Ohm mismatches....
OK I know you can do 4ohm out into an 8 or 16 cab, but Ive got 2 4ohm outs on the back can I run one int oa 4 ohm cab and one into an 8 ohm cab simultaniously???
Don't let somebody elses world make yours unhappy...
It is always a bit ambiguous... In all probability, the *total* load must not be less than 4ohms - ie. 1x 4ohm cab, or 2 x 8ohm cabs (that's why there are two holes...)
(That is, unless you *know* the amp will drive 2ohms.... in which case it will take 2 x 4ohm cabs...)
edit: I'm assuming you are tallking about a solid-state amp here...
Last edited by AlanP2008; 3rd February 2010 at 06:35 PM.
1985 Sunburst Fenix Strat (Wez'd neck), 1991 Pacific Blue Levinson Blade JM/L,
2009 Sunburst US Delux Strat, 2009 Honeyburst quilted maple TelePartsCaster
2000 Candy Apple Red Deluxe Active Jazz Bass
Hot Rod DeVille
It kinda depends on the type of amp, the rated outputs, how they're configured etc
It will really help if you can tell us the make and model of the amp.
Originally Posted by nocaster
"It will really help if you can tell us the make and model of the amp."
Yes! Really!!!! in fact that information is vital and future posters please note an answer CANNOT be given without it!...........However........
Valve amps: Load within 25% of tapping value is safest. If you must, running a lower speaker impedance on the next tap UP is ok but with big amps, say 50W and up expect a fuse to pop now and again and valves to age faster.
E.G. amp set 16R load 8R ok.ish
amp set 8R load 4 ok, again ish.
amp set 4R load 8 or 16 not a good idea.
And for completeness. If you want to run bass guitar thru' a lead valve guitar amp, ok at bedroom levels but don't gig it.
Transistor amp: Max power is transferred usually when the load is at the lowest R suggested by The Book. Normally this will be 4Ohms but biggger, usually bass/PA amps will drive 2 Ohms..BUT ONLY IF IT SAYS YOU CAN!
You can take MODERN sstate amps as 4Ohm capable( and if they are of ANY kind of quality, bombproof) but many older tranny amps were rated only down to 8Ohms. I have a 100W (dream on!) TUAC so rated and my son's Traynor combo was 8R only.
If a tranny combo does not have an extension speaker socket you delve and connect at the amps peril.
Higher loads than 8 can be safely driven with power loss but DO NOT assume a sstate amp will live if you take the load off at full drive! Always, with ANY kit, plug up dead, re check, vols at min, turn on, advance vols' slowly watch for smoke!............And buy a cheap continuity/test meter f.c.s!
Do not, under any circumstances connect large low R transformers to the output of amplifiers. This is especially so for transistor amps.
Dave.
Its a boogie express...
Don't let somebody elses world make yours unhappy...
Then the easy answer is... do you really want to have to pay for a new output transformer at official boogie prices.
Sibella: He says he wants to go to Europe to expand his mind.Louis: He certainly has room to do so.
Doesn't Dusty Hill, bass in ZZ Top use three JCM900's and cabs as his live rig? Not arguing with your science, just wondered how he get's away with it.
Don't worry about the world coming to an end today. It's already tomorrow in Australia.
"Doesn't Dusty Hill, bass in ZZ Top use three JCM900's and cabs as his live rig? Not arguing with your science, just wondered how he get's away with it."
Three is the clue! He has the headroom and no individual amp is being stressed too badly.
All this "mismatching" and general naughtyness is level dependant and also ultimately goverened by the quality of the amp.
I dare bet a "certain" 200watter would make a perfectly fine bass amp, might pop the odd anode supply fuse! Iwould still rather lug 500W of sstate for bass, preff' class "D" with SMPS!
Dave.
ohm are for what?
Kosher Wedding
I found this link to be useful: http://www.marktaw.com/recording/Ele...dSpeakers.html
Seems my band mate hasn't had much luck with his EVH 5150 III (Fender, isn't it?). A power interruption turned the power off and on quickly the other week after everyone else in the band had left, and he said the amp seemed to work fine afterwards (my Peavey 5150 mkI blew a fuse when that happened to me once), but then I think he plugged into a 4R cab and an 8R at the same time. I don't know what he set the amp to (our amps have 2 taps, switchable to 16, 8 or 4 Ohms) but my sums work out a resistance of 2.666 which would be too low even for the 25% margin of error if the head was set to 4 Ohms. Oops.
It still worked, but with a dramatic loss of volume, and I think gain too. I think at least two of his power tubes were poorly, and I don't know if his preamp was affected or not.
Even before all the power cuts and dual mismatched cab issues though, the amp would make weird squeaking when not playing anything. It didn't sound like microphonic tubes.
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