James901 Posted November 24, 2012 Share Posted November 24, 2012 Hey I'm looking for a little bit of advice. I'm looking to buy a Sansamp RBI to use as a preamp alongside a power amp which will be connected straight to a cab. The only thing i'm finding is that most power amps tend to be 1000w+ which a standard 410 cab rated around 500w wouldn't be able to handle. Any advice on this? Much appreciated. Quote Link to comment Share on other sites More sharing options...
BassPimp66 Posted November 24, 2012 Share Posted November 24, 2012 It's not a problem if your amp rates higher than your cab. Just don't push the amp all the way and listened to any sign of the speakers being worked too hard. Quote Link to comment Share on other sites More sharing options...
James901 Posted November 24, 2012 Author Share Posted November 24, 2012 Cool. I think I just like the assurance that I couldn't drive the cab too hard. Could you recommend any reasonably priced power amps? Thanks for the advice. Quote Link to comment Share on other sites More sharing options...
dincz Posted November 24, 2012 Share Posted November 24, 2012 Is light weight important? Quote Link to comment Share on other sites More sharing options...
MarshallBTB Posted November 24, 2012 Share Posted November 24, 2012 I use an Ashdown LG1000 as a power amp, run my Pod X3 Live into the line in, works well for me. Small, lightweight and only 200 odd new from thomann. Comes with rack ears as well! Quote Link to comment Share on other sites More sharing options...
BassPimp66 Posted November 24, 2012 Share Posted November 24, 2012 Define "[color=#282828][font=helvetica, arial, sans-serif]reasonably priced".[/font][/color] Quote Link to comment Share on other sites More sharing options...
Jack Posted November 24, 2012 Share Posted November 24, 2012 The Peavey IPS stuff is great, but a lot of people are looking at far eastern brands and doing very well. There's some brand beginning with W that keeps getting recommended all over the place. Obviously not enough because I can't remember the name. If weight isn't an issue then there are bargains to be had on ebay with old lead sleds. Everybody is downsizing, reap the rewards! Crest, Crown, QSC, Peavey, Powersoft, Yamaha. They're the top-flight brands to various degrees. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted November 25, 2012 Share Posted November 25, 2012 [quote name='jimi_1985' timestamp='1353761636' post='1878179'] Cool. I think I just like the assurance that I couldn't drive the cab too hard. Could you recommend any reasonably priced power amps? Thanks for the advice. [/quote] Doesn't really work like that. You can drive an amp too hard with an amp with a lower watt rating, because that isn't the thing that drives amps too hard. Quote Link to comment Share on other sites More sharing options...
skidder652003 Posted November 25, 2012 Share Posted November 25, 2012 (edited) [quote name='Mr. Foxen' timestamp='1353810232' post='1878710'] Doesn't really work like that. You can drive an amp too hard with an amp with a lower watt rating, because that isn't the thing that drives amps too hard. [/quote] im confused, are there some spelling mistakes here? shouldn't Jimi-1985 have said he likes the assurance that he[b] shouldn't [/b]drive the cab too hard? He should be ok with a 1000w power amp if he's careful not to drive the cabs too hard shouldn't he? Edited November 25, 2012 by skidder652003 Quote Link to comment Share on other sites More sharing options...
BassPimp66 Posted November 25, 2012 Share Posted November 25, 2012 [quote name='skidder652003' timestamp='1353830704' post='1878727'] im confused, are there some spelling mistakes here? shouldn't Jimi-1985 have said he likes the assurance that he[b] shouldn't [/b]drive the cab too hard? He should be ok with a 1000w power amp if he's careful not to drive the cabs too hard shouldn't he? [/quote][quote name='Mr. Foxen' timestamp='1353810232' post='1878710'] Doesn't really work like that. You can drive an amp too hard with an amp with a lower watt rating, because that isn't the thing that drives amps too hard. [/quote] What is meant here is: small amp wattage + big speaker wattage = DANGER for the amp. If you try to drive a 500W cabinet, with a 10 W amp, the amp may burn/explode/disintegrate trying to keep up. However, if you have bigger amp wattage , say 1000W amp, compared to 500W cabinet, that's fine. Quote Link to comment Share on other sites More sharing options...
skidder652003 Posted November 25, 2012 Share Posted November 25, 2012 thats what i thought Quote Link to comment Share on other sites More sharing options...
