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Using a head as a mic preamp?

Johnny5

Johnny5

Mar 5, 2006
374
1
Calgary, Canada
#1
I have a Mesa Walkabout head. Great warm tone, and I would love to apply some of it to some vocal recordings. My plan is to run a mic into the head input (passive) and run the head to my laptop, this is where I hit the wall. How is this done - is it through the speaker out in the back, or effects loop, or something else? I have no idea how these things work. Gimme some love..
 
#3
when I wanted to record a demo for a class I was in, I ran an acoustic guitar through his marshall head's preamp and ran a cable from the preamp out to a digitech jamman looper - the mic out from that to a mixer.

so signal -> head preamp out-> 1/4" to mic converter -> mic to mixer (an old tape deck)
you could go
signal -> head preamp out-> 1/4" to usb converter -> usb to computer

so all you need is something that converts a 1/4" inch cable to something else you can use - mic cable or usb.

some mixers have this, some effects pedals do (loopers such as the boss rc series or the digitech jamman)

hope that helps.
 
#4
Then there is the impedance of the mic to factor in, going to be a very hot (or is it cold, haven't had my coffee yet :crying:) signal going into the amp.

Think of it this way... if you need a DI box to take your bass up to a mic level signal so it can be plugged into a mixer, do you not think the same applies if done in reverse? Except that now you need to change the signal going into the amp and coming out of it. (to make it safe for the laptops tiny little input buffers to handle).

By the time you bought all the adapters, line transformers and the like, you could have just bought one of these:

tubemp.png


Which will warm things up as well as do everything you need and then some.

Or better yet, for a few $$ more, the USB version so you can go straight into the laptop via USB and make your life even easier still.
 
#5
You need a passive direct box that normally you would use to convert high impedance guitar signals to low impedance mic signals. In this case you'd just reverse it, plug your mic into the direct box (you'll need a female-to-female XLR adapter and go from the 'in' on the direct box to the 'in' on your amp. As to where to tap from, NOT from the speaker outs. If you have a 'pre' out that's the right spot, or you can try the effects loop out. Depending on your amp you may have to do additional impedance matching on the way to the computer interface, quite probably in fact. Good luck.
 
#7
bkbirge said:
You need a passive direct box that normally you would use to convert high impedance guitar signals to low impedance mic signals. In this case you'd just reverse it, plug your mic into the direct box (you'll need a female-to-female XLR adapter and go from the 'in' on the direct box to the 'in' on your amp. As to where to tap from, NOT from the speaker outs. If you have a 'pre' out that's the right spot, or you can try the effects loop out. Depending on your amp you may have to do additional impedance matching on the way to the computer interface, quite probably in fact. Good luck.
Click to expand...

Wait, let me get this straight.... Your suggestion is to buy a passive DI box, an XLR gender bender adapter, then plug into the amp, and from there take the PRE signal from the amp?

Umm... please feel free to correct me if I am wrong, but why bother plugging into the amp at all if you are taking the signal pre EQ? It defeats the purpose of using the amp to warm things up. If you go this route you want it to be Post EQ, not Pre.

Don't forget about the input on a laptop's sound card, it's not going to be very forgiving if you hit it with too hot of a signal. There is 4 (yes, this is an over simplification, but anyway) common types of signal levels... Speaker, Mic, Line and Consumer. Your laptop has a consumer level input on it (not unlike your home stereo), typically that is not directly compatible with Mic or line levels, you'd need some form of a mixer to pad it down and buffer it.

By the time you add up everything you need, you could have bought the USB version of the Tube MP. The normal version will do everything that you need it too.

Do yourself a favour, save both you, your amp and your laptop a load of grief. Spend the $39 and get the Tube MP at L&M.
 
#8
Subculture13 said:
Umm... please feel free to correct me if I am wrong, but why bother plugging into the amp at all if you are taking the signal pre EQ? It defeats the purpose of using the amp to warm things up. If you go this route you want it to be Post EQ, not Pre.
Click to expand...

Sorry, wasn't clear. I meant 'preamp out'. And yes, if the EQ is what is warming up the guys sound then by all means go post eq. The warmth you can get from your amp may have nothing to do with the EQ (most of the time IME), in that case go right after the first gain stage if you can. The less circuitry you stick on the signal, generally the less phase issues and signal degradation issues you have. If the amp has a mic input then he doesn't need the DI on the front end but depending on the signal coming out the back he might still need one there. Maybe my amps are too old but matching impedance is very important if you want that good tone, it isn't just a question of signal level. Then again, I probably wouldn't use a bass amp for a vocal mic preamp but I wouldn't stop anyone either, whatever floats your boat.
 
#9
bkbirge said:
Sorry, wasn't clear. I meant 'preamp out'. And yes, if the EQ is what is warming up the guys sound then by all means go post eq. The warmth you can get from your amp may have nothing to do with the EQ (most of the time IME), in that case go right after the first gain stage if you can. The less circuitry you stick on the signal, generally the less phase issues and signal degradation issues you have. If the amp has a mic input then he doesn't need the DI on the front end but depending on the signal coming out the back he might still need one there. Maybe my amps are too old but matching impedance is very important if you want that good tone, it isn't just a question of signal level. Then again, I probably wouldn't use a bass amp for a vocal mic preamp but I wouldn't stop anyone either, whatever floats your boat.
Click to expand...

All very good points. Your last statement is best though, whatever works for you.

I read an interview with Daniel Lanois on his technique for recording vocals. At times he plugs a mic directly into some old tiny little 5 watt tube combo amp and mics that up to get the warmth and breakup from the amp. Far from "proper," but who is going to argue with Daniel Lanois over "proper" recording techniques? He's one of the most successful producers of our era.
 
#10
Subculture13 said:
At times he plugs a mic directly into some old tiny little 5 watt tube combo amp and mics that up to get the warmth and breakup from the amp.
Click to expand...

True dat. I've got a couple Silvertone amp-in-case tube amps that we've abused that way a few times. Stereo tremelo tube breakup sounds cool on vocals but it's really just an effect and not something I record with most of the time. Sounds killer on a Memorymoog though. Most of the time I try to get good solid sounds on tape and f*** with 'em later. Really whatever you do to get the sound in your head (or a happy accident) is ok. There are guidelines to follow if you want specific results but there's usually more than one way to get there.
 

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