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Cleaning up the M pulse sound

Discussion in 'Amps and Cabs [BG]' started by theshadow2001, Nov 3, 2005.


  1. theshadow2001

    theshadow2001

    Jun 17, 2004
    Ireland
    So I find that my m pulse is an incredibly dirty sounding amp which is fine but sometimes a cleaner sound is required and I just can't seem to get one. When I play at home its ok because the volume levels are alot lower but when it comes to gigging it just gets real dirty because I have to crank it a bit. when I play live I usually set the gain at 10 o clock and the master around 12 or 1.

    Am I just running out of headroom? I find the amp slightly underpowered for what I need, granted Im only running a single 8 ohm 1x15 but I wouldnt like to push the master much more for the fear of clipping (Damn the lack of clip indicaters!!) plus it would most likely dirty things up even more if I did. Would different pre amp tubes make a noticable difference to the dirty factor? Or is this machine simply a one trick horse just dirt and growl all the way?
     
  2. The M Pulse is a hybrid amp tube pre and SS power yes?

    Turn the master volume all the way up (it isnt like power tubes that will give that loverly overdrive), and use the gain control as a volume, that way you'll get a much cleaner sound
     
  3. theshadow2001

    theshadow2001

    Jun 17, 2004
    Ireland
    Thats an interesting idea mohawk. Would this pose much of a danger to the amp or speakers running the master up like that? I mean would it send the power section into clipping? Or would I be danger of doing damage since I do have to crank it a little bit? Does anyone else do this? I'll give it a go anyways
     
  4. Tash

    Tash

    Feb 13, 2005
    Bel Air Maryland
    The Mpulse also has driver tubes controlling the MOSFETs. That means when you crank the master you are actually cranking a tube, which in turn cranks a transistor. This gives it a more tube like reaction to being cranked and is pretty easy to hear as you push the master up high. You get distortion but it builds slowly rather than coming on all at once the way a fully SS amp will do.

    I've found the biggest factor in keeping the MPulse running clean is the mid scoop knob. If you want clean volume make sure you are not scooping mids. The "mid" knob on the preamp EQ can ONLY scoop, so running it at 12 is actually cutting out some midrange. You need to run it all the way to the right to have flat midrange. You cannot boost the mids on an MPulse without using the parametric EQ.

    Also you are only getting 320 watts into that 15. I would strongly consider adding a 210 or 410 to increase your cone area and push your power up to the full 600 watts. I have no projection problems with my M-Pulse into a Powerhouse 1000 (410+115 @ 4ohms).
     
  5. karrot-x

    karrot-x Banned

    Feb 21, 2004
    Omicron Persei 8
    I have no problems with my M-Pulse 600 into a Powerhouse 4x10.
     
  6. +1 on all the above comments. Seems your main problem is you are using only a percentage of the amps power by running into an 8ohm cab... and it's a small (1-15) 8ohm cab at that. You need a second cab... either another 8ohm 15 or a 210, or something like that. That should result in a lot more wattage.

    Also, while I would never recommend running a the master all the way up, I would back off the input gain a little bit more (maybe to 9 o'clock) and then turn up the master a little more.
     
  7. theshadow2001

    theshadow2001

    Jun 17, 2004
    Ireland
    Ok so thats what tube driven MOSFET is. Im still unclear though. Will turning up full as mohawk suggested and using the gain as volume pose any danger to the amp or cab in terms of clipping?

    Actually the mesa's passive mid control is boost only so its flat when completle rolled off and boost from there and I refer you to this thread I started a while ago billfitzmaurice does some good explaining about the whole thing.

    I fully intend on buying a powerhouse 4x10 and 1x15 (or possibly 2x15 :bassist: ) later down the line.A 4x10 will be my next purchase. I just picked up the GK cab I'm using cheapish so I could use something whilst I get some more money together. I also think this would improve things alot, as well bring things a bit closer to ear level when stacked.
     
  8. Tash

    Tash

    Feb 13, 2005
    Bel Air Maryland
    Well think of it this way. In a "normal" Tube+SS amp you have a tube in the preamp and transistors in the power amp section. The preamp section takes the signal from the bass, shapes it according to the EQ and voicing filters used, boosts it according to the preamp gain control setting, and passes it to the power amp to be made louder. The power amp doesn't shape the signal (well it does, but that's not its job). It only boosts it depending on how high you turn the master volume.

    A tube driven power section puts tubes between the preamp and power amp, almost like a second preamp section. These tubes aren't there to create gain (like the power tubes of a tube amp) but rather to provide additional shaping to the signal as it enters the power section. If you turn the master knob up you will send more power to the driver tubes, which in turn send more power to the transistors. How precisely they do this isn't clear to me, if I knew Mesa would probably send a team of Patent Ninjas to my house to kill me anyway, but the end result is that you get a form of tube overdrive when you crank the master volume on a Mesa MPulse, even if the gain knob is not set high enough to drive the preamp tube. You also get some of the neat "push pull" interpaly between pre and power sections that you get with fully tube amps. You can still clip the power section of course, and it will probably not sound real good either since it is still a SS amp, but you can get a lot of very tube like sound from an MPulse. I like it, its warm but its a clean crisp sort of warm.

