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Can you help me pick out a new head?!?

Discussion in 'Amps and Cabs [BG]' started by rsrhcp, Mar 17, 2008.


  1. rsrhcp

    rsrhcp

    Feb 23, 2007
    Cincinnati
    Ok, so first of all I would like to thank you for reading my post. I am very new the world of cabinets/head and need all the help I can get!

    So I have been playing bass for quite some time now, and have always used a combo amp, so I never really had to deal with the complications of heads/cabinets. I was thinking about getting some GK's, due to the fact that I am an AVID Flea fan, but I am not sure what else to base my judgments on.

    The main area's I am confused about is the stuff about the Ohms and the Impedance, and stuff like that. Currently I am a senior in high school taking a college level Physics class. We just got done the Electromagnetism section, which dealt heavily with circuits/wiring, so I feel pretty comfortable with all of those words. The problem here is that, I do not know where to apply all of these to Bass cabinets.

    Do the Ohms apply to the circuitry of the heads, or the cabinets, or both? Because it would seem that if the Ohms was pertaining to the circuitry, then the less Ohms would be best, because this would decrease the heat build-up. Or, do the Ohms refer to the speakers themselves? Meaning less Ohms would give more power...

    Besides Ohms and Impedance, what else should I look for in heads/cabinets. I want a head that is versatile and will give me Flea's sound (anywhere from his J-Bass sound on Stadium Arcadium to his MM sound on his earlier stuff).

    Thanks so much!
    ~Ryan :D
     
  2. Rob Mancini

    Rob Mancini Guest

    Feb 26, 2008
    Flea's sound comes from his hands. Any instrument he plays sounds basically the same.
     
  3. xlows

    xlows

    Oct 21, 2006
    Minnesota
    The only real difference sound-wise you'll get out of different heads is the difference between solid state or tube. I recommend you just go out and try a bunch, see what you like within your budget, and take it home. Impedance stuff is matching head impedance to cab impedance, something which has been explained here countless times. Use the search feature.
     
  4. TrevorOfDoom

    TrevorOfDoom Supporting Member

    Jun 17, 2007
    Austin, TX
    what was the brand of combo amp you used to play? did you like your sound? perhaps look into whatever offerings that brand has...
     
  5. rsrhcp

    rsrhcp

    Feb 23, 2007
    Cincinnati
    Ah, ok, well I have used the search feature, and it came up with over 100 results, and for a good reason.

    I have a Fender Bassman 100. It sounds fine, I just want to upgrade to something louder.



    Haha xlows, nice signature, "Don't Panic", great book! I watched the movie today btw!
     
  6. butchblack

    butchblack Life is short. Do good. Find and do what you love.

    Jan 25, 2007
    Waltham Massachusetts
    Ohms apply to both the head and the cab. The head is rated in power (watts) at different ohms. The lower the ohms the higher the wattage the head puts out. They will list the minimum ohms the head will handle. You can safely use more ohms, not less ohms.

    Cabinets are rated in ohms, generally 4 or 8 ohms. Remember from your physics class that 2 8 ohm cabs will give you 4 ohms so your choice of cabs should be dependent on how many cabs you want and the minimum ohms your head requires.

    Cabs are also rated by how many watts they will handle. You want to have cabs that will handle the max watts your head puts out at the ohms you're running. Remember that 2 cabs of the same ohms will get half the rated power, so if you get a head rated at 500 watts at 4 ohms and you are playing through 2 cabs each cab only needs to handle 250 watts.

    You don't mention what type of music you're playing, or if you're in a gigging or near gigging band. Though your reference to Flea gives us some idea. GK makes some versatile heads and there are a lot of them on the used market, it's a good place to begin. Err on the side of getting more, not less wattage then you think you'll need. Headroom is a good thing. Avatar makes some great cabs at very reasonable prices and they're a great company to do business with. Given the fact that a J bass with single coil pups is going to sound very different to a MM with humbuckers I don't know that you would be able to emulate all those different sounds. Where you have a J now I'd shoot for that sound.
     
  7. Arx

    Arx

    Jan 22, 2008
    The main difference in SS amps will be the tone control/eq setup.

    The ohms you're asking about is often confusing since a lot of people give advice without knowing how it works.

    The ohm rating on a SS amplifier has pretty much nothing to do with its output impedance. It's the minimum load impedance it's rated for. Usually the output impedance of the amp is very low, which helps keep dissipation low, as you said.

    On a solid state amp, going higher than the rated impedance is safe, but you'll usually get less power. Often not really a big deal, depending how oversized your amp is. If you go lower than the rating it's risky (read:stupid), since you can easily put out more current than the output devices are designed for.

