Telefunken V76 popping sound when chaning HP filter settings

[Chris Blancke]

My V76 start to act weird when changing the HP filter knob.
A fairly loud pop can be heard when selecting 80-12-300hz settings, no matter how the gain is set.
All electrolytic caps are replaced and measuring fine.
Preamp works great otherwise.
Where to start looking ?, thanks

 

[gyraf]

I've never worked with a V76 that was popfree when changing lowcut. But as you don't change setting while recording, this dosen't matter really - unless it gets very loud...

Looking at the schematic, I don't really see any possibility of the lowcut filter NOT popping when switched - it sits at a rather high DC voltage.

Are you sure it was pop-free earlier? And actually worked while switching silently?



Jakob E.

 

[Chris Blancke]

[quote

Are you sure it was pop-free earlier? And actually worked while switching silently?



Jakob E.
[/quote]

Good question. I can't remember since I don't often use the filters.

Looking at the schematics myself , I only see the inductors in circuit all the time , I doubt these can't be the source of popping.

 

[gyraf]

The filter part sits at +175V, no AC-decoupling from previous anode...