PlungerModerno Posted November 25, 2012 Share Posted November 25, 2012 (edited) [quote name='BassPimp66' timestamp='1353833327' post='1878749'] What is meant here is: small amp wattage + big speaker wattage = DANGER for the amp. If you try to drive a 500W cabinet, with a 10 W amp, the amp may burn/explode/disintegrate trying to keep up. However, if you have bigger amp wattage , say 1000W amp, compared to 500W cabinet, that's fine. [/quote] I thought that with the master and gain etc. 'volume' controls you were regulating the voltage reaching the output of the power amp . . . which controlled the watts or power reaching connected cabs . . . meaning you can send 10W from a 1000W head to a 500W cab when keeping the output low. Is this the underpowering mullarkey? Don't you have to damage or totally overdrive a poweramp to get far over the specced output at a heightened distortion level . . . which can send too much power to a cab and blow speakers? That's the gist I get from reading engineers discussing this kind of thing. I think this is useful: http://barefacedbass.com/uploads/BGM57,%20Aug2010.pdf Edited November 25, 2012 by PlungerModerno Quote Link to comment Share on other sites More sharing options...
3below Posted November 25, 2012 Share Posted November 25, 2012 (edited) [quote name='BassPimp66' timestamp='1353833327' post='1878749'] If you try to drive a 500W cabinet, with a 10 W amp, the amp may burn/explode/disintegrate trying to keep up. [/quote] The speaker is rated to thermally disspate 500W, it does not demand 500W from the amplifier. The 10W amplifier is rated to supply 10W (rms, AES, peak, phony Watts, makebelieve Watts, whatever) to the speaker. If the amplifier burns/explodes/disintegrates it is either due to a fault condition or poor design engineering and implementation, i.e. unable to operate at maximum power. Edited November 25, 2012 by 3below Quote Link to comment Share on other sites More sharing options...
James901 Posted November 25, 2012 Author Share Posted November 25, 2012 Thanks very much for the advice guys. I'll probably opt for an Ashdown or Peavey pre-amp as there are some good deals going at the moment. I hope I reap the benefits from changing my set up this way. At the moment I have a 550w head and an 800w cab. Changing to the 1000w pre-amp should hopefully work out ok. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted November 25, 2012 Share Posted November 25, 2012 [quote name='BassPimp66' timestamp='1353833327' post='1878749'] What is meant here is: small amp wattage + big speaker wattage = DANGER for the amp. If you try to drive a 500W cabinet, with a 10 W amp, the amp may burn/explode/disintegrate trying to keep up. However, if you have bigger amp wattage , say 1000W amp, compared to 500W cabinet, that's fine. [/quote] That isn't what I mean. You can put a 10w amp into a 500w cab fine, you can put any amp into any cab fine. But the cab can't handle 500w thermal rating, because thermal ratings are not the place where amp power breaks cabs, the excursion limit is where bass guitar breaks cabs, and that is about a quarter to a half of the thermal rating in the passband of a cab, and less outside it, and it is easy to be outside it with silly eq. Thermal ratings of cab are pretty much meaningless, and should be ignored. Quote Link to comment Share on other sites More sharing options...
Mikey R Posted November 25, 2012 Share Posted November 25, 2012 [quote name='BassPimp66' timestamp='1353833327' post='1878749'] What is meant here is: small amp wattage + big speaker wattage = DANGER for the amp. If you try to drive a 500W cabinet, with a 10 W amp, the amp may burn/explode/disintegrate trying to keep up. [/quote] I dont know how this myth got started - please could everyone stop saying this please. Quote Link to comment Share on other sites More sharing options...
dincz Posted November 25, 2012 Share Posted November 25, 2012 Driving at 30mph on tyres rated for 150mph is equally dangerous - i.e. zero danger in both cases. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted November 25, 2012 Share Posted November 25, 2012 [quote name='jimi_1985' timestamp='1353844431' post='1878860'] At the moment I have a 550w head and an 800w cab. Changing to the 1000w pre-amp should hopefully work out ok. [/quote] If you are changing your set-up for the extra watts; stop NOW! You won't generally be able to get any more volume out of a 1000 watt amp than you are getting out of a 500 watt. Have a look in the stickie section for clarification. However... if you are changing for other reasons then I may well have a QSC power amp for sale that would suit your needs (I also have a preamp but it isn't a cheapie one). Quote Link to comment Share on other sites More sharing options...
Guest bassman7755 Posted November 25, 2012 Share Posted November 25, 2012 (edited) [quote name='PlungerModerno' timestamp='1353840482' post='1878820'] Is this the underpowering mullarkey? Don't you have to damage or totally overdrive a poweramp to get far over the specced output at a heightened distortion level . . . which can send too much power to a cab and blow speakers? That's the gist I get from reading engineers discussing this kind of thing. [/quote] Agreed (I think) ... its hard clipping distortion from an over stressed amp that damages speakers. The higher rating your amp - the less likely you are to ever get this [b]for a given volume level.[/b] Ergo ... [b]use the highest rated amp that you can afford irrespective of the speaker rating[/b]. Well within reason anyway, certainly its quite common to over spec the amp by 1.5 - 2 times the speaker nominal handling. Counter intuitive I know but you shouldn't be selecting a deliberately low powered amp in some misguided attempt to "protect" your speakers. In terms of specific amp recommendations "pro" PA amps such as Crown and QSC are generally usually the weapons of choice for a hand picked separates setup. Look for a high damping factor, Both Crown and QSC amps for example usually have > 500. For a 500 w speaker personally I'd be looking for an amp at in the 1200-1800 w range as ideally you want to be running the amp at no more than 1/3rd power in order to get the cleanest sound (you want to get all your "tone" from the sansamp, not from the poweramp). Something like a QSC plx1802 or Crown XLS 1500 or if your on a very tight budget the behringer NU3000 Edited November 25, 2012 by bassman7755 Quote Link to comment Share on other sites More sharing options...
