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'nuther vintage delay bug

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jzucker
Joined: Apr 8 2008
Posts: 29

'nuther vintage delay bug

jzucker
April 25, 2008 - 09:04 am

So, I figured out that if you use the vintage delay and set the bit width to 14 or less and hit a note, you will hear a distorted ghost note sustaining along with the real note. My guess is that this is some sort of rounding/truncating error.

It's very repeatable. Happens 100% of the time. I will record an example if anyone's interested.

Jaz
 

DGillespie's picture
Eventide Staff
DGillespie
Joined: Jan 29 2008
Posts: 1015
DGillespie
April 25, 2008 - 12:25 pm

Hi jzucker, I believe the sound of the distorted ghost note you are talking about is the sound of a low bit-rate. What happens is you are truncating the guitar signal into a smaller and smaller number of steps which makes it look more and more boxy and adds a specific type of noise and distortion. The normal 24 bit audio that we use in the pedal has 16,777,216 different levels at which the signal can be. This is such good resolution that doing things like turning the light on and off in your room will have more of an effect on your sound. However once you get down to 14 bits there are only 16384 different possible steps, 10 bit is 1024, and 7 bit is only 128 steps. The result is that as you move from 20 to ~16 bits you'll get a bit of a softer and warmer sound with a bit more noise, as you move below 16 bits it will start getting much softer and you'll start hearing noticeable distortion and noise, it can even get a bit fizzy and spitty. Below 10 bits you will really start destroying the signal with very noticable distortion and noise. Is this the sort of sound you were talking about? Was there something else you were looking to get out of the knob that you didn't find? Dan
jzucker
Joined: Apr 8 2008
Posts: 29
jzucker
April 25, 2008 - 01:23 pm

I don't think so Dan. This sounds like a truncation/rounding/overflow type of error. I've used plenty of 12 bit delays and reverbs that don't do this. I will record an example and post a link. I think it's just a bug and should be fixable in software. I could see if I was trying to run an 8 bit delay but 14 bits of plenty. There's no reason a guitar with it's limited dynamic range couldn't be represented in 14 bits. 

arcadesonfire
Joined: Feb 13 2008
Posts: 36
arcadesonfire
April 29, 2008 - 10:23 am

 I think that the nasty gross distorted ghost note your talking about is Eventide's intention with the low bit depths. When i first heard that, i thought it was a bug too, because i was assuming that when i lowered the bit depth, i would get a thicker, more smeared vintage delay sound.

So i posted a complaint about that "bug" a long while back, but Eventide convinced me that that's what low bit depth vintage digital delays would sound like. Considering my lack of experience with the vintage digital delays, i believe Eventide.

However, many people here (myself included) would prefer that the x-knob provided something more musical on the vintage delay and tape delay settings rather than ugly noise, but to my knowledge, we haven't heard any plans from Eventide to change them. Nevertheless, I think Eventide has been very patient to hear this come up over and over again.

That's what i think the situation is at least. 

drfrankencopter
Joined: Apr 8 2008
Posts: 12
drfrankencopter
May 03, 2008 - 04:28 pm

 Is there any chance that Eventide is doing sample rate reduction as well as bit reduction? If so, the ghost note could be the result of aliasing... 

Cheers

Kris 

jzucker
Joined: Apr 8 2008
Posts: 29
jzucker
May 05, 2008 - 09:31 am

 bump - Let's get this resolved. No excuses. Can we get the software guys to look into this?

DGillespie's picture
Eventide Staff
DGillespie
Joined: Jan 29 2008
Posts: 1015
DGillespie
May 09, 2008 - 11:50 am

 Hi Guys,

Sorry it took me so long to get back to you on this.

As jzucker said, it is truncation noise/distortion.  You bit reduce a signal by truncating the sample to a specific number of bits.

If you are running the latest beta version of software, the background noise when you are not playing should be gone.  Let me know if that isn't 

The bigger question is, what were you guys expecting/hoping to hear at 14 bits that you are not, and how can we improve it to help you guys out.  I obviously can't promise that we can or will do everything.  But I'd like to try.

For what it's worth, I am the DSP engineer that designed and coded the sounds for this product, so the software guys are looking into it.

Dan 

jzucker
Joined: Apr 8 2008
Posts: 29
jzucker
May 12, 2008 - 11:43 am
Hi Dan, It's jzucker from the forum. I'm the author of Sheets of Sound for Guitar and write a column for Guitar Jam Daily. I've also got a ton of product demos up at www.youtube.com/sheetsofsound I'd be happy to work with you on this bug. I'm using the latest beta software and I'm still getting the sustained distorted note at 14 bits. Let me know how I can help .