So... yes, the post above looks correct. Saying that a different way: The front row of 3 pins is connected to the rear row and is for the left channel, and the two middle rows are connected and are for the right channel. So you can use either the front/rear for left and either of the middle...

The source impedance is basically the resistors in series with the output, between the opamps and output jack. You can replace R29 and R30 - now 10 ohms, 1/4W - with something smaller. A couple of notes and precautions: there is a 270uF capacitor in series with the output as well. At 20Hz this...

Yup, that is fine, if the caps will fit in the space available. Dale RN55 are fine too. Pete

That should work fine. Pete

An interesting discussion about the audibility of inverted polarity: https://hydrogenaud.io/index.php/topic,55323.0.html Pete

It is normal to hear a pop when the power is turned off. It's easy to delay the operation of the output relay to kill the turn-on pop, but when you power off, the voltage collapses fast and it takes some time for the relay to drop. I measure about a 1.5V pulse at the output that lasts about...

It should be OK. Pete

After quite a few requests, I finally designed a balanced (truly differential) headphone amp / line amp using the Korg Nutube. You can find details on my web site: http://www.pmillett.com/Nutube_bal.html It is a true differential amp, with the dual triode sitting on a CCS tail as a diff...

Sounds like WiFi. It can cause a ticking noise, especially if it's near a router. Pete

About 6.5V RMS into 30 or 150 ohms, or 1.3 watts into 30 ohms. Pete

Sorry about that, just updated it. (I assume the only dimension that was wrong was the height (should be 3.125)? Pete

The actual current draw of the amp is about 80mA. So that would provide plenty of current for this amp. Pete

One way to find out - try it! Try moving the bias up, and also down, maybe 2V at a time, and see what happens. You can't hurt anything... Pete

Sure. Korg quotes the lifetime at 30,000 hours. That's 3.42 years if you leave it on all the time. As far as I can tell, this is based on the lifetime of a vacuum fluorescent display as quoted by Noritake. The Nutube may actually last significantly longer, since the plate current used is...

What Tomb says :) You might be able to fit in the 10uF Wima MKS part. I used it on the class D hybrid. For a 10uF film cap it's pretty small. One goal with this design was to make it as affordable as possible. That's why I used the electrolytic coupling caps there and also the switching...