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Amps and 'Headroom' (Tube vs. SS)

Discussion in 'Amps and Cabs [BG]' started by westland, May 29, 2005.

  1. westland


    Oct 8, 2004
    Hong Kong
    Thanks IvanMike (Unofficial Bag End Spokesman & Moderator) for some great reference material. I've learned recently from your posts about amps and ohms (I especially like "Reality Check - Amp price, performance, tone ..." and "Ohms FAQ") and you've convinced me that you get what you pay for, there is no such thing as a free lunch, and best of all, "you canna change the laws of physics captain!"

    So I'd like IvanMike to enlighten me (another FAQ perhaps) on amps and headroom (assuming I haven't missed a thread ... in which case perhaps you can give me a link). Where and how is headroom important, and how is the headroom provided by tube vs. solid-state amps different? What about the onboard bass amp; what role does that play? (Prior posts seem to indicate a qualitative difference; can these be translated into the so-called 'laws of physics'?)
  2. Tash


    Feb 13, 2005
    Bel Air Maryland
    I'm not Mike but I'll take a stab at this. You can think of headroom as simply having more power than you need.

    Lets say that you need 500 watts to produce volume level X from a give speaker cabinet. You want to maintain volume level X, or as close to there as possible for the duration of a gig.

    Amps to not put out constant amounts of power, they vary, sometimes by quite a lot. An amp rated to 500 watts might be putting out 250-1000 from second to second. Obviously this varies a tremendous amount from amp to amp, but the key thing to keep in mind is that when you put the dial at 500 watts, you don't have a perfectly steady 500 watts, you have an average output of 500 watts over time.

    Now lets say the amp you are using maxes out at 750 watts. To maintain that average 500 watt level its going to have to work pretty hard, probably hard enough that it will begin clipping (hitting its maximum output).

    If you used a different amp with a maximum output of say, 1000 watts, keeping an average level of 500 watts doesn't tax it so much, making clipping much less likely.

    This is headroom.

    The tube vs. solid state issue comes in from the clipping angle. Generally speaking tube amps clip nicer than solid state amps. For the most part SS amps will sound fine until they reach a certian point, then they will immediately start clipping. Tubes will begin to clip gradually as they approach their makimum output, and this clipping actually sounds very nice to most people. Functionally that means a tube amp will be "louder" than a solid state amp of the same rating. In truth its not, 500 watts is 500 watts, the difference is that a 500 watt tube amp can use its entire 500 watts and still sound really nice, where a 500 watt SS amp will start clipping at say 400-450.

    This is a grossly simplified explaination of course, but I'm sure there are plenty of people here who can dig into the real physics at work.
  3. westland


    Oct 8, 2004
    Hong Kong
    That sounds pretty convincing to me. Is it the gentle clipping that some bassists like so much about tube amps (they seem like a lot of trouble, so I'm curious)?
  4. Tash


    Feb 13, 2005
    Bel Air Maryland
    Yup. Tubes don't "clip" a sound so much as gradually squeeze it, and its a rather nice sort glowy sound that a lot of people like.
  5. they aren't though, they just have removable, replacable tubes instead of the solid state counterparts. You just hear about them being repaired more because they are worth keeping well into the 'vintage' years. After the similar aged solid states stuff has been tossed because of dried up capacitors, loose solderings, etc etc etc... people are still getting tube amps fixed.

    I much prefered the 'quickness' of solid state stuff for most of my playing years. My first amp was all tube (holy grail fliptop Ampeg even) and I HATED it. I replaced it with a high wattage, solid state rig quickly. It wasn't untill I gave up gigging for a couple years and took time to love listening to music again that I discovered what was missing in my tone was tubes ;)

    That said, I replaced a 900 watt poweramp with a 400 watt tube head and cannot percieve any loss in volume or headroom.

    My only sacrafice is the fact my 40lbs poweramp turned into 100lbs of copper and glass :bassist: but it's worth it to me to get the tone I have now.
  6. westland


    Oct 8, 2004
    Hong Kong
    Tell me more. If I feed an Aguilar DB 900 Tube DI box into a solid state amp, can I get the same sound that you like from an all tube amp?

    How about selecting a Valve Amplifier on my BOD, and feeding this into a solid state amp?

