Should I Change My Pre Phase Inverter Master Volume To A Post Phase Inverter Master Volume?

Discussion in 'The Workbench' started by kingsxman, Mar 16, 2016.

  1. Michael RT

    Michael RT Well-Known Member VIP Member

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    http://www.marshallforum.com/index....n-black-live-guitar-cover.89070/#post-1486561
     
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  2. kingsxman

    kingsxman Member

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    Tone is completely subjective. Maybe some (like myself) dont like the overly compressed signal you get with a cranked amp. I dont recall if I said this in my initial post or not (and too lazy to go re-read it) but I am really digging the tone from the pre-phase inverter and throwing on a KLON to push the amp. It keeps the openess of the tone (i.e. low compression) but adds enough grit to get it sounding very good. Plus I like the increased pick sensitivity. I'm just curious how much a pre vs post master volume changes the tone.

    I actually just sold my Fryette power station as, while the tone was good from a cranked amp, I found it a bit too limiting.
     
  3. jack daniels

    jack daniels Well-Known Member

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  4. jack daniels

    jack daniels Well-Known Member

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    http://www.guitaramplifierblueprinting.com/files/Phaseinverter.pdf


    The most important tube in your amp? The Phase inverter!
    Many people think that V1 (the first gain stage) is the most important tube in an amp. This is true in some cases but not in all cases. V1 (usually the preamp tube closest to the input jack) has the largest impact on your tone and gain but has less impact on your output distortion touch dynamics and output stage distortion than the phase inverter. The phase inverter is generally the preamp tube that is the most close to your output tubes in most amps.

    Let’s think about this for a moment. Today’s amps come in many “flavors”. There are three basic amp topologies looking at things from one viewpoint.

    • Non Master volume amplifiers

    • Master volume amplifiers

    • Channel switching amplifiers



    In master volume amps we have pre and post phase inverter master volume controls. These work differently but for this piece of writing I will put them in the same master volume category. Rolling down the master does what? It allows the front end to be driven harder and thus we hear our front end distort. At some point we can drive some amps so hard in the front end that the tone becomes so compressed and distorted that even I can sound like a decent player! Your mistakes are covered up in the mush and distortion of ti all. This distortion is passed down the signal chain where it is reproduced and amplified by the output stage of the amp. This has nothing to do with output stage distortion. This type of distortion is not touch sensitive. This type of distortion is not something that most articulate players would favor for a sweet tone, blues tone, or even classic rock tones. This is NOT what people refer to as the “brown sound”.


    ** In the Groove Tube Amp Book, the same thing is stated about pre MV amps (loss of touch sensitivity w/MV amps) **
     
  5. wakjob

    wakjob Well-Known Member

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    Outta respect for everyone here, I'll keep this as civil as possible.

    You have to know what kinda sound... AND tone someone is trying to achieve BEFORE giving any advice.

    This whole one vs the other mentality is ridiculous.
     
  6. jack daniels

    jack daniels Well-Known Member

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    I'll bet you didn't even read the #1 post from the OP, because if you did, you'd see he asked for, The Pre vs. Post MV question.
     
  7. MarcoR

    MarcoR Member

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    I had a conversation with one of my guitar idols (who will remain nameless) about an amp I played (which I will not name) that he used to use... He mentioned it was okay but all the distortion came from the preamps section and he preferred power tube distortion. I love this player but at that moment, I knew he didn't know what he was talking about... I think a lot of players who think they like power tube distortion haven't really heard it and probably wouldn't like it if they did. None the less, I rather enjoyed the amazing tone that player had that night; while he's power tubes were cooking for sure, the distortion was alas, from the preamp. Sorry for getting off topic..
     
  8. GuitarMutant

    GuitarMutant Well-Known Member

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    A lot of this depends on the amp as well. 99% of the time, I prefer the preamp distortion. Some amps have bad sounding preamp distortion (to my taste) and others sound good this way. My amp selection is usually based on how the preamp sounds cranked, then 75%, then at halfway, then at 25%. If it sounds good at regular gigging volumes at all of those settings, it's a keeper. It needs to have headroom in the power section for me (again - 99% of the time) to allow the loop effects to come through clean. This can be another argument - loop vs. straight in and no effects. I need a level of versatility in my amps. I'm not a purist. I'm not a corksniffer. I'm not a tone snob. Make it sound good and I'll play it. But the versatility must remain.

    What about the other 1% of the time, you ask?
    I've tried a number of NMV amps, and I've sold them all. Except one. I have a GR Amplifiers 36w Plexi style. It's the ONLY NMV amp I've ever owned that sounds glorious when almost pegged. No loop, no pedals, no nothing. Just guitar to amp. I cannot tell you why it works where others have failed. Usually power tube distortion to me has been far from ideal. Too compressed for one. Also limites the effectiveness of the tone controls (I find they get less reactive the louder the power amp is pushed). Etc. But that thing just sings for some reason. Terry made a monster there.

    I guess what I'm trying to say is - from MY experience - it depends on ALL factors. User's ears and desires, the amp itself and how the circuit is built, the need/desire for flexibility, the typical playing volume, blah blah blah. Not just what others' opinions are. (Although - others' opinions are still a great place to start so you can get descriptions and reasons why others have chosen the path they did)
     
  9. AlvisX

    AlvisX Well-Known Member

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    The OP said '76 JMP ,but didn't indicate if it was a 50 or 100
    IIRC,the '76 50w 2204 /2104 were the ones with a "master vol", but a non cascaded preamp...???
    If indeed that's the OP's case, I'd say yeah to a PPImv

    As for cascaded amps,I've never thought a post phase master did anything for them .When I get one that has it, I always change it back
     
  10. jack daniels

    jack daniels Well-Known Member

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    Speaking of NMV amps that sound glorious when turned up, supposedly some of Ken Fischer's Trainwreck amps were great examples of this scenario. The key to Ken's amps were in the selection of transformer (types/brands).
     
