Early Marshalls are single channel clean amps?

Discussion in 'Marshall Amps' started by wonderingape, May 17, 2020.

  1. wonderingape

    wonderingape Active Member

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    Some people are saying the earliest Marshalls such as the JTM45 and other Marshalls before the 70's are single channel clean amps (so they can't distorted) but they actually have two channels which are High Treble (Loudness 1) and Normal (Loudness 2). Is High Treble basically the overdrive or gain channel while the Normal is the clean channel?
     
  2. FutureProf88

    FutureProf88 Well-Known Member

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    I mean technically they are two channel amps in the same way that old Fenders are two channel amps. In that way you could sort of argue that the JCM 800 is a two channel amp because the low input cuts off a gain stage. But they're not channel switching unless you want to rig up an ABY pedal, and even then you're running a shared EQ which I've found to not sound good set the same for both channels. So they are technically two channel amps, but from a practical sense they are single channel amps, so I think that's what guys are getting at.

    They are non master amps, too, so both channels are "clean" channels unless you wind them up. But if you listen to the old Cream records you're hearing the Normal Channel running flat out, and its very woolly.
     
  3. steveb63

    steveb63 Well-Known Member

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    I have a JTM 45, it's clean, to me, still has a little hair on it.

    But make no mistake, there is no "clean" or "dirty" channel. If you want break up there's pedals or extreme volume. Love it's natural distorted sound, can't handle the volume pressure.

    But when I'm recording with a load dump, my oh my, can't find a unusable tone. It just sounds GREAT.

    Of course, all this is subjective, imo, ymmv etc......

    Nothing like a Marshall non- master volume workin' it's ass off.
     
  4. What?

    What? Well-Known Member

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    All the early amps were clean amps (Fender and Marshall). That doesn't mean that they don't overdrive when pushed. The higher gain amps (master volume amps with preamp gain) came later as there was a want for overdriven amps at lower volumes. And that lead to more gain, and more gain. And nowadays, lots of people are running those 'clean' amps with attenuators, PPIMV's, and power scaling, because preamp gain just doesn't sound like an overdriven amp.
     
  5. Kinkless Tetrode

    Kinkless Tetrode Well-Known Member

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    The JTM45 is pretty clean unless you run it very, very, loud. The 50 watt and 100 watt plexi gets more dirt.

    The way these amps are played is that once you get them up to the volume they want to be at, often called the sweet spot, you get over driven tones by turning up your guitar volume, and you get them to clean up by rolling down the guitar volume.
     
  6. scozz

    scozz Well-Known Member

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    I don' know, they're not "clean" amps in the way I think of clean amps. I guess that's something else that's subjective in this,...um,...I guess a hobby for me. I don't have much experience with 60s era Marshalls, my earliest Marshall amp experience is a early 1970s 50 watt head that the other guitar player had in a band I was in when I was a teenager..

    The way he used that amp there were not many clean tones at all, that's not to say they weren't there, its just he never used them. The only time I heard anything that even remotely sounded like a clean tone was when he turned the guitar volume down.
     
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  7. dro

    dro Well-Known Member

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    One of the sweetest sounds to my ears is a JTM45 Channels jumped and Dimed. The weakest Strat in you're arsenal will ring for as long as you can hold down the note. Put a nice Les Paul in it and it's bliss to my ears." Am not now, nor ever will be a banger." It's a 60's thing. That being said, It's one of the best pedal platforms out there. But there again it is old school. Everything goes in the front.
     
  8. guzzis3

    guzzis3 Well-Known Member

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    Clean dirty and channels are all terms and ideas that came later.

    The electric guitar was developed because accoustic guitars were getting lost as gigs got bigger and horns etc were in the mix.

    In the 50's bands played to small clubs so a 15W amp was enough. Fender built the bassman so bass players could get enough clean volume to keep up. Guitar players plugged in dimed them and found wonderful sounds.

    In england bassmans were expensive so marshall built a copy with a few tweeks and local components. Guitar players bought them and found wonderful sounds. Marshalls had the hi/low inputs but also 2 volume knobs one with a low cut on it for lead the other without for bass or vocals.

    Mid 60's guitar players started running them flat out which delivered both output valve distortion about 2-3% and speaker saturation and break up. The sound became more popular.

    Late 60's gigs kept getting bigger and guitars weren't put out through a PA so bigger amps were requested. Townsend and Entwistle were in an arms race on stage each trying to drown the other out, hence the early 100w heads.

    Some wanted more distortion so extra gain stages were added to some models.

    Things stayed loud until the late 70's when people wanted distortion without volume. Master volume happened.

    I can't remember when but about 1980 someone came up with the clever idea to make one high gain preamp and a normal preamp and allow switching. There didn't seem to be a need for an amp that could take both a mic or bass and a guitar. This is what is normally called channel switching and dirty and clean channels. This was the start of the "modern" guitar amp.

    Marshall built whatever people were willing to buy. He listened to his customers and tried to meet what they wanted. But what he was building really predates the terms you're asking about.
     
