Mark IV reverb........................WTF ! ! !

[ksime1]

Hi all,

Every time I add reverb on the lead channel it alters the tone drastically. It changes from liquid smooth distortion to a horrible thin raspy distortion the minute I add any amount of reverb. It sounds like some of those really cheap distortion pedals, not an amp worth just under £2000 !

Any ideas what is going on? Ever since I have had it it has been like this!

Kenny

 

[MusicManJP6]

Try swapping out the reverb tube. Make sure it's a 12AT7 too.

 

[newfinator]

I posted a thread about this before and it is a very common, if not consistent, experience. It seems that it simply works that way.

 

[boogietone]

If your MKIV is a B revision you need a 12AX7 in the reverb slot. I found that having the channel master up around at least 4-5 alleviates the problem. At least on mine. I also ordered a new Accutronics reverb tank for mine and removed the foam that is glued to the inside of the tank itself. It seemed to help the quality of the reverb a little. The first iteration of the MKIV uses a 12AT7 in the reverb slot. I personally like the reverb much more on my A than my B. I use a Lee Jackson Mr. Springgy reverb with my B. Hope this helps. Both the A and B are great amps! The reverb on the B is an unfortunate thing though at low volume.

 

[ksime1]

My Mark IV is the B version, I'll try it with the volume cranked and see what response I get. If that fails I'll look at another reverb valve.

Just as a side-note, I have had the amp since December last year and this is the only problem I have had. Rock solid amp, and it sounds soooooooooooooooooo good!

 

[boogietone]

My Mark IV is the B version, I'll try it with the volume cranked and see what response I get. If that fails I'll look at another reverb valve.

Just as a side-note, I have had the amp since December last year and this is the only problem I have had. Rock solid amp, and it sounds soooooooooooooooooo good!

I hear ya buddy. Guess that's why I have two .

 

[fpoon]

That's just what happens when your on the lead channel, it's normal. Just use it for clean.

 

[metalmm785]

Agreed. I had the same thing happen on my Mark iv B combo. Surprisingly, my IV A head doesn't do it, which is kinda odd/cool.

 

[trem]

This may not be related, but ever since I had a Mullard ECC81 as the reverb tube, the reverb has way less drastic effect on the lead channel. Previously I had a weak Sovtek 12AX7WA in there and I had to turn off the reverb everytime I engage the lead channel. I don't know whether this is part of the design or not. It's the A version BTW.

 

[boogietone]

I put a Mullard CV4024 in my A version and that reverb sounds great. I have a Lee Jackson Mr. Springgy reverb pedal I don't use anymore on that amp now. My B version is a different story though. The best I could come up with is what I posted earlier in this thread. It is a lot better but not great. Getting the channel masters up over 5 really helped me in not distorting my lead channel on my B version.

 

[badguitarist]

When I first got my Mark IV I turned the reverb knob up, played a few notes and immediately turned it dead off. Haven't used it again since then