JVM sounds like crap. help!

Discussion in 'Marshall Amps' started by dale5150, Mar 28, 2012.

  1. Poweramp

    Poweramp New Member

    Joined:
    Jan 11, 2016
    Messages:
    3
    Likes Received:
    2
    My 215c was the same. Thin, Sterile, Cold and Digital...sounded bad. Fitted a Celestion G12T-75 which are in the 1960 cabs. Slight improvement only. Was about to trade it, but first before giving up on it, I opened it up, checked the biasing and found it was set way too low at only 29mv per side. So I Put new JJ EL34 power tubes in and changed V5 for a Westinghouse ECC83 balanced tube. Left the original pre amp tubes in ( they are decent). Rebiased the new power tubes to 35mv per side and wow, big difference...night and day. This amp has now gone from being an amp I hated to the one I love. The clean sound is full and warm almost fender like. I have a fender deluxe reverb too and the JVMs clean tone is now right up there too since I made the changes. Tempted to try back the stock speaker again but the Celestion G12T-75 sounds great. Glad I tried this. Don’t give up on your JVM, they really are incredible amps. My little 215c will take on anything now and staying as my main gigging amp. Just why they send them out sounding like crap and underbiased beats me. This is why people often claim they prefer the sound of the Vietnamese made DSL40s better than what they see as thin sounding JVMs. The DSLs come biased correctly from Vietnam. If you’d sold your JVM because you didn’t like the thin sound that’s a real shame as it’s such an easy cheap fix...you could try to get another one and make the changes yourself if you know what to do and are comfortable working on it. If not pay a tech for half an hours labour to do this for you.
     
    John BNY and Deep Purple fan like this.
  2. Poweramp

    Poweramp New Member

    Joined:
    Jan 11, 2016
    Messages:
    3
    Likes Received:
    2
    Hope you still have it. As per my post above. This amp will become your favorite amp with some decent power tubes and setting the bias properly.
     
  3. spacerocker

    spacerocker Well-Known Member

    Joined:
    Feb 6, 2009
    Messages:
    1,506
    Likes Received:
    895
    Location:
    UK
    Why has no-one explored the possibility of a defective pre-amp valve - or have I missed it? Sounds like a gain-stage has gone down to me?....Simple fix - buy a spare ECC83/12AX7 and swap the pre-amp valves in turn....
     
  4. Jay76

    Jay76 Active Member

    Joined:
    Jul 12, 2011
    Messages:
    111
    Likes Received:
    120
    Location:
    London
    I bought my JVM205H second hand a few years back. It came with a half stack of G12T-75's. for £450 total. It sounded good, but VERY bright. I changed the speakers to 2 x Greenbacks and 2 x G12 35XC's in an X pattern and it sounds excellent. I changed V1 and V3 with Chinese Beijing NOS 12Ax7's I wouldn't change a thing on it now. Sound excellent (dirty and clean).
     
    Mitchell Pearrow likes this.
  5. RLW59

    RLW59 Well-Known Member

    Joined:
    Nov 30, 2017
    Messages:
    605
    Likes Received:
    459
    Has to dime the gain on green, but orange and red have more than enough gain -- my first thought is a preamp tube.

    Welcome to the world of tube amps. Tubes are a lot more rugged and reliable than the impression you might get from the internet, but they can indeed fail at any time. Often for no apparent reason. Could have been fine when you bought and died from vibration on the car ride home.

    All tube amp owners should have a spare preamp tube (at the very least). Ideally, you buy the spare while the amp is working properly and plug the spare in to make sure it's working properly. (Because brand new tubes can be dead before you open their box due to rough handling in shipping.)

    One thing you can do right now is just swap the preamp tubes around. If the green channel sounds good but orange/red get weak, or if all the channels get weak, you'll know if you have a bad tube.

    If nothing changes after moving the tubes around, you'll know the tubes are probably ok and the problem is probably some other component in the green channel.
     
    Mitchell Pearrow likes this.
  6. Jethro Rocker

    Jethro Rocker Well-Known Member Premium Member

    Joined:
    Mar 11, 2011
    Messages:
    7,401
    Likes Received:
    7,771
    Location:
    Saskatoon, Canada
    Also, just sayin. OP disappeared after this. 7 years ago... good advice for others though!
     
  7. marshallmellowed

    marshallmellowed Well-Known Member

    Joined:
    Jun 26, 2009
    Messages:
    3,334
    Likes Received:
    3,603
  8. Delete!!

    Delete!! Well-Known Member

    Joined:
    Jun 29, 2018
    Messages:
    233
    Likes Received:
    288
    Location:
    San Joaquin Valley, Ca
    I have been using my 215C stock for almost a year now. I have contemplated a speaker change at times. What I hear in mine isn’t necessarily thin, I would describe it more as “tight”. It sounds massive on stage so I haven’t bothered to mess with it. The only time I really think I have an issue is when I play it at home, but as soon as I play on stage with it I’m happy again. The bias info is good to know, I will definitely keep that in mind for future reference.
     
  9. Alter Ego

    Alter Ego New Member

    Joined:
    Dec 20, 2019
    Messages:
    3
    Likes Received:
    10
    First post. New to the forum but not new to Marshall or tube amps. For any late arrivals to this old thread I would have to say that any tube amp that is brand new or used but new to you, after first passing your "ears" test would have to be shortly followed by a tube check and bias check. Once all that is in order and proven to be in good shape then the amp settings, speaker, guitar, and all those other hump-teen variables come in to play. Just saying.
     
