Mesa 400+ EQ Questions
 

Okay, I bought myself a 400+ a while back and I'm having some weird issues with EQing the thing.

First of all, I am getting a good tone that I like, and I'm pleased with the amp, there are just some things I don't understand. Also, I tend to not use the graphic EQ, though it seems to be working as I would expect. I have read through the user manual and understand how most of these eq knobs are supposed to work and how they work together.

Some things that don't work as I would expect:

Unless I pull the treble knob, the amp has zero low frequency, no matter the rest of the settings, no matter the cabinet I have it hooked to. Knob in = thin, weak, no-punch sound. Knob out=sudden boost in bass frequencies. Also, the treble knob is way more powerful and sensitive in tone-shaping than any other.

The mid knob doesn't seem to do anything. I can sweep it up and down 100% and nothing happens. This is true regardless of the where the rest of the knob are set.

Anybody with 400+ experience ever run into anything like this? Perhaps I just don't know what I'm doing, or does it sound like my amp may have a problem?

Thanks for reading, and thanks for any help.

Sounds to me, you need an amp tech to have a look at it. That's not normal.

I dont ever pull the treble knob on my 400+, and I get plenty of lows, but I'll try to fire mine up later today or tomorrow and confirm this.

Until then, try these experiments with yours and let us know the results:
First turn your bass, mid and treble knobs all the way down and try to play a note on your bass. (no sound at all, right?)
Now try this same test with your treble knob pushed in, & pulled, and I'll do this same test with mine.

Now just turn only your bass, mid and treble knobs up one at a time, (with the other 2 set at 0) and tell us what frequencies you hear. Do this same test twice, first with your treble knob in, and a second time with your treble knob pulled, and then post your results. I'll try to do all these same test with mine, and post my results later today or most likely tomorrow.

PS: always make sure your effects blend knob is set to 0, unless your patching effects into the loop...

Okay, thanks. I'll give that little experiment a shot later today and let you know what takes place. Should be interesting.

Alright, here are the results:

All knobs at zero, treble pushed or pulled=nothing (good so far!)

with treble in:

only treble up: harsh, mostly briltle sound, very loud, big range of control with the knob, yet still has just a touch of low mids/bottom

only bass up: super low, practically inaudible, weak volume, very little noticeable difference between low setting and high,

only middle up: very, very quiet, thin, trebly, tone, even weaker/quieter than bass, even less change from low to high setting

with treble pulled:

only treble up: damn near the same tone I was getting by using all the knobs together! Lots of low mids, upper lows, still lots of harsh tones at high settings, but more rounded overall

Only bass up: mostly the same as before but with a noticeable volume and low-end bump

Only middle up: not much different from before at all

Okay. This things needs to see a technician I'm thinking. It kind of feels like the entirety of the EQ is tied into the treble knob. Like I'm rolling three up at the same time by rolling just that one knob. And true mid-mids seem to be missing in action. Hah...I wonder what this thing is going to sound like when (and if) it gets right...

How old are your tubes? I found many problems with tube amps can be cured with new matches Boogie tubes

I think it being a valve issue is very unlikely

While it still sounds like something is amiss with the push/pull, the treble knob is the most powerful on the 400+ IIRC. The mids knob is passive cut only and set flat at 10.

From the manual:

Sounds like something is wrong with your amp.

The starting point for tone ("flat") on this is something like-

Mid 10
Bass 2
Treble 2

Mid is only cut, Bass/Treble are boost. If you crank the treble (anything past 3 for me is "cranking" it) you will pull the voicing of the amp way up. Could be part of the problem.

+1 to this- when I had mine, I rarely had my Bass control above 3-4 and Treble around 3 and it was super full and extremely punchy (especially with the Bass knob pulled and some midrange sculpting with the Graphic EQ). Either you don't understand how the EQ works on that amp or there is something very wrong with it! Also- what channel are you using? Channel 2 is voiced noticeably fuller/thicker/louder/gainier than the other (sort of like Active vs. Passive inputs on other amps), though I was always able to get a full sound from either channel.

