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Separate pre- and power or bass head?

Discussion in 'Amps and Cabs [BG]' started by Woodboy, Jun 9, 2003.

  1. Woodboy


    Jun 9, 2003
    St. Louis, MO
    I can see the appeal of a separate pre- and power amp, especially with all the great preamps out there. Plus, pick whatever power you need and rumble on. However, it seems like there is a potential for problems, like 2 pieces of equipment to go bad instead of just one, differences in impedances, and something that I have seen mentioned, but have not figured out, that some people don't like to bridge their power amps. Is this a reliability question or sonic one? I can see the advantages of an integrated bass head: complete compatability of the various stages, and some type of "sonic signature" that would probably exist by having the same designer do the whole enchilada. That being said, I am still drawn to a separate pre- and power amp. I play fingerstyle with TI Flats and am running an Ampeg BXT-410HL with my blues and r&b 4-piece band. Any real world experiences would be appreciated!
  2. savagelucy


    Apr 27, 2002
    I'm also thinking about buying a seperate pre- and power- amp for my next rig. So, any input and experiences would be helpful for me too.
  3. IvanMike

    IvanMike Player Characters fear me... Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    well i'm a fan of the modular approach for a variety of reasons
    first, you are unlikley to find a head that will put out optimum juice for loud gigs and/or to power some of the newer speakers while leaving some headroom
    Poweramps get much more powerful than heads and, if you go with a reputable company i think you'll find that the quality of their amp will be better than the one in an integrated head.
    I'm a wimp so i am a big fan of stewart and qsc plx amps because they're light and sound terrific
    one cruise around the board will echo my sentiment
    as for as preamps go, most are of better quality than those in heads and are often more "pure" in their tone. plus when you get fickle you can always swap out a preamp rather than having to buy a whole new head.
    as far as impedance goes, with some exceptions, there usually are no glitches.....these things were made to be used together
    likewise, amps were made to be bridged, it's not voodoo, tone could be different and amps like the stewart dont require a load on both amps so you can just use one side if you want

    all that said, i really like the lil heads edens, walter woods, etc if youre gonna buy a head, you might as well get one the size of you day planner that puts out 1000 watts!
  4. JimboBass


    May 23, 2003
    I agree, a seperate preamp and power amp is the way to go. If you get an amp around 1000W, you will have a much more round and full tone. The extra headroom will keep your amp from clipping and save your speakers.

    Brett at Epfiani
  5. g4string

    g4string Supporting Member

    Sep 19, 2002
    Melissa, TX
    I went from SWR 750 to a modular set up that includes a QSC PLX-1602 and a Demeter HBP-1.

    I used to think that 750 watts was a lot. I was always almost clipping my amp and never had any headroom with the 750.

    I now have 1600 watts of power. I have tons of headroom. My amp never clips. IMO, having tons of headroom makes your sound fuller, tighter, and sound 10x's better than what you have experienced before.

    Make sure that you get a good power amp. IMO, the power amp is the most important link in the chain if you go this route. You can have the best preamp in the world, but if your power amp is junk your bass will sound like junk.

    QSC and Stewart are great choices for power amps. The favorite preamps on this baord seem to be the Demeters, Alembics, and Aguilars.

    This will easily set you back 1G - 1.2G. But it is worth it. The 1.2G was the best investment I have spent on my bass in a while. I am no longer gassing over amp heads and my bass tone has improved x's 10. BTW, my rack weight decreased by 20lbs.
  6. g4string

    g4string Supporting Member

    Sep 19, 2002
    Melissa, TX
    IMO, bridging a 1600 watt power amp at 4 ohms is safer than using a 750 watt head at a 4 ohm load. Here is why:

    When I used my 750 it was a 4 ohm load. The amp was always hot to the touch. And since I was always close to clipping and had no headroom, I was constantly working the amp.

    With the 1602, I bridge it a 4 ohms. I still drive to get the same level of volume as I did with the 750. However, I am not working the amp as hard as the 750 and I always have miles of headroom to spare.

    Get my drift? :D

    This is just my opinion. I could be wrong.
  7. Fuzzbass

    Fuzzbass P5 with overdrive Gold Supporting Member

    A consolidated head has a preamp and a poweramp, so it has the same number of pieces as a basic rack system. The difference is, all the pieces are contained in the head, so if any one piece fails, you need to bring the entire head to the repair tech.

    My rack rig contains a preamp, compressor, and power amp (and sometimes an additional EQ). When my preamp went bad, I simply rearranged the cables to bypass it, and used the compressor as a preamp. Also: I bring a SansAmp Bass Driver pedal to every gig, and could use that alone directly into my power amp.

