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Old 19th September 2010, 06:24 AM   #1
pof@ is offline pof@  Denmark
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Default FFT for adjusting tubes

Iím looking for a new oscilloscop. The old one is more that 30 years things are not really working anymore.

I havenít seen a description anywhere but I got the idea to use FFT to adjust for minimum distortion when feeding an amplifier with a pure sinus wave. Is this possible at all and is it possible with a low-cost scop like this one? Rigol DS1052E

What I want to do is to find the best working point of a tube and best bias and stuff like that.
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Old 19th September 2010, 07:18 AM   #2
chrish is offline chrish  Australia
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I have that scope, and the FFT is pretty basic. I believe that the resolution is only 8 bits, leaving it somewhat lacking for this purpose. I purchased a cheap HP distortion meter and use this. I think I read somewhere that you can use the distortion meter output to feed in to scope and use this too to help with distortion reduction.

Hope this helps,

Chris
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Old 19th September 2010, 07:56 AM   #3
pof@ is offline pof@  Denmark
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Thanks.

I didn't notice the 8 bit before - must have mixed that up with another scope I was checking (12 bit).

Ok, I need a seperate distortion meter I guess.

With a 10:1 probe is this scope ok for tubes? I noticed the 300 V inputs.
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Old 19th September 2010, 11:49 AM   #4
chrish is offline chrish  Australia
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Yes, OK for tube use with 10:1 probe. Also have a 100:1 for power supply and plate.
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Old 19th September 2010, 01:11 PM   #5
pof@ is offline pof@  Denmark
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Quote:
Originally Posted by chrish View Post
Yes, OK for tube use with 10:1 probe. Also have a 100:1 for power supply and plate.
Isn't 10:1 probe ok? 300V x 10 = 3000V
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