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Quick question.
| Message Board > Gear Buy & Sell > Quick question. |
| almix12 User Info... | I just gotta ampeg SVT-3 pro which I have a question about. I'm running it through a ampeg 410. the amp has 2 quarter inch output jacks and a banana plug (old speakeon pretty much). It's rated at 275w @ 8 ohm and 450w @ 4 ohms. As far as i know my cab can go down to 4 ohms. Can i/am I getting the full 450w running one quarter inch speaker cable from one of the outputs on the amp to one of the inputs on my cab? If i'm not (so i'm only getting the 275) how can i get the full volume? - Thu, 20 Dec 2007 2:06am | ||
| ::Saint:: User Info... | The cabinet is either 8ohm or 4ohm, it doesn't "go all the way down to 4ohm", it's just one or the other, as decided by manufacturer. It'll be the amp that can go between impedances. But basically, if your amp is rated at 450w @ 4ohms, and your cabinet is 4ohms, then you'll be getting the full 450w. If your cabinet is rated at 8ohms then you'll be getting 275. I don't believe it matters which plug you use. Most 4X10 cabs at 8ohm, though, with a few exceptions among the Ampeg models that are actually 4ohms. - Thu, 20 Dec 2007 8:51am | ||
| almix12 User Info... | Right thanks. So if I was going to use both quarter inch outputs and the banana plug could i use them all at the same time for 3 cabs? how many ohms would it... put out then? - Thu, 20 Dec 2007 2:38pm | ||
| ::Saint:: User Info... | Well.. I don't think most amps are designed to run three cabs at a time, though I suppose it might be theoretically possible if all three amps were like.. I dunno.. 16 ohms each or something. Most amps are unstable under 4ohms, though .. so you'd want to be careful what you plug in. 2 8ohm cabs would be fine. If your amp goes down to 2ohm, which some do, you could get away with 2 4ohm cabs.. so I guess potentially you might be able to get away with 3 8ohm cabs.. providing it will even use all three outputs at the same time. The impedance out of 3 8ohm speakers is 2.667 ohms .. so I guess in theory you'd be able to run that on a 2ohm amp. The upshot is that if you were able to run at 2ohms you'd get a lot more wattage out of that amp. If it's 450w@4ohm, you'd probably be up to 700+ @2ohm. I wouldn't really bank on it working though. Best bet is to go with 1 4ohm cab or 2 8ohm cabs. And don't try running at below 4ohm unless you check the amp first to make sure it can do that. - Thu, 20 Dec 2007 2:56pm | ||
| almix12 User Info... | Hm, thanks for the info. It just seems like the amp is really quiet for 450 watts when its plugged into my definitely 4 ohm cab (checked it out). so you're sure if i took 2 cables from the quarter inch outputs to both inputs of my cab it wouldn't... activate so to speak so extra wattage since its a 4 ohm cab? meaning each quarter inch output would be 8 ohms? possible? - Thu, 20 Dec 2007 10:12pm | ||
| ::Saint:: User Info... | Well.. you could try it, I guess. I've never heard of anyone needing to do it this way. Maybe give the bass department at Long & McQuade and see what they have to say about it. Is the amp new or used? Tube or SS? If it is tube, you might have a tube issue going on.. - Fri, 21 Dec 2007 8:30am | ||
| ::Saint:: User Info... | I'd also recommend registering at talkbass.com .. there is an incredible amount of resources on that forum that I have gotten all kinds of good info about any product you can imagine. - Fri, 21 Dec 2007 8:44am | ||
| almix12 User Info... | It's got a tube pre-amp and solid state/MOSFET power amp. I'll try the talkbass forums thanks a lot! - Fri, 21 Dec 2007 12:33pm | ||
| superslacks User Info... | I hate poking my nose into this private conversation, but I'd hate for you to cook your amp . . . . . Most of the info above is bunk. Impedance of multiple speakers depends on the wiring config. Also, the amp cannot deliver any more power just because you drop the impedance. If you try to to mess with it that way you could fry it. If your amp sounds quiet, there could be something wrong, get someone who knows about these things to check it out. - Fri, 21 Dec 2007 3:31pm | ||
| superslacks User Info... | OK, go here for the user's manual . . . http://www.ampeg.com/pdf/SVT-3PRO.pdf If you know your cab is definitely 4ohms, then maybe look into these things; Are all the speakers working? Try a more robust speaker cable. Use the "speakon" jack, which supposedly is better for higher outputs. outside of those suggestions, you might need to have the head serviced. Good luck. - Fri, 21 Dec 2007 4:25pm | ||