    This technology isn't unique to Mesa either. The SVT3/6 use tube driven transitors as well to acheive a sound more like a fully tubed head.

    As for clipping, that depends on your cab. Its been argued to death here weather or not you can kill a cabinet by driving a clipped (square wave) signal into it. However you will most certainly hurt your cab if it can't handle 320 watts, however I cannot say for sure that you will not hurt either you head or cab by running the power section to full all the time.

    Personally I have never liked to leave the master open fully on any amp. I hear this suggestion a lot and think "Well if it sounds so great, why the hell do amps come with seperate gain and volume controls?" I prefer to run my power section only as loud as I need to and use the gain control to shape and define my tone in conjunction with my EQ.

    Re the Mid control. I'd read in so many places that it was a cut only control. That thread you linked made sense though. It certainly sounds like its boosting mids. I will need to reevaluate how I use my EQs

    Oh yeah, I strongly urge you to check out the Powerhouse 1000 cab. If you like the 410+115 combo its great. Its heavy but the handles and kick back casters make it much easier to move around than the Powerhouse 410 I bought originally. The slide rails are handy to. Great cab that sounds like it was made for the MPulse. I'd really like to try a Berg NV610 as well though.
     
  9. theshadow2001

    theshadow2001

    Jun 17, 2004
    Ireland
    I guess the answer is pretty much obvious: reduce the gain and increase the master volume. It annoys me that theres no clip indicater on the m pulse. Ive damaged another cab from running clipped waves into it for too long. Although it did take a good bit of abuse before it start showing signs of damaging. It still works its just a little bit fuzzy on the low notes.

    Anyway the speaker arrangement on the powerhouse is probably better than that of a 4x10 and 1x15 stacked together. But the size of the cabinet would make it impractical for me. I like the idea of being able to use one cabinet like the smaller 1x15 to bring to practice as opposed to bringing a fridge sized thing. Plus I dont drive and might not always be in a band with a van so its more a logistical reason I wouldnt get the 1000. Plus im planning on upgrading the speakers gradually since they are quite expensive. Its obvious that I need another cabinet to make this rig work. So ill get a 4x10 and use it with my GK 1x15 (which can handle the wattage it has a replacement speaker rated higher than the original) then get the power house 1x15 (or 2x15 depending on my volume needs) Leaving me with a working cabinet that I can sell off with my peavey head. I've got it all sussed out. My current cab is a means to an end.

    On the other hand if I cant clean the sound up I'm not sure if I'll hold on to the m pulse. I might yet go down the pre/power road. It cost me a small fortune so far and thats before I buy and cabinets so Im hoping it works out. If it doesnt work out I know I'll be left with some good quality high wattage rated cabinets.

    Do other m pulse users find it quite dirty or is it just me? Does it operate cleaner with the powerhouse cabs?
     
  10. Tash

    Tash

    Feb 13, 2005
    Bel Air Maryland
    I don't find it dirty at all, and I'm usually pretty picky about clean amp tones. Its warm, not perfectly clear the way a SWR or GK head sounds, but its definately not muddy. But that's my opinion, if super clean tone is what you are after you might want to check out some other heads. A 1001RB-II could be the ticket in your case.

    Another thing to consider is the compressor settings. If you have the ration too high and the threshold too low it can cause the sound to get muddy.

    Honestly though I think the real issue is yoru cab. 15s by themselves are notoriously muddy and not usually super efficient. A few 10s could really, really help things.
     
  11. theshadow2001

    theshadow2001

    Jun 17, 2004
    Ireland
    yeah the 1001RB II was a nice head but I prefered the sound of my mesa Id probably prefer an SWR to a GK as well. I dont necessarly want super clean just cleaner than what I've got. Anyway it'll take another couple of months gigging before I will be able to save enough money to get the 4x10 but I'll post again when I do get one or if I get the opportunity to try out a set of tens for a while.
     
  12. Tash

    Tash

    Feb 13, 2005
    Bel Air Maryland
    You might want to look into an Avatar 410. They are much, much cheaper than the mesa ones and are supposedly very good.
     
  13. I never knew it had a tube driver section, but it should still be cleaner than a cranked pre gain

    Turning it all the way up will only send the power amp clipping if you have the gain up too much, when you have the master all the way up you'll be surprised how little you should need to turn the gain up to get the volume you require
     
  14. From reading through this fully

    You should be able to tell when your power amp is clipping, it will not sound good at all!

    And maybe the sound you are looking for is more a HiFi one?
     
  15. theshadow2001

    theshadow2001

    Jun 17, 2004
    Ireland
    I'll give it a shot anyway turning my master up more and my gain way down. (maybe not turning it all the way up) Maybe a more Hifi sound would be in order Im not too sure really but I'd like to stick with the mesa try out some cabs and see how it goes