FFT for adjusting tubes

pof@ · 19th September 2010, 06:24 AM

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

I haven’t 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.

chrish · 19th September 2010, 07:18 AM

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

pof@ · 19th September 2010, 07:56 AM

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.

chrish · 19th September 2010, 11:49 AM

Yes, OK for tube use with 10:1 probe. Also have a 100:1 for power supply and plate.

pof@ · 19th September 2010, 01:11 PM

Quote:

Originally Posted by chrish

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

19th September 2010, 06:24 AM	#1
pof@ diyAudio Member Join Date: Nov 2008	FFT for adjusting tubes I’m looking for a new oscilloscop. The old one is more that 30 years things are not really working anymore. I haven’t 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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19th September 2010, 07:18 AM	#2
chrish diyAudio Member Join Date: Oct 2003 Location: Sydney	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

19th September 2010, 07:56 AM	#3
pof@ diyAudio Member Join Date: Nov 2008	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.

19th September 2010, 11:49 AM	#4
chrish diyAudio Member Join Date: Oct 2003 Location: Sydney	Yes, OK for tube use with 10:1 probe. Also have a 100:1 for power supply and plate.