| ::Saint:: User Info... | "Most of the info above is bunk." It is not bunk! Yes, you WILL get more power out of an amp at lower impedance - it's the reason that amp rated at 450W@4ohms only puts out 275W@8ohms. The same logic DOES apply down to whatever impedance the amp is rated to run at. I also said he should check the amp before trying to run it at 2ohm, as YES, if it isn't designed to run that low, he can cook it. But, should it be able to run at 2ohms, he will get more power out of it. This is not "messing with it", this is the way amps are designed to work. Case in point, my MarkBass SA450 is rated at 500 watts, at 4ohms. Right now I've got 1 8ohm cabinet hooked up to it, therefore I am only getting 300 watts. If I were to hook up a second 8ohm cabinet, or a different, 4ohm cabinet, I'll get more power out of the amp. That is how it is meant to be run. The reason I brought up the possibility of running his ampeg at 2ohm is because there are some amps that can run that low, would, indeed, provide a bump in power. The Mesa Big Block (for example)is rated at 700 or 750 Watts (can't remember which off hand), but only because it is stable down to 2ohm - at 4ohm you get something like 400-450. And how does wiring config come into play - he's not hooking up individual speakers to the amp, he's hooking up a bass cabinet, rated at 4ohms. Providing it hasn't been modified and isn't broken, the wiring doesn't matter. The cab is 4ohm, therefore his amp is going to put 450W into it. Your other suggestions are quite right, if a little bit obvious. Of course, if the cabinet is broken it isn't going to sound as loud :/ Cables MIGHT make a difference to the volume, but I doubt it would be dramatic.. as long as he is using a speaker cable and not a patch cable (you ARE using a speaker cable, right?). I've heard that Speakons have the same conductivity as a regular 1/4" plug .. the only difference is that the jack is more secure and doesn't rip out as easily, and in some amps allows for bi-amping (i.e. Gallien-Krueger's Horn Management System). - Fri, 21 Dec 2007 4:55pm | ||
| almix12 User Info... | I agree with saint. slacks, my cab is fine, i just upgraded from a gallien krueger that was 300w at 4 ohms and was louder than i can push this one which makes no sense. yes i'm using speaker cable... a beefy one at that. If i was going to use speakeon i'd have to get a banana plug-->speakeon cable which are hard to find/expensive. My amp is only supposed to be at 4 ohms at the lowest. putting out 475 and ya my cab can handle 500 at 4 ohms. so no 2 ohm anything here. I suppose i'll get it checked out if i don't get this sorted by asking at the talk bass forums. like 275 watts isn't all that bad (if that is in fact what i'm getting) just would be nice to have the extra headroom if i needed to say... play a small stadium with no PA?? haha or you know... times will arise when it'll be a bother. - Fri, 21 Dec 2007 6:19pm | ||
| Tambo User Info... | well, I had a 400 watt solid state head, and I never got it past about 7 before it was DEFINATELY loud enough. I'd get the head checked out, sounds fishy. - Fri, 21 Dec 2007 6:32pm | ||
| superslacks User Info... | Sorry, Saint, if my reaction seemed harsh, I just didn't want someone using bad info and killing his amp. To answer you comment that wiring makes no difference; if you're using 3 cabs (as was being discussed) it sure as shit WILL matter if you connect them in series, parallel, or series-parallel. (ie. the difference between 24ohms and less than 3). And the problem with connecting a load that has an impedance below what the amp can deliver, is that the power devices (in this case MOSFETs) try to deliver more current than they should, which causes them to either over heat, or affects the power supply when it can't deliver enough voltage to sustain the demand. There are so many things wrong with suggesting anyone run an amp below it's rated impedance, all I can say is read a book. Its basic physics, you can't create power out of thin air. Sorry to burst your bubble. ;-) . . . . and if you think asking obvious questions is a problem, you obviously haven't done very much troubleshooting. - Fri, 21 Dec 2007 11:11pm | ||
| almix12 User Info... | Well would it have something to do with it being a tube pre-amp and the power amp being "mosfet"? I'm not very familiar with the technology. - Fri, 21 Dec 2007 11:12pm | ||
| Tambo User Info... | Seriously dude... Take it to a profesional. You're obviously not tight on a budget if you're owning an SVT-3 pro, it's just a matter of going down to L&M or wherever and asking them... It'll also be alot faster than posting on a message board and hopefully getting an answer from someone who you don't know if they're qualified to even answer your question. (not saying you guys aren't, just saying he doesn't know you...) That's what I would do at least... - Fri, 21 Dec 2007 11:25pm | ||
