Crate gx-1200h

[Gunn_Slinger]

Hi guys
While im tearing apart my vox....got a question about a crate gx-1200h i picked uo cheep.
It says that the speaker out can work into a load as small as 4 ohms, yet it is rated at 70 watts in 8 ohms and 100 watts into 4 ohms.

I know tube amps need to impedence match but can solid state amps output into anything 4 ohms or higher??
This was a no-no in my day
thanks for any info
Clay


and yes my avatar is a 1959 gretsch chet atkins country gentleman, 1 owner since 59....me...lol
later ace i got to go

[Enzo]

It was never a no no. SOlid state amps put out a signal voltage, and the load draws the current it needs. The lower the impedance, the higher the current for a given voltage out. SO if an 8 ohm speaker draws 25 watts from an amp, leaving all the controls alone, if you swap a 4 ohm speaker into it, then the amp will produce 50 watts.

There will always be a limit to the current the thing can source for your load, and that translates into a minimum load impedance. If you go below that, then the amp will overheat, possibly burn up, go into shutdown, whatever - nothing good. But any higher impedance load will simple draw less current and the amp is happy as a clam.

In a practical world, the direct proportion won't extend to the limits, so instead of a 140 watt rating at 4 ohms, it is derated to 100.

If you leave the load off a solid state amp and crank it to the max, it will produce no output power. it will still use some power from the mains, but until there is a load, no output. Unlike a tube amp, it is perfectly OK to run it loadless, something we do on the bench all the time.

YOu may safely operate this amp into any load from 4 ohms up to an open circuit.

[Gunn_Slinger]

thanks Enzo
In my day we only had tubes until i think 1960 when i built my first and only solid state guitar amp.
Never knew that it would work into different loads, As you say, tubes dont like mis-matched impedence.
well, back to the vox tear down...lol
thanks again
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