    What is different with these hybrid setups?
  7. IMO.... no

    I feel it's the tube power section! It's the way the power tubes react to input and also react to resistance from the speakers. The entire rig just seems more sensitive to the subtleties of my playing. Maybe it just makes me play with more finese... but whatever it is, it works for me :bassist:
  8. I haven't owned a full tube amp yet, but from the experience I have had with hybrids, you can get some of that nice tube tone when recording DI'd out (ie. sound straight from the preamp), but once it goes through the ss power section, it loses alot of the tube warmth that it got from the preamp.

    So as James said, IMO no, you can't get the same sound...

    as to which sound is better? thats up to you ears only...
  9. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    Like James said, you need power tubes to get that sound. Of course, different power tubes have different sounds as well, it's lots of fun to experiment with them!!!
  10. I've finally learned how much more pleasing tubes can be than SS.
    I was a SS junkie for years but I would go through at least 1 head a year, sometimes 2 or 3.
    I always had plenty of volume (except with an SVT350h), but I could never get the tone in my head.
    A few weeks ago I ran through my friends old Traynor bassmaster from 68. I'm not sure of its exact power rating but it was at the least 50watts, maybe up to 200 but I doubt it.
    I had exactly enough volume to sit right in with 2 guitar halfstacks and a fairly loud drummer. Most of all I had the tone!

    I've come to the thinking that it isn't always just headroom that you need, I've had plenty SVT4, SVT5, Peavey Firebass, WT600.
    Each of those heads can move a ton of air, you can feel them, the SVT4 I noticed really could knock you off your feet. But I couldn't cut through the mix with it.

    Now I'm wondering how I would like it to have a big SS rig with lots of headroom to just push out low end coupled with my all tube YBA200 giving me the sound I want to hear.

    Actually, I better stop wondering that cause my girlfriend will kill me if I get any more gear.
  11. mmmm... its a pitty that aguilar stopped making that tube poweramp, otherwise that combined with a big ss poweramp and a good preamp in a bi-amp setup...
  12. hmmm... you don't say...


    imagine the power... a man could go mad with that kind of power
  13. ezstep


    Nov 25, 2004
    north Louisiana
    I totally agree. I had an 18-year old tube head where I had to replace tubes only ONE time. In that same time, I went through a few solid state amps. Don't tell me about "reliability."

    I have seen tube amps fall off the loading dock, fall out of the back of a moving truck, get rained on in the back of a truck, dropped when taking one out of a car trunk, even saw one tumble down a staircase (about 10 steps). . . and everyone of them cranked up and played four hours immediately. I have seen many solid state amps fail after not nearly so much abuse.

    IMHO, I think tube amps are more reliable.
  14. popinfresh


    Dec 23, 2004
    Melbourne, Aus
    James (Or any other all tube users) - How 'quick' is your amp. I hear many people (SS users in particular) complain about all tube amps been to slow to respond. Just wondering if you could actually tell much of a difference? The only amp i've ever played that seemed to have a slower response that was really noticeable was the Mesa M-Pulse line when EQ'd certainly. They didn't sound really slow, just kind of 'cusion-e'.. If you get my drift. Is that what an all tube amp is like when people refer to them as slow?
  15. westland


    Oct 8, 2004
    Hong Kong
    I'm sure there is something to the 'tube' thang, even if it is difficult to articulate.

    On high end audio systems (my brother in law is into this) I myself can hear the 'warmth' of tube amplifiers, even though I would think that this same warmth could be engineered into a SS amp (isn't that what MOSFET circuits are about?).

    If there are dynamic interactions with the player and groove, I'm sure the 'tube' effect would be even more pronounced. It's fun to hear experienced bass players try to articulate the differences.
  16. I'm finding tubes slow, coming off most recently Eden and Hartke stuff. Its taking some getting used to.
  17. popinfresh


    Dec 23, 2004
    Melbourne, Aus
    BER - What amp are you using now? I've been looking at a Sunn 300T as I want warmth and cutting punch, yet nice growl too.
    I was thinking about the Eden line as I think both Dirk Lance and the bassist from Grinspoon both get wicked growl and punch from their eden setups, although it kind of lacked the fat warmth I like too.
    Is it neccesarally a bad thing? Or can you get used to it?
  18. yeah, when you guys say that tubes are slow, what exactly do you mean? is it like a latency issue? secondly about that Sunn 300T, is it also slow like the other tube amps you guys re refering too? I know it has slightly more modern features than most other tube amps...
  19. Tash


    Feb 13, 2005
    Bel Air Maryland
    Tube amps, at least most of them, feel 'slow" to me as well...I don't know if there is something real at work regarding damping factor or what, but it does sound like my notes are a hit longer in developing, like I don't get the real tone of the note until its been ringing for a split second.

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