EPS-16 Plus Anti-Aliasing Question

Hey Guys,

I recently picked up an EPS-16 Plus and in contrast to the ASR i noticed you could select a filter rate (not sample rate) in advance to cut out certain frequencies above that rate.

So this is where i dont quite grasp the anti aliasing features. So if i change the filter cutoff rate to "Off" will that result in an anti-aliasing effect? This effect only kicks in when pitching down correct?

Thanks fellas and pardon my ignorance on the topic.

I guess when it's set to off it's off so aliasing is the result. The effect kicks in when the source signal has frequencies above the nyquist frequency (which is samplerate / 2). The lower the samplerate the more you can hear it at original pitch. If you don't want to lower the samplerate for whatever reason you'll need first pitch up the source (so it's high frequency range hit the nyquist point) and pitch it down in the sampler cause the aliasing might be in a too high frequency range for your ears.
peace

For any questions about the EPS I recommend The Daydream Sound on youtube. He's got massive knowledge on the EPS and is very kind when it comes to answering questions.

peace

Peter,

So if i understand correctly you think i should try setting it to OFF, then sample at 45 rpm or so and pitch it back down and see if i notice any of the artifiacts?

Pitching down on the EPS will not give you artifacts in the same way I believe you're leading to, such as ring modulation right?

Ring modulation is something different richie.

Oh gotcha ok well i do notice the sped up pitch down thing def sounds better to me on the eps16 plus than the asr. So i dont know if that's the anti aliasing feature or not.

Perhaps its because i was sampling in at 22.3 vs 29.6 or whatever on the asr..not sure??

richie wrote:Pitching down on the EPS will not give you artifacts in the same way I believe you're leading to, such as ring modulation right?

you are right here, the pitch-ed down low-sample-rate artifacts do usually sound like a ring modulator

the anti-aliasing just is going to give you weird artifacts IF you have frequencies that go above your sampling rate...as you start to get things at higher frequencies they will start to 'reflect' (or 'alias') back down into the audible band.

the best way to hear this is to take a sine wave that just constantly raises in frequency. once it gets higher and higher, close to the 1/2 the sampling rate...you'll hear it kind of disappear, then, as it gets even higher, you will hear it start to fall back down in frequency. its crazy when you actually hear it like that.

if i may try to type the sound out, youd hear it go woooooeeeeeeee.....eeeeeeoooooooow (up, then back down)

peterpiper wrote:Ring modulation is something different richie.

I fully understand that, which is why I posed the comment as a question as it seems that many desire to have the effect of the SP/EMAX with the same sounding harmonics and ring modulation when pitching down.

@golden era: I don't know how the EPS behave. You probably won't hear anything if you sample at a samplerate of 44100 although you sampled with cutoff=OFF and at 45RPM. Thats because most instruments won't give you a relevant signal at 22050Hz (nyquist for 44100Hz) or above.
Think about the SP samplerate. Its fixed at 26040Hz. That means every signal which has frequencies above 13020Hz will cause artifacts. This is a range in the spectrum 'normal' adult people are able to hear and many instruments have relevant overtones.
When you shift the frequencies of the source signal to an even higher frequencies(pitch up) it will result in more artifacts and if you shift the signal back to its original range (pitch down sample after sampling) the artifacts become more present because they(the artifacts) will get to a frequencyrange that is even lower than 13020Hz and 'better' to realise.

In short: Try cutoff=OFF and lower the samplerate to something in the 20k and sample at 45rmp. It should sound...... interesting at least It might also help to 'sample hot' (raise the gain of the source so it might overdrive the input amp a bit) but like I said I don't know how the EPS bahave in that case. Some samplers really don't like it and produce digital clipping which sound really bad. Other samplers behave like a normal analog amplifier and add nice overtones or kind of work like a compressor/limiter.

peace


BTW I once had a Doepfer MS404 analog synth which had an input in to use the filter and envelopes on external audio. So I fed the output of my DJ mixer into it and played with it till I found out that it produced nice 'ringing' on the signal from the the turntable with the LFO set to be really fast (4-5kHz LFO?WTF?? ) modulation the filter. So the filter will open and close at a really fast rate. This will result in cutting up the audio 5000x per second. I would call it 5kHz samplerate emulation

@tapedeck:
For your listening pleasure (1st = original sinesweep, 2nd = SP1200 normal pitch from the unfiltered ouput 7/8, 3rd = SP1200 - 8 semitones again out 7/8)



and to make it an experience for the more visual people....


