to all R2R DACs) and then lower the volume in analog mode. Result: deep black in the headphones. When playing the file, silence, at maximum volume that would burst your ears on a music file, there is no noise. Dead silence. During playback, using the volume potentiometer is very convenient. It allows you to 'turn it down' for those modern and racy recordings and 'turn it up a bit' instead on classical or jazz where you want to savor all the various passages, even the lighter ones. The dynamics and timbre are typical of a CD player from the golden age of the 12 cm disc; I own several of them from various years and I can vouch for it. Don't expect it to be as satiny as the modern headphone DACs you hear at various fairs. I don't own one, but I've listened to them a few times. This one scratches. It's a present, dynamic, and damned real sound. I must admit I prefer it to my MiniDAC with TDA1543. Not so much for the sound timbre, which they are similar; perhaps the 1543 is even more mellow, perhaps too much. But the depth of the image, most likely due to the distance from the background silence, is much better. And this, very importantly, without emptying the fullness of the instruments, which is what I really like about R2R DACs. What else can I say? Maybe we're getting closer to the definitive DAC? Until the next experiment.