    On a tube amp, you'll usually have a maximum and minimum impedance follow the rules on these. Also there are frequently switched taps on the transformer, and you'll get the same power regardless of what you're hooking up to it. This can be a good or bad thing. One could argue that it gives you more versatility, though usually a SS amp in the same price range will make as much power with the worst combination as the tube makes in all 3.

    So, if you want it to sound like a tube amp, buy a tube amp. I think that's the only reason you should.

    If you're looking for reliability, and idiot-proofness, solid-state is the winner.

    The cabinet will usually have a lot more effect on your sound than the amplifier.
     
  8. Rob Mancini

    Rob Mancini Guest

    Feb 26, 2008
    Arx, the technical stuff sounds accurate but you made two gross misstatements:

    "The main difference in SS amps will be the tone control/eq setup."

    If that were the case, every SS amp would sound identical. They clearly do not.

    "If you're looking for reliability, and idiot-proofness, solid-state is the winner."

    A good tube amp is no less reliable than a good solid state amp. This business that they're not...I have no idea where it got started, but it's completely false. Look at TB...there are people who report as many problems with SS amps as tube amps.
     
  9. rsrhcp

    rsrhcp

    Feb 23, 2007
    Cincinnati
    Thanks butchblack and Arx for the info! That really tied lots of loose ends together!
     
  10. Arx

    Arx

    Jan 22, 2008

    A couple notes I'd add. On a tube amp, the same rules don't apply as far as changing load impedance goes. Stick to what the amp is rated (and set) for, higher impedance is not okay.

    you can also wire 2 cabs in series if you want more impedance, instead of less.

    And for the last point, You can use a head with more output than your cabs can handle, as long as you're not stupid enough to crank it too high. In fact, a too-small amp that's cranked all the time can be easily as dangerous to your gear. Firstly, hard clipping is rough on speakers (some amps will soften this out though, which is a good feature) Second, if you've got it maxed out all the time, it puts a lot of stress on the head. Occasionally when an amp fails, it fails in a bad way, killing the speakers as well. This obviously all depends on the gear. I would expect the more reputable manufacturers gear to be designed with wider safety margins, and less likely to be damaged by normal (but hard) use.

    I knew a guy back in highschool who had a 1500W amp hooked up to a 15" and 4 10" with a total rating of something like 500W. He never had any problems, but he also never really turned the volume above 2. ;)

    -Nick
     
  11. Arx

    Arx

    Jan 22, 2008
    Well, I expect if you pulled all the front end buffer/eq stuff out every SS amp would sound pretty much the same (close anyways). I should clarify that there's some effects in the tone/eq which aren't entirely intentional, or obvious. based on the numbers on the knobs. often the relatively simple topology of the circuit causes interactions between the controls. Different amps have different topologies, so I'm not saying set everything to 5 and they'll all sound the same. ;) I should have stated it more clearly that I'm mainly contrasting it against tube amps, which will vary more, due to both tube distortions lending their colour, and the fact that with the higher impedance, your speaker's impedance peaks and dips tend to contribute more as well. Add this to some more unintentional EQ due to parasitic capacitance/inductance in the output transformer, and it's a lot less predictable.

    As far as the reliability thing goes, I guess it depends on your definitions.
    Perhaps durable would be a better word.

    Don't get me wrong, there's some really well built, well designed stuff out there, and I'm certainly not trying to recommend against tubes, but it is a factor to keep in mind. A tube amp will need new tubes occasionally, and its lifespan is definitely more likely to be affected by mistreatment/mistakes. I know I always feel bad when I notice that I've left my tube amp on overnight. I had a couple friends over at my apartment, and plugged in a small SS guitar amp that I almost never use. When we were done playing, I forgot about it, and noticed a few weeks later that it was turned on. No biggie.

    Arguably, if you maintain it properly a tube amp will last just as long as a SS amp, but by the same token, if I replace all the electrolytic caps in an SS amp occasionally it'll last pretty near forever.

    So, my opinion is that tube amps can be reliable, but SS amps can be more reliable.
     
  12. Rob Mancini

    Rob Mancini Guest

    Feb 26, 2008
    Right, and every person on earth would look the same if you pulled off their skin and muscles ;)
    Tubes can last decades, or they can blow up tomorrow. Same with FET's.
     
