Hello,
I have a Kt88 tube amplifier that I ran some tests on with The Stuff Made audio analyzer suite. In the THD Test after it hits 10k hz the distortion drops like a cliff. I dont have a whole lot of experience testing amplifiers and would like to know if anyone can tell me if this is normal. I attached a screenshot.
Thanks
I have a Kt88 tube amplifier that I ran some tests on with The Stuff Made audio analyzer suite. In the THD Test after it hits 10k hz the distortion drops like a cliff. I dont have a whole lot of experience testing amplifiers and would like to know if anyone can tell me if this is normal. I attached a screenshot.
Thanks
Attachments
It depends on circuit topology. If it has nfb with frequency dependant constants, probably it's ok.
I'd recommend you do a loopback test, to identify the frequency response of your test setup, and the baseline distortion response in your test setup. Note that you have a frequency span of 20kHz, but also a bandwidth of 20kHz, such that a test signal of 10kHz can only be assessed for its 2nd harmonic level at 20kHz, as any higher frequency harmonics are excluded by the bandwidth limit. Effectively you need a 96kHz bandwidth (192kHz sampling) to measure the first 10 harmonics of a 10kHz signal. Also best to exclude the N aspect of THD+N, if your interest is just harmonic distortion.