please help! preenfm2, distortion noise on pure sine wave tone

[hen__]

hello everyone, i just bought a preenfm2 from a second hand place, it seems pretty clean and the guy who sold it didn't use it much, but i've been having some distorted frequency on all the sounds, doesn't matter the volume, it's all the time there.
anyone have an idea if it's possible to remove this noise?
i've seen that there have been issues with the yellow oled with high pitch frequency, i'm not annoyed from that, i just want to be able to get a clean sine wave
i've attached an audio file

[Xavier]

Difficult to say anything from the mp3.

Try the following :
Set the number of voice of I1 to 1. The other I2, I3, I4 to 0.

Instrument 1 :
Set velocity to 0.
Use Algo 2. And make Sure mix1 is 1.0.
Is it better ?
There's good chance what you hear is the limit of the preenfm2 DAC when the oscillator have no enough bits.

You may want to verify the resistors 115K and 1.8K they're used to link the 12 bits DAC with 6 bits of the other one to make a good sounding 18bits DAC.
If those resistors are wrong, the resolution is only 12 bits.

[hen__]

Hello Xavier, thank you so much for your quick reply, i did exactly as you said and yes the noise is much lower but it's still there, not sure if it's normal to have this small distortion on a sine wave ?
I've attached a link for the audio file below

i also checked with a multimeter the resistors and they're right, also the guy i bought the preen from him , he told me that he bought it from vaandal prebuilt.

https://www.dropbox.com/s/1axns0fesi9kwqa/preenfm2%20noise%20test%202.wav?dl=0