Nobelium Troubleshoot Hiss

[Rippin_85]

Hey Everyone,

I recently built the C2CE Nobelium Preamp and I am experiencing a significant amount of white noise hiss when the preamp is on. The hiss is present regardless of the volume level, HPF, or EQ settings. It is there even if there is nothing plugged into the input.

I have tried powering it with a godlyke power-all as well as from a cioks dc-7. Same results

I am very new to this hobby and have built up about 15 pedals since diving into it 6 months ago. My builds to date consist of a mix of BYOC kits and PPCB boards. This is my first attempt at anything tube based, and I am at a loss where to look and what to look for in diagnosing this issue.

Can anyone recommend where to start?

Thanks!

 

[Creach]

Hey Everyone,

I recently built the C2CE Nobelium Preamp and I am experiencing a significant amount of white noise hiss when the preamp is on. The hiss is present regardless of the volume level, HPF, or EQ settings. It is there even if there is nothing plugged into the input.

I have tried powering it with a godlyke power-all as well as from a cioks dc-7. Same results

I am very new to this hobby and have built up about 15 pedals since diving into it 6 months ago. My builds to date consist of a mix of BYOC kits and PPCB boards. This is my first attempt at anything tube based, and I am at a loss where to look and what to look for in diagnosing this issue.

Can anyone recommend where to start?

Thanks!

Hello, Rippin_85,

Do you have the white noise when using the XLR output?

Do you have a multimeter or oscilloscope?

 

[Rippin_85]

Hi Creach,

I don’t have a method of testing the XLR output, yet.

I do have a multimeter, but no oscilloscope.

I should note, that I do get signal when I play my bass through the preamp, and it sounds good. It’s just the constant hiss that I find distracting/ concerning

Rippin

 

[Creach]

You can use your multimeter (set to AC) at the XLR output, i will guess pin 1 to pin 2, XLR volume at max. If no measurement it can be that it is to be done at pin 1 to 3.
And you can also do the measurement at the jack output from tip to ring on the jack. Jack's volume at max.

Update : Actually you may not be able to make a measurement with your multimeter, i use to do it but i try to make a measurement for a reference and one of my meter can, an other cannot... Maybe the frequency too high for this meter.

 

[Audandash]

Can you verify what inductor you used? I am not saying it won’t work but i know it is not the one from tayda. It looks larger.

 

[Rippin_85]

Can you verify what inductor you used? I am not saying it won’t work but i know it is not the one from tayda. It looks larger.

Yeah, it is a little bulky.

I purchased the Inductor Mouser. I thought I hit the specs, but honestly I find the rabbit hole of sourcing components to be quite overwhelming so I wouldn’t be surprised if I missed something crucial.

 

[Audandash]

I know its a pain but can you get us some shots of the solder joints underneath the board?

 

[Rippin_85]

I know its a pain but can you get us some shots of the solder joints underneath the board?

 

[Tassieviking]

Good news and bad news.
Good, very nice solder work
Bad, I can't see anything wrong at all.
Hopefully someone else have better eyes then mine

I think the 2 wires running to the XLR board can be used as a line out for testing, the transformer changes it from normal line output to balanced output.
You should be able to put a jack socket on those 2 wires and use it to check the output for noise.

You should be able to use one of those transformers by itself to change from 1/4 jack socket to a XLR socket as far as I know, but I could be wrong of course.

 

[Rippin_85]

Good news and bad news.
Good, very nice solder work
Bad, I can't see anything wrong at all.
Hopefully someone else have better eyes then mine

I think the 2 wires running to the XLR board can be used as a line out for testing, the transformer changes it from normal line output to balanced output.
You should be able to put a jack socket on those 2 wires and use it to check the output for noise.

You should be able to use one of those transformers by itself to change from 1/4 jack socket to a XLR socket as far as I know, but I could be wrong of course.

Thanks for the compliment on the solder work!

I’ll try hooking up the 2 wires to a 1/4” jack when I have some time this weekend. I seem to recall reading about only one tube being used when the signal is processed through the XLR?

One thing I have been considering is the possibility of a dodgy tube causing the hiss. I purchased them new, but I wonder if I maybe got a dud? They are JJ 12au7’s.

Thanks for the everyone’s help.

 

[Lekky]

I seem to recall reading about only one tube being used when the signal is processed through the XLR?

One thing I have been considering is the possibility of a dodgy tube causing the hiss. I purchased them new, but I wonder if I maybe got a dud? They are JJ 12au7’s.

Yep. The signal to the XLR out only passes through the two gain stages in the outer V1 tube; the inner V2 tube is only for the 1/4" output buffer. Try swapping tubes around while listening through the XLR.

 

[Tassieviking]

I think the Sushi Box Neptunium pedal is basically the Nobelium up to the volume pot, the volume pot goes straight to the 1/4" output. (maybe through a capacitor).
The Neptunium is supposed to be the first half of the Nobelium as far as I know, just the one tube.
I think I might even mod my Nobelium with a switch to get the 1/4" output from before / after the 2nd tube stage.

 

[Rippin_85]

Ok, so I hooked the XLR out to a 1/4” jack and the hiss was noticeably lower. I swapped the V1 & V2 tubes and there was a little more hiss coming through the 1/4” XLR. When I plugged into the standard 1/4” out, so the signal was passing through both tubes, the hiss was still there but slightly less than before… certainly within my tolerable range and doesn’t cause the distraction while playing as it did before.

Now if I dime the volume of the nobelium, the his gets ridiculous again, but I don’t see myself needing to do that.

Could one of the tubes be the culprit and it’s amplified by the second one… depending on the order?

I don’t know enough about this stuff to know if that is a possibility

Thanks

 

[Rippin_85]

I think the Sushi Box Neptunium pedal is basically the Nobelium up to the volume pot, the volume pot goes straight to the 1/4" output. (maybe through a capacitor).
The Neptunium is supposed to be the first half of the Nobelium as far as I know, just the one tube.
I think I might even mod my Nobelium with a switch to get the 1/4" output from before / after the 2nd tube stage.

That’s a cool idea, would you use a DPDT (on/on) switch to achieve that? Would you have to add an additional 1/4” output jack, or could you utilize the existing 1/4” out?

If you did that, would you replace the XLR trim pot with an external pot?

 

[Tassieviking]

I would use one jack and switch from the output to the viper of the volume pot.
I would leave the XLR circuit alone

 

[SamuelG]

I got a lot of hiss from some second hand tubes… could you borrow another pair? It doesn’t have to be 12AU7’s… you could try any swap-able tube like a 12ax7. If the hiss goes you know you’re up for new tubes.

 

[Rippin_85]

I got a lot of hiss from some second hand tubes… could you borrow another pair? It doesn’t have to be 12AU7’s… you could try any swap-able tube like a 12ax7. If the hiss goes you know you’re up for new tubes.

Yeah, I could try and source another pair of tubes, but swapping the tube positions seemed to do the trick and brought the hiss down to acceptable levels. I’m not sure how to mark this as solved on the thread

Would 12ax7’s not have too much gain on tap? Potentially causing unwanted distortion?

 

[SamuelG]

Yes, much more than you want. However, it won’t hurt the pedal but will run “quiet” if it’s a tube issue… which, by the sound of your solution, it is.
I have a pair of quality long plate 12AU7’s and the Nobelium runs almost silent.
I reckon “noise” is one of the more valid reasons to swap out tubes.