WinterMute Posted November 25, 2012 Share Posted November 25, 2012 I have a crown XTi1000, got it off ebay for £250.... 1400w bridged into mono. The Behringers are a good bet if you can get over the name and the fact they weigh nothing, just don't trust the posted number on their outputs. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted November 26, 2012 Share Posted November 26, 2012 Please will people stop repeating the myth that low power amps are more likely to damage speakers than high power ones. It has no basis in fact or any scientific justification. If a 500W speaker is driven by a 100W amp there is no way it can be blown by the electrical power. If a 500W speaker is driven by a 500W amp it is only under rare conditions that it can be blown by the electrical power alone. If a 500W speaker is driven by a 2000W amp it would be relatively easy to blow with electrical power, Though not easy if you actually played undistorted music through it. Even the Xmax thing is a bit of a red herring. Speakers coils don't leave the magnet gap at Xmax, they just leave the linear bit of the magnetic field into the less linear bit. At the limits of their movement prudent designers will restrict the free movement of the cone so that it will return correctly to its resting position. It will distort, make a nasty noise if it hits the back of the magnet, it won't give you any extra useful sound but by and large it won't break unless you go on doing it for a long time and depending upon the design sometimes not even then. Speakers mainly break through wear and tear, sometimes through manufacturing faults and very rarely through burning out or over excursion. The myth about lower power amps damaging speakers started in the 60's when amplified music first hit the mainstream. The speakers of the day were unsuitable for the high power involved and weren't rated for instrument use. Coils were wound on paper formers and ordinary household adhesives used to stick them in place. The heat form the coils soon melted the glues and distorted the paper formers so the coils shorted against the magnet and the current increased burning the coils out. Amps can give 1.414 (the square root of two) times their rating in electrical power if their power supply is up to it with the extra 0.414 being distortion. Guitarists introduced very high levels of distortion at the time by overdriving their amps at full power which did blow the speakers of the time. Bassists didn't do this anyway. I'll repeat, the main causes of speaker failure are wear and tear and manufacturing faults. Obviously the more often you play it and the harder you push it the quicker it will fail but a sudden catastrophic failure of a new speaker due to the amp being too big or Xmax being too small is rare to vanishing. I hate it when something said in one forum or said by a salesman in a shop gets repeated as well meaning advice on the internet. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted November 26, 2012 Share Posted November 26, 2012 Oh the exception to this is the compression drivers on high frequency horns. These have a low thermal power rating usually 20-50W and are often built into 3-400W speaker systems and driven by 300W amps. Distortion is effectively extra high power energy and so burnt out compression drivers aren't unusual. Driving a 20W driver with a 300W amp in the expectation that only 10% of the sound is high frequency doesn't always work. Quote Link to comment Share on other sites More sharing options...
dincz Posted November 26, 2012 Share Posted November 26, 2012 [quote name='WinterMute' timestamp='1353874040' post='1879266']The Behringers are a good bet if you can get over the name and the fact they weigh nothing, just don't trust the posted number on their outputs. [/quote] To be fair to Behringer, they do list both RMS and peak power figures - at least for their power amps, but not for guitar/bass amps. Quote Link to comment Share on other sites More sharing options...
BassPimp66 Posted November 26, 2012 Share Posted November 26, 2012 Can you damage an [u]amplifier[/u] when pairing a small wattage amp with a big wattage cab? YES/NO I am not mentioning speaker damages here or tales from 60's. Just asking about damaging the amp. Quote Link to comment Share on other sites More sharing options...
dincz Posted November 26, 2012 Share Posted November 26, 2012 (edited) [quote name='BassPimp66' timestamp='1353962732' post='1880355'] Can you damage an [u]amplifier[/u] when pairing a small wattage amp with a big wattage cab? YES/NO I am not mentioning speaker damages here or tales from 60's. Just asking about damaging the amp. [/quote] No, and just to be sure, no again. The amp's power rating tells you how much it can deliver. The cab's power rating tells you how much it will accept - just like maximum speed ratings on tyres, there's no problem for the car or the tyres if you choose to only drive slowly. By the way, it was the same in the 60's and in the 20's for that matter. Edited November 26, 2012 by dincz Quote Link to comment Share on other sites More sharing options...
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