    Power amp failure is a significant problem no matter what kind of amp system you have, but if my power amp failed I would only have to bring that in for repair, and not my entire rig. Also note that some amps are 'dual monaural', such as the Stewart World 2.1 in my rack: each side is separate including power supply, so chances are that if one side failed, I could get through the gig by using the other side.
  8. BruceWane


    Oct 31, 2002
    Houston, TX
    An integrated head doesn't have fewer components to break - they're just all in the same box. You've still got a preamp section and a power section - but with an integrated head, if either one breaks, BOTH go off to the shop.

    Problems with compatibility between preamps and power amps are rare. There are a few preamps out there that have very low output levels (I think the SWR Interstellar Overdrive is one) that don't work well with some power amps straight out of the box, but you can have the input sensitivity adjusted if needed. Not really that big a problem, and certainly not insurmountable.

    The advantage of having a separate pre and power amp are that if either one breaks, that's all that goes to the shop, making it a little easier to get by in the meantime. If you want to change your sound, you can get a new preamp for less than an integrated head. Also, the upper limit for wattage in an integrated head is quite a bit lower than in power amps. You aren't going to get 2000 (or more) watts out of an integrated head.

    About the only advantage I see for an integrated head is simplicity......also, if you want an SVT sound, there is really only one way to get the true, classic sound of an SVT, and that is by USING an SVT, and they only come one way.

    There's lotsa preamps that sound great in their own way, and some can even get very close to the SVT sound if you want it.
  9. FretNoMore

    FretNoMore * Cooking with GAS *

    Jan 25, 2002
    The frozen north
    I've done the preamp/efx/poweramp thing (Ampeg/Alesis/Crown), and while it is more flexible as many have already said, the drawbacks as I see it:

    - Bigger and heavier rack
    - More cables and connectors that can malfunction
    - Potential for grounding problems and hum

    Make sure you use quality cables and connectors, and use balanced signalling everywhere possible between the units in the rack.

    The "big and heavy" was inconvenient enough for me to downsize.
  10. g4string

    g4string Supporting Member

    Sep 19, 2002
    Melissa, TX
    SWR 750
    - 3 Rack Spaces
    - 40 lbs

    Demeter HBP-1/QSC PLX1602
    - 3 Rack Spaces
    - 30 lbs (Demeter 10 lbs, QSC 20 lbs)

    No offense FretNoMore, but with the variety of different pre's and power's you can easily have a rig that is the same size and weigh less than your current rig.
  11. g4string

    g4string Supporting Member

    Sep 19, 2002
    Melissa, TX

    The pre and power rig has one more cable than an amp head. That cable is the cable that connects the preamp to the power amp. That's it, one extra cable.

    As far as noise goes. IME, when ever I have had noise problems it is from an external source other than my rig. That does not matter weither I use a head or a modular rig. Most noise will come from your pu's via flourescent lights, neon lights, or through a dirty power source.
  12. FretNoMore

    FretNoMore * Cooking with GAS *

    Jan 25, 2002
    The frozen north
    OK, perhaps I didn't quite answer the original question.

    A rack rig seldom stops at preamp+poweramp. Just look at the pics in this forum, many rack cases grow to 8+ units, and there are not just one extra cable in there. I know from my own experience.

    But OK, in a straight comparison between an integrated head and pre+power amp there can be as little as one interconnecting cable. (And actually one extra power cable, to pick nits).

    On the weight issue, I know there's lightweight poweramps, but they cost more so most people buy the cheaper heavyweights.

    Just relating my experience, perhaps I should have added the customary IMHO, YMMV, AFAIK, etc.

    Peace. :)
  13. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Well, two if you decide to plug both of the power cords in :D

    "Tons" of headroom between 750 and 1600 watts? 3.3 dB actually. I wouldn't call that TONS...

    Bridging to 4 ohms means both channels see a 2 ohm load, so the amp will run hotter than if each channel saw 8 or 4 ohm loads and it's more sensitive to speakers that dip below nominal impedance. The distortion figures are also worse when bridged. This is why some pros prefer to NOT bridge amps. The reason to bridge the amp is to deliver full power into ONE speaker; using a stereo amp is wasteful and noone makes super high power mono amps.

    As far as separate preamps being "better quality" that's not 100% correct. The SWR preamps are built the same as their integrated amps (I own both the Baby Blue and the Grand Prix and have had them open). A Demeter pre may be super high quality, but a Peavey TB-Raxx pre sure isn't. As usual, price has a lot to do with how good the preamp is.

    While your Demeter plus QSC may be lighter than your SWR 750, how about comparing it to SWR's SM-900...2 rack spaces, 26 pounds which is smaller AND lighter. Not to mention the 7.5 pound 1200 watt Walter Woods heads.

    Finally there's no question that separates of similar quality will always cost more. Go price pre/power rigs vs. integrated heads from makers that sell both. You also have to buy a rack (more $$ and weight), something many integrated heads don't need.

