Korg Nutube preamp noise issue.

Hi all, I’m new here to please be gentle.



Wondering if someone could help me,
my lovely partner bought me a Korg Nutube pre amp but unfortunately I’m having a problem with it.

I followed the diy guide and it works and plays but there is quite a lot of hiss coming through both speakers when it’s turned on, it also gets louder when the volume is increased.

Is there a check list I can run through to try and eliminate it?
Many thanks.

Lloyd.
 
@Osvaldo de Banfield
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Hiss and not hum?

How much hiss... can you hear it with music playing quietly?

please post a series of well-lit, in-focus photos to help the troubleshooting. 🙂
Will have to put it re assemble it again, wiring was as per diy guide, i do have a pic of the board.
 

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This one. If the noise is still present, we can suppose the culprit is the tube or the JFET follower.

But IMO this design can be enhanced notoriously. Why use a JFET follower (high input impedance, desirable) and using only 1600ohm gate resistor (3300 paralleled)? (Less than a germanium transistor).
 

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This one. If the noise is still present, we can suppose the culprit is the tube or the JFET follower.

But IMO this design can be enhanced notoriously. Why use a JFET follower (high input impedance, desirable) and using only 1600ohm gate resistor (3300 paralleled)? (Less than a germanium transistor).
Hi. I removed the 10uf capacitor and the noise is still present. But obviously now doesn’t get louder with volume.
So what’s the next step get a replacement Nutube?

Many thanks.