What makes a bass amp a bass amp?

Discussion in 'Amp Central Station' started by alexwilds, Jun 17, 2019.

  1. alexwilds

    alexwilds TDPRI Member

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    I took my lovely 5E5-A Pro to a gig tonight. My Tele sounded beautiful through it. The bass player plugged into it. It sounded awful - weak, thin, tinny, distorted.

    My Pro has blackface bassman PT and OT, 15" bass speaker, and big 7581 tubes. I would have thought it would be great for a bass. So what makes a bass amp a bass amp?
     
  2. radiocaster

    radiocaster Poster Extraordinaire

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    The speaker and speaker cab, but also how it's voiced, the eq in particular.

    Some amps made for 6 string guitar may sound good for bass through a bass cab, but many may not.
     
  3. kbold

    kbold Tele-Meister Silver Supporter

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    Many guitar amps work well with guitars, but not with bass. I believe the 5E5 is in this category.
    Conversely, bass amps often make good guitar amps.

    And what radiocaster said.
     
  4. Old Deaf Roadie

    Old Deaf Roadie Tele-Holic

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    2 words: clean & loud.
     
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  5. 11 Gauge

    11 Gauge Doctor of Teleocity

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    The lower the frequency, the more power is required to amplify it.

    Generally speaking, you don't want clipping to occur at lower frequencies (even if it's guitar and not bass). What we tend to find pleasing with harmonic distortion occurs at the higher frequencies.

    And generally speaking, a lot of bass players don't want any clipping from their amplifiers.

    Now, not all bass amp cabinets and speakers are of the same design - the older ones typically had the same general purpose full-range drivers that were also used for guitar. The dimensions and cabinet construction oftentimes didn't seem to be optimized for bass (e.g. weren't regularly sealed and ported, especially with a combo). This is why the older designs tend to sound okay for bass, but as good, or maybe even better, for guitar.

    Once you get to non-tube bass amps, the designs evolve to include some things you won't find in guitar amps, like active EQ controls and compressors. They can really optimize how things should s

    Lastly, bass-specific speakers are designed to handle much more power, and more movement (or excursion) at the voice coil. They won't have the same frequency response as your "typical guitar only" speaker, as a result, because the voice coil, spider, cone, and surround are all typically very different, WRT a guitar only speaker. And just because a speaker is a bigger diameter doesn't mean it's better suited for bass.
     
    Last edited: Jun 17, 2019
  6. Digital Larry

    Digital Larry Tele-Afflicted

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    You're also going to need to consider the low frequency rolloff which has to go down at least another octave. This is usually the result of several coupling capacitors throughout the amp so without seeing a schematic, hard to give you a simple answer.
     
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  7. 11 Gauge

    11 Gauge Doctor of Teleocity

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    Actually, many guitar amplifiers won't typically have a lot of high pass filtering to exclude the bass at 60Hz and below, other than at the tone controls themselves. They just can't reproduce that stuff cleanly.
     
  8. schmee

    schmee Poster Extraordinaire

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    -Tone stack
    -Cabinet and speaker (deep cab, closed back, and high power speaker) (deep enhances lows)
    -Power. Takes a lot of watts for good clean bass response.

    The most important of the 3 is cabinet IMO.
     
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  9. 11 Gauge

    11 Gauge Doctor of Teleocity

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    I think they're all equally important.

    And something we're kind of skipping over is how much headroom does the preamp have? Lower headroom with your typical guitar amp might actually be preferred. With bass, you'd want it as high as possible.
     
  10. schmee

    schmee Poster Extraordinaire

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    Plug your bass amp into a Deluxe speaker and open back cab vs plug your bass into a Deluxe amp and bass cab... and then let's discuss it! My bassist uses my little amp head into a bass cab (JBL 15) at rehearsal and it sounds fine, albeit limited volume if you tried that at a gig I suppose!
    Just sayin'...
     
  11. JD0x0

    JD0x0 Poster Extraordinaire

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    Power supply. Tube rectified class A/B tube amps do not handle high loads well. They 'sag' because they can't keep up with demand. You generally don't want 'sag' with bass as this tends to sound loose and farty, and like the amp can't handle the low frequencies. Low frequency amplification is a big load for an amp.

    IMO, that's the main thing. You can get good bass tone through guitar speakers, until the speakers blow from overheating. Cab design is extremely important in producing and controlling low frequencies. Tonestack and frequency filtering tends to be more of a voicing thing, IMO. If the power supply and cab are up for it, those wont necessarily make or break the amp. Most guitar voiced tonestacks work fine with bass, and cutting some lows (as some guitar amps may do) tends to help, as the fundamental can sometimes sound muddy on the lowest bass strings.
     
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  12. radiocaster

    radiocaster Poster Extraordinaire

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    I was going to jam with this guy at one time with my Greta, which sounds great through a bass speaker, but then I turned it up a bit and it started distorting a lot. Only drum machine, but I figured we might want to turn up so I set up a regular bass amp.
     
  13. alexwilds

    alexwilds TDPRI Member

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    Thanks for the replies, but I am still at a bit of a loss. As I said, my 5E5A Pro has Bassman PT and OT, a massive 100 watt 15" speaker salvaged from a Roland bass amp, and 7581 (35 watt) tubes. With a guitar it has headroom all the way up the dial. It should have been great sounding with a bass. Apparently the difference is in low pass filters and other voicing decisions in the circuit. I guess my next build will be a 59 Bassman just to learn what's going on in there. Thanks again.
     
  14. BigDaddyLH

    BigDaddyLH Telefied Ad Free Member

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    What percentage of current bass amps are tube amps? (Not including hybrids that have a since 12AX7 in the preamp)
     
  15. teletimetx

    teletimetx Poster Extraordinaire

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    - A few more suggestions.

    One thing that might help is running a bass through a compressor pedal first, to attenuate the much larger amplitude spread hitting your amp. You didn't mention whether or not that was tried.

    using a guitar and bass at the same time : the amp eq for your guitar might not be optimal for the bass guitar - I'd be inclined to try the bass on it's own and work the eq on the amp and the pickup/eq choices on the bass.

    you didn't mention the kind of bass/ bass pickups involved - another source of why guitar and bass at same time might not be optimal.
     
  16. JD0x0

    JD0x0 Poster Extraordinaire

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    Look at the power filtering, as I mentioned earlier...

    http://schematicheaven.net/fenderamps/pro_5e5a_schem.pdf


    16uF for the mains, 16uF for the screens. That's PATHETIC for a bass amp. Hiwatts and Dumbles use like 100uF for the first node and those aren't even bass amps. Those are just what I would consider tightly filtered guitar amps. Having a bass speaker and 35 watt tubes is not going to compensate for such a small amount of filtering. It has no juice. Think of it like using AAA batteries where D batteries are needed.
     
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  17. magicfingers99

    magicfingers99 Tele-Afflicted

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    bass response, whats the difference between a tweeter and a woofer?
     
  18. Syrinx

    Syrinx Tele-Meister

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    Very few in number- the SVT being the main known one-and even though it is a single issue, a lot of people buy them-and those that dont still would like to emulate the tone. I dont play much bass-but bought a SVT classic stack for my bass players to use.
     
  19. Obsessed

    Obsessed Telefied Ad Free Member

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    In reverse, I know a local guy who only plays his tele through a bass amp. Of course he does play it very loud.:rolleyes:
     
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  20. Dacious

    Dacious Poster Extraordinaire

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    Duplicate
     
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