Bass Knob sensitivity on Mark IV Lead Channel

[thecordova]

I recently cleaned some of the pots on my Mark IVa with contact cleaner, and now the Bass control on the Lead channel is very loose. the Bass setting is very flubby past the 2-3 mark and the change from 0-3 to 4-10 on the knob is a drastic increase in bass/flubbiness.

I also did a complete tube swap with some new JJs on the same day. Anyone have any experience with an issue like this ?

 

[MarshMesa]

For what it's worth, I never turn my bass up past 4 on my Mark IV. I get muddy / fubby sound if I do. Also, JJ preamp tubes to my ears, are a little more muddy / dark than my standard Mesa preamp tubes.

 

[thecordova]

Yeah, I've always heard that the bass on IV's are best in the 0-3 range, but the sound changes drastically at around 4. It is not a gradual adjustment at all and I was just curious if I should take the amp in for repair.

 

[MarshMesa]

The most common mistake people make is putting the bass up on 6 or 7 and then they wonder why it sounds nothing like what they hear on recordings. If you want more bass, there are other ways to increase it. Putting the 80 slider up near the top will boost the bass, as well changing other settings with how the amp is functioning (using the Simulclass option, etc.). I find the Mark IV has plenty of bass for me, even when dialed at 2 or 3.

Another option that I used to do sometimes is simply dial the bass high and then use an overdrive pedal. I don't use this much anymore, as I like to get a one-source distortion sound. However, it can still sound great. Zakk Wlyde was using a Boss overdrive for years with his Marshall JCM800. These days, I mostly use the overdrive pedals as a solo boost, or if I'm playing a darker (muddier) sounding guitar. Another option would be adding another EQ in the effects loop.

 

[SquierJVs]

Hello thecordova,

If I understand your question correctly, you are trying to determine if the Bass control on the Lead channel of your amp is behaving "normally".

I think it depends on the amount of Gain & Drive you have configured.

I have the same amp and I ran a few experiments.

With high values of Gain & Drive (e.g. both 8-10), then changing the Bass value from 3 to 4, resulted in a change from "tight" to "flubby" bass. (Was it "drastic"? Well it was easily noticed. I had the Output level very low to avoid waking others. I expect that the difference in sound would be more obvious at higher volumes)

Then I set the Gain & Drive both to 3, adjusted the Lead Master so the volume was similar to the previous level and then changed the Bass control. As you might expect, no "flubby" bass sounds even with Bass at 8. Instead, there was simply smooth, predictable changes in the amount of bass.

I would suggest that you try a similar experiment with low Gain & Drive. If your Bass control has a problem, then it should be obvious when you move it through its range of values.

Lastly, my other settings were: Triode, Class A, Harmonics and Tweed (I told you, it was quiet

Good luck. And let us know your results.

 

[thecordova]

Thanks for the reply. I'll try working with lower gain settings and experiment when I get off work today.

 

[swbo101]

For what it's worth, I never turn my bass up past 4 on my Mark IV. I get muddy / fubby sound if I do. Also, JJ preamp tubes to my ears, are a little more muddy / dark than my standard Mesa preamp tubes.

I was under the impression that Mesa's pre-amp tubes were just rebranded JJ's

 

[MarshMesa]

For what it's worth, I never turn my bass up past 4 on my Mark IV. I get muddy / fubby sound if I do. Also, JJ preamp tubes to my ears, are a little more muddy / dark than my standard Mesa preamp tubes.

I was under the impression that Mesa's pre-amp tubes were just rebranded JJ's

I read that too somewhere, and you could be right. I will just point out that my Mesa preamp tubes in my Mark IV are old, possibly from when Mesa was using tubes from other sources. I have no way to verify if they were produced by JJ or not.

 

[thecordova]

While playing around with different settings, the Bass Knob became completely unresponsive. Looks like it's going to get replaced!

 

[sduck]

On my mark IV I have the clean channel bass set to 3, and the lead channel set to 1.