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So what is the down side to using a pre-amp with a Crown or other power amp.

Discussion in 'Amps and Cabs [BG]' started by TUEP, Jun 27, 2012.

  1. TUEP


    Apr 8, 2007
    I know there are alot of bass amps and rigs out there but with preamps and modlers sounding better and better....what would hold back a good preamp + a very powerful power amp like a Crown or such?

    Seems like if you could use a sansamp or something similar into a power amp that has thousands of watts then you wouldn't need to worry so much about a 700 watt Ampeg vs. a 700 Watt (insert brand) dilemma.

    So educate me. What would be the issue with using a pre-amp vs. a pre-amp and massive power amp unit?
  2. Oobly


    Jun 19, 2008
    Um... it will never sound EXACTLY like an all tube amp with the power tubes overdriven? That and with some power amp / cab combinations it's beneficial to add a highpass filter if the power amp doesn't have a suitable one built-in.

    I run a tube preamp into a solid state booster / highpass filter into a Crown XLS power amp into a fEARful 15/6/1 cab.

    There are quite a few benefits to this setup.

    1. I consider the highpass filter, power amp and cabinet to be "static" gear, ie I will always use them in my chain. If I want to change my tone it all happens before the filter.
    2. If I need more volume I can simply add a fEARful 15sub, or actually any fEARful cab.
    3. The DI signal going to FOH is the same as what goes to my power amp / cab setup, and my amp and cab sound a lot like what the FOH will, so the onstage sound is very similar if not identical to what the audience hears.
    4. (really a side-effect of 1) Preamps, tone shaping pedals, etc. cost less than heads and cabinets, so I have more tonal options for less money.
  3. Mostly the rack of stuff to cart about.

    Bridging a large power amp into a monster amp can be a problem for your cabs!
  4. Gabriel51


    Sep 30, 2008
    I use an tube preamp into a Crown XLS bridged, it's a very good combination and the amp only weighs about 10 Lbs and has a lot of head room plus you can by-amp with this set-up if you desire to.
    There is not any real down side except the set-up is a little larger, I use a three space rack case because I have a Korg tuner also.
  5. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    * Carrying a larger piece of gear (although not necessarily that heavy)
    * Not that many innexpensive pre-amps to choose from
    * Not as necessary these days as so many regular or micro amps now available with 500 - 1,000 honest watts

    That being said, I do have an Ampeg tube pre w/ an old school lead sled amp; lovely tone but too heavy
  6. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    True. It can make for a heavy box which is why I carry a handtruck. On the plus side, I can power any cab thrown at me and roll preamps thru (I have 3) as my taste dictates. Used preamps are a good value and secondhand power amps can be had for cheap if you search locally.

  7. Gabriel51


    Sep 30, 2008
    Class D amps are very light.
  8. scowboy

    scowboy Supporting Member

    Jun 9, 2006
    Sacramento area
    My only amp at this point is an amp/preamp setup. Not for lack of trying others but when I bring this rig out it brings on lots of positive comments. I'd love to add a few more preamps to my herd also so I can adapt as my tastes or tonal mood changes. I love the Navigator though it's got all the right stuff for this player.

    Total weight is about 25 pounds.
  9. amimbari


    May 6, 2008
    Pittsburgh, PA
    25 lbs? that Eden must weigh 10lbs by itself.
    My whole box weighs 23lbs.
    people tend to forget that running a poweramp in stereo at 8ohms is usually only a few hundred watts, it's only when bridged that the real watts are produced for that fun driver damaging area you want to avoid.
  10. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    Most speaker failures are caused by UNDERPOWERED power amps. I use a 3000 watt amp to drive a cab rated at 500 watts and have never had a problem. Power amp clipping is what usually blows speakers and that happens when you run out of headroom.

    I have a four space rack that has an Alembic F-1X, SWR Grand Prix and a QSC PLX 3002. When I need a powerful rig, this delivers and I choose the preamp that best fits the gig.

    I usually use a Shuttle 9.0. Easier to carry and sounds lovely.

