Post Phase-Inverter Master Volume & Taming Stage Levels

There are more important things than tone. I know…the very nature of that seems heretical. But, if we have established that our evoking-of-tears-anti-solo-with-sweet-Johnny-Buckland-ripoff-reverb-decay actually means nothing without the chord structure from the bass, piano, acoustic, rhythm electric, cello, whatever……then if you also cannot hear the chord structure from the bass, piano, acoustic, rhythm electric, cello, whatever……then there comes a point where cranking your amp to get the tubes warm and the the preamp and power amp sections ‘pushed’ for stellar tone, actually succeeds only in making that amazingly sweet tone mean absolutely nothing.

And of course, this is the point where most guitar articles usually go into the ‘next killer amp modeler’, or tube-buffered direct box, or some other gimick that is supposed to emulate a cranked amp. Which it won’t. There is no ‘emulation’ of signal actually passing analog through tube-driven amplification, and certainly no emulation for actual sound waves naturally coming through speakers and literally moving air. Now, I can’t tell you what you like and don’t like. (Much as I wish I could…hehe.) So it is possible (though I cannot see how… ;) ) to like sound from amp modelers and such. But it’s their own sound. Not a live amplifier with real tubes misused and overdriven. Just as you can get string sounds from synthesizers that you can like for what they are; but they’re not an orchestra. There’s a reason actual films still use the London Symphony Orchestra and LA Philharmonic for their scores. Well, most films. ‘Raptor Island’ definitely used keyboard strings. And ‘Rats.’ You know, the one where half-finished computer-animated rats float on top of people as they gnaw their ears off. (And they’re not supposed to be floating…that’s due to the afore-mentioned ‘half-finished’ nature of the animation.) All the while the synthesizer is banging out some unfortunate ‘string’ part that makes me want to hurt myself.

Raptor Island
(They never use the gun. I have no idea why. And this movie vaguely reminds me of some other movie…can’t think of it right now…something about ‘Jurassic’? I guess if it works once, may as well rip it off and do it again…and at lower quality. And you don’t even have to rip it off, either. You can have the copyright, and still do a lower quality ripoff. Like Jurassic Park 3. A whole hour of the same rubbish I’ve already seen 4 times. I mean, uh……2 times. I didn’t watch Raptor Island. Or Raptor Island 2. Yep, there’s a ’2′.)

So I guess what I’m saying is that amp modelers are the ‘Raptor Island’ of tone. (*Barricades himself behind stacks of point-to-point wired tube amps for the onslaught of Lincoln Brewster videos that are sure to come flooding in.*) But seriously, if you use them and are getting tears of sweet tone, more power to you. Make that music, be that person, and rock. But for me, maybe I’m crazy, but it’s gotta be a bit more real. And I’m not talking about killing stage volume altogether, or getting a 1/2 watt ZVex amp or something. You need volume. Tubes need to be hot, every amp has a sweet spot on its gain knob, speakers need to be pushed, and air needs to be moved. A little stage volume is a good thing. Keeps things feeling fluent and live. Too pristine gives off a sterile feel that looks good on paper, but feels awkward live. But you have got to be able to find a way to get this tone and feel at volumes that can still blend with the band, and can still give your sound tech enough control to be able to blend with what he hears at the front of the house. Because like it or not, we cannot face-melt and run sound at the same time. I mean, I guess you could get a wireless system and do it, but knowing us, we’d just end up cranking our gain knob on the actual sound board. Because ‘these go to eleven.’

Enter post phase-inverter master volume. It comes at the end of the preamp circuit, as an overall, well, master volume. And when done right, it allows stacks of tube saturation without any noticeable tone loss, warmth loss, high end less, frequency response loss, feel loss, or weight loss. (This is like an infomercial.) Beautiful. I had this mod put into my Divided by 13 RSA23 by Jerry Blaha in Hollywood. And he does a fantastic job, with some of his own ideas thrown into the mod…such as placing it after the power amp. Which I love the sound of, but does go against the definition of most ‘post-phase inverter’ master volumes. However, he describes it as sounding most like ppimv. But there are many techs and amp builders who can do this. Gives you the tone you want, without having to get an amp-in-a-box, run your amp in a closet, or build a little house for it on stage.