  9. wonderingape

    wonderingape Active Member

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    So I heard that the overdriven sound produced by cranked 60's (non-master volume) Marshalls were not actually produced by the power tubes as many people believed but actually comes from the preamp, phase inverter and speakers. Makes sense to me because as far as I know pure 100% power tube "distortion" isn't real and preamp tubes, phase inverter, etc. are necessary to produce overdriven sounds. When the loudness is increased (that's what the power tubes do) on those 60's Marshalls, the preamp and phase inverter started to distorted heavily. The speakers started to distorted and become saturated.

    I used to think there are no preamp tubes or circuit in those earliest Marshall models, so that's why I think those overdriven sound of 60's Marshalls are purely power tubes but actually not. There are preamp tubes even in the earliest Marshalls which means the cranked overdriven sound may have majorly come from the preamp stage (of course, the other components such as phase inverter, power tubes and others are necessary too), so that's why I think those Marshalls are not really single channel clean amps, technically speaking.
     
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  10. dro

    dro Well-Known Member

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    Technically Speaking "Whatever" All I know it the sound they (JTM45) produce can only be achieved in one way. And that is with a JTM45 head into a greenback loaded 4x12. The Bluesbreaker works nicely too. Have never seen a pedal that can emulate it. Have never been much of a fan of emulation anyway.
     
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  11. What?

    What? Well-Known Member

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    I wonder if any of the techs here have scoped and compared each stage of some amps to see what is going on in way of distortion. Either way, amps that are designed to develop alot of distortion in the preamp do sound very different than amps that were designed to be clean but can be overdriven into distortion. But I am very curious on the point of where distortion develops in cranked up classic amp designs.
     
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  12. Kinkless Tetrode

    Kinkless Tetrode Well-Known Member

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    I have run my JTM45 with EL34s and it gets more distortion with those than it does with KT66s.
     
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  13. neikeel

    neikeel Well-Known Member

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    :applause:
    I’ve often wondered that.
    - time to break out the scopes and do some probing
    :applause:
     
  14. What?

    What? Well-Known Member

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    Definitely let us know what you find. I guess you could probe before and after the phase inverter and use subtraction of the 2 channels to see what happens there. Or maybe you have some better thoughts on how to go about it.
     
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  15. Mystic38

    Mystic38 Active Member

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    kinda on/off topic..

    The only amp i know that can provide exclusively power tube saturation is the Orange Rocker 30 on the "natural" channel... it (unnaturally) has a single gain stage, where most "clean" channels have at least two.

    Diming it is a real treat..assuming you are in the next room..lol
     
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  16. guzzis3

    guzzis3 Well-Known Member

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    Oh FFS really ? Where are you people getting this rubbish ?

    Look at a JTM45 schematic. Each preamp uses 2 sides of a 12ax7. 2 stages for low cut 2 for "normal" then they go to the splitter. Running flat out you do get some distortion, but compare the signal coming out of the phase splitter to the output of the power valves and the signal is different. The later amps have at least one more 12ax7 in them for preamp distortion.

    Pentode and triode distortion sounds completely different. As someone said above if you change output valves the sound changes completely. That alone should tell you a lot of the sound is coming from teh output stage.

    You have to remember that the distortion levels in 60's Marshalls were pretty low even at full tilt. If you remove the neg feedback you get a bit more. Class A has massively more, about 3 times the THD of a class AB1.

    Speaker breakup definitely played a part but pure volume really adds to the experience. No one has come close to the joy of the wind off your speakers flapping the legs on your jeans....and jiggling your innards..
     
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  17. guzzis3

    guzzis3 Well-Known Member

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    If you really think plexi/jtm sounds come only from the preamp and speakers build a preamp and output it through a SS power amp and see how it sounds.
     
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  18. wonderingape

    wonderingape Active Member

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    Well I say most of the components, not just the preamp, play parts in producing the "distortion".
     
    Last edited: May 19, 2020
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  19. wonderingape

    wonderingape Active Member

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    Well, if you read the whole statement I said all the other components play parts too, not just the preamp, to produce the mild overdriven sound. Yes, the "distortion" (actually more like saturation rather than distortion) produced by maxed out non-master volume (and maxed out master volume with the preamp knob on zero) Marshalls including the Class A 18 watter Marshalls compared to real distortion sounds of later amps, the power tube "distortion" sounded more like clean sound on roids. Sounded too low gain and too soft for my taste.

    That depends on the circuits, in many other circuits the power tubes don't completely change the sound. In those early amps like those of 60's, maybe the power tubes make noticeable differences.
     
    Last edited: May 19, 2020
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  20. South Park

    South Park Well-Known Member

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    Early Marshall’s are not clean amps by any means . The load lines on the first tubes was made to clip the top half then it goes to the second tube it inverts the signal . So Now you have a square block Hitting the phase inverter and off to the drivers. If you ever put a scope on one of these amps and see what it looks like
     

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