| superslacks User Info... | I'll second Tambo. If your speakers are fine and you're not using telephone wire to hook it up, it's probably time to take it in. Often it's something really simple and it just takes someone in the know to spot the problem. The only other thing I can think of to address is the tubes. Preamp tubes usually last a long time but OCCASIONALLY one can go flakey. You can have them tested (Pacific TV in Esquimalt) on your own before you take it in. It wouldn't hurt to eliminate that fro the possibilities, tho I'd be surprised if that was it. Your power section is solid state (that's the MOSFETs), which is generally quite robust. You can't check that on your own, but an electronics tech can. - Sat, 22 Dec 2007 12:16am | ||
| Aidan Logins User Info... | Turn up the good, turn down the suck. That oughta fix it. - Sat, 22 Dec 2007 9:35am | ||
| ::Saint:: User Info... | Yeah the 3 cab thing I wasn't really recommending ;) I just said it could be possible, but I certainly wouldn't do it! And of course, I wasn't recommending running it with more load than it is designed for, so you're absolutely right there. I was really just referring to standard amp / cab setup, i.e. 2 cabs, 2 cables.. nothing fancy. It sounds like a fishy head issue to me as well though.. I'm only getting 300 Watts out of my Markbass SA450 / Mesa PH 1x15, but it is plenty loud, and I've never had to crank it up past 7 either. Mind you I still want a Mesa 2x10 to put on top ;) - Sat, 22 Dec 2007 11:09am | ||
| superslacks User Info... | More voices (ie speakers) will always give you more sound, whether it's more volume or more broad range of frequencies. But the other thing to consider is if the cabinet is open (ported) or sealed. A sealed cab will generally be quieter due to the air resistance. Soooo . . . . if your amp checks out fine, maybe its your speakers that are giving you the perception of quiet? Sorry I don't know the cab you're using. Just a thought. If you're taking it in to L&M for repair (not sure that your best bet), maybe use the opportunity to try it out with other cabs and see if it makes a difference. - Sat, 22 Dec 2007 2:55pm | ||
| almix12 User Info... | i'm just hesitant to take it to be professionally fixed for the money factor. The cab is sealed. its a 410 HLF ampeg - Sat, 22 Dec 2007 4:21pm | ||
| IAN JOHNSON User Info... | Hey, this is ian johnson, i work in the bass dept at long and mcquade, if you want i can take a look at your head, also saint is pretty much spot on on the way bass amps ohms and watts work. dont plug three cabs in one head its a bad idea. the hlf is 4 ohms and can handle way more watts than the 3pro puts into it, so it should be plenty loud might be a problem with the preamp tube, also make sure you put mids in you eq. cutting the mids sounds great when ur playing by yourself it also takes away alot of audible freq when playing with a band, thus making your amp seem much less rocking! saint by the way i play an sa450 aswell it fucking kills eh! - Sat, 22 Dec 2007 7:14pm | ||
| almix12 User Info... | Hey Ian! It's alex who sold you guys the Gallien-Krueger 800RB like a month ago. I'll bring it in give or take a few days around the start of the new year. - Sun, 23 Dec 2007 5:16pm | ||
| ender60 User Info... | hooking 3 cabs up tp your amp will not be a prob providing the combined ohmage is not less than what your amp is rated for. my amp can handle 2 ohms so I'm safe with 3x8 ohm cabs,,1x4-2x8 ohm cabs,,, any combination not less than 2 ohms. if your not sure how to calculate ohmage this is a handy site http://www.sadowsky.com/audio/impedance.html I agree with pretty much everything saint says and sorry slacks,,,but I have to say your wrong on some points. any amp with a solidstate poweramp section WILL! put out more wattage when facing lower ohmage resistance. tube poweramps on the other hand, and this may be what slacks was thinking, do not change. A tube poweramp that is a 100 watts at 8 ohms will be 100 watts at 4,,,2,,,16 etc. you may be thinking COOL!! if this is the case 4 ohms will sound twice as loud as 8 ohms!! the sad and irritating truth is, twice the power only makes about a 3 decibel difference in volume. there are so many factors involved, speaker efficiency, cabinet design,,equalization,room characteristics etc etc. bottom line is,, as slacks said,,the only real way to increase sonic volume is to move more air, and the only way to do that is more speakers. thats my 2 cents!! - Sun, 20 Jan 2008 1:12am | ||
| superslacks User Info... | I thought this post died when almix said he was too cheap to have it fixed properly. Thanks for reminding me why I gave up servicing amps for the general public years ago! And, yes, I originally thought he had a tube power section. oops. Regardless, ANY amp loaded below it's rated impedance is a bad practice. But hey, feel free! I love buying people's busted shit for pennies on the dollar and fixing it! Just kidding . . . . - Mon, 21 Jan 2008 3:12pm | ||
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