Balanced input headphone amplifier

[Mr. Triatic]

Visible dist or not, the oscilloscope stacks some pixels and i dont really take any notice about them not being 100% even, i cant see any oscillation when i zoom in anyway.

I pulled out a FFT from the oscillscope @1kHz

An externally hosted image should be here but it was not working when we last tested it.

third harmonic is there, not giving me any listening fatigue, but still..

regarding my distortionmeter...i never said it is calibrated, although it will show severe distortion and there is no trace of that here.

 

[artosalo]

regarding my distortionmeter...i never said it is calibrated, although it will show severe distortion and there is no trace of that here.

Your distortion meter shows 0,01 % THD, which is not severe, but very very low value. So in FFT spectrum there should be no harmonic peak exceeding - 80 dBc level. (i.e. 80 dB below 1 KHz peak).

I can not read/see the scale of your FFT picture.

 

[Mr. Triatic]

i'm not best friend with my scope yet, i can only get the FFT on lower portion of the screen...irritating!

by manually moving the cursor i can see a difference of 60x between the 1kHz and the third harmonic but i cant get it to measure more exact and express in dB unfortunately, i have to dig out the scopemanual :/

 

[AndrewT]

3rd harmonic at 60times lower than fundamental is ~ -35dB or about 1.6%
To me that corroborates the 2nd harmonic (not 3rd) I thought I could "see" in your trace.

 

[Mr. Triatic]

No one built this yet?

I did some minor adjustments, lifting the filament to some 40V or so, rerouted some wires, it still sounds very nice, tubey and no listening fatigue at all so i use it pretty much every day now.

The bass is outstanding even with heavy-to-drive cans!!