peace

Thanks to hovaone who was so kind to sample the sinesweep in his SP1200 (6 years ago AFAIR)

peterpiper wrote:@golden era: I don't know how the EPS behave. You probably won't hear anything if you sample at a samplerate of 44100 although you sampled with cutoff=OFF and at 45RPM. Thats because most instruments won't give you a relevant signal at 22050Hz (nyquist for 44100Hz) or above.
Think about the SP samplerate. Its fixed at 26040Hz. That means every signal which has frequencies above 13020Hz will cause artifacts. This is a range in the spectrum 'normal' adult people are able to hear and many instruments have relevant overtones.
When you shift the frequencies of the source signal to an even higher frequencies(pitch up) it will result in more artifacts and if you shift the signal back to its original range (pitch down sample after sampling) the artifacts become more present because they(the artifacts) will get to a frequencyrange that is even lower than 13020Hz and 'better' to realise.

In short: Try cutoff=OFF and lower the samplerate to something in the 20k and sample at 45rmp. It should sound...... interesting at least It might also help to 'sample hot' (raise the gain of the source so it might overdrive the input amp a bit) but like I said I don't know how the EPS bahave in that case. Some samplers really don't like it and produce digital clipping which sound really bad. Other samplers behave like a normal analog amplifier and add nice overtones or kind of work like a compressor/limiter.

peace


BTW I once had a Doepfer MS404 analog synth which had an input in to use the filter and envelopes on external audio. So I fed the output of my DJ mixer into it and played with it till I found out that it produced nice 'ringing' on the signal from the the turntable with the LFO set to be really fast (4-5kHz LFO?WTF?? ) modulation the filter. So the filter will open and close at a really fast rate. This will result in cutting up the audio 5000x per second. I would call it 5kHz samplerate emulation

Piper, great info i will try your suggestion appreciate it. Thanks. Really liking the EPS16 Plus sound.

golden-era wrote:

peterpiper wrote:@golden era: I don't know how the EPS behave. You probably won't hear anything if you sample at a samplerate of 44100 although you sampled with cutoff=OFF and at 45RPM. Thats because most instruments won't give you a relevant signal at 22050Hz (nyquist for 44100Hz) or above.
Think about the SP samplerate. Its fixed at 26040Hz. That means every signal which has frequencies above 13020Hz will cause artifacts. This is a range in the spectrum 'normal' adult people are able to hear and many instruments have relevant overtones.
When you shift the frequencies of the source signal to an even higher frequencies(pitch up) it will result in more artifacts and if you shift the signal back to its original range (pitch down sample after sampling) the artifacts become more present because they(the artifacts) will get to a frequencyrange that is even lower than 13020Hz and 'better' to realise.

In short: Try cutoff=OFF and lower the samplerate to something in the 20k and sample at 45rmp. It should sound...... interesting at least It might also help to 'sample hot' (raise the gain of the source so it might overdrive the input amp a bit) but like I said I don't know how the EPS bahave in that case. Some samplers really don't like it and produce digital clipping which sound really bad. Other samplers behave like a normal analog amplifier and add nice overtones or kind of work like a compressor/limiter.

peace


BTW I once had a Doepfer MS404 analog synth which had an input in to use the filter and envelopes on external audio. So I fed the output of my DJ mixer into it and played with it till I found out that it produced nice 'ringing' on the signal from the the turntable with the LFO set to be really fast (4-5kHz LFO?WTF?? ) modulation the filter. So the filter will open and close at a really fast rate. This will result in cutting up the audio 5000x per second. I would call it 5kHz samplerate emulation

Piper, great info i will try your suggestion appreciate it. Thanks. Really liking the EPS16 Plus sound.

Thanks. The EPS16 seems like a hell of a machine. Beside the SP its my most wanted sampler but unfortunetly it is not very often on ebay here in germany. Again if you havn't already watch the EPS videos on Daydream Sound channel. Many infos there
https://www.youtube.com/user/TheDaydrea ... ?query=eps

peace

dope demo peter. lots of stuff going on there. love how you can see it. thanks

The first thing I noticed with my EPS is that when I sample a drum loop at a higher pitch and then pitch down, the transients are still in tact.

It was in stark contrast to what I experience on my Akai units and a bit surprising at first. I hope to experiment some more when I am able to prioritize the time to.