rob aylestone
Moderator
I ordered some very cheap Chinese inline preamps - one was average, but the other equally as good as the FET FP1 that I use here with an SM7B
I dreamed up a way to compare them - not particulary accurate or complicated, but sort of real world testing.
Record normally. Normalise to full scale, then in the gaps you can see how far down the noise is. Now clearly the noise is a combination of hiss, room noise, like fans, and even breathing - but the electronics noise rapidly overtakes the ambient 'silence. Swapping one pre-amp for another, and removing it totally produces pretty well what we expect, when we have to turn the gain up - extra noise. Oddly, I discovered that the camera preamp I use is pretty good with the preamp in circuit, but not good when the level lowers, and bringing it back up in the DAW is not good. The noise floor shoots up. The Zoom H6 I also use, manages gain much better and removing the preamp on that gives a very small difference in noise when normalized - where as the camera audio when boosted in the DAW is much worse. I also tried it on tones too - 1K, then a gap, then 1K produced other interesting 'artefacts'.
In the video I edited out the start and end of each tone burst - I had to. I recorded the first version usuing the camera and the waveform was a real mess - as the tone started, it overshot, then settled and when it cut, it did the same - every abrupt start and stop produced these peaks which I had to edit out to be able to normalise. I blamed the camera - thining it had some kind of limiter, but discovered the zoom did exactly the same thing. I tracked it down to the active loudspeakers - recording the speakers on the vido editor, there was no overshoot? I have never seen this before - but clearly this must happen when they are playing music. These are not 'quality' speakers, just active PA speakers that sound quite nice, but the onboard amplifier must be badly designed or even faulty? I don't know.
Once I edited out the nasty start/stops, all was fine.
So - not that scientific really, but it showed that one preamp was actually lower gain, but noisy, and that one Chinese pre-amp was as good as the FP1 that I normally use. The video is best listened to on headphones. Interestingly, I cut out the FP1 noise and butted it up to the Chinese noise and they were indistinguishable = for £12 plus shipping and the VAT.
I dreamed up a way to compare them - not particulary accurate or complicated, but sort of real world testing.
Record normally. Normalise to full scale, then in the gaps you can see how far down the noise is. Now clearly the noise is a combination of hiss, room noise, like fans, and even breathing - but the electronics noise rapidly overtakes the ambient 'silence. Swapping one pre-amp for another, and removing it totally produces pretty well what we expect, when we have to turn the gain up - extra noise. Oddly, I discovered that the camera preamp I use is pretty good with the preamp in circuit, but not good when the level lowers, and bringing it back up in the DAW is not good. The noise floor shoots up. The Zoom H6 I also use, manages gain much better and removing the preamp on that gives a very small difference in noise when normalized - where as the camera audio when boosted in the DAW is much worse. I also tried it on tones too - 1K, then a gap, then 1K produced other interesting 'artefacts'.
In the video I edited out the start and end of each tone burst - I had to. I recorded the first version usuing the camera and the waveform was a real mess - as the tone started, it overshot, then settled and when it cut, it did the same - every abrupt start and stop produced these peaks which I had to edit out to be able to normalise. I blamed the camera - thining it had some kind of limiter, but discovered the zoom did exactly the same thing. I tracked it down to the active loudspeakers - recording the speakers on the vido editor, there was no overshoot? I have never seen this before - but clearly this must happen when they are playing music. These are not 'quality' speakers, just active PA speakers that sound quite nice, but the onboard amplifier must be badly designed or even faulty? I don't know.
Once I edited out the nasty start/stops, all was fine.
So - not that scientific really, but it showed that one preamp was actually lower gain, but noisy, and that one Chinese pre-amp was as good as the FP1 that I normally use. The video is best listened to on headphones. Interestingly, I cut out the FP1 noise and butted it up to the Chinese noise and they were indistinguishable = for £12 plus shipping and the VAT.