Good luck- and these amps are capable of THUNDEROUS lows, so I hope you find the issue quickly and get to pissing off your neighbors ASAP!

Thanks for all the help and replies. I'm using channel two with my 4001, and channel one with a six string wish bass.

Now that I've really messed around with the controls extensively, I've come to the conclusion to take it to a repair shop. The bottom line...ba-dum-tish...is that with the treble pushed in, there is not even a single, remotely useable tone on the amp, nothing that even resembles a viable sound for recording or playing, regardless of how anything else is set. I'm not convinced that the middle knob is doing it's job correctly either. It's possibly just extremely subtle, but subtle almost to the point of worthlessness. The bass seems to want to do something, but relies on that pulled treble knob to do it.

Now I hope I can find a place around here that really knows how to work on these things.

The Midrange knob is very subtle and most people I know that have or have owned a 400+ just leave it at 10 all the time. It is completely passive, so cut-only, whereas the Bass and Treble controls are active and flat at around 2, so are mostly capable of boost. I would usually leave my Treble and Bass knobs pulled, both of which put more predominance on the midrange. The Bass/Treble controls are also highly interactive (as described somewhat in that Manual quote from above), so they take some time to find the sweet spot.

Out of curiosity- do you have your Graphic EQ and FX loop both turned off? Also did you try turning gain all the way down on whatever channel you aren't using?

I hope you are able to find a good tech in your area that has experience with these amps!

No joke, I just saw Black Tusk and the bass player was running through one of these. The bass was so boomy and overwhelming. I guess it sounded good where he was but every time he hit the strings it sounded like an explosion. There was no tonality I could not tell which notes he was playing.

Of course, I have heard people make these amps sound great. The point is this amp is an amp you can make sound bad if you aren't careful.

Thanks to the link above I found a local authorized repair place that I didn't even know existed. Better yet, they even carry a bunch of vintage gear for sale, so it should be a fun visit when I drop off the amp.

I keep the Graphic EQ off most always, but everything on it seems to function just fine when I use it. The pull-function on the treble knob just does something to the way the amp operates. I keep the volume and master levels under three on each channel and that ammount of volume seems fine so long as the treble is pulled. If it's not pulled, then nothing I do with the controls would be able to compete with the average drumset, unless I wanted to maybe make my bass sound like a China cymbal.

pulling the bass or treble knobs moves the corner frequency into the midrange.
The bass moves up, the treble moves down.

I will say that when I had my amp fall over at a show once it damaged the treble knob so that it was only functional on 6. And when turning it I would get all kinds of weird jumpy EQ shifts until I found that spot.
I would certainly take that amp to a tech.
And yes I have generated absurd amounts of low end with Bass 400.
knock stuff off of walls, get the guitarist mad kind of low end.

Umm!
 

In my experience a 400+ makes no sound at all without a loudspeaker.
I don't have any information about your cabinet so I will make the most scientific analysis with the scant information you have supplied.
The problem is you are either running the amp into a fearful 15/6 cab and the fifteen inch driver has blown or become disconnected, or you have a pre amp eq tube failure, so get a spare 12ax7 and start finding the offending tube by substitution.
:bassist:

I'm not sure what you mean by no sound at all without a loudspeaker. For clarity's sake, though, I've been using a Mesa Powerhouse 4-ohm 410 as well as an Ampeg 410Hlf. Sometimes both together at 2-ohms. I've also used it through an SWR 210. The EQ characteristics are true when played through any of these cabinets.

I've got some new 12ax7's laying around, actually. If a tube can cause what I've been expeiencing, then perhaps I should look into that.

It could be but i very much doubt it. The mid range knob normally has a pretty huge effect on the sound. I think somethings come loose or gone wrong in the tone stack circuit.

The tone stack is essentially all passive. Inductors and capacitors. The only active parts of the tone stack are the tubes, so if they are damaged or blown a tube swap could fix it. However IME preamp tubes rarely just die. They usually go microphonic and get noisy first.