grommes g5m problem...

[jeff]

Archived from groups: rec.audio.pro (More info?)

hi, so my grommes tube mixer (g5m) has been sounding weird lately.
it's been recapped and has solid tubes in it, so i'm a bit baffled.
the low end drops off really sharply at about 400hz, making it sound
really thin and rather grainy. can anyone suggest some things for me
to check?

thanks,
jeff

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

jeff <uniformrecording@earthlink.net> wrote:
>hi, so my grommes tube mixer (g5m) has been sounding weird lately.
>it's been recapped and has solid tubes in it, so i'm a bit baffled.
>the low end drops off really sharply at about 400hz, making it sound
>really thin and rather grainy. can anyone suggest some things for me
>to check?

Check the supply voltage before anything else.

You say it was "recapped." Did you do the supply caps, or also all
the coupling caps? If a coupling cap is gone bad, you'll get this
sort of thing.

By "solid tubes" you mean metal can types? They are still worth putting
on the tube tester and checking. If the problem is on all channels, look
at the makeup gain amp stage.

If the coupling caps are good and the tubes are good, check the cathode
and plate voltages at each stage and see if they are more or less in the
ballpark. Put a 20 Hz signal in the input and trace it stage-by-stage
with a scope and see where it goes away.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."