Why is it that combos cant drive cabs?

[astrozombie]

Why it is that say, my peavey transtube 212 cant run my marshall cab?

or say, my MG50?

why doesnt it work?

i mean it does, but the volume is VERY low...

why?

 

[Rich_T]

Re: Why is it that combos cant drive cabs?

That shouldnt be the case. If your impedances match, and you are using the speaker out, then it should work fine.

 

[danglybanger]

Re: Why is it that combos cant drive cabs?

I do it. All the time. Plus it just looks more impressive to appear to have 2 4x12 amps on the stage

...(wish I didn't have to...) Check impedance

 

[Sludgenutz]

Re: Why is it that combos cant drive cabs?

Why it is that say, my peavey transtube 212 cant run my marshall cab?

or say, my MG50?

why doesnt it work?

i mean it does, but the volume is VERY low...

why?

The manufacturers are wisely protecting musicians from themselves! I assume those are both solid state amps. Solid State amps (and even home hi-fi stereo amps) are not affected by impedence mis-matches...as long as the speaker load is greater than that specified by the amp.

The external jack is likely wired in "series" to your combos internal speaker. Adding another cab just piles on a lot of impededance, which pulls down the amount of power that the amp can generate.

If the external speaker jack were wired "parallel", many users would would fry the amp, due to a mis-match where the impedence seen by the amp would be lower than what is was designed for.

 

[danglybanger]

Re: Why is it that combos cant drive cabs?

hmm... trying to figure on this...

I use a 4 ohm Solid State, 100 watt amp into a 4 ohm cabinet. I know I could use a cabinet with more ohmage, but I do just fine, and am plenty loud hooking the amp up to a cab.

So it's because I currently have no speakers at all (which is why I need the cab) in the amp then, so there's nothing else to pull it down.

 

[astrozombie]

Re: Why is it that combos cant drive cabs?

i tried the peavey again, it said 8 ohms minmum and the cab has 8...it worked.

i guess the other amps dont?

 

[Sludgenutz]

Re: Why is it that combos cant drive cabs?

Just a thought...
Perhaps the easist way to see if the combo's speaker output jack is in series with the internal speaker, would be to....plug a speaker cable (just the cable, not attached to any cab) into the external speaker jack of the combo. If the main combo speaker does not produce any sound...its a series connection.

 

[Sludgenutz]

Re: Why is it that combos cant drive cabs?

i tried the peavey again, it said 8 ohms minmum and the cab has 8...it worked.

i guess the other amps dont?

Cool! Glad it works for you!

 

[Kac]

Re: Why is it that combos cant drive cabs?

I've done it multiple times with different amps... I'm runin' my Mesa cab with my Blues Jr. right now.

Rock ON ~ Kac

 

[Kane17]

Re: Why is it that combos cant drive cabs?

A couple weeks ago my friend brought over his Peavey Studio Pro combo. Out of curiousity I plugged it into my 8 ohm 2x10 cabinet just to check it out and it totally muted his internal speaker from what I remember.

I think that says theres more to it than just a series/parallel connection to the external jack. I dont know for sure though.

 

[LesStrat]

Re: Why is it that combos cant drive cabs?

Peavey generally wires their combos for using external speakers.

 

[devastone]

Re: Why is it that combos cant drive cabs?

The external jack is likely wired in "series" to your combos internal speaker. Adding another cab just piles on a lot of impededance, which pulls down the amount of power that the amp can generate.

All the ones I've used are wired in parallel which makes sense because if you are hooking up more speaker, you probably aren't doing it to be quieter. Actually, come to think of it, the Peavey Combo I had not long ago disconnected the internal speaker when you plugged into the external speaker jack.

What kind of cab are you trying to run, what's its impedance? What does the external speaker jack say is the minimum load? Hard to help without enough information.