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Thread: Poweramp with higher wattage output than speakers?

  1. #1
    snessiram is offline Newbie
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    Poweramp with higher wattage output than speakers?

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    Hi,

    There are lots and lots of discussions about the subject to be found about this subject on the internet and from what I've read, the basic rule is that the speaker wattage should either match or be higher than the poweramp wattage (rated for the load of the speakers off-course). For PA systems, it seems to be the other way around.

    My question now is if a poweramp with a higher wattage than the speakers can be used by controlling the poweramp's volume?

    I have an Orange PPC212-ob cabinet which is 120W at 16 Ohm.
    I'm interested in a Rocktron Velocity 300 solid-state poweramp which is rated at 170W at 16 Ohm.
    Can this combination be used by controlling the volume of the Velocity 300? And if yes, what is the relation between the volume knob and the output wattage? In other words: how far can the volume knob be turned without damaging the speakers?

    Btw, I know there's a lower specced Velocity 100 (which has no mono bridge and is missing definition and reactance controls) and an older Velocity 120 (which is missing the reactance control and seems hard to find) but the Velocity 300 seems superior...

  2. #2
    Jim Lad's Avatar
    Jim Lad is offline Why 2K?
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    Links to your specs would be a great help.
    Cheers ♫
    Jim

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    stevieb is offline Just another guy, really.
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    No doubt specs would be helpful, but in the meantime, let me try to answer in a general sense:

    It's the other way 'round for PA's because nothing destroys speakers faster or more sure than a heavily-clipping signal sent to them- they just go into spasm and come apart. Ouch.

    TUBE guitar amps are usually rated at "X" wattage, at the volume knob setting that still produces a clean signal. This harks back to the days when distortion was not fashionable. Thus, a Fender Twin might produce 100 watts at a vol. setting of 6 or 7, but dimed it is putting out more wattage, albeit a distorted sound. But, it is not "clipping," it's just "getting dirty," (I can't really explain the difference well enough to pass muster with the OCD types on this forum, but the heck with them and their issues,) so the amp does not destroy speakers. SS amps guitar amps are designed to replicate tube characteristics as much as possible, so they may behave in a similar manner- hard to say for sure, as different makers do that in different ways, and SS amps can come close, but not exactly, to tube performance. (I'll leave ragging on SS amps for someone else to do.)

    So, to answer your question as best I can: I would say that with the volume knob at somewhere between 7 and 10 (if the knobs are marked 0-10) would be full output. Only way to know for sure is to talk to someone at Rocktron who both knows and is willing to tell you (rather an esoteric question, likely most support people will not know, but will guess/try to answer as best they can,) or get some test equipment and find out for yourself.

    But, really, I see no need to worry: As stated in the manuf's websites, "The Velocity 300 provides 150 watts/channel when used in stereo applications," and "The PPC212-OB... can handle up to 120 watts of power" (presumably mono,) just use one half of the V300 into the two 12's in the Orange. The 30-watt difference should not cause any trouble.

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    Jim Lad's Avatar
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    Actually, the amp should be capable of delivering twice as much as the speakers are rated for.
    "Not enough power" is what destroys speakers.
    How about some links to your specs?
    Cheers ♫
    Jim

  5. #5
    Lt. Bob's Avatar
    Lt. Bob is offline Spread the Daf!
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    Quote Originally Posted by Jim Lad View Post
    Actually, the amp should be capable of delivering twice as much as the speakers are rated for.
    "Not enough power" is what destroys speakers.
    that's ONLY true if you turn the amp up to clipping levels in an attempt to get more volume than it's capable of.
    As long as you keep it clean a 'lower than speakers' rated for' amp won't damage a speaker at all.

    But I agree ..... I don't see a problem ...... it's unlikely that he's ever gonna have that amp constantly putting out 150 watts a side.
    If you know the secret codes you can get by the mastering boss on level 8.

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    bruiser1964 is offline Dedicated Member
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    From the Rocktron Site "The Velocity 300 provides 150 watts/channel when used in stereo applications or 300 watts mono bridged into a 8 ohm load" you wont get a 16ohm solid state amp.
    The square wave thing is largely regarded as a myth unless you are hammering your speakers and it applies to the horn (tweeter component)which the Orange doesn't have.There is no answer to "how far can you turn it up" if the amp and the cab are not miles apart in their stated specs it should work - turn it up until it sounds bad then back off 10%
    Cab specs are usually highly unreliable but tend to err on the side of caution.

