Amp Issue help (Sunn 1200 rack/Fender Bassman 1200) & replacement suggestion (M6 or M9)

Discussion in 'Amps and Cabs [BG]' started by eyeballkid, Jan 12, 2018.

  1. eyeballkid


    Jul 19, 2009 a couple questions for you all that are kinda specific and hope you have some good informed suggestions.

    The first question is about a functional issue/problem my amp has been recently exhibiting. I KNOW 15 people are going to say "take it to a tech" but unfortunately our local tech just retired and the closest one is now a 2 hour drive away. So... If I can avoid two half days in the car in ANY way Im really happy to. Anyway... Recently I started getting a crackling popping noise on louder lower notes. Its only at practice/performance volume and only on the E string usually, so it seems it has to do with the force of the note and the power draw. At first I thought it was the tweeter of the cab crapping out. nope. Then I thought, cord? nope. pedals? nope. Dying battery in my bass? nope. Speaker cable? nope. Preamp tube being unseated or going bad? nope. Crackling pot? nope. Bad output jack on the amp or input on the cab? nope. I also tried working the effects loop jacks to make sure there was no corrosion/dirt. I THOUGHT that was it because it didnt make the noise for almost 20 minutes of playing, but it came back. It does seem to be an issue moreso after the amp has warmed up a little instead of an immediately apparent phenomenae...
    any ideas?

    That aside, this amp has been a work horse for 15 years but Im toying with the idea of getting another amp. If you look thru my gear list youll see Ive tried alot over the years and few things lasted for me. What im wondering (especially from guys who have used the Sunn1200 or Bassman 1200) is what other amp has the great clear SOLID tone of this thing and most importantly the heft and low end slam of power? Ive had soooo many amps that had great tone but lacked "ass" in a dense mix no matter how you EQd it. That attribute has been its main attraction to me, not to mention its versatility and reliability up til now.

    My "main contender" is the Mesa M6 or M9 Carbine as from what Ive seen and my brief use of one seem to have the same character of raw heft. BUT.... whats the long term reliability on those now? I know they both had heating issues that were "fixed" but are they really? Is either REALLY reliable at duration and volume? Especially the M9, as that on board compressor is a nice feature. Ive seen a few for sale still at the original 900 watts. Is that just tempting fate or.......?

    responses from guys that have used either my current amp or the mesa are really valued for their insight.
    are there other amps I should consider? (no class D please).
    oZZma likes this.
  2. JGR

    JGR The "G" is for Gustav Commercial User

    Jun 29, 2006
    President, CEO, CFO, CIO, Chief Engineer, Technician, Janitor - Reiner Amplification
    Hey Jason,

    Check the preamp ground connections on your amp. I and several folks had similar issues with Ampeg CL's way back. IIRC the preamp board ground was made through a metal standoff on the PCB to the chassis - adding a star lock washer between the screw head and PCB ground trace took care of it. Take it with a grain of salt though, its been over a decade!

    Last edited: Jan 12, 2018
  3. coreyfyfe


    Nov 19, 2007
    boston, ma
    Had a similar issue with a VHT/fryette amp recently as well. Ground in the HT supply filter cap area though. Started out similar to this with crackling on low notes, got to the point that it wouldn't output anything except sputters. Worked fine when it was upside down (ie open on the bench) as the weight dropped the PCB back down onto the bolt for the ground post.
  4. eyeballkid


    Jul 19, 2009
    I'll look to see of I can find any loose grounds
  5. Primakurtz

    Primakurtz Registered Nihilist Supporting Member

    Nov 23, 2011
    Denver, Colorado
    Regarding the M6 and M9: I think the M6's with the vented top panel are extremely reliable, and definitely have the heft you are seeking.
  6. Random thought here.
    The effects jacks have a contact that you'd have to open the amp to clean.
    From your description, it sounds as though it might be a bad solder joint
    or some other bad connection that is being moved by vibration and/or heating.
    If you use a long speaker cord and put the amp some place away from the speaker cab, does it act differently?
    How about if it is on one end or the other, changing what gravity does to components contact to the circuit board?
    John Ferguson likes this.
  7. eyeballkid


    Jul 19, 2009
    I'l test that!
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Those amps are very complicated and difficult to work on. They are also quite easy to catastrophically damage on the bench. It's an amp that I am familiar with.

    Call Fender's consumer service guys and see who they recommend, they may suggest one of the higher level specialty shops that are in their service network. A run of the mill tech is likely to have a rough time with these amps, especially power amp problems.
  9. eyeballkid


    Jul 19, 2009
    Thanks for the word to the wise. That's good to know, even if it's kinda bad news.
    agedhorse likes this.
  10. jastacey


    Feb 8, 2009
    Kinda late .... but you might want to check out the Fender 800 Pro, same power amp as the Bassman 1200 Pro, it has the same heft to each note, used to have the Bassman 1200 Pro
    oZZma and agedhorse like this.