    I'm just saying it's not so cut and dried. Rack rigs were very trendy in the 70s where many pros were using Alembic, Ashly or Yamaha pres into Crown or Crest power amps. Integrated heads came back in vogue with the GK 800RB and SWR SM-400. Now rack rigs are getting trendy again as power amps have gotten cheaper than ever in dollars per watt.
  14. deepestend

    deepestend Supporting Member Commercial User

    Feb 21, 2003
    Brooklyn via Austin and NOLA
    Guitar/Bass Builder and Social Media at Sadowsky
    I live in NYC and most clubs have their own bass rig. More often than not, though, it's a crappy Peavey that's been beaten up for years. I got a sansamp pre and have most recently been using a digitech bp8 that has a tube pre so that I can bypass the club's amps pre- (which is often hard to get a good sound out of if I'm unfamiliar with the controsl and only have a few minutes) and get something closer to my signature sound.
  15. IvanMike

    IvanMike Player Characters fear me... Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    wow peavy mark IV
    still an interesting subject. i guess the more watts per dollar and the lightweight poweramps have really helped out.
    I personally refuse to go over 6 rack spaces, the only reason i use a 6 is cause i use a furman pl-pro (protection counts!). One dude in town had a very hip setup with his power amp in its own 2 space rack (gator?) and his pre and goodies in another. Definitely a cool idea esp if you record or want to avoid a big stupid rack.
  16. BassAxe


    Jul 22, 2002
    Culpeper, VA
    I agree with the modular-approach crowd.

    Otherwise, my favorite approach is to keep it simple: Play acoustic. :D
  17. g4string

    g4string Supporting Member

    Sep 19, 2002
    Melissa, TX

    QSC has designed their power amps to be run safely and effeicently at bridged 4 ohm loads. All I can say is that with the 750 the face plate was extremely hot to the touch. I was always set around 7 (1-10) on my pre gain and 7 (1-10) on the master gain settings, as well as the clip light flickering on and off the whole night.

    My QSC is different. I am always set behind the 12:00 posistion on the power amp gain settings (pre amp set at about 7, [1-10]). The amp is always cool to the touch. And, I have never seen this amp come close to clipping, unlike the 750 which the clip light was on and of the whole night.

    Going from having your master gain set from (on the 1-10 scale) 7 to 4 is a big difference. That to me, is tons of headroom.

    The extra cost and weight of the rack case is not important to me. IMO you should always rack you equip (protect your investment), especially with the top $ higher volume rigs. I have had the same 4 space rack for several years now. I make it a point to keep it that way. Never will I exceed four spaces.

    1 space - Korg Tuner
    1 space - Demeter HBP-1
    2 spaces - QSC PLX-1602
  18. lo-freq

    lo-freq aka UFO

    Jan 19, 2003
    DFW, Texas
    I came very close to getting an EA iAmp-800 instead of the rack rig I got. If there had been a closer dealer, I might have. Preamp, power amp and tuner in one 2 space 19 lb. box, sounds appealing to me.

    If I had the jack, I would check out the Walter Woods heads too.

    In the end, the final deciding factor for me was the tone of my whole system or I wouldn't be happy regardless.

    Right now I'm very happy.
  19. JPJ


    Apr 21, 2001
    Chicago, IL
    The big difference between the two is usually cost vs. flexability. Integrated heads are usually cheaper, but you also (usually) don't get much power for your dollar. While the power of integrated heads is increasing, they're usually better suited to practice/low volume/studio situations. With modular pieces, you have MUCH more flexability as far as tone-shaping tools are ocncerned, in addition to the level of power that you can match with your preamp.

    I recently switched from an SWR Redhead to a SWR IOD/Stewart 2.1/Epifani 3X10 rig and have been very pleased. It was more expensive, but I was able to selectively pick the exact components that I wanted to faithfully reproduce the tone in my head. As far as reliability problems are concerned, if you choose good equipment, you shouldn't have problems. Further, with my rig, I have tons of "back-up" devices built in. The IOD is essentially 2 preamps in one, so if my tubes go bad, I can always switch to the solid state portion of the amp. The 2.1 is two amps in one, so if one side goes bad, you can always quickly swith to the other side of the amp.

    Finally, there is nothing worse than an underpowered rig, and most prepackaged heads just don't give you much power. Going with components will give you all the headroom you need. Good luck.
  20. cassanova


    Sep 4, 2000
    I just bought a QS PLX3402 a few days back. 700 watts @ 8 ohm, 1100 @ 4ohm.

    Im still deciding if I want to buy another svp pro preamp & something like a night bass to go with it or buy a mixing board and p/a bins. Decicisions, Decisions.

    But for now Ive been using the 700 watts into my Carvin 4x10 with a home stereo graphic eq. Sounds good and no problems as of yet. Its nice not have the speakers distort as quickly at higher sound levels anymore.

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