Mesa M9 "post" D.I....too noisy?

Discussion in 'Live Sound [BG]' started by Kijuer, Jun 18, 2019.

  1. This is a rant. Period. As such, it might be full of wrong assumptions, which I don't mean to offend anyone with (starting from the title). Thing is, I'm so disappointed now, I hope you'll understand.

    I have this beautiful Mesa M9 Carbine head. It cost me an eye but I love it. The graphic EQ and the built-in comp are two little gems I thought I could rely on to color my sound when needed during a show, to the point I got rid of EQ and comp pedals.

    Saturday night we have this show booked. I set up my stuff, plug the XLR cable, I set the D.I. out to "post" (for obvious reasons), and there it is: tremendous noise floor and static. Ground switch does do nothing, changing cable routing/power cord/power plugs, using a cable instead of wireless, removing the pedalboard....nothing works. The only thing that works is setting the D.I. to "pre". Ok, that's fine, I'll do it, I have a show to play, but...what the hell...That graphic EQ, that compressor, that "voice" knob, those are all tools I am actively using to create my sound(s). I turn the graphic EQ on and off depending on the sound I'm looking for, because I NEED it, and now you're telling me I've got to skip all of them when I use a D.I. because it makes too much noise??? I play with gain at 1 o'clock, I understand that might raise the noise floor (but I could hear nothing wrong out of the cabinet), but I have a tube preamp section for a reason, right? When i switch to pre-EQ the D.I. signal is dead silent, but what do I do with such a head, with all these tools built-in, if they are unserviceable in the moment of need? I don't see honestly any point using a "pre" signal on such a head given that I'm using it to change my sounds. Similarly, I can't use an external D.I., since some of the "core" sounds I have comes from the features available on the head, and I have no parallel out or preamp out to use. It would be like having eq, comp, and effects o your board, and you have to skip all of them and go direct beacuse they're too noisy. It screws you up.
  2. charlie monroe

    charlie monroe Gold Supporting Member

    Feb 14, 2011
    Buffalo, NY
    Mic your cab up.
    Goatrope likes this.
  3. two fingers

    two fingers Opinionated blowhard. But not mad about it. Inactive

    Feb 7, 2005
    Eastern NC USA
    Sorry you are dealing with this.

    I got my Mesa Walkabout serviced a couple years ago (at Mesa). There was a little noise before the service. It was dead quiet when I got it back.

    Perhaps a tech could get it worked out for you?
  4. s0c9

    s0c9 Supporting Member

    Jan 9, 2014
    1964 Audio artist, Fractal Audio Beta Tester
    While I can't say for sure - being that you are in Italia and we're over here in the US of A ... but it "sounds" like your power source is not grounded.
    There is a venue I've played numerous (50+) times that has has a number of power dual-gang outlets embedded in the stage floor and around the drums riser.
    Nice easy power access, right? Umm yes.. but NO!!
    NONE appear to be grounded and will generate that dreaded 50/60Hhz "noise" when powering an amp. I tried everything you listed above, even changed amp EQ to "try" and remove the noise... before I pulled some of the outlets apart to find no grounding.
    I then took my fully-grounded 4-outlet 50 foot extension cable (which I always use at gigs), running it across the drum riser and into a grounded power outlet connected to the house power amp racks - instead of into the stage power outlets. :)
    I've done that for more than half of the 50+ gigs at that venue with ZERO noise.
    Might be something similar to consider/look at with venue staff?
    PS: They don't like the noise either!
  5. I checked at home with an audio card into garageband, just the quickest way had to do it....when the DI is set to "post" the noise is there. Not really a 60-cycle hum, but a lot of hiss. No way to get rid of it at any volume/gain settings. It's...."inside". Just wondering if it's supposed to be normal...if it is, I would assume that the power sources in that venue only added more, yet it makes me cringe that out of 3 bands and 3 bass players with 3 heads, mine was the only one sounding so bad.
  6. Wasnex


    Dec 25, 2011
    OK, I set up my M9 and ran an experiment and I think my results are pretty much the same as yours. Whenever the DI is set to Post there is a lot more hiss. I didn't experience any other increased noise with mine.

    There are a few things worth noting. First, it's normal for a Post DI to be a bit noiser the Pre. This is actually one of the reasons I don't like using Post DI. The reason this occurs is because the signal is going through a lot more circuitry. EQ in particular tends to be rather noisy. I do agree the S/N ratio seems to be significantly worse when the DI is set to Post, but this could partially be due to gain staging; I'll get into that more later.

    Next the Post DI is fed after the Master Volume which is a bit unusual. When you set the DI to Post you get a little extra noise even when both the DI Level on the back of the amp and the Master Volume are set fully CCW.

    The M9's Master Volume is scaled so the power comes on really fast. I think the problem may be the Post DI is gain scaled to work when the amp is being played really loud. In other words when the Master is relatively high and the Post DI Level is turned way down. Most people can't run the amp this way because it would be brutally loud.

    As I said earlier, most of the extra noise is hiss. This hiss is well above most of the tone of an electric bass unless you are into a spitty slap tone.

    About the only advice I can give is get the best possible S/N ratio by experimenting with gain staging, and then use EQ and an LPF on the mixer to deal with the hiss.

