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Noise problem when key is pressed

Noise problem when key is pressed

2015-04-13 by freb101@yahoo.com

Hi guys,

I recently bought a fantastic Korg Mono/Poly which unfortunately has a strange noise problem I didn't noticed when I picked it up.


I hope you guys know this synth better then myself and can give me some help figuring out if there's something to recap.The noise I'm talking about it's different from the typical noise floor every analog unit has. 



I tried to do the following test and I have attached an audio sample:

First part:

- All VCOs vol =0 / Cutoff =0 / Noise = 0   ( I change the attack and release time knobs in the vca section)


Second part:

- 1 VCO vol=50%  / Noise =0  ( I change the cutoff and attack time knobs)


As you can hear the noise is very audible at low cutoff value and it's not affected by cutoff, vco volumes, resonance. 


What do you guys think could it be? Could it be a VCA problem? 



Thank you in advance for the help.





Re: [korg_mono-poly] Noise problem when key is pressed [1 Attachment]

2015-04-13 by Florian Anwander

Hello

There are two noises: a 50Hz "buzz" from the power line and real "noise".

The buzz sounds more like it is induced by neon light or something
similar. But it might be the transformer itself. I can't judge that from
here.

The noise seems to me the normal noise of the synths output (it _is_
noisy to a certain level), but the internal signal seems to be low. That
is normal for 50% Level. Use 100% Level for VCO1 and make the recording
again.

Basically: the signal level in the MonoPoly is that way laid out, that
you can work always with all VCOs at 100% level. There is plenty of
headroom. If you do not use this headroom, you will hear the noise.

Florian

Re: [korg_mono-poly] Noise problem when key is pressed [1 Attachment]

2015-04-13 by freb101@yahoo.com

Thank you for your answer Florian. You are right about the two noises, I didn't noticed the 50hz buzz.

I recorded a new file with VCOs vol at 100%. EG intensity is at 0. 
At high cutoff settings the noise it's not so easy to distinguish but, at low and medium cutoff settings, it's imo very audible, especially listening to the recording with headphones.  

Maybe it's a normal thing of all Mono/Polys, I don't know. The thing that made me think there's a problem with mine is that it's not a noise floor , which is always present even if no key is pressed, but it's something that pass thru the VCA and goes to the output, even with all VCOs at 0% volume.









Re: [korg_mono-poly] Noise problem when key is pressed [1 Attachment]

2015-04-14 by Alan Dicker

The monopoly actually has two post filer VCA's these are transistor VCAs. The first is to counter act the reduction in level when the resonance is turned up. the second is the VCA controlled by the amp envelope generator.  These two stages add a little noise each and make the output of any monopoly a little more noise than some of it's contemporaries.  Also as Florian mentioned there is lots of head room going in to the filter as you have four oscillators passing in to the same filter and these can all be sdtacked in hard sync which is pretty loud so your going to here the noise floor if running single oscillators at less than 100%.
To address this issue Lazlo who developed the midipoly kit MIDIpolis was also developing a new vca modification using an IC design.  Maybe get in touch with him and see how that has come on.
 
 
 
 
 
 
 
MIDIpolis
Minerva, the ultimate Juno 60 MIDI retrofit is released on 28th of March along with the improved version of Io, the Jupiter 4 retrofit. Minerva highlights =========...
View on midipolis.blogspot.c...
Preview by Yahoo
 

From: "freb101@yahoo.com [korg_mono-poly]" <korg_mono-poly@yahoogroups.com>
To: korg_mono-poly@yahoogroups.com
Sent: Monday, 13 April 2015, 17:35
Subject: Re: [korg_mono-poly] Noise problem when key is pressed [1 Attachment]

 
[Attachment(s) from freb101@yahoo.com [korg_mono-poly] included below]
Thank you for your answer Florian. You are right about the two noises, I didn't noticed the 50hz buzz.

I recorded a new file with VCOs vol at 100%. EG intensity is at 0. 
At high cutoff settings the noise it's not so easy to distinguish but, at low and medium cutoff settings, it's imo very audible, especially listening to the recording with headphones.  

Maybe it's a normal thing of all Mono/Polys, I don't know. The thing that made me think there's a problem with mine is that it's not a noise floor , which is always present even if no key is pressed, but it's something that pass thru the VCA and goes to the output, even with all VCOs at 0% volume.