Robinette Box with Only 4-Pin XLR Output
This adapter will work with single-ended and balanced output speaker amplifiers.
I appreciate the work that went onto your Box, and may build one.
I have a couple questions which I will split into two posts.
I tried several L-Pad calculators for loudspeakers found on the internet, and all agreed: for 8 ohms and 12 dB attenuation the resistors should be 6 ohms and 2.68 ohms, not 6 and 2. I upped the headphone impedance in your calculator to 1000000 ohms, to simulate an open, (no headphone connected). I changed the amp impedance a lot, up and down. In all cases I got only small changes. No or small changes are good. But the results for R3 being different is puzzling.
So I am wondering, how did you arrive at your L-Pad calculations?
I suspect there is more going on here than meets the eye.
I do realize that speakers and headphones usually have a reactive component and being “in the ballpark” is often fine. However when tuning my speaker crossover, padding my tweeter to match the midrange, I found 0.1 ohm of difference, out of about 1.5 ohms, made the sound “snap” into focus (like focusing a camera lens). It was startling. This could not be calculated easily: it was found by trial and error. (The amp then was a Yamaha SS receiver of good quality, not tubes, but this "focus" persisted with any amp I used.)
Have you compared the sound of your L-Pad network to a simple series resistor, for use with a stable solid state amp?
I am currently using a (upgraded) vintage 50 watt per channel SS receiver and its circuit goes from speaker out, through a 470 ohm resistor for each channel, to the headphone jack.
I am wondering if I would get any improvement by getting fancy, i.e., building a box, or at least an L-Pad?
PS. Love your “People for the Ethical Treatment of Plants” Web page. Reminds me an email I wrote some years ago calling for “Plants Rights”. :-)