Mark IV lead channel and reverb don't get along... why not?

[newfinator]

I noticed that using the reverb on the lead channel in my Mark IV completely messes up the tone. It add tons of high end and makes it very shrill and horrid. It seems to function fine on the other two channels though.

I did a search for references to that problem here and it seems to pop up from time to time but most threads dissolve into suggestions of using external reverb but no attempts at explanation the cause.

Does this happen to everyone and is there a reason for it?

 

[zenabI]

It's the same for me but only when I have a lot of reverb. I don't use to have a lot of reverb but I discovered this when I forgot that I had a lot of reverb on and first I tought it was something wrong with the amp! (perhaps there is?) But then I turned the reverb down and it disappeared, so I have the same problem with my Mark IV.

 

[boogietone]

Mine does it to. But, I noticed it goes away if you turn the channel master on the Lead channel up. Like around 5 and higher. At least mine goes away. I fought with this for awhile when I first got my B version. I hadn't played out with it yet and had it way down for bedroom levels. Then I finally got a chance to get some real volume and my reverb was much better. My A versions reverb is much better than my B for wahtever reason. I guess the cicuit is different. The A uses a 12AT7 and the B a 12AX7. At any volume. In my troubleshooting, I also pulled the foam that's stuck inside the tank. Not sure if that helped. I did that to an extra tank I had so the original tank is still good. Hope this helps!
:wink:

 

[mrd]

I think the reverb is meant to sound better at higher volumes. Set it to 1 or 2, and crank it up, it will sound fine. I play my amp at max volume sometimes, and even with the reverb at 0, I can still hear it a bit. If you're playing quietly, and the reverb is set to like 5 or 6, then it will be shrill.