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Early B.
02-04-2005, 12:01 PM
Changed out the smaller tubes in my Jolida SJ502A. Formerly used EH but swapped them out for Mullard 12AT7s and a pair of Groove Tube 12AX7M's. So far, I'm hearing a little more detail, but not a significant change in SQ yet. More to come...

Anyway, I turn on my system and let it warm up, but when I pop in the first CD, for the initial 2 or 3 seconds, I get static. I believe the static is emanating from the Groove Tubes. I never had an issue with the EH's. So why am I getting static? Any damage being caused? Will it go away after break-in?

I had this issue with my tube CD player with the stock Chinese tube. Once I changed the tube, the problem went away. I'd like to keep the GT's, but not if it will cause problems.

Thanks.
Tour2ma
02-04-2005, 04:02 PM
Hummmm... Goes away when you roll the EH's back in?
organ
02-05-2005, 04:51 AM
Does it do this all the time for 2-3 secs?

Maurice
Early B.
02-05-2005, 09:24 AM
Does it do this all the time for 2-3 secs?
No. Only the very first CD immediately upon warm up.
BlueMDPicker
02-05-2005, 10:17 AM
Check the pins for oxidation - with special attention to pins 2 and 7 (counting clockwise from the open space.) It sounds like the control grid of one or both triode sections may not be at negative potential until a signal is presented for amplification.
Tour2ma
02-05-2005, 03:41 PM
BMDP,
Was thinking pins, or sockets, myself. There's enough "wiggle room" in sockets that sometimes a new/ different tube's pinch points are not in the exact same location. So you can run into oxidation on an unused area of one or more contacts.

It's in apart why I was wondering if rolling the EH's back in eliminated the static...
Early B.
02-05-2005, 07:00 PM
Interesting you mentioned the sockets. One of the sockets looks like it's been in a war zone and took heavy fire. I'd love to replace it someday because it looks worn (i.e., burned -- it has brown discoloration).
Tour2ma
02-05-2005, 07:30 PM
Ahhhh...

Socket ceramics will discolor with heat over time so it may not have been any acute incidents... then again could have been one of Mike's recent fireball episode in it's past... :eek:

A pipe cleaner and a little deoxit may help...
BlueMDPicker
02-05-2005, 09:52 PM
Cleaning the sockets and pins is a great first step. I'm inclined to think that you may have a load or control resistor out of tolerance. Some triodes won't complain, others will exhibit behavior as you've described when they don't see enough resistance across the control grid - especially the high mu triodes. Marshall guitar amps are classic for this type behavior.