'67 Spec - What Is It Exactly?

Discussion in 'Let's Talk Vintage' started by jaymz1977, Mar 19, 2017.

  1. jaymz1977

    jaymz1977 Member

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    hi all.
    Long time Marshall fan here, first time poster.

    I'm just wondering if someone can summarise for me what '67 black flag spec actually consists of?

    I've read bits and pieces of information but I want to try to get all the info in one place.
    My understanding is that it is basically 0.022uf on v1b, v2a not bypassed and 100k/8ohm tap.
    Is there anything I am missing?

    I put a turret board with Sozos in my 1987x and now I'm just tweaking it to taste.
    All help appreciated.
    Cheers
     
  2. jaymz1977

    jaymz1977 Member

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    Seems as though they had lower filtering as well...
     
  3. neikeel

    neikeel Well-Known Member

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    Welcome jaymz.
    We need to roll back a bit. The 67 preamp is the same as 64-66 and the bass amps that came later it is jus that in early 68 the first split cathode lead amps came in.
    So to be true 67 spec you have shared V1 cathode (820R/250uF) all 0.022uF (x5) couplers (except for x3 0.1uF in the PI)
    Tone stack is 56k/250pF with 470k mixers and 500 to 560F bypass cap on channel 1.
    The NFB on these amps is 27k on the 16ohm tap.
    The 67 amps had 32uF dual preamp can, and the 50w had 32uF mains, 32 PI and 16uF screens

    What specs are you actually after?
    The '68 lead amps that came in are similar to your 1987x (split V1 cathode, lead tone stack, 0.0022uF on V1b) 0.68uF over V2a cathode, 0.022uF couplers in output of PI but 47k/8ohm tap NFB.
    You will only find 100k NFB post 71 and even then hooked up to the 4ohm tap (these amps dropped the 0.68uF on V2a and in 73 ish had 0.68uF on the presence.
    Hope that helps?
     
  4. jaymz1977

    jaymz1977 Member

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    Thanks for that info.

    TBH I'm not really sure exactly what specs I'm after. I just read that the Solo Dallas SD-50 was basically a black flag spec amp, and with Fil being the foremost expert on AC/DC sound I thought that may be what I want. I'm just trying to tune my amp for the ultimate AC/DC sound. I seem close one day, then the next I'm not so sure.
    I do have a Storm pedal (Schaffer replica) which is a large part of it. I just can't seem to get that right amount of mid range ring. I don't even know how to describe it.
    As I write this I have a great tone but there seems to be too much gain. If I roll back the gain a bit the tone changes.
    I know these old circuits are supposed to be quirky, but GEEZ!!!

    I guess I'm on the same quest as everyone else, to find the tone in my head. Can someone peep inside and tell me what it is?

    Thank you for your reply.
     
  5. neikeel

    neikeel Well-Known Member

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    If you want control and punch, try the higher NFB, for now move the purple wire onto the 16ohm tap and see. If it gets you closer then swap the resistor on the board for a 27k.
    If you have a true early circuit then they are not particularly quirky (IMO!) they respond to the guitar and your technique - but it is more difficult to hide behind a wall of distortion. From the clips I have seen of SD then a JTM spec amp wound up is the sound. I will not get into all the variations that Angus has used over the years but I amp pretty sure the cranked JTM45 with an ISO speaker under the stage is pretty consistent?
     
  6. jaymz1977

    jaymz1977 Member

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    I should perhaps give some more background on my amp.

    It is a 1987x, the one with the loop. I decided to replace the stock pcb with a turret board for ease of modding plus I wanted to try the sozo caps.
    At first it was a stock 1987x circuit. I then modded it by sacrificing the normal channel to create a switchable 2204 mode. The bright channel remains the same (except there is now a master volume after the tone stack and the "bright vol" essentially acts as a gain pot now) and I switch to 2204 mode via a push pull gain pot mounted in one of the normal channel jack holes.
    The amp still has all 50uf filter caps as per stock 1987x. It's has 33k/ 500pf tone stack as stock as well. I have played with the bright cap values and settled on 100pf for 2204 mode and 220pf for 1987 mode (from memory). The latest thing I did was remove the 0.68uf bypass cap on v2.

    So I'm kind of just trying things to see how I like them at this point.
    I also can't help but wonder if an extra 2 output tubes are responsible for what I feel like I'm missing...

    Cheers
     
  7. jaymz1977

    jaymz1977 Member

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    You may be right about the jtm45...

    Does anyone else have a clue what I mean when I talk about that mid range "brassiness "? I don't even know the correct acronym to describe it but it's so prominent. I can't be the only one who hears it.

    Cheers
     
  8. jaymz1977

    jaymz1977 Member

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    There is something about Angus's tone that seems so clean. Is that a 100w thing?
    Cheers
     
  9. jaymz1977

    jaymz1977 Member

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    Anyone else with anything to share?
     
  10. jaymz1977

    jaymz1977 Member

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    I just found a really good article on the evolution of Marshall circuits that gives technical details, not just the visual changes like most do.

    http://folk.ntnu.no/roef/JTM100.html

    Can anyone confirm if this info is in fact correct?

    Cheers
     
  11. neikeel

    neikeel Well-Known Member

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    Yes for 100w amps, couple of the amps featured are mine too;)
     
  12. jaymz1977

    jaymz1977 Member

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    There seems to be less info out there about the 50wers.
     
  13. jaymz1977

    jaymz1977 Member

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    One thing I found interesting in that article was the mention of ghost notes in the 67 section.
    Last night I was playing some git and I kept hearing ghost notes. I really noticed it when I was playing the Back in Black riff when I did the pull off on the high E string.
    I wasn't real keen on that, but the amp is quite punchy ATM which I do like.
    I might have a go at 68 spec and see how I like it.
     
  14. neikeel

    neikeel Well-Known Member

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    It would be unusual to hear ghost notes on a 1987x as the mains filtering is 100uF, screens 50, PI 50 and dual 50 in the preamp. The place I can get ghost notes on most early Marshals (particularly 100watters as anything before 69 is relatively under filtered) is with the amp cranked above 80% and then noodle with some big G and B string bends on the neck pick up around the 12th and 14th frets, particularly with single coils. I wonder what you are hearing?
     
  15. jaymz1977

    jaymz1977 Member

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    Hmmm... maybe what I was hearing was not necessarily what the article was referring to.
    I was getting this odd effect (and I had the phase "ghost note" in my head before reading the article) where the G-E pull off in the BIB intro was very unclear and had what seemed like ghost notes or harmonics muddying the notes I was playing. It was only noticeable on those particular notes.
    From memory I was able to get rid of it by turning the bass (or was it the gain/ bright vol) down a bit.

    It frustrates the hell out of me that the words that seem obvious to me to describe a certain sound are not the same words that others use or are obvious to them. It makes getting to the bottom of something quite difficult at times.
     
  16. soundboy57

    soundboy57 Well-Known Member

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    Every head I have had has ghosting, some more than others.

    Don't forget the output transformer...IME it is a huge deal. The modern stock Marshalls don't have that
    brassy kerang, and dirty edge of the old ones, IMHO.
    I had a Malmsteen signature head that I sold because all the old JMPs I had
    smoked it for tone. growl and grind.

    A Merren, Marstran or Mercury will get you more clarity and chime like the originals.
    All the board parts in the world won't get you there without great trannies, IME.

    The secret to Angus tone is that he didn't have a lot of overdrive...kinda like Jimmy Page....all in the fingers, with the amp on the edge of breakup.

    My two cents.
     
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  17. jaymz1977

    jaymz1977 Member

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    You could well be right about the OT. I'll put that on my future mod list.

    Yeah, you are right about Angus being fairly clean and therein lies my problem. To get the EQing right I end up with too much gain to my ears.

    With the above in mind, should I maybe reinstall the v2 bypass cap and go back to 0.022 on v1b. Would that better suit the direction I am going in? I am still yet to try lowering the neg feedback resistor or changing taps.
    How about the tone stack? Is 33k/ 500pf the right combo for this sound?

    Cheers
     
  18. jaymz1977

    jaymz1977 Member

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    Another thing... reading though that article I posted above it seems my plate voltages are lower than "normal". Last time I checked I think they were around 420-430v. The dropping resistors are both 10k. If I drop one to 8.2k would that bring them up around the 450v mark?
     
  19. pleximaster

    pleximaster Well-Known Member

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    I my experience the louder you play the more influence of the power stage (and filtering, transformers rectification as well as speaker saturation) influence the sound. So when dimeing a Marshall even a major change in the preamp like shared or split cathode makes less differences.

    plexi
     
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  20. jaymz1977

    jaymz1977 Member

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    Thanks for your reply.
    I am running through a Rivera RockCrusher so i can dime it fairly hard.

    Anyone got any comments on the plate voltages?
     

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