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The warning means that if you apply DC to the input it will pop your SA's front end, like an AC signal with a DC offset.
Get a DC block and have it permanently attached to the SA input.
A further clarification of the input spec is found in the manual.
5 Hz is below the normal working range of the analyzer, so any readings taken at this frequency will not be accurate, especially in the AC coupled mode.
I don't have an 8560E, I have an 8594E which is a similar, but lower spec analyzer.
If the input attenuation is 10 db or greater the input is connected to an attenuator which has a 50 or 75 ohm input impedance. Any DC applied to the input uses up the dynamic range of the attenuator, and thus reduces the acceptable amount of RF (or other signal) which can be applied. A low level 5 Hz signal will not hurt anything, but I wouldn't connect the analyzer directly across say a subwoofer.
The input attenuation defaults to 10 db and I would leave it there for anything but very low level signals. The attenuator can be manipulated by pressing amplitude, then switch the atten to manual and enter the desired attenuation.......leave it on auto unless you have a reason to set it to zero. I do this when hunting RF leaks or weak cell tower signals.
The input coupling defaults to AC but can be switched to DC by pressing the amplitude button, then "more" twice.
These things were designed for RF applications, hence the 50 or 75 ohm input impedance. A high impedance choice is not available although an external buffer amp could be used for audio applications.
5 Hz is below the normal working range of the analyzer, so any readings taken at this frequency will not be accurate, especially in the AC coupled mode.
I don't have an 8560E, I have an 8594E which is a similar, but lower spec analyzer.
If the input attenuation is 10 db or greater the input is connected to an attenuator which has a 50 or 75 ohm input impedance. Any DC applied to the input uses up the dynamic range of the attenuator, and thus reduces the acceptable amount of RF (or other signal) which can be applied. A low level 5 Hz signal will not hurt anything, but I wouldn't connect the analyzer directly across say a subwoofer.
The input attenuation defaults to 10 db and I would leave it there for anything but very low level signals. The attenuator can be manipulated by pressing amplitude, then switch the atten to manual and enter the desired attenuation.......leave it on auto unless you have a reason to set it to zero. I do this when hunting RF leaks or weak cell tower signals.
The input coupling defaults to AC but can be switched to DC by pressing the amplitude button, then "more" twice.
These things were designed for RF applications, hence the 50 or 75 ohm input impedance. A high impedance choice is not available although an external buffer amp could be used for audio applications.
There are HP SA's with a 1M input that work fine for audio though the THD is not spectacular. My favorite had a noise cal mode that gave plots directly in nV/rt-Hz (IIRC 7nV floor) it was useful for looking at far out of band stuff like images and oscillations. I could have had one with a burnt out CRT for free but it was too much effort for me to rebuild it.
Many diyers are going to a probe, soundcard and software path for audio bench work, or a cheap digital scope with fft. All paths lead to Rome, and typically have a learning and hassle curve. Well worth battling on.
I've got past the hassles with the soundcard option, and imho it works a treat for audio spectrum analysis for vintage amp work.
I've got past the hassles with the soundcard option, and imho it works a treat for audio spectrum analysis for vintage amp work.
Say hello to Melbourne for me, born and raised in the eastern suburbs. Yea, I admit I am not real computer savvy and like the old school stand alone purpose built stuff but I may have to venture down that path to keep up with the current trends.
What would be a good example of a worthy fft digital scope? I have an old school Tektronix 2247A.
What would be a good example of a worthy fft digital scope? I have an old school Tektronix 2247A.
The quite common Rigol range I think come with reasonable FFT, but are a fully fledged scope. Google and check Test Equipment - Page 1 or this sub-forum for Picoscope, or others in that market space. I don't think the cheaper pocket oscilloscopes (eg. on ebay) do spectrums, but the scene is changing fast.
The hassle with digital scopes can be lack of voltage resolution from 8-10 bit adc's, whereas a soundcard is min of 16 and up at 24bit, and so spectrum noise floor even with 16bit USB $1 device is circa 90dB. I just adore seeing a measurement noise floor below the amps noise floor, then I have faith in what is popping up out of an amps noise floor (intentionally or not).
The hassle with digital scopes can be lack of voltage resolution from 8-10 bit adc's, whereas a soundcard is min of 16 and up at 24bit, and so spectrum noise floor even with 16bit USB $1 device is circa 90dB. I just adore seeing a measurement noise floor below the amps noise floor, then I have faith in what is popping up out of an amps noise floor (intentionally or not).
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