Simple PP vs. Tubelab SE

[Tubelab_com]

George: I think you mean FE126?

Probably. I'm not good with numbers, so I became an engineer. Go figure.

Didn't go to college until I was nearly 40 years old. My company paid me to get a degree.

 

[Evenharmonics]

This is flat out INCORRECT. P-P cancels even order harmonics generated WITHIN the amp - it DOES NOT affect the music's harmonics, second or otherwise.

A good SE amp will have the second harmonic as its primary THD component.

A good P-P amp will add some second harmonic, and the primary THD component will be a mix of third and some second harmonic. Some higher order harmonics will be added on strong signals.

A well balanced fully differential P-P amp will add nearly no second harmonic and its primary THD component is third harmonic.

I did some measurements of Tubelab SE (SET) and push pull amp Dynaco ST-70 (restored original PC board w/ updated power supply) with my cheap tools (not lab grade) and noticed some differences when fed the same signal. What does this mean about Dynaco ST-70?

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

I also measured Parasound HCA-750A (P-P transistor amp) and noticed the diminished even order harmonics and prominent 3rd, 5th, 7th and 9th order harmonics. So I'm wondering, is this common with push pull amps?

 

[rknize]

Yes, an SE amp will have a dominant 2nd order harmonic while a PP will typically (though not necessarily) have a dominant 3rd, 5th, etc. The feedback loop on the ST70 helps clean up the rest of the harmonics. The TSE has no feedback at all. Do you have a spectra of the source you are using?

 

[Evenharmonics]

Yes, an SE amp will have a dominant 2nd order harmonic while a PP will typically (though not necessarily) have a dominant 3rd, 5th, etc. The feedback loop on the ST70 helps clean up the rest of the harmonics.

But I noticed almost same level of 3rd harmonics from both and yet there is a significant reduction of 2nd harmonics from P-P circuit.

The source I used was 1KHz sine wave that was part of ARTA program I downloaded.

 

[RolandPSP]

One question : What sounds better The Tubelab or the Dynaco ? Please PM if you'd be so kind !

 

[Evenharmonics]

One question : What sounds better The Tubelab or the Dynaco ? Please PM if you'd be so kind !

Sorry, I haven't done a proper side by side comparison of the two and I sold Dynaco a few years ago.