Please evaluate my new EL34 Amp (waveform attached)

vax9000 · 16th March 2008, 10:42 PM

Hi guys,

Finally I got my El34 amp done. Here are some waveform photos that I shot. Please let me know whether they are good or bad. Thank you! The former 4 photos were with a 3.9 Ohms resistor; the later 4 are with a 4 Ohms speaker. My amp has 8 Ohms tab only, but I have no resistor or speaker with that value so I used 4 Ohms ones anyway. The Oscilloscope has DC 1V/grid on top (measured at input) and DC 10V/grid on bottom (measured at load).

vax9000 · 16th March 2008, 10:43 PM

With speaker load

Iain McNeill · 16th March 2008, 10:55 PM

seems reasonable enough. 1Vp-p in produces 10V p-p out = about 6watts into 4ohms. Pretty loud huh?

The rounded edges of the square wave is due to hf roll off and the sloping top of the square wave is due to lf roll off.
Looks like your generator is a bit soggy at high frequency too - the top trace is the input right?

How does it sound with music?

Miles Prower · 16th March 2008, 11:18 PM

Quote:

Originally posted by vax9000
Hi guys,

Finally I got my El34 amp done. Here are some waveform photos that I shot. Please let me know whether they are good or bad.

Those look pretty reasonable, no obvious defects. Square wave tests don't tell all, however. What does it sound like?

vax9000 · 16th March 2008, 11:19 PM

My generator is HP 211A tube type generator. 6W square sound was unbearable when I was taking photos.

It sounds great to my ears. But I have no chance to listen to others' tube amp, I do not know how it sounds comparing with others.

Their is still some noise that I need to fight against.

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16th March 2008, 10:55 PM	#3
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	seems reasonable enough. 1Vp-p in produces 10V p-p out = about 6watts into 4ohms. Pretty loud huh? The rounded edges of the square wave is due to hf roll off and the sloping top of the square wave is due to lf roll off. Looks like your generator is a bit soggy at high frequency too - the top trace is the input right? How does it sound with music?

16th March 2008, 11:19 PM	#5
vax9000 diyAudio Member Join Date: May 2006 Location: Cleveland	My generator is HP 211A tube type generator. 6W square sound was unbearable when I was taking photos. It sounds great to my ears. But I have no chance to listen to others' tube amp, I do not know how it sounds comparing with others. Their is still some noise that I need to fight against.

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