Explain how amp heads, compressors, cabinets, etc work?

Discussion in 'Amps and Cabs [BG]' started by bass element, Feb 8, 2005.

  1. hey guys, i am currently just playing out of a 50watt crate amp. its kind of a beginner setup i guess, but im proud of it, it sounds good, i've mastered all the tonal controls on it, it actually gets pretty loud and is good for small gigs.

    however, if i ever upgrade to something larger, such as an amp head, cabinets, etc. i'd like to able to know how they all work and fit together.

    for instance, ive seen pics of bassists playing thru a single cabinet but with two amp heads. how does this work? why two and not just one?

    anyways, if someone could just explain the workings of this, im sure i could figure out all the rest.

  2. uglybassplayer


    Aug 24, 2001
    New Jersey
    First off, I doubt the bassists in the pictures you're talking about are actually running two heads at the same time into a SINGLE cabinet (That would definately NOT be a good idea.. You'd blow one or both of your heads and probably your speakers as well). More likely, they have the head there as a backup. A combo amp is just an amp head plus a speaker (or speakers) in a single cabinet. A separate head/cabinet arrangement is just that... An Amp head (which consists of both a preamp and poweramp combined in a single unit) connected via a speaker cable to a speaker (or speakers) in a cabinet (or multiple cabinets).

    - Ugly.
  3. playmybass


    Mar 28, 2004
    Tucson, Az
    Or it could be a stereo cab, but it is still unlikely.
  4. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    sit down and hold on..............

    a preamp amplifies the signal from your bass to a level that will effectively drive a power amp. Preamps generally contain EQ sections and may have a built in compressor (which smooths out dynamics and is really a question for effects and a flame war or two) :p preamps also often have a DI which converts the high impedance signal to a low impedance one suitable to run to a mixing board/pa. Stand alon preamps have "preamp out" jacks

    A poweramp takes the signal from a preamp (thru the input jacks. remember those preamp out jacks?). and amplifies it to the level needed to power speakers. there are output jacks (1/4", speakon, or bannana) that you use to run speaker cable to your cabs.

    a head has both a preamp and poweramp in one box.

    a cabinet has one or more speakers and may have a passive crossover to seperate the signal for woofers and tweeters (and perhaps midrange drivers). Figuring out how many cabs you can use with a given head takes knowing the impedance of each cab and the impedance your head can safely power. (search for ohms faq)

    two heads are either 1-for looks, 2-for backup, 3-they're being run as slave amps and each head is powering one or two cabs.
  5. Passinwind

    Passinwind I Know Nothing Supporting Member

    Besides IvanMike's useful ohms FAQ, there's also a very well written comprehensive amplifier FAQ on Talkbass. Take a look at it: http://www.talkbass.com/ampfaq/
  6. thanx a ton for the info guys. i learned a lot :D .
    also, i found out that the second head that i was talking about before was indeed a backup. i just was not sure at the time.
  7. When i saw SOIA in november last year the guitarist was using 3 amp heads into 2 cabs, im not 100% sure how he did it, but i think it was just along the lines of running the bottom 2 preamps, cus at one point he switched off the 2 bottom amps and it changed the distortion alot! , but i dont know, just a guess
  8. Can you attach amp heads to big amps?

    For instance, I have a Genz Benz M Line 200 Amp. Could I attach an amp head to it? Or is that not what they're for?
  9. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    You can usually find a way to hook any head up to any other that you want, but it's always different how you hook them up, so check with the manual on how to do it for yours.

    However, at that point, most people just either get a more powerful head or a preamp with a separate power amp. With the gigantic amount of wattage you can get in a small package these days, it really doesn't make sense to run multiple amps unless you either like all-tube amps or you want to run two different rigs for the sound.
  10. So technically my amp that I have right now has a sort of head amp? That being the knobs and settings? I'm not really too sure on these kind of things.
  11. Yes, the part of your amp that isn't a speaker is a 'head.'
  12. I getcha. So would it be okay to get a separate head for it? Maybe for more options in my equalizer, or maybe effects or something? I dunno. I just wanna check out some heads.

    And assuming that you can buy heads, you can buy just speakers?
  13. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    If this is what you have:
    Then that is an amp head, no "technically sort of" about it. That's just what an amp head is, looks like, and does.

    If this is what you have:
    Then that is a "combo amp", which contains an amp head and a speaker cab combined in one unit.

    So there is no need or point to adding another amp to that amp, it is an amp already.

    There are ways of hooking multiple amps together, but honestly it's usually a lot more trouble than it's worth. Usually it makes more financial and practical sense just to invest in a bigger amp and bigger speaker cab if the amp you have isn't quite enough. You might think you'd save a few dollars by buying an extension for the amp you've got, but then you're doing what's called "throwing good money after bad", i.e. spending money on a patchwork solution that doesn't solve the problem as well as a smarter investment would.
  14. I see. Yeah I have the ML 200-210T. Okay. Thank you very much. Because I was looking into amp heads, but I see now that I'd need speakers for it. However, if I have an amp head, I'd need speakers for it, right?
  15. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Yes, if you have just a head then you have to get speakers- otherwise how will you hear it? :) The combo amp includes its own speakers, but an amp head by itself does not.

    Some combo amps allow the option of adding an extension speaker in order to get a bit more "loudness" out of the amp. Check the manual for your amp to see if that is an option for you.

    If you want to try out different equalizers, effects etc. it's cheaper and easier to buy those in pedal form than to buy a whole new amp head whenever you want to try a new feature. Read over in the Effects forum to learn all about pedal options. Be sure to start with the FAQ. :)
  16. Some pedals you can get are accually preamps, like the Sansamp BDDI, and the Boss bass eq pedal
  17. Okay cool! I've been wanting to get pedals for a while now, but I was just wondering what would be a better investment. I'm fine with my amp, pedals is the way to go. I'll definitely look into them. Thanks a lot, guys =D
  18. robykost


    Jan 16, 2009
    I'm new as well to the whole cabinet and amp head deal as well

    so could I just but a cabinet and attach any ole bass amp head to it?

    kind of something like
    and this?[​IMG]
  19. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Yep. The only thing you need to worry about is that the total impedance of the speaker cab(s) (measured in ohms) is OK for the head. In the case of the Little Mark II, it will accept any speaker load that is no lower than 4 ohms. So you can plug in one 4 ohm cab or two 8 ohm cabs (makes a total of 4 ohms).
  20. ReillyReilly


    Sep 27, 2009
    LA County
    Check Craigslist and EBay for good used deals on amps and pedals and see where your budget fits. For now pedals will make you feel better but you're eventually gonna wanna have a cab and a head with some good power.