Amp out into line in?

Sorry for the complete n00b question, but I couldn't find a good explanation, so I thought I'd risk embarassment and ask you folks...
 
What can and can't you plug into a line-level input?  Obviously, you can plug various line levels in, but what happens if you plug a powered signal in?  ...like if someone plugged a speaker cable from an amplifier in to a line in?
 
I'm asking because I was looking to get a line out from a guitar amp to record and I don't want to fry anything.  Someone had told me they plugged in a cable from an output from a guitar amp into the mixer, but it sounded like it was for an external cabinet (i.e. powered connection) and not the 'line out'.  That should have blown something up, shouldn't it?
 
Can someone explain this to me concisely?  I'm feeling really stupid...
 
 

I use a speaker out, into a line in all the time (just to get the tubes). Just keep the volume way down on the amp (like 2).
To do it "right", you should have a Direct box in between.

All that said, be careful.

A DI signal is usually very sterile sounding..and stiff. The best option is to mic it. That allows the amp and speaker to really do what they do and you capture that with the mic.

A second good option is to use a simulator...software or hardware based.... I use a POD 2 hardware modeler.


I would not use a speaker output to a line in on an interface.

I'm asking because I was looking to get a line out from a guitar amp to record and I don't want to fry anything. Someone had told me they plugged in a cable from an output from a guitar amp into the mixer, but it sounded like it was for an external cabinet (i.e. powered connection) and not the 'line out'. That should have blown something up, shouldn't it?

 
To 'properly' record from the amp's speaker output, you'd want a DI box with a speaker input (like the Avalon U5). Be careful to have a load/speaker on tube amps... but this scenario works just fine.
Then... all you're simulating ITB is the mic'd speaker cab.
 
 

OK, circuits lesson:


Amp output impedance +/- 1 ohm is nicely "matched" or bridged into a 8 ohm speaker.

If the amp puts out 25 watts into 8 ohms then you need something close to a 25 watt speaker to make it all trustworthy at full volume.

If you plug the amp with the +/- 1ohm output into a 1500ohm preamp input the amp will put out less current... I don't know how much less... If you turn the amp down to put out very few watts you may not melt the input circuitry of a preamp... but if you turn it up you probably will. I don't know how many watts your preamp can take before stuff starts melting. Usually the electronics in a solid state circuit are good to 52 volts AC or DC but their current capacity can range from really really small through small current capability.

The feature on the Avalon Jim mentions is a special purpose circuit not unlike the Palmer. I am not familiar with the specifics of it, but I imagine it has been designed with all the stuff mentioned above in mind.

best regards,
mike

GET THIS:



AND YOU"LL PROBABLY WET YOUR PANTS FROM THE THRILL OF LISTENING TO IT.


i did.





all in good fun :-)

Who just said they plug a speaker output into a line in??? I guess if you want distortion that's one sure fired way to get it!
And I'm also blown away by the suggestion of a DI box on a speaker output.

It is called a DI box because it takes the hi impedance, low voltage direct signal from the guitar/bass/keyboard and splits it off to the amp directly and to the PA as a converted signal ( via a transformer)  to become a  balanced signal. A speaker load would probably fry that box shown in the picture.
There are special boxes made for taking a hi voltage speaker loads but they are not called DI boxes they are called Speaker output  to balance line converters. A DI box  gives you the sound without the amp. A speaker converter box gives you the sound of the amp. A good one will set you back more than a good mike so they are not very common. Radial makes the best DI's etc.
I've never seen the back of an amp that was not clearly marked  Speaker out.  
or Line out or Send or etc.
For recording if your amp has a line out then try it, it might be excellent, I have one on my custom Fender Princeton and it sounds almost as good as a mike, but the tech who put it there knows his stuff. I would need a power soak if I disabled the speaker. My reason for using it is I can blast the studio monitors while tracking without leakage. Another solution is put a speaker cabinet in another room with a long speaker extension cable. Disable the amps speaker.

FWIW, I explained the parameters that must be observed to allow you do so without mishap in a post above.

But I have to admit, if you did it in my room... I'd probably just scratch my head and wonder why.

all the best,
mike