What’s happening to the signal

[ourclarioncall]

Wondering what happens to the signal the moment it goes into the input jack of an amp then goes through the amp

I know it goes to preamp to amplify the signal , but before that is there something happening at the amps input jacks ? For example many amps have two inputs which do what ?

I’m going to guess one input does nothing to the signal and another input acts a bit like a volume pot or series of resistors which sends a certain amount of signal to ground

The reason I’m guessing this is because if one input amplified the signal even a little then it kinda like a preamp before the preamp . But maybe it is a small boost in the signal ? But I’d be more inclined to believe it would be cut instead of amplified

The two inputs are for different guitars with pickups that produce different strength of signal right ? Say a strat would go in one input and a les Paul would go in a second input with a cut in volume /power to balance things out and not introduce too much gain in the preamp at the beginning ?

Sorry about lack of technical terms

[newey]

Sept 13, 2020 8:39:18 GMT -5 ourclarioncall said:

For example many amps have two inputs which do what ?

The answer to this is, it depends on what type of "two inputs" to which you are referring. For example, some amps offer a Guitar/instrument input as well as a "line level" input, which offers a different input impedance for mics, mixers and other "line-level" sources. But I'm going to assume that isn't what you're referring to here, so we'll put that aside for the moment.

If we confine our discussion to instrument level inputs, there are still different types. Many amps feature a "Hi" and "low" input jack. These offer differing input impedances. It's not that one would use one type for an LP or for a Strat, as you suggest. Typically, the "low" input is for use with active pickups, and the Hi input for passive. But you could plug either type of pickup-equipped guitar into either input. The Low input will offer more clean headroom, but will cut some output (i.e., volume).

Fender (and other mfrs) have also offered "Normal" and "Bright" inputs. On these, a "bright" capacitor is used to attenuate certain frequnecies to brighten the sound. This only affects things at lower volumes- crank the amp to "10" and both inputs will sound the same.

Fender sometimes had 4 inputs "Bright Hi", "Bright Low", "Normal Hi" and "Normal Low" on 2 separate channels). Vintage Bassman amps had this setup, and it's one of the reasons lots of guitar players loved those old Bassmans(and still do).

I'm sure someone else can give you a more technical explanation (and someone probably will . . .), but that's my layman's take on this.

[sumgai]

Sept 13, 2020 9:45:28 GMT -5 newey said:

I'm sure someone else can give you a more technical explanation (and someone probably will . . .), but that's my layman's take on this.

No need for any further intervention, newey has covered it correctly. (No laymen were harmed in the making of his post.)

[ourclarioncall]

Thanks Newey,

anyone point me to the most simple guitar amp schematic in existence ?

[sumgai]

Sept 13, 2020 11:47:06 GMT -5 ourclarioncall said:

..... anyone point me to the most simple guitar amp schematic in existence ?

Simple? You want simple? OK, go back and look again at frets' on-board preamp - that's using an LM386, one of the best known power amplifier devices available. Simply plug her board into a speaker, and Voila!, you have a dirt-cheap and dirt-simple guitar amp, complete and ready to go.

But I have to be honest, it won't sound very pristine - when I said "dirt... dirt...", I wasn't speaking only to cost/simplicity!

HTH





sumgai

[thetragichero]

robrobinette.com/How_Amps_Work.htm

robrobinette.com/How_the_Marshall_JCM800_Works.htm

[ashcatlt]

Like I said in the other thread (!!!), on many amps where there are two inputs per channel, those are essentially equivalent parallel inputs which are mixed together. Neither is significantly different in either impedance or volume from the other, though if you plug two different things in, it will probably attenuate both a bit so that the mix of the two isn’t as much louder than either one as you’d otherwise expect.

Edit- Oh and newey mentioned the bright channel on some Fenders, which is basically same as on a Vox Top Boost model. It happens at the volume control, which is after the first active stage. It’s actually wired exactly like the basic treble bleed that we often see on guitar V pots.

[ourclarioncall]

Thanks y’all

Just watching a few uncle Doug vids on YouTube.

Even at this basic layman explanation, it’s too complicated for me . I need kindergarten explanations 😐

As a teacher myself i know it’s easy to forget basic things are not always that basic for beginners . A bit like grandparents who forget how hard having a new baby is 👶 🍼 😊

[ashcatlt]

Yeah sorry we’re here to help. I can see where the bangs in my post above looked like exasperation or frustration, and I didn’t really mean to discourage you from continuing to ask questions. Sometimes, though, if asking the same question twice gets you the same answer and you still don’t understand, you need to look for a different question.

[ourclarioncall]

Sept 13, 2020 13:45:58 GMT -5 ashcatlt said:

Yeah sorry we’re here to help. I can see where the bangs in my post above looked like exasperation or frustration, and I didn’t really mean to discourage you from continuing to ask questions. Sometimes, though, if asking the same question twice gets you the same answer and you still don’t understand, you need to look for a different question.

No sweat 😉

I blame me most of the time, lol, I’m trying to speak In a language I haven’t learned

And often my communication is bad as I don’t take time to think through how it sounds to others.

I also have a theory , I think American kids in general are much smarter, maturer and better educated than British kids (so that’s my excuse 😊)

I Think I just need to accept That if I really want to understand this stuff I’m going to have to enroll in a college course or something and get a proper foundation laid. I appreciate many things are hard to simplify or explain if I don’t have that

It’s all good tho, onwards and upwards 👍

[frets]

Hey Clarion,

You wanted the simplest amp in the world? Sumgai referenced the LM386 route. Here are the incredibly simple amp diagrams you’ll ever find.



For a little portable or headphone amp, those work pretty well.