Nobelium build done. Thin sounding DI output

D

Djowel

New member
Hi all,

I've build a Nobelium which I got through Musikding in Germany.

Build went well, although I have some issues.

First issue: DI out sound very thin and lower in volume compared to line out. I know Line out has an extra gain stage, but the DI almost sounds out of phase.
Bass and Treble do work, but also a night and day difference with the jack out, which all has the tubey goodness and thickness.
I've reflowed the Unagi xfomer solder pins. Pin 1 is orientated correctly.

I did measured a plate voltage drop to around 60V at pin 1 of V1.


Second issue: the potmeter shaft thread is to short. Including faceplate, the thread barely sticks out. I already filed away a lip on the potmeter chassis. That worked for 2 of the 3 potmeters, but one still wont grab on to the nut.

Anyone got a suggestions to solve these issues?

Thanks!

Joel
 
Small update. I hooked the wires out to DI Section to a Jack output. It tests fine. Full tone and volume. So problem must be at the DI board.
I've desoldered the xformer. Pin 1 and 8 measures 100.8Ω at secundary. No continuation at pin 4 and 5. So, that would be a faulty primary?
Still makes me question why it did put out a signal at XLR. ,

If anyone can help me out. Also with the plate voltage drop and nut on potmeter problem, that would be very appreciated!
 
Would you be able to take some pictures of the pot side of the board so we can see if there is a problem ?
If you post some pictures it might be obvious to someone else what the problem is.
Thanks
Mick
 
Djowel said:
Small update. I hooked the wires out to DI Section to a Jack output. It tests fine. Full tone and volume. So problem must be at the DI board.
I've desoldered the xformer. Pin 1 and 8 measures 100.8Ω at secundary. No continuation at pin 4 and 5. So, that would be a faulty primary?
Still makes me question why it did put out a signal at XLR. ,

If anyone can help me out. Also with the plate voltage drop and nut on potmeter problem, that would be very appreciated!
Click to expand...
DCR at pins 4-5 should be around 2.4kΩ, if you're reading more than that then it could indicate damage to the transformer. An open primary would certainly result in a very low/thin XLR output.

I'm all out of transformers at the moment but I'm expecting to get a bunch more in about 2 weeks, I could send you a replacement if that ends up being the issue.
 
Hi @vigilante398,

Big fan of your creations!
Just did a rehearsal with the nobelium in a in-ear setup. Used a Bo Hansen DI I put together. Sounds huge so far! Cool that you can really play with B/T to get more or less of the mids.

How can I verify an open primary or faulty transformer? I run a small music gear repair shop, so I do have some testing equipement at my disposal.

I've already mailed Klaus, since he is my purchasing vendor. But if you want to take over customer care, if needed, thats fine by me.

@Tassieviking Here are the photos of the pcb. The smudges and lint are a combination of IPA, qtips lint and canned air that froze a bit.
FullSizeRender 2.jpg

FullSizeRender.jpg
 
Last edited:
Djowel said:
Hi @vigilante398,

Big fan of your creations!
Just did a rehearsal with the nobelium in a in-ear setup. Used a Bo Hansen DI I put together. Sounds huge so far! Cool that you can really play with B/T to get more or less of the mids.

How can I verify an open primary or faulty transformer? I run a small music gear repair shop, so I do have some testing equipement at my disposal.

I've already mailed Klaus, since he is my purchasing vendor. But if you want to take over customer care, if needed, thats fine by me.

@Tassieviking Here are the photos of the pcb. The smudges and lint are a combination of IPA, qtips lint and canned air that froze a bit.
View attachment 93066

View attachment 93067
Click to expand...
I mean you basically already did, if a multimeter set for resistance is showing a high resistance or an open, then the primary of the transformer is damaged. So if you want to double check obviously that's not a bad idea, but I trust your readings. I've had this a couple times as I've tested things that I've built.

Klaus orders transformers direct from me since Unagi Magnetics is also my company, and I don't think he carries any extras of those as he typically just orders as many transformers as PCBs. So I can get you a replacement transformer if you want to shoot me a message with your shipping information. As I mentioned though it will have to wait a couple weeks as I am currently fresh out of transformers, I'm waiting on my next batch which is set to finish production April 10 and should be in my hands by mid-April.
 
The only thing I can pick on is that it looks like you soldered the pots onto the PCB without mounting them in the box first, otherwise it looks like a good build.
When you solder pots and switches onto the PCB it is best to mount them loosely onto the PCB, maybe bend the leads a tiny bit so they grip the PCB better, and then mount the whole lot in the box and tighten the nuts on the pots and switches before you solder them in place.
If you solder the pots without mounting them in the box they might be at slightly different heights and one of them will be lower then the others, you will never get the nuts on then.
See if you can un-solder the mounting pins on the pots and then see if you can get the nuts on, you might have to redo the pots to get it right.

Cheers
Mick
 
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