OTL Headphone Amp project.

[DrNomis_44]

Update:

I managed to set up my test bench so that I could take a screenshot of the two outputs of my OTL Tube Headphone Amplifier build working into a 33 Ohm resistive load, I used two 33 Ohm/1%/1W metal film resistors to simulate a pair of 33 Ohm headphones, it may not be entirely accurate, but for this quick test, it is as they say "close enough for government work".

I adjusted the volume control for the highest output signal level with the least amount of distortion, but you will notice some soft-clipping on the bottom peak of the output waveform, in the screenshot, the yellow trace is the left-hand channel going into a 33 Ohm load, and the pink trace is the right-hand channel going into a 33 Ohm load.

So, it looks like the amp can easily put about 600mV of drive signal into a 33 Ohm load, I'm guessing that the signal level into a 38 Ohm load would be higher, since a 38 Ohm load would present a lighter load to the amp, it looks like the amp has a low-enough output impedance to easily drive loads down to 32 Ohms impedance.

I just did some calculations and, assuming my calculations are correct, my OTL Tube Headphone Amplifier is capable of putting 4.968 milliwatts RMS into a 33 Ohm resistive load, I'm guessing that it is most likely capable of putting a total of 5.0 milliwatts RMS into my pair of Audio Technica ATH-M50X headphones that are rated at 38 Ohms impedance, due to the lighter loading.