  11. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    You've been a member here since 2000 and you still believe that underpowering kills speakers? :crying:
  12. I should probably do a search but how would under powering a speaker hurt it. All your doing is not using it. Does letting it sit there hurt it? Not a serious question.
  13. Gabriel51


    Sep 30, 2008
    That's not what he said; Over driving a speaker with an under powered amp can/will harm a speaker.
    But you already knew that right?
  14. Right but lets look at the competition of sub 30 pound amps. There are a slew of 500 watt or so micros out there. These are ratings at 4 Ohms, the 8 Ohm ratings are anywhere from 275-350 watts. Thats right around where my Peavey IPR 1600 is on one channel (for both impedances actually). But what have I gained? Each of those channels is 2 Ohm stable. I can run 3 or 4 of those 8 Ohm cabs per side. Yes there are more powerful heads out there in the weight class, but how many of them are as versatile in power options?

    If one does have a cab that can handle some serious power and bridging might happen (I do both at 8 and 4 Ohms), then just like with any other set up some commons sense and listening to your drivers for sounds of distress is in order. Anyone that over powers their speakers isnt actually listening to what they are playing, or is using so many effects that it is masking the sounds of the cab being pushed past its limits.
  15. So wait... are you under or over powering the speaker?

    And if this is the case why are so many guitar players using over drive and not damaging their speakers?

    regardless of the amps rated power what happens is the driver is pushed past its mechanical limits. Can you do this with low power amp that is being pushed into clipping? Yes, but here is something to take into consideration. A 100 watt amp is rated so at some Total Harmonic Distortion level. Some of those levels are pretty low. This doesnt mean that the amp cant produce more power than 100 watts, just that it wont do so cleanly. Once you get into some level of distortion, the sound of the distortion can cover up the sound of your driver failing.
  16. chadds


    Mar 18, 2000
    A downside is that an integrated head has a perfect match between it's pre and it's amp. Voltage, level and impedance all agree.
    With a pre and power amp you select the power amp with an input sensitivity appropriate for your preamp. (not so difficult)
    You set your levels, input gain of pre, output level of pre, input attenuators of power amp for best signal to noise ratio.
  17. +1 This is key, and many end up very disappointed that their 'monster rack rig' doesn't sound as good/loud/full as an integrated bass head that is 1/4 the size and weight and absolute power.

    Also, the 'voicing' of various preamp/power amp combinations can be problematic if the user doesn't understand hi pass filtering, etc.

    Finally, massive power, at best might give you a touch more headroom than 'big power', at worst, might result in driver failure when pushed. It is an unusual cab or cab combination that can really use more than a true, honest 500-600 watts.
  18. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    Or, for that same 7 pounds, I got the IPR 3000. It's 460w at 8ohms per side, and just under 1000w @4ohms per side, and 1490w @2ohms per side. Bridged it gives me 2980w at 4ohms. I don't know of any bass amp that can provide that for me. Or the flexibility to run my cabinets in any configuration (2 on one channel, or one on each channel, or bridged).

    Right now I'm underpowering them because my amp isn't even turned on. :bawl:

    Bass gear making folks and power amp folks don't seem to have gotten on the same page very well do they? That leaves it up to the bass players to figure out if their preamps will produce enough level for their power amps. That can be a crap shoot, as input sensitivity is all over the place with no standard. Many bass players don't understand input sensitivity nor output levels with the amount of detail that it might take to pair your components well. One of the reasons I chose the IPR 3000 was that it had an extremely low sensitivity compared to what else is around in that price range...knowing that it should be good for most preamps.
  19. Gabriel51


    Sep 30, 2008
    Really? Really?
    The term originated when we all ran tube type amps and it refers to overdriving the input stages of the amp.
    Using any type of overdrive is not at all the same as having an overdriven output stage that causes the driver to exceed it's excursion limits, not mention excessive coil winding current and heat related to square waves.
    Like a lot of threads here, some comments stray far from the topic.
    I think I will unsubscribe at this point, have fun, I'm done!
  20. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    No, I don't believe that clipping kills speakers, I KNOW that clipping kills speakers and that is what happens when you drive a power amp too hard.

    A power amp can only amplify to its design limits. Let's say that it can produce minus 15 volts to plus 15 volts. If your preamp drives it to the point where the clean signal would be minus 20 volts to plus 20 volts the power amp cannot put out that level so the signal is clipped at plus/minus 15 volts. That causes your nice rounded signal to clip or become flat at the limits of the power amp.

    Think about what that does to the speaker. The cone is moving in a direction and has to stop abruptly and this causes overheating of the voice coil and can physically damage the cone.

    Yes, I have been a member here since 2000 which is about when I got a computer. I have also played bass since 1958 and am an old dude who also worked for years in electronics.


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