Gefell m582 noise problems

[David_H]

Hi!
I am trying to get rid of excess noise in my m582, and the behaviours I am experiencing are very weird, to say the least. So I am at a little bit of a loss really.

Backstory: I have 2 m582s, and a total of 3 Um70/M71 capsules, as well as a pair of M94 and M70s.

Here comes the strange part - only ONE of my UM70s plays nice with ONE m582 and is virtually noise free, with all other capsules there is a high background tube noise that makes the signal unusable.

What I know so far: It's not the capsules. Apart from the fact that the M94 were serviced by Thiersch, ALL of the capsules sound fine/normal on my MV692 transistors bodies.

But, it kind of IS the capsules, or at least their connection to the m582 bodies - i have noticed that the working UM70 threads a little further onto the headamp (ca. Half a turn) and the connector pin seems to be ever so slightly thicker then all the others.
Has anybody else experienced this with their m582s? I am pulling my hair out over this, the mics seem completely fine, right voltages inside, tube swap makes no difference etc...

Thanks for the help,
David

 

[RuudNL]

Is the output level lower with the 'bad' combination of capsule and amplifier body?
You could try this: power up the amplifier body and put on the capsule.
At a certain point you should hear a change in background noise and suddenly the output level will become higher.
Try to compare the 'good' and the 'bad' combinations.
It could be that in the 'bad' combinations there isn't a good contact with the capsule head.