Vintage Modern 2466 PPIMV for High Dynamic Range only

Discussion in 'The Workbench' started by George Marshall, Dec 15, 2019.

  1. George Marshall

    George Marshall New Member

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    Does anyone know if it is possible to add an additional MV to the High Dynamic Range only?
    If so then the amp could be used as a 2 channel amp. Clean and Lead.

    thanks,

    GM
     
  2. anitoli

    anitoli Well-Known Member

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    Wouldn't it be easier just to get a two channel head?
     
  3. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Yes, it is.
    You will have to mount a potentiometer somewhere for the HDR MV.
    It can be placed at R15, the 470k 1/2W resistor.

    Are you related to the Marshall amplification people?
    If it is used in production or as a modification for profit I want to be compensated. :)
     
    Last edited: Dec 15, 2019
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  4. George Marshall

    George Marshall New Member

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    No.. no relation. Thanks. I'm not an electronics guy at all but I know one so I'll talk to him about it with your info. It would be great to be able to bring it down closer to the low range so they can be use together instead of one or the other.

    thanks again,

    GM
     
  5. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    :thumbs:
     
  6. headcrash

    headcrash Active Member

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    I wouldn't implement a MV around R15, since this is before the typical second triode-pair-stage including the cathode follower, and also before the EQ. I would put it after R42 and R48, which is after the FX and Reverb return signals are brought into the signal chain (FX of course only, when engaged). This is also after the EQ (treble wiper), which would be kinda the classic position for the master volume. Though you'd miss the phase inverter distortion, since the Master on the VM is post phase inverter. Maybe the dynamic range is gainy enough, so the master as I would implement ist, would be like a seperate "lead channel volume".
    You could also implement a second post phase inverter master volume, but it is more prone to popping than anywhere else and I have not seen it yet on any amp but the old mid 90s Fender Tone Master, where they switch the PPIMV in for the gain channel.
     
  7. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    He said "add an additional MV to the High Dynamic Range only" and that is what I suggested or rather told him how to do.
    The key word here is "only" which means he did not want it to affect anything else.
     
    Last edited: Dec 16, 2019
  8. RLW59

    RLW59 Well-Known Member

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    But in the title he specified a PPIMV. And the context of the first post indicates he wants a second PPIMV, with the stock one working only on one channel and the second one working only on the second channel.

    That's way beyond me -- I think that would need relays tied into the channel switching circuit.
     
  9. anitoli

    anitoli Well-Known Member

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    Wouldn't it be easier just to get a two channel head, again?
     
  10. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Well yes, like a Jubilee. :thumbs: Or a JVM or something like that.

    But all that may require selling and buying while he likes his VM and just wants the fairly simple modification.
     
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  11. headcrash

    headcrash Active Member

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    You're right.
    I always had in mind, that if someone modded it the way I suggested, he will have to involve a 2nd relay. But I should have written about it :)
    Several weeks ago I saw someone selling a VM in Germany with that exact mod. The modder left out the lamp, installed a classic red rocker switch, and used the hole from the lamp for the new pot.
    Of course what you suggested will work, and is much easier to do, but IMO it is just not "the whole thing", considering you would dampen down the signal before the two very Marshall-y stages.
     
  12. JohnH

    JohnH Well-Known Member

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    I love my VM, and have never felt a need for a mod like this. I get plenty of tone/drive change with volume control, from the guitar or by stepping on a pedal in front of the amp.

    But If I did, id still do it externally, rigging a footswitch with cables that go to the LDR/HRD socket, and others into the loop sockets to engage a passive volume pot in the loop to bring the HDR level down a little. The main MV would still control it all. Its not an independent PPMV volume control though.
     
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  13. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    He only wants or needs the extra volume control to match the two signal levels better for the his clean and lead (HDR) channels when swithing back and forth. It does not have to dampen or dull his sound and besides he has other controls and an effects loop to manipulate the signal.

    Honestly Marshall should have placed a volume there since most never know how strong a tube is going to be or the tolerances of the other components involved.

    Also, by the way, the two very next stages are basically copies from a Fender Bassman.
     
  14. BftGibson

    BftGibson Well-Known Member

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    The work around is a dedicated clean pedal like LPB1 or EQ to bring LDR up to HDR. Even 1 on board & 1 in loop. Or whatever. This amp can do a lot all on it's own with a few simple pedals place right in signal chain. Just use the pedal to retain the goodness at required level. Sometimes I use a Rat cause of the filter knob sweep is so great at dialing in ..can run humbuckers about 2 O'clock & then switch to strat & put it on 10 O'clock--never have change amp settings to accommodate the brightness..turn a dial a lil. Most my pedals are for stuff like this vs tone changers..like my amps natural tone too much to mess with
     
  15. JohnH

    JohnH Well-Known Member

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  16. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    I remember that thread.
    The guy (kot) never answered my question.
    That is a lot of work to balance the two signals especially if the difference is not that much.

    How much is the volume difference from normal to HDR?

    If the concern is the HDR signal being too low afterwards then the senses would say raise the BODY and DETAIL volumes and lower the MV to suit both channels.

    I do not think it is fair to cut down LDR and leave HDR free willy to do as it pleases. :D
     
    Last edited: Dec 18, 2019
  17. George Marshall

    George Marshall New Member

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    Thanks all for the replies. LDR to HDR is a big jump. Probably 20db?? Too much to use live. The kot mod looks like the fix but I wonder if adding a separate volume pot on the back can be used instead of the reverb pot.
     
  18. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    I still think its better to turn up the BODY and DETAIL while turning the MV to suit loudness. It should be able to get much closer doing that and using a potentiometer at R15 to control HDR level.

    Why would Marshall design a 20dB or more difference? 6dB, maybe 10 or so I understand. Another Marshall goof.
     
  19. BftGibson

    BftGibson Well-Known Member

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    never thought body & detail was anything other than blending both channels of a 4 holer. Set it the same as i do to them.,,treble side up to taste & normal to bring up bottom end to desired level..just went & looked..Vm is set just like the others...

    the LDR on this amp combined with the g12c cab is a seriously good channel. The amp likes all guitars.
    The other day was messing with SD1 & TS...it turns into a monster on HDR side..the body & detail can dial in anything ya want
     
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  20. headcrash

    headcrash Active Member

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    I have never owned a VM, but from my understanding by reading the schems Body and Detail both are gain knobs for different frequency ranges, if you like (technically it's not exactly that). So both are functional in LDR and HDR modes. Both want to mimic blending jumpered channels on a Plexi, as BftG mentioned. Takeing a look at the schem it does exactly that, with the jumper cable built in, albeit with some changes to the "original" circuit.

    I played a VM several years ago in a shop at low volume and didn't like it. At the time, I had no clue of the schematic. Now that I know what it does, and how it is built, I know why I didn't like it (PPIMV at really low volumes just does not the trick). But I think with some decent level, that amp will sound killer. I think Marshall did a bad job marketing-wise when they where introduced. They reissue it, and should maybe built in that HDR pot (at the place I suggested :cheers:), and put in the power scaling from the AFD or YJM.


    However, as I proposed above, I would have a tech throw out the lamp, install a lit power switch and put the HDR master into the hole of the lamp.
    Where that new pot sits circuit wise depends on taste. Mickey would put it where R15 is, I would put it later in the circuit.
    For my solution, the tech would have to install a second relay parallel to the relay, that switches to HDR mode, to disable the new pot for LDR. Mickey's soution doesn't need a relay. Heck, I would maybe test Mickey's solution first, and check out if this works soundwise (comparison between R15 stock or new pot).
     

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