Considerable Gain Loss in CH3

[nsgelocos]

After having my Mark V head for a year, I have noticed in recordings I had made when I first got it that I have lost some gain from the amp. (in all modes) I have my gain at 3 o clock, treble around 2, bright switch on, and my GEQ treble sliders far up and still am not getting the gain I used to have. I noticed while playing a new Mark V at GC (after mirroring my settings of course considering tube amp dynamics) that my amp has lost way too much gain. The one at GC was extremally saturated and had to back off the gain and treble knobs a little to get a conforting feel and tone. (this was a new mark V, not an abused one) I was using active EMG 81. I have ruled out all other gear from the issue (cables, pickup batteries).

However things I think may be contributing to the issue.
>I have had a tube issue last year involving a rectifier shorting and blowing a fuse.
>Moved to EL34s
>replaced a microphonic preamp tube (screeching on CH3, unfortunately I have forgot which one it was)

I have noticed there is alot of background humming or hissing on CH3 and when I had replaced the microphonic tube, it still didn't remedy it.

Id figure I would ask people here before I do anything to my amp just yet.

Any Help would be greatly appreciated.
Thanks, Aaron.

 

[Bullen]

It´s probably a preamp tube issue.

Is the gain loss noticable on the other channels? If not, check the tube chart in the manual and find the tubes that effect ch 3 (which is pretty much all of them). V4 and V5 are ch 3 drive and reverb tubes. Does the reverb sound weak? If so one of these might be the problem. V6 is also a gain stage for ch 3, it also functions as the fx return stage. Does the fx loop work well?

Good luck!

 

[nsgelocos]

Thanks!

I did replace the V6 tube and it seemed to help a little but did not completely remedy the problem. It is a gain state tube so I'm going to order a couple more 12AX7s and hit the other two gain states for the CH3 and see what that does.

 

[phyrexia]

Your Mark V manual tells you which tube sockets are used in which channels. 8)

 

[nsgelocos]

Well, checked every preamp tube that may have anything to do with channel three (6 of 7) and nothing has worked. I have the gain a three o clock, treble at two o clock with the bright on with the eq treble sliders up and still sounds thin. Idk where to look now. Any ideas?

 

[Gjeven]

I'm having the same exact problem with the Mark V head I bought in the beginning of July of this year. I've lost a lot of gain, haven't lost any volume its still a very loud head. But the saturation is gone, I have a Dual Rectifer head also. The Mark V used to have as much gain as the my dual rec, now when I hook up my Dual Rec its an extremely noticeable gain increase over the Mark V.

I've tried changing all the preamp tubes, but it didn't do much.