by sampleandhold » Tue Nov 07, 2006 12:38 am
Well, first. You may not want to use the test tones from the emu. They are a bit noisey. I would get wave forms from Wavelab, as I did so many years ago.
You'll also want to sample them in mono. Which I mean you'll sample in stereo, but have only one input receiving signal. You want to unplug the cable from the emu not the from the source. A connection left un used can cause bio or environmental feedback. So you want nothing plugged into the emu that you don't intend on sampling. Once you have your stereo sample that happens to have only the right or left channel with a signal, you'll want to convert to mono. When you convert to mono, the sample will sound stereo. They will infact go through both speakers instead of just the left. You will have a cleaner image if you do it this way. You will also save polphony. And you will have stable filter responses.
Image. When sampling, and this can go towards all samples, not just test tones, if you take a stereo sample, both channels with signal and convert it to mono, what the sampler will do is sum the two channels together. Basicually it lays the left on right and vice versa. What will occur is destructive and constructive interference. More so that you will get destructive interference. The sample will lose it's high end due to phase cancelation in essence. I had a break that sounded muffled after converting to mono, so my sampling method is of this type. One signal into stereo mode, convert to mono to get a stereo sound. See?
Polphony. The emu counts stereo samples as two voices. So if you have poly up to 64, you can only have 32 stereo samples playing at once. But what happens with this occures is the next issue...
Filter stability. When you have a high poly count, more so with alot of stereo samples, the filters, more specifically the lpf, will cause strange distortion bursts. Loud snapping and popping. The stuff people the house over will hear. It's very bad. I am not quite sure what causes this, some kind of over load of polyphony or perhaps the lpf's curve (it bells at about 100hz, in other words, it actually gets louder at that frequency, whether that is because the various sine waves are combining as they become a signulairity, or that the filter was designed to have a slight Q response at the range is hard to tell) which when coupled with eight stereo voices may cause a quick spike in signal that causes the sampler to distort. But this phenomina is not isolated to just filter sweeps, it usually occures at the attack stage of the sound. Just something to avoid.
The emu also does something kind of odd. At 68 samples, I found that I could play all those test tones in a preset at once with each of them detuned slightly and I still had polphony left, yet I should only have 64 so I think there might be something else the emu is doing when samples are mono. I think it might drop voices as well. but I doubt you'll go so far as to create a 68 voice patch.
Any questions, just shout. I check this from time to time.
snh
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