    Mitchell Pearrow likes this.
  10. Lukas

    Lukas Well-Known Member

    Joined:
    Apr 21, 2013
    Messages:
    324
    Likes Received:
    394
    Location:
    Canada
     
  11. Lukas

    Lukas Well-Known Member

    Joined:
    Apr 21, 2013
    Messages:
    324
    Likes Received:
    394
    Location:
    Canada
    I wouldn’t say the DSL’s come biased correctly. I have a DSL40CR I bought new that was biased at 29-30mv and it still sounded ok. That’s on the cool side. I think they do this because it’s safe and it still works. They don’t know where the amp is going in the world and what the plate and screen voltage is going to be hence they adjust it cool. I’ve never seen a new amp that was biased hot from the factory. I installed new tubes and biased to 36 and it sounds awesome now. Even my new tube amps when I get them I check it and research it and usually adjust it even if it sounds ok. I’m sure a lot of you guys do, and it’s easy if you have any mechanical ability. Not all of us do tho haha. I got buddies that don’t do they’re own oil changes, to me being a man and not doing your own oil is kinda sad. The same kinda goes for tubes but it can be very dangerous so I’d understand if a guy didn’t wanna mess with it. On that note I gotta a buddy with a DSL 100H that does sound thin and crappy, it almost has since day one but he never noticed, or thought it was normal.... I don’t know how. I finally convinced him to buy new tubes from the tube store and we’re going to install, measure, and bias it here over the holidays. Chances are I’ll bump it up to around 37mv. I’m very curious to see what this ones biased at. I also want to show him what a TS9 sounds like out front on a DSL and guaranteed he’ll be pickin one up for it after he hears it and what it should sound like with good tubes.
     
    Last edited: Dec 21, 2019
    Mitchell Pearrow likes this.
  12. Deep Purple fan

    Deep Purple fan Well-Known Member

    Joined:
    Nov 1, 2014
    Messages:
    2,473
    Likes Received:
    2,341
    Location:
    Virginia
    What do you have it plugged in to? The cab and speakers are a big part of the sound.
     
    Mitchell Pearrow likes this.
  13. The Dose of Harmony

    The Dose of Harmony Well-Known Member

    Joined:
    Nov 21, 2014
    Messages:
    444
    Likes Received:
    385
    That was the first thing it came to my mind!
    Every time i get a new tube amp i manage to put new ir very lightly used tubes and bias it
    Thats for me the rule!
     
    Last edited: Dec 21, 2019
    Mitchell Pearrow likes this.
  14. Shae201

    Shae201 Well-Known Member

    Joined:
    Dec 20, 2015
    Messages:
    600
    Likes Received:
    640
    Tubes tubes tubes. Anytime I buy a used amp I always check the tubes and sometimes replace them for my own assurance. Same thing when I buy a used car, I always give it a tune up no matter what the previous owner says.
     
  15. Lukas

    Lukas Well-Known Member

    Joined:
    Apr 21, 2013
    Messages:
    324
    Likes Received:
    394
    Location:
    Canada
    Exactly, plugs, oil and filter, air filter and good to go. Add another $150 and do tubes I’d say. I own a 210H also and the only time it dropped off was when a pre amp shit the bed. Put new tubes in and bias between 35-38mv and it’ll rip roar. Or get someone to do it so you don’t “Ride the lightning”. JVM’s should never sound thin. They might not be your cup of tea but should never sound thin or like crap, even straight out of the box, even on the cool side. I’d say something’s not right and yes it’s probably shitty old tubes. Tube amps are a completely different animal than solid state tho. I’d say less room for error when playing and a lot of the tone lies more in your hands. They do take some getting used to but when you do you’ll love it.
     
    Last edited: Dec 21, 2019
    Mitchell Pearrow likes this.
  16. Shae201

    Shae201 Well-Known Member

    Joined:
    Dec 20, 2015
    Messages:
    600
    Likes Received:
    640
    I think it's great when players pull the trigger and get Valve amps, it's alot like a car. When you own a car it's a good idea to know how to change a tire, oil and even spark plugs if you will. With a valve amp, get to know the tube layout and what each position does and what bias is. It's not only fun but also familarises yourself with your gear, creates a bond and even a love-hate relationship for some of us. Wait a minute...sounds like my marriage. :run:
     
    Mitchell Pearrow likes this.
  17. rolijen

    rolijen Well-Known Member

    Joined:
    May 19, 2019
    Messages:
    101
    Likes Received:
    297
    One more thing: just in case, make sure you’re using a speaker cable between the head and cabinet. NOT a guitar cable. Using a coaxial instrument cable is a sure way to ruin your tone and screw up your amp.
     
    Mitchell Pearrow likes this.
  18. The Dose of Harmony

    The Dose of Harmony Well-Known Member

    Joined:
    Nov 21, 2014
    Messages:
    444
    Likes Received:
    385
    You are right on that one two plus the impedence must match just to rule out any potencial
    Problem
     
  19. spacerocker

    spacerocker Well-Known Member

    Joined:
    Feb 6, 2009
    Messages:
    1,506
    Likes Received:
    895
    Location:
    UK
    No amount of mis-match would account for the OP's description of the problems. JVM is very tolerant to some degree of impedance mis-match!
     
  20. The Dose of Harmony

    The Dose of Harmony Well-Known Member

    Joined:
    Nov 21, 2014
    Messages:
    444
    Likes Received:
    385
    I was just giving my whole amp maintenence routine and steps that go afte i get an amp
    I dont trust any used amp, i go by the book
    New tubes , Bias , speaker cable , proper impedence and a good visual look after i have it on for a while sometime even and noise!!!
    Last time my Jmp was making a noise so i look for a while and realize that one of the screws of the transformer was loose!

    every time its new one Lol!
     
    Mitchell Pearrow likes this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice