Amp for both Guitar and Voice

Duck Dodgers · 06-16-2009, 07:58 PM

Recently completed a single channel AB763 clone for my Son that worked out pretty well.

For the next project (there's always a "next") he would like an amp that has a microphone channel on it as well.

I was planning on a 6G12A Concert with the 2 1/2 tube trem and an added reverb for the guitar side.

Could I use the normal channel reconfigured for a microphone? I know nothing about microphone pre-amps. In fact, I'm only guessing they're different.

Don't even know if this is practical given the power section.

I tried a search but didn't have any luck. If someone could point me in the right direction I would appreciate it.

mooreamps · 06-16-2009, 08:15 PM

Plugging a mic into a guitar amp will work, but normally mic's require a much higher input impedance than what most guitar amps are set up for. I would just go to the music store and pick-up a mic preamp.

-g

txstrat · 06-16-2009, 09:16 PM

If you still wanna build it on your own you could have a look at the Fender PA 100/135 schematic (schematicheaven.com).
If you follow one channels signal path you might find what you're looking for. The reverb is a quite complex circuit but you could try the guitar signals reverb setup and see if it works out ok.

daz · 06-16-2009, 10:25 PM

No good guitar amp is going to work well for guitar or visa versa. the only way i can see to get both to sound good is to compromise on the guitar end and use or build a PA type affair with a PA type speaker setup and run the guitar thru a modeler that has cab sims and the whole bit. Trying to use a mike thru a amp that sounds good with guitar would be impossible. For one thing running a mic thru a guitar speaker will sound horrid no matter what you do. But if you accomodate the mic with a PA type speaker the guitar will now sound horrid. A modeler however can sound good thru a PA, so as far as i'm concerned at least the only way is to run a guitar modeler thru a PA type system. The guitar won't be near as good, but the opposite scenario will have the moc sounding practically un-usable.

In short, the speaker is the biggest issue more than the amp. Now if you build a STEREO tube amp then you could use a stereo speaker setup with one side being a PA type and the other a regular 12" guitar speaker or two. that way you could make one side of the stereo guitar circuit and the other side a flat PA circuit. Of course now you have a monster it would take an army to carry. Theres really no good solution.

Don Moose · 06-16-2009, 11:03 PM

I agree with Daz unless you're talking about John Lee Hooker style blues where you want that nasty honk to the vocals.

You could (maybe) overcome the guitar speaker's limitations with some heavy EQ, but ...

Duck Dodgers · 06-16-2009, 11:26 PM

What I get from the posts is that a Guitar amp and a PA amp are different animals. Different input impedances, frequency response and speakers.

Short term it sounds like buying or building a mic preamp and pluging into the guitar amp would work. Sort of.

Could anybody point me towards a simple PA amp design? The Fender ones on Schematic Heaven look pretty massive.

Educational as always.

Thanks guys (and gals?)

Enzo · 06-17-2009, 01:26 AM

I want to build a car. I want it to be good for racing, but I also want it to be good at hauling tons of gravel.

PAs and Guitar amps serve totally different functions. The PA tries to faithfully reproduce the input signal out the speakers. It tries not to add anything of its own. The guitar amp on the other hand is designed to add something of its own. it is PART of the instrument. That is why some guys play a Marshall and others a Fender. If they all sounded alike, they would be PA systems too.

Guitar amps - well mainly their speakers - tend to roll off the high end after somewhere int he 3kHz to 5kHz area. PA speakers cover the whole range. Guitar amps are anything but flat, PA systems are intended to be flat.

An amp that does both will be a compromise to either. If you have to do it that way for budget reasons or the old "this is all we have" reasons, I can certainly understand that, but I would not really want to try to do it as my goal in the first place.

BackwardsBoB · 06-19-2009, 03:43 AM

I think the big show-stopper is the power amp. If you want power amp distortion for the guitar (I know I do), the vocal will get distorted at the same time.

Sweetfinger · 06-20-2009, 05:48 PM

Quote:

Originally Posted by Enzo

I want to build a car. I want it to be good for racing, but I also want it to be good at hauling tons of gravel.

YouTube - Truck Drags

I think our civilization may be doomed.

06-16-2009, 07:58 PM	#1
Duck Dodgers Member Join Date: Oct 2008 Location: S.F. Bay Area, USA Posts: 35	Amp for both Guitar and Voice Recently completed a single channel AB763 clone for my Son that worked out pretty well. For the next project (there's always a "next") he would like an amp that has a microphone channel on it as well. I was planning on a 6G12A Concert with the 2 1/2 tube trem and an added reverb for the guitar side. Could I use the normal channel reconfigured for a microphone? I know nothing about microphone pre-amps. In fact, I'm only guessing they're different. Don't even know if this is practical given the power section. I tried a search but didn't have any luck. If someone could point me in the right direction I would appreciate it.

06-17-2009, 01:26 AM	#7
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,366	I want to build a car. I want it to be good for racing, but I also want it to be good at hauling tons of gravel. PAs and Guitar amps serve totally different functions. The PA tries to faithfully reproduce the input signal out the speakers. It tries not to add anything of its own. The guitar amp on the other hand is designed to add something of its own. it is PART of the instrument. That is why some guys play a Marshall and others a Fender. If they all sounded alike, they would be PA systems too. Guitar amps - well mainly their speakers - tend to roll off the high end after somewhere int he 3kHz to 5kHz area. PA speakers cover the whole range. Guitar amps are anything but flat, PA systems are intended to be flat. An amp that does both will be a compromise to either. If you have to do it that way for budget reasons or the old "this is all we have" reasons, I can certainly understand that, but I would not really want to try to do it as my goal in the first place. __________________ Education is what you're left with after you have forgotten what you have learned.

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06-16-2009, 08:15 PM	#2
mooreamps Senior Member Join Date: May 2007 Location: Silicon Valley ; USA Posts: 453	Plugging a mic into a guitar amp will work, but normally mic's require a much higher input impedance than what most guitar amps are set up for. I would just go to the music store and pick-up a mic preamp. -g

06-16-2009, 09:16 PM	#3
txstrat Senior Member Join Date: Mar 2008 Location: Germany Posts: 752	If you still wanna build it on your own you could have a look at the Fender PA 100/135 schematic (schematicheaven.com). If you follow one channels signal path you might find what you're looking for. The reverb is a quite complex circuit but you could try the guitar signals reverb setup and see if it works out ok.

06-16-2009, 10:25 PM	#4
daz Senior Member Join Date: Jan 2007 Posts: 1,071	No good guitar amp is going to work well for guitar or visa versa. the only way i can see to get both to sound good is to compromise on the guitar end and use or build a PA type affair with a PA type speaker setup and run the guitar thru a modeler that has cab sims and the whole bit. Trying to use a mike thru a amp that sounds good with guitar would be impossible. For one thing running a mic thru a guitar speaker will sound horrid no matter what you do. But if you accomodate the mic with a PA type speaker the guitar will now sound horrid. A modeler however can sound good thru a PA, so as far as i'm concerned at least the only way is to run a guitar modeler thru a PA type system. The guitar won't be near as good, but the opposite scenario will have the moc sounding practically un-usable. In short, the speaker is the biggest issue more than the amp. Now if you build a STEREO tube amp then you could use a stereo speaker setup with one side being a PA type and the other a regular 12" guitar speaker or two. that way you could make one side of the stereo guitar circuit and the other side a flat PA circuit. Of course now you have a monster it would take an army to carry. Theres really no good solution.

06-16-2009, 11:03 PM	#5
Don Moose Senior Member Join Date: Jul 2007 Location: Indianapolis Posts: 676	I agree with Daz unless you're talking about John Lee Hooker style blues where you want that nasty honk to the vocals. You could (maybe) overcome the guitar speaker's limitations with some heavy EQ, but ...

06-16-2009, 11:26 PM	#6
Duck Dodgers Member Join Date: Oct 2008 Location: S.F. Bay Area, USA Posts: 35	What I get from the posts is that a Guitar amp and a PA amp are different animals. Different input impedances, frequency response and speakers. Short term it sounds like buying or building a mic preamp and pluging into the guitar amp would work. Sort of. Could anybody point me towards a simple PA amp design? The Fender ones on Schematic Heaven look pretty massive. Educational as always. Thanks guys (and gals?)

06-19-2009, 03:43 AM	#8
BackwardsBoB Senior Member Join Date: May 2008 Location: Los Gatos, CA Posts: 159	I think the big show-stopper is the power amp. If you want power amp distortion for the guitar (I know I do), the vocal will get distorted at the same time.

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