  13. Arx

    Arx

    Jan 22, 2008
    Yep.. I was just trying to get across the general point that solid state amps tend to sound more alike as a group than tube amps. Maybe you disagree? You've probably got more actual experience. I'm just hypothesizing based on what I understand of the electronics, and my experience with amps in general (not all guitar/bass specific)

    Sure it can happen, but if you're trying to equate the lifespan in general, I think you're just plain wrong. Tubes have a useful lifespan of what? maybe a few years, more with lighter use of course. You can use them for longer, but they definitely degrade. A FET really doesn't. sure, maybe if it's operated continuously for MANY years at high temperature (like several decades) there might be enough electromigration to significantly change things. I don't really know though. I've never really worried about it.

    Barring accidents a FET should easily outlive the amplifier. A tube, probably not.

    Obviously fets blow up due to other failures in the circuit, external conditions, or bad design, but tubes are obviously in the same boat here, and possibly moreso, due to the extra heat they produce, and relative sensitivity to things like load impedance.

    -Nick
     
  14. Rob Mancini

    Rob Mancini Guest

    Feb 26, 2008
    I don't think SS amps sound any more alike or different than tube amps, and I've played a ton of both over 30 years. An Acoustic 370 sounds worlds different from an SWR SM-900, which sounds worlds different from a Markbass Little Mark II.

    As for tubes, I have some original tubes in my 69 SVT, as well as some original tubes in my 73 Fender Super Reverb. I also have bought tubes that lasted a month. But that's not a reflection of the amp. You're trying to fault the amp when a tube blows. Might as well fault the amp when a fuse blows, too, you know? Also, FET's require biasing occasionally just like tubes, if my SVT 3 Pro is any indication, so it's not like you can install them and forget them. Will it cost a little more to keep a tube amp running? Sure. But the reliability of tube amps vs SS amps is the same. To be honest, I've had more problems with SS amps than I ever had with tubes.
     
  15. Arx

    Arx

    Jan 22, 2008
    As I say, I'll trust you on that one. My impressions are definitely based on a much more limited range.

    I usually do fault the amp when a fuse blows. It shouldn't blow fuses unless something is damaged.

    And it does reflect on the amp if I'm sitting here with an amp I can't play, because it's blown a tube. To me that is a "reliability" thing, even if it's not the amp's fault.

    Once again... I'm not saying tubes are bad. The small amount of additional maintainence necessary can be entirely worthwhile if that's the sound you want. I just think it's worth keeping in mind, how big a factor it is depends on the user.
     
  16. Rob Mancini

    Rob Mancini Guest

    Feb 26, 2008
    Good point. Didn't think of that at the time ;)
     
  17. butchblack

    butchblack Life is short. Do good. Find and do what you love.

    Jan 25, 2007
    Waltham Massachusetts
    Nick's point on clipping is valid. One other thing to be aware of when comparing heads is the THD (total harmonic distortion) at max power. Less is better as it allows you to crank the amp up if necessary without the sound quality degrading. Most good newer heads have THD of 1% or less. Older heads often had much higher THD, I used to use an Acoustic 220 head back in the 80's that IIRC had a THD around 10%. One of my band members owned an amp repair business. We put my head on his scope, the amp would start clipping (square sine wave) once the volume knob hit 5 (and put out a whopping 80W at 8 ohms). It's not always easy to find out the THD of a head, not all manufacturers list it. I believe most of the GK heads are 1% or lower, if others know differently please chime in. His point on using a head more powerful then the cab rating is also valid, but it's too easy to turn it up too far, so as others have said I'd rather err on the side of caution and have the cabs safely able to handle the head's power. Going back to square sine waves, another point is that a distorted signal can wreak havoc much quicker on a cab, so even if the power is within limits the bad signal can do you in.
     
  18. Arx

    Arx

    Jan 22, 2008
    Yeah. THD is a tricky one on guitar amps, because they're not really linear to begin with. So, while your point is mostly correct what's actually important is the reason and nature of the distortion.

    Clipping will cause THD and is a bad thing, but some non-linearity is what gives an amp its character (and one of the reasons people like tube amps)

    So the THD spec can be a bit misleading. You could have a good sounding, powerful, but distorted amp which has a tone you like. an equally powerful amp that's distortion free may sound a little thin/clinical/harsh as some tube fans often say SS amps are.

    It certainly can be an indicator. If an amplifier's max power is stated with a very high THD% it's probably because they're trying to stretch their numbers.

    Don't go out of your way for a very low THD% though. It's not an all-important factor on an instrument amp.

    I definitely agree with the point about it being too easy to turn up the volume. Some protection could be offered by a fuse on the cabinet output. This way if you turn it up a bit too loud it'll blow the fuse, and everything gets quiet. This is a bad idea on a tube amp though. SS only. Also it won't stop your cones getting ripped out of the speaker because someone was monkeying with your amp and turn it on with it set to 11.

    -Nick
     

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