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Please evaluate my new EL34 Amp (waveform attached)
Please evaluate my new EL34 Amp (waveform attached)
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Old 16th March 2008, 10:42 PM   #1
vax9000 is offline vax9000  United States
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Default Please evaluate my new EL34 Amp (waveform attached)

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).
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Old 16th March 2008, 10:43 PM   #2
vax9000 is offline vax9000  United States
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With speaker load
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Old 16th March 2008, 10:55 PM   #3
Iain McNeill is offline Iain McNeill  United Kingdom
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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?
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Old 16th March 2008, 11:18 PM   #4
Miles Prower is offline Miles Prower  United States
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Default Re: Please evaluate my new EL34 Amp (waveform attached)

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?
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Old 16th March 2008, 11:19 PM   #5
vax9000 is offline vax9000  United States
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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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