Finished beautiful Gyraf G9 build

[Majestic12]

Fired up my G9 for the first time in the middle of the night, after working nearly two years on this project.
Nothing special on this, the only thing I did was the 15kHz noise mod and a metal screening around the transformers. The components are WIMAs for the capacitors and JJ tubes.

Both channels are working equaly fine, no hum or hiss. It's just beautiful. I can recommend this preamp to everybody who wants to get into tube projects. For me it was the first time working with tubes and it went very well.

The only thing I'm a bit worried about is the really loud 50Hz hum coming from the transformers. It' s really loud, I'm not sure if I have to be worried about that and how I probably can fix this.



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[gyraf]

A nice one indeed!

Jakob E.

 

[sam system-d]

Nicely done, I've built mine 4 mounth ago, can't go around without it!

 

[Majestic12]

After moving the transformers around and reversing the sec. connections there is still this annoying hum. I ordered a new 230/12V 30VA transformer, hope that replacing the old one will fix this problem....

 

[gemini86]

Is it both of them? or just the mains to 12v one? I fried one that should have handled the load, but didn't. It was a cheapy. It was really noisy up until the windings melted and the fuse blew...in that order.

 

[Majestic12]

No, it's the second 12V to 230V 30VA one that makes that hum. The main 230V to 15V 30VA transformer is absolutely silent.

 

[kante1603]

No, it's the second 12V to 230V 30VA one that makes that hum. The main 230V to 15V 30VA transformer is absolutely silent.

Hello,

you´re talking of a mechanical hum,no?
If so then yes-I would change the transformer.When mounting the new one don´t overtighten the nut-this can definetely kill it.

Nice build,congrats (the panel is generated from frank´s fpd-file?).

Cheers,

Udo.

 

[Majestic12]

Yes, it's mechanical hum. I can also feel the transformer vibrating when I touch it. The screw isn't very tight, so it shouldn't be a problem. Let's see what happens when I change the transformer.

The frontpanel was made out of Franks fpd file with some minor changes.

 

[Majestic12]

I fixed the hum problem. I just swapped the cheap 12V transformer from Reichelt with a quality model from Farnell and the hum was gone

BTW, I just finished a second unit for my studio. Now I have 4 channels of tube amplificiation for drum overheads and room mics...

 

[mich]

Great job!

Now I have 4 channels of tube amplificiation for drum overheads and room mics...

- Why not for bass drums and snares too? ;D