Marshall DBS problems.

[sponboy]

Hey guys I'm new-ish to the board and was just wondering if anyone could advise me my situation.
I've got a Marshall DBS 7400 head and the matching 7410 and 7115 cabs (the 410 is wired as a 210 at 8 ohms to give an overall load of 4 ohms in parallel as opposed to 2.xx).
I noticed after a short time, a month or so, that notes E to roughly A on bottom E were giving slight distortion through both cabs but more so the 115.
I have tested with a Fender deluxe MiM Jazz and a Pedulla rapture, both yield the same farty distorted sound and have also replaced batteries in both to ensure it wasn't a dead. This had no effect.
I also have rotated between solid state and valve preamp sections and both produce the same distortion.
I was willing to live with it until tonight. It has started to happen all over the neck on both basses.
Cutting the frequency in the range 320-2500hz helps but doesn't cure. Specifically drastically cutting 2500 almost solves the problem but the sound is muddy and hardly cuts through in a band situation. Having the bright and deep switches out also aids in sound quality but again doesn't solve the problem, and I am having to use the amp in a very limited way.

Just wondering if any of you guys could give any advice and if any other 7400 owners out there have had similar problems.

Apologies for the lengthy post, but I feel I have covered all bases in my explanation and once again any advice is appreciated.


Wood.

[B-string]

Have you tried the head with different cabs? Could be the speaker cabs have been hurt.

[RickenBoogie]

+1 my first thought as well.

[sponboy]

Thanks for the replies guys.
Will do ASAP. I also thought this, but thought it would be unlikely as I bought the cabs about a month apart. Didn't notice the problems until just after the addition of the 15.

As suggested will try with different cabs.

Thanks again,
W.