    Hopefully this helps a little.
    Last edited: Jun 19, 2019
    s0c9, Kijuer and Stumbo like this.
  7. Hi! Thanks, it surely does, at least it reassures me that there's nothing wrong in my head...or we both have the same problem LOL.

    I was pretty sure that all the gain stages would contributo to a strong raising of the Boise floor, just I didn't expect it to be SO high. Too high. Anyway, thank you for your help!
  8. Wasnex


    Dec 25, 2011

    :bag: Okay I redid the experiment this morning except I changed how I was feeding the amp. Yesterday, I fed the amp with my guitar pedal board which has a DD7 that I can use as a looper. I did this because my M9 is down stairs and my mixer is upstairs and I wanted to setup a loop so I could compare signal and noise levels at the mixer.

    Today I wanted to see if I could narrow down where the noise was getting into the signal path and possibly improve results with gain staging. I plugged in my XWire XR905 wireless instead of using the pedal board, and with the wireless, the noise difference between Pre and Post is much less severe. There is some additional noise, but I would say the Post DI signal is useable.

    Apparently the results I got yesterday were skewed by the self noise generated by a few of my pedals; most likely the compressors. The noise from the pedals is not normally a problem because I use it with guitar, and guitar speakers rolloff below the frequency of the hiss. The M9 equalization I am using apparently emphasizes the frequencies of the hiss, so when I switch the DI to Post, the hiss becomes very apparent in the signal.

    So if you are running pedals, try plugging straight into the amp and see if the problems improves. Also if you are running an active bass, you may want to check to see if it is the source of the noise.
    s0c9 likes this.

  9. Tried today..before reading your post, actually :)
    No matter what setting I use, pedalboard or straight-in, cable or wireless, even with gain and master all the way down, and pedalboard muted, as I switch the DI to "post" the hiss comes in. I've managed to tame it down a bit with the onboard EQ without screwing my sound, but it's still too noisy to be considered "clean and usable". Ok, that's virtually five gain stages in a row (gain, first eq, graphic eq, voice knob, master), but literally 90% of the real noise comes as I switch the DI to "post". What the hell??? Now I'm starting to regret my Markbass TTE800... That head sounded sterile in comparison, but good God, it had a post-only D.I. which was dead silent.
  10. Wasnex


    Dec 25, 2011

    Are you adjusting the DI level on the back of the amp as well?

    I called Mesa for you. The M9 has a solid state buffer before the tube, and the Pre DI is taken off after the buffer, but before the tube. You could try replacing the tube and see if that reduces the hiss. Perhaps you can borrow a 12AX7 if you do not have a spare. You can buy tubes that are graded for noise if this makes a difference.

    If a new tube does not resolve the issue, then unfortunately there is something wrong with the DI circuitry that will require a technician's services.
    Kijuer likes this.
  11. So kind of you. Thank you very much!

    BTW yes, I adjusted the DI level on the back to the point that it was barely up but with everything (gain, master, voice flat, di level, bass volume, pedalboard volume) set to "zero" the noise is already there (in "post" mode).

    The thing is: wouldn't a faulty tube affect speakers with noise and/or hiss as well? My cabinets are dead quiet instead.
    Wasnex likes this.
  12. Wasnex


    Dec 25, 2011

    Yes the tube would send hiss everywhere. But if you speakers don't have an extended high end response it may not be noticeable
  13. s0c9 and Wasnex like this.
  14. Can you SEE my frustration? :D:D:D

    Attached Files:

    Wasnex likes this.
  15. Now HEAR it! :roflmao::roflmao::roflmao:

    Gain zero
    Graphic EQ off
    Voice flat
    Master zero
    DI level 12 o'clock

    Guess when it switches from pre to post...oh, ground is lifted.

    Attached Files:

    Wasnex likes this.
  16. Wasnex


    Dec 25, 2011
    Yes...its beautiful looking and great sounding rig. If you can borrow a tube I suggest trying the swap. Then you can assess what you want to do next.

    You might want to try this first: If you have another DI, you could also try feeding the DI from the M9's effects send. This will be a line level out, so you may need to pad the DI down a bit. The idea here is to see if the signal path is hissy. Also if the M9's Post DI is toast, it may give you an way of achieving your tonal goals without paying for the repair.

    The amp is held in the Bronco case by a wood slat that is placed over the amp and screwed in from the bottom of the case. I believe there are four screws to release, and the amp should slide out the back of the case.
    Kijuer likes this.
  17. I have an Artec D.I. splitter somewhere....I'll put it in the effects loop and see how it sounds.
    I don't think one of these will do, as the noise comes from "inside" the head, am i right? IceCube - Radial Engineering
  18. Wasnex


    Dec 25, 2011
    The IceCube is XLR to XLR. You need something that will convert 1/4" TS to XLR. A 1/4 to XLR adapter cable into the IceCube might work. The Artec would probably be a better choice.
  19. Sorry I meant regarding the noise in the XLR out. Ain't gonna help, is it?
  20. IMG_20190621_132825.jpg

    It works...or so it seems! From my soundcard the sound is clean and no noise seems to add up to the signal. Guess I'll have to check with a real FOH though. At least I feel some relief :)

    It's also unobtrusive and easy to plug and unplug. Maybe one day I'll replaced it with a JDI .

    Thanks for your help!
    Wasnex likes this.