Storm Trooper in San Diego (small)
(Speaking of bad movies, my wife took me on a date yesterday…yep, she took me…she’s amazing…to one of our favorite lounges and a show in downtown San Diego. Little did we know it was the first day of Comic Con. And there were so many things I did not understand. Costumes, people who looked like they were in costumes but you could tell they wore that every day, lines that wrapped around 4 downtown blocks of girls waiting to see the guy from Twilight…and for once I don’t know the actor’s name, and I would like to keep it that way…please do not tell me what it is…, and oh ya, storm troopers outside Dussini’s. My wife snapped that picture. Most times, you don’t need comedy films or stand-up clubs. You just need people who are into video games, Twilight, and galaxies far, far away. Because of course we guitarists never get into our stuff at all. ;) )

Last month, I posted an article on the different ways to get stage volume down. There’s power dampening, attenuators, master voltage, closets, etc. I’ve tried almost all of them, with the exception of master voltage. And thus far, a well-designed post phase-inverter master volume circuit is the best I have tried. I did a quick video on it, complete with playing through the click channel on the RSA23 with the gain dimed. And if you’ve ever had the opportunity to crank gain on a KT88 or EL34 amp, ya…it’s not quiet. But so incredibly saturated. So, with the ppimv mod, you can actually use the cranked gain sound.

So here’s the video, complete with me trying to figure out what exactly you’re supposed to do with a cranked gain Marshall/HiWatt sound. It was awkward. But hopefully you can hear the tones from the amp that the ppimv allows you to achieve:

Yep. Sounds like Jimmy Page without the talent part. But the gain that you can get, as well as clean tones on the verge of breakup, are pretty cool; and at bedroom, club, and church volumes. Obviously, you’re not pushing the speakers as hard…but you are giving them a broad spectrum of sound with the added gain, even at low volumes, which pushes them in a different way. And with a well-done ppimv circuit, you can turn it all the way up, and still get the sound of the amp wide open as if the master volume wasn’t there. With stuff like this available, I simply cannot see why you would ever have need of amp modelers. (Okay, maybe for reliability, tonal constancy regardless of temperature, versatility, etc……but that stuff just ruins my point. So I’m not going to mention it.) But the main thing is that you can still get your tone, feel, dynamics, warmth, and either gain or clean on the verge of gain (whichever your preference is for the given situation) at volumes that will still blend with the music. Because, unfortunately, music is kind of the point…and our guitar and it’s subsequent tone (hopefully) are there to support the music. Which sucks sometimes, because I do like it to be about me. Less tears at night. But I guess if it can’t always be about me, post phase-inverter master volume is the next best thing.

Oh and speaking of storm troopers (haha…such awesomely smooth transitions today), if you’ve never seen this, watch the right side of your screen:

hehehe

Splendid.
Karl.

33 thoughts on “Post Phase-Inverter Master Volume & Taming Stage Levels

  1. $240 plus parts, usually. Unless it’s an unusual circuit and he has to build a schematic. Which is way cheaper than a good attenuator, but also of course not transferable from amp to amp like an attenuator.

  2. This is exactly why I am looking at the Matchless Lightning as my new amp. I was amazed at how incredible it sounded even at lower volumes.

    I have discovered, to my dismay, that our sound guys at church pull the guitar out of the mains because they can clearly hear my amp au’ natural. I have been trying to get a lower volume with the same tone for months and I just end up turning up the amp in the end. I installed a weber attenuator in my Traynor which did make a big difference, but it still just isn’t quite the same.

    Besides. The Matchless amp is just plain cool. It lights up.

  3. Tom–haha The lighting up is absolutely the best part. :)

    But ya, that’s another great reason for bringing stage volume down. Because so many times you’re asked to turn your amp sideways or backwards or something, but then you’re still so loud, you’re taken out of the house anyway. Now the only thing the congregation or audience is hearing is the secondhand mud bouncing of the side wall. hehe And ya, Matchