Why do amps have two sides to them?

Discussion in 'Tonefreaks' started by barchiola, Sep 15, 2017.

  1. barchiola

    barchiola Senior Member

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    Was just reading through posts and didn't understand a few amp references so I've got to ask, why do a lot of amps have the one set of controls and inputs plus another set in the same amp?

    My old Music Man has it's more complicated set on the right with Master Volume, gain, reverb, etc. but then it also has a very simple side with just tone and volume on the left.

    Why?

    Thanks
     
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  2. rockstar232007

    rockstar232007 Senior Member

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    Different channels.

    Most amps have multiple power stages (clean, overdrive, gain, effects, etc), each with their own sets of controls.
     
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  3. Frogfur

    Frogfur Senior Member

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    Because 4 sides is too crowded..??
     
  4. ARandall

    ARandall Senior Member

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    Because its a 3D object. Be pretty hard to have only 1 side.
     
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  5. Axis39

    Axis39 Senior Member

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    Initially, when the early amplifier makers were designing amps, a whole band played through one or two amps. You'd plug your instrument in one channel and the mic in another. Heck, the Fender Excelsior is (VERY) loosely modeled on older amps and has three channels, guitar, mic and accordion! LOL

    Then as amps began evolving, and PA systems became better, the mics started getting plugged in somewhere else and everyone started getting their own amps. But, amps still had a couple of channels... So guys started hot rodding one channel to make them both useable for guitar. Eventually amps got a clean and dirty channel. Then came clean, dirty and dirtier... and on and on.
     
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  6. sonar

    sonar Senior Member

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    More or less what Axis39 writes. It was a leftover that lasted for years until engineers figured out decent channel switching systems, but then again, most channel switching amps don't sound as good as the old amps. Go figure.
     
  7. barchiola

    barchiola Senior Member

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    thanks for the replies! i'll have to try running a mic through my amp, sounds fun

    :)
     
  8. Kaicho8888

    Kaicho8888 Senior Member

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    Oh yeah... that's what we use to do in the '60s in small gigs. Mic on one channel and instrument in the other channel. Now, we have specialized amps/mixers galore!

    The two channels are 180 out-of-phase. This worked well with my ES-345 stereo since the pickups where out-of-phase to each other.
     
  9. guitfiddle

    guitfiddle Senior Member

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    I have a Music Man amp, too
    The simple side is for bass, and the other is voiced more for guitar. Try running your guitar into either side, then use another cord to go out to the other side. Then you can mix them how you like. This is especially useful if you run out of the first side, then into an OD, then into the second side. That way you can get a huge variety of tones, depending on how the channels and OD are set.
     
  10. Axis39

    Axis39 Senior Member

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    On my old Bassman 50, I used the channel jumping thing almost like an effects loop. It was fun to run reverb there. But, most of the time I was lazy and just plugged into one channel or the other.... Two channels meant lots of knobs to turn! LOL
     
  11. Dolebludger

    Dolebludger Premium Member

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    Used to have a 63 Fender Pro amp. It had two separate inputs with two separate sets of controls, and you couldn't footswitch from one set to another. One set had vibrato and the other didn't. Back in those days two players would share the same amp, and I believe that was the reason. I used the non-vib input for a mic. IMHO, that didn't work very well, but a lot of players used to do it. I haven't seen amps made like that in decades.
     
  12. ivan H

    ivan H Member

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    Most amps have multiple "pre amp" stages, one power stage, aka output stage. The difference between the two is pre amp stages amplify voltage & the power or output stage amplifies current to drive the speakers. Cheers
     
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  13. Dolebludger

    Dolebludger Premium Member

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    Ivan,

    I think you are posting about a different sort of amp than the OP is. I have three modern amps. All of them have just one input. But one of them has separate controls for gain, volume and EQ for two channels. And it has a foot switch to switch channels (like clean to overdrive). The other two are pretty much the same configuration with one input with foot switch to change from clean to overdrive, but they share the same EQ. The OP is talking about amps with TWO inputs with TWO separate channels that cannot be switched, and each have totally separated EQs. These (as far as I know) are very old amps. They were made for two instrument inputs (or an instrument and a mic) and the channels could not be switched. This is a design of amps that went out back around 1970 (earlier for most amps). But I know that you can't find a new amp today with this design.
     
  14. ivan H

    ivan H Member

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    Regardless of an amp being a vintage type with multiple inputs, or a modern, single input, channel switching type, the gain, volume, eq controls are part of the PRE AMP circuit that is made up of multiple stages. On a channel switcher, sometimes some of these stages are switched in or out, sometimes parts of the supporting circuitry is switched in or out (ie; gain, volume, tone controls), & sometimes stages & parts of the supporting circuitry is switched in or out, but channel switching is done in the PRE AMP. Even most master volume controls precede the power amp. Though there have been a few designs comprising two power amps, the vast majority of amps, vintage & modern, have one power amp. Controls that operate within the power amp circuitry are "post phase inverter master volume's (PPIMV's), presence controls & resonance controls. These are found in tube amps but regardless of tube or SS, this is common topology, voltage amplification & tone shaping is done in the pre amp while the power amp supplies the muscle to drive the speakers. I stand by what I said in the previous post. Look into it a little, you'll realize I am correct on this. Cheers
     
    Last edited: Sep 25, 2017
  15. Mockbel

    Mockbel Senior Member

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    I believe if you have a close look at the amp you will find out what each set of controls is related to... usually controls are grouped and it is written whether they are for "Clean", "Overdrive", Input 1", "Input 2", "Master", etc...

    Just read the label !
     
  16. Dolebludger

    Dolebludger Premium Member

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    You are correct, sir. But the OP asked about amps with separate inputs going to separate controls and EQs (unless I misunderstand). He was not asking about channel switching amps with a single input, with separate channels with separate controls. The type of amp the OP was asking about (unless I am wrong) was one here if you plug into one input, you get one set of controls. And if you plug into the other input, you get the other set of controls. With the type of amp the OP described, there is no way to switch controls from those dedicated to the input into which he plugged in. In the type of amp I understand was described, of course there was only one power amp, and the differences were only dictated by which input (pre amp) he plugged into. My only point is that these types of amps are largely obsolete. Some of them have great value to collectors of vintage amps. But for players today, they are of little worth. And I know of no current amps of this design.
     
  17. ivan H

    ivan H Member

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    Yes, but regardless, the controls are within the PRE AMP, that comprised multiple stages that then feed into a SINGLE POWER AMP. No matter which way you shake it, multiple pre amp stages, single power amp which is the simple correction I made in my first post. Cheers
     
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  18. Dolebludger

    Dolebludger Premium Member

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    True that.
     
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