Thinking of buying a radias, but I need help first.

creepysuitguy · Post by **creepysuitguy** » Tue Nov 24, 2009 1:34 pm

Hello, I have a R3 that is based on the radias engine, and I have an x50, my x50 seems to have some aliasing on the high notes, my R3 only has it on 2 notes and the notes that it happens on are not even the ultra high but they are on the high end, so my question is does the radias have aliasing at all? Because according to Korg it has the program from the Oasys that eliminates it, I work a lot with high notes, I do film scores and dance music so I need something that eliminates aliasing and i'd prefer to stick with Korg.

When my R3 would start aliasing it would be one octave up when I would transfer from the 2nd to the 3rd key from the left side, so if you have a radias I'm not sure where it would be but if you could check it out for me I would be most grateful!

xmlguy · Post by **xmlguy** » Tue Nov 24, 2009 5:27 pm

How do you know that what you're hearing in aliasing and not one of many kinds of "normal" wave interactions? Are you looking at the signal on an oscilloscope?

creepysuitguy · Post by **creepysuitguy** » Tue Nov 24, 2009 6:46 pm

I didn't look at it under a scope but I actually took the synth to a Korg repair shop thinking that something was wrong and the repairman tested it and checked it out under a scope and said it was aliasing, because what would happen was it sounded like when you would transition it would produce a high frequency that was almost ear piercing as if it was a faulty key or something of that nature, which turned out to be aliasing.

xmlguy · Post by **xmlguy** » Tue Nov 24, 2009 7:39 pm

I would not accept that answer from the service guy. It sounds like its another hardware related problem. Is the patch a preset, or a custom program? I've never heard any such high frequency problem on any notes on the R3. You could take the same program and load it on another R3 at a store and see if you can reproduce the problem. If another R3 doesn't do the same thing, then you know the serviceman was just BSing you, which is what I suspect.

creepysuitguy · Post by **creepysuitguy** » Tue Nov 24, 2009 9:11 pm

Ok I'll look into it, so you have never had a problem with your R3? Did you try what happened to me?

xmlguy · Post by **xmlguy** » Tue Nov 24, 2009 9:38 pm

Nope, no problems with high notes causing any harmonic distortion, at least not that I've noticed, and particularly nothing like an ear piercing upper harmonic. I could try to reproduce it, but it would be a lot harder for me to reproduce the circumstances without having the identical programs and all relevant setting, while you could do the same test on your own first. If you confirm that the problem occurs on another R3 in the same situation, then if you send me all the details I'll take a look at it in depth.

It's my understanding that the Korg MMT engine uses the same low-aliasing design as OASYS. I'm wondering if the program you tested was using one of the basic waveforms or one of the DWGS waves. Have you tried starting with a init program and basic sine wave to eliminate other variables in the program itself?

creepysuitguy · Post by **creepysuitguy** » Tue Nov 24, 2009 10:03 pm

I believe it is one of the basic programs it is the strings patch, I believe the first one, am I doing something wrong or is there something in the R3 I need to turn on so it doesn't do this? I turned the noise level filter all the way down to 0 and I thought that would be all i needed to do.

Timo · Post by **Timo** » Tue Nov 24, 2009 10:55 pm

creepysuitguy wrote:is there something in the R3 I need to turn on so it doesn't do this?

It's a bit of a "how long is a ball of string?" type thing. Could be attributed to a (possible) whole number of things, it's hard to narrow it down when you don't have it in front of you to tweak. Could be simple phasing of two oscillators, or the DWG/PCM waveforms as mentioned, or literally anything.

If you could start with an initialised patch, and then tell people what to do to invoke the problem in order to replicate it, then answers will be found.

I'm half deaf though, so I don't notice aliasing (if was there any) so much! I also have a Radias, not an R3, so am not much help.

axxim · Post by **axxim** » Wed Nov 25, 2009 1:08 am

Hi creepysuitguy,

why don't you tell us what program and keys you use to get the effect? If it is a custom program, set it for download and we could try to reproduce and analyze it.

xmlguy · Post by **xmlguy** » Wed Nov 25, 2009 2:18 am

creepysuitguy wrote:I believe it is one of the basic programs it is the strings patch, I believe the first one, am I doing something wrong or is there something in the R3 I need to turn on so it doesn't do this? I turned the noise level filter all the way down to 0 and I thought that would be all i needed to do.

A strings patch is far from a basic program, and none of the presets are basic programs, in that they all are far more complex than an init patch with a sine wave assigned to OSC1, and nothing else to modify it.

