Roland JC120 not much base

Discussion in 'Amps and Cabs [BG]' started by Mac Daddy12, Jul 11, 2020.

  1. Mac Daddy12

    Mac Daddy12

    Jul 11, 2020
    My 1977 JC 120 Jazz Chorus does not have much bass. I just got it from a guy and I have the bass all the way up. Not much different now matter how much I I set it to.I figured with 2-12’s it would rumble pretty good but no.
    What’s up?
  2. Stumbo

    Stumbo Guest

    Feb 11, 2008
    AFAIK, that's an open back guitar amp made to be super clean, not bass rumble. Be careful if you're playing a bass through it, you may rumble it to death.

    "The one the only, Roland Jazz Chorus-120 guitar amplifier. First introduced in 1975. This amplifier is still manufactured today, a sign which tells you that it is still popular and a studio and industry standard. Every stage and studio has at least one of these.

    This particular one is the first series that came out in the 70's. Not sure on the exact year. It still sounds amazing for a 40+ year old amp! It has the true and lush stereo effect chorus and known for its fantastic clean sound. A few light marks but other then that it really is amazing! Please come down and try this amazing amp."

    PDF Manual:

    Roland Jazz Chorus-120 (JC-120) 1977
    Last edited: Jul 12, 2020
  3. DigitalMan

    DigitalMan Bring Back Edit/Delete

    Nov 30, 2011
    Bay Area, CA
    It’s a fine guitar amp. Sounds like it’s working normally.
  4. JTE

    JTE Gold Supporting Member

    Mar 12, 2008
    Central Illinois, USA
    It's an open-back 2x12 guitar amp, like playing bass through a Fender Twin Reverb.
    HolmeBass, Chrisk-K, bbh and 8 others like this.
  5. A further testament to the quality of this model that playing a bass through it with the bass pot turned full up the speakers did’t blow. One of the best solid state guitar amps ever made.
  6. sunbeast

    sunbeast Supporting Member

    Jul 19, 2006
    Denver, CO
    Those are great amps for nearly everything except bass in my experience! There’s some great footage from the 80s of the Talking Heads with a wall of JC-120s behind them, the stage amplification for the entire band apart from the bass player.
  7. DTRN


    May 10, 2019
    Twin Cities, MN
    Definitely an industry standard. The only SS guitar amp I care for...but still love tubes better.
    TN WOODMAN likes this.
  8. Wasnex


    Dec 25, 2011
    Try disconnecting the internal speakers and plugging into an actual bass speaker.

    I am actually very surprised the internal speakers are not farting out. I have played bass through a JC120 and the speakers became audibly distorted at a very low volume, as they were exceeding their excursion limits.

    Also the JC120 cab is fairly shallow, open-back design. Because of this, the low frequency waves from the front and back of the cabinet will tend to cancel. Keep in mind the waves coming off the front and back of a speaker are out of polarity with each other. As the cone moves forward the front creates a pressure wave, and the back creates a vacuum. Without a large baffle to separate them, the high pressure wave and low pressure wave essentially just cancel out for the most part.
    TN WOODMAN likes this.
  9. JW56789

    JW56789 Guest

    Feb 18, 2017
    They don't distort well either:

    The genius of the JC120's is that after the preamp/chorus/vibrato are TWO low distortion amps, one for each speaker. Think one of those 'stereo' pedals with a mono IN split to a stereo OUT. That's why the chorus is just gorgeous on them, and the gain structure doesn't lend much distortion. Notable users who had to have distortion for their guitar parts that required it usually ran them with a Tube Screamer or other distortion pedal. On the other hand, one of the best guitar amps for clean tones, especially with chorus. In continuous production for a long time, it can almost be thought of as the Twin Reverb of Japan. It's been built in many formats over the years (click the link below). Built like a tank, rare to see many in repair shops.

    Used carefully, they can be brilliant practice amps for bass, with that chorus, but it's a guitar amp: Lots of guitar amps have 12's, but they're completely different, not the 12's designed and built into bass cabinets. But for use a bass amp on stage or much else, they will not cut it, and 120w total output wouldn't take you very far anyway.

    Roland - 40 Years of Roland Jazz Chorus
    Last edited: Jul 12, 2020
  10. Mac Daddy12

    Mac Daddy12

    Jul 11, 2020
    I appreciate the information. I am playing guitar through it. There just isn’t any low end compared to for instance my Twin reverb or even my Laney Lionheart. Hardly any bass at all.
    TN WOODMAN likes this.
  11. lowphatbass

    lowphatbass **** Supporting Member

    Feb 25, 2005
    west coast
    While it’s not the “bassiest” guitar amp ever built it should be able to deliver somewhat warm and musical tone at reasonable volume. All that being relative I couldn’t tell what may be wrong or if anything is wrong with your amp.
    Omega Monkey and TN WOODMAN like this.
  12. Wasnex


    Dec 25, 2011
    Perhaps the speakers have been replaced and the polarity was accidentally reversed on one of them.

    Could just be ganked.
  13. Mac Daddy12

    Mac Daddy12

    Jul 11, 2020
    It does not have the original speakers. (I wish it did) I’ll check that. I love the amp. Very clean just no balls on the low end
    mindwell and TN WOODMAN like this.
  14. winston

    winston Supporting Member

    May 2, 2000
    East Bay, CA
    My older brother had a JC-120 when I was a kid, he had it set up against the wall in a corner. Sounded great for bass at low volumes, but as others note an open-back guitar amp won't pump out satisfying low end at higher levels.
    TN WOODMAN likes this.
  15. Guitar players that want bass balls are the bane of bass players.
  16. Wasnex


    Dec 25, 2011
    The polarity of the speakers may be the source of the problem, or the speakers may just have very weak low end.

    If the speaker do not match, you can't necessarily rely on them having the same polarity convention especially if they are older drivers. I believe it is now standard for a positive voltage applied to the positive terminal to cause the cone to move outward, but there are some notable vintage drivers that move in the opposite direction.
    TN WOODMAN likes this.
  17. nilorius

    nilorius Inactive

    Oct 27, 2016
    Riga - Latvia
    If i am not wrong - this combo is for guitar not bass.
    TN WOODMAN likes this.
  18. yodedude2

    yodedude2 Supporting Member

    Nov 19, 2005
    san antonio, texas
    try different speakers, or run the amp output into a bassier cab. i bet the amp is fine and that the speakers are your issue.
    TN WOODMAN likes this.
  19. If speakers sound decent otherwise rather than changing them out you could try an EQ pedal to bump up the low end. An EQ pedal is a useful pedal to have in your arsenal to begin with even if you decide the speakers aren’t cutting it.
  20. arbiterusa


    Sep 24, 2015
    By design. That’s their sound. Best amp for clean tones ever made.
    DTRN and TN WOODMAN like this.

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