  11. kingsxman

    kingsxman Member

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    Bump an old thread. Still have the amp and now im going to be gigging it shortly. I've had a Landry LS100 G3 for 6 months that i love. But am going to have to sell it to get some $$ to fund a guitar. So the 76 Marshall 50 watt jmp is coming out now on gigs.

    If i wanted to replace the pre phase inverter master with a post PIM....does anyone have a recomendation on where to get parts and a schematic/instructions for the change?
     
  12. RickyLee

    RickyLee Well-Known Member VIP Member

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    This man hit the nail right on the head

    This past weekend I had my '76 Twin Reverb out and was cranking it hard here at the house, doing some testing on the bias circuit, power amp circuit and testing a couple different grid leak resistor (bias feed resistors) values. I had the amp cranked. Channel volume on 10 as well as master volume on 10. This amp sounds glorious cranked but much different than my '70 Twin Reverb which breaks up much more.

    The pull knob out on the MV distortion circuit does not sound very good though. But I did find a use for it as it sounds cool and is fun to use when you have the MV set real low as in a late night trying not to wake anybody up type volume. Very saturated and lots of sustain at that setting.
     
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  13. RickyLee

    RickyLee Well-Known Member VIP Member

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    I found this thread that talks about the LAR MAR PPIMV that I have used on both my Jubilee Clone and one of my hot rodded Plexi builds. Scroll down a bit in it for the pics/layout. Looks as if there is some discussion on it as well.

    http://el34world.com/Forum/index.php?topic=3496.0
     
  14. kingsxman

    kingsxman Member

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    THanks.
    Thanks. Looks good. I'll check that out. I still am not sure if all the extra work will be worth it or not.

    Here's what I'm noticing right now: On my 76 JMP 50 watter, I have volume 1 around 3:00. (Any less and sound is far too bright and shrill). I turn volume 2 at around 10:00 (with nothing plugged into any of the inputs. No jumpering as that "channel" is too muddy. It does fatten sound a bit even with nothing plugged into inputs). The tone is pretty good. Adjusting the pre-phase master on back I can adjust the volume pretty much to where I want it. However, the amp doesnt clean up "great" when rolling back the volume on my guitar. Overall the tone is a bit on the thin side unless I bring up the volume a bit more on the master.

    Will I get a bit fatter tone with a post phase master? (I dont want muddy bottom though). I'm guessing the ability of the amp to clean up with rolling guitars volume back is more a function of the "amp" rather than the master volume...but thought I'd ask.
     
  15. tremojem

    tremojem Member

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    For what it is worth...a good friend of mine and I looked into this and in an uncontrolled test we discovered the following.

    Test material used:

    Ceriatone Super Lead 100W 1968 W/PPIMV.
    Marshall 1960B 4x12 W/GT75s.
    Hotplate Attenuator.

    Firstly, using nothing but guitar into amp and maxing the PPIMV, I am of the opinion that there is not much to gain after adjusting your channel masters past 50%. Not much increase in volume, just compression and really not feeling or sounding good at all.

    We switched back and forth from using the Hotplate to using the PPIMV. At no time was either in use in combination with the other. We maintained almost 50% of volume by attenuating with the Hotplate or the PPIMV.

    I leaned heavily towards the PPIMV, as the attenuator sounded a little less clean and more compressed, or just plain shitty, for a lack of a better word. Neither way offered better touch sensitivity.

    When you use an attenuator LESS IS MORE. So if you only attenuate very little, it sounds fine, but if you dime a Super Lead 100W and expect to play in your living room while your family is in the kitchen baking cookies, it will sound like ass.

    I will say that if you must push the amp to 50%, which is ideally the sweet spot, using the PPIMV, and then attenuate a little with the Hotplate...it is all good, but still loud...not too loud though, as I play loud anyway.

    So, to each his/her own.
     
  16. tonejunkie99

    tonejunkie99 Member

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    nearly anything would sound better than a ppimv and this is why --- The JMP preamp in it's stock form is not hot enough source of overdrive/distortion. As a result many of the harmonics that are essential for good tone will be compressed away to oblivion in the phase inverter and what little remains will increasingly drop out as the PPIMV resistance decreases... Basically the more you turn down the master, the crappier and crappier the amp will sound, much below 7 or 8 you will be left with a very cold feeling amplifier with zero dynamic response because the power tube grids are getting tickle fed a bunch of harsh nasty bits...

    To get good sound at low volumes I jump channels to boost lows and keep the bright volume down to that point just above where it starts to come (ON).
    Some players say I use the amps like slaves, pushing the front end with Bixonic Expandora / Tubescreamer ETC.
    these simple tried and true methods may not work well for others but it works extremely well for the blues and stoner rock I do...
    Trower Cream Hendrix Bad Company ZZ TOP ETC. All use similar Pedals ---
    . View attachment 37446 View attachment 37447 View attachment 37450
     
    Last edited: Oct 16, 2016
  17. tonejunkie99

    tonejunkie99 Member

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    .
     
    Last edited: Oct 16, 2016
  18. SmokeyDopey

    SmokeyDopey Well-Known Member VIP Member

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    LMAO! :lol:
    I agree, though.
     
  19. sinner 13

    sinner 13 Well-Known Member

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    ^^^YUP^^^
     

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