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    gecko zzed's Avatar
    gecko zzed is offline audio illusion
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    You can, in most cases, safely use a power amp with double or even triple the speakers' rated handling.

    See this explanation from Crown:How much amplifier power do I need?
    http://homerecording.com/bbs/image.php?type=sigpic&userid=45599&dateline=1256715193
    I have a theory about that

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    ncguy77 is offline Registered User
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    For one thing, the square-ish edges of a clipped signal is loaded with unusually large energy at very high frequencies that will make short work of tweeters.

    So yes, more power in reserve helps prevents clipped signals. A speaker will handle a 200W clean transient sine wave much better than a clipped 100w signal.

  9. #9
    snessiram is offline Newbie
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    Thanks everyone for the answers!

    I actually rewired my cabinet to stereo, 60W @ 8 Ohms a side, and bought a Marshall 8008 which is also stereo, 80W @ 4 Ohm but around 55W @ 8 Ohm according to some internet sources. It felt like a better wattage match to me so I don't need to worry about overpowering the cab.

    However, for the sake of discussion, let me list the specs:
    Rocktron Velocity 300:
    - Stereo, 150W @ 4 Ohm
    - Stereo, 75W @ 8 Ohm
    - Stereo, 37.5W @ 16 Ohm
    - Mono, 300W @ 8 Ohm
    - Mono, 170W @ 16 Ohm

    Orange PPC212-OB:
    - Mono, 120W @ 16 Ohm
    - 2 Vintage 30 speakers: 60W @ 8 Ohm (so wired in series)

    So as you can see, in stereo mode using only one side, I would only get 37.5W, and in mono mode, I would get 170W, which is too much.

    When reading on the net about the wattage matching between amps and speakers, I came to the conclusion that generally speaking, guitar amps should be rated the same or lower as the speakers, while for PA amps, it is the other way around.

    With PA equipment you have the risk of driving the amp into clipping which could melt the speaker cones. So for PA, it is better for the amp to have a higher wattage rate and to not turn it up all the way (and thus keep a very clear signal).

    For guitar amps on the other side, it is better to have a lower wattage than the speakers. Especially for tube amps this seems to be true, as they can output a wattage that's far greater than what they are rated at. The sound would be distorted, but that is probably what most are looking for in tube amps :P. With tubes, there also is no risk for the clipping to melt the speaker cones as the current doesn't pass the tubes.

    I contacted Rocktron support by e-mail. Jim, a really nice guy, said that there's no direct relation between the volume knob and the output power, and that it depends a lot on the signal coming in. So, potentially, I could blow up my speakers if I turn the unit up too much.

    I also contacted some other knowledgeable people on the subject and they seemed to agree that there is the potential to blow up the speakers, and that there's no direct relation between the volume and the output power. However, they also seemed to agree that as long as you are careful with the volume knob and turn it down as soon as something doesn't sound right, it should be ok.

    In the end, I think that the poweramp can have a higher wattage than the speakers, as long as you use the volume sensible and don't drive the poweramp into distortion.

    Personally, I didn't feel confident enough that the Rocktron wouldn't blow up my speakers. It only takes one person to turn the volume up too high without me knowing and it could be too late.

    The Rocktron also has this nice "reactance" control, which gives it a more tube-like feeling. I really liked it, it gave this extra "umph", especially when you are playing damped power chords. But thos are low tones, which as far as I know produce the most power, so... high reactance with high volume = high output power = blown up speakers... I might be totally off base, but I didn't want to risk it.

    As the Rocktron unit I had was defect (after about 30 minutes, the volume suddenly went down and the ventilation never came on, even though it should according to Rocktron support), so I needed to send it back anyway, I decided to ask a refund and got the Marshall second hand. It doesn't have the reactance knob, but except for that I like it . It goes really loud, I haven't even put it past 1-2 yet (but band practice is only in a few days).

    Feel free to correct me on any of the statements I made, I'm no expert at all .
    Oh and for those wondering, I'm using the Marshall with a Digitech gsp-2101.

  10. #10
    MOFO Pro is offline Opinions are like SM-57s
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    You gave us all the specs for the Rocktron and then brought it back for the Marshall. I also don't know that saying the the volume knob has no direct relationship to power is accurate... I think I understand your meaning... but turning up the volume, turns up the wattage to the speakers, that's a pretty direct correlation. I think what you're implying is that 2 on a scale of 10 on a 100 watt amp is not necessarily a 20 watt output. The input has as much to do with the output as the volume control.
    It's not just the signal chain... It's the hands that touch it

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