If you aren't already very familiar programming the R3, then the sound you hear is very likely to be an unintentional side effect of something that was intentionally programmed on that specific strings patch you used. That's why you need to eliminate as many variables (parameters) as you can by starting with a newly initialized program with all the parameters reset to defaults.

creepysuitguy · Post by **creepysuitguy** » Wed Nov 25, 2009 4:33 am

I have reset to the default settings and go to the strings and it will be the first patch when you turn the big knob to the strings section, the only thing I have done is turn the noise level down to 0 everything else is the same as the facorty settings, if you press the left octave button that tunes it up the keys that is producing the effect is the 2nd white key (from the right side which is the high side) and then transitioning to the 3rd white key (the key on the left side of the key I mentioned before). Does this make sense and help? The sound I am hearing is a high frequency that last for around a second and its almost an airy frequency that from what I am told isn't supposed to be there and is called aliasing, the frequency almost sounds like something starting or turning off it is very odd.

TrrP · Post by **TrrP** » Wed Nov 25, 2009 1:58 pm

The R3/Radias does start aliasing at a certain point as do all digital synthesizers. I hear it alot because I also use alot of high pitched sounds in my music. It gives about the same effect that you get when applying the decimator effect. Aliasing is not the same as harmonic distortion. Read more here if you are interested: http://en.wikipedia.org/wiki/Aliasing
There is also an audio example on this page (although I must say that aliasing can sound alot different to this example).

To tell if this is aliasing or not you will have to send us an audio example. It's impossible to know what you're hearing. + Send us the patch aswell so we can compare. (btw I'm using a Radias but the engine is identical and I can copy settings exactly except for DWGS waveforms)

creepysuitguy · Post by **creepysuitguy** » Wed Nov 25, 2009 3:56 pm

Ok I'll get an audio sample up tonight, thanks for the help.

xmlguy · Post by **xmlguy** » Wed Nov 25, 2009 6:52 pm

TrrP wrote:The R3/Radias does start aliasing at a certain point as do all digital synthesizers. I hear it alot because I also use alot of high pitched sounds in my music. It gives about the same effect that you get when applying the decimator effect. Aliasing is not the same as harmonic distortion. Read more here if you are interested: http://en.wikipedia.org/wiki/Aliasing
There is also an audio example on this page (although I must say that aliasing can sound alot different to this example).

To tell if this is aliasing or not you will have to send us an audio example. It's impossible to know what you're hearing. + Send us the patch aswell so we can compare. (btw I'm using a Radias but the engine is identical and I can copy settings exactly except for DWGS waveforms)

By the way, I didn't say that aliasing was the same as harmonic distortion. Aliasing can cause harmonic distortion. When the OP stated the problem "would be one octave up," I interpreted that to mean he was referring to the frequency of the note he was hearing, but his later messages clarified that he was referring to pressing the Transpose Octave Up button on the keyboard. That's why I suggested the need for an oscilloscope (or other method of frequency analysis) to observe the nature of the kind of distortion with some precision, rather than guessing what the problem is based only on hearing it.

Aliasing becomes insignificant in a number of scenarios, such as when the highest frequency is sampled at a rate significantly higher than the minimum needed Nyquist frequency, such as using a 24bit/96K rate or 1-bit (sampled in Mhz). Most musical notes are well under 6KHz, and only harmonics and noise are in the 6-20KHz range, with most 2way PA speakers only reproducing up to 16KHz.

In this specific case, the only evidence that aliasing is occuring at all is the word of some tech who is motivated to explain something away to stop from having to fix something (possibly under warantee). This falls under a wide range of common answers that are used to blow people off, since you have to take the techs word for it if you don't know what the problem is and how to verify that diagnosis yourself. Usually the bluff works, until it is used on someone who can call the bluff. It's much too convenient to blame aliasing for _any_ digital synth, regardless of the real problem that usually has nothing to do with aliasing at all.

TrrP · Post by **TrrP** » Wed Nov 25, 2009 9:18 pm

xmlguy is right in that you have to find out what this is you're hearing. I've had terrible advice given to me by repairmen/tech guys. Alot of them will say anything to save themselves the hassle or make themselves more money.

But I must say that I still find aliasing a big problem on all digital synths. Having a real analogue next to a digital will immediately let you hear the difference. I don't mind too much though. I embrace the digital character of the Radias. In fact it can give some pretty cool effects just like the decimator. Thats why I loved the microKorg. It could give you some pretty messed up sounds. The Radias especially aliases with high resonance on the comb filter on high notes.

I'm guessing the Radias/R3 operates at 48khz meaning that any frequencies the Radias/R3 'trys' to produce above 24khz (half the operating frequency) will start aliasing. Basically the aliasing will 'fold' any frequencies above 24khz down to lower frequencies producing unwanted noises. So the actual frequencies of the aliasing are below 24khz.
Example: 25khz frequency will become 23khz. 32khz will become 16khz.
I don´t know for sure but I think osc sync on the R3/Radias will produce even more aliasing because of phasing. I also believe that FM (VPM on the Radias-R3) and cross modulation will also produce aliasing more because of phasing meaning that aliasing will start well below 24 khz.

creepysuitguy please send the patch also so we can definitely compare!

PS. Hey, I'll send an audio example this week of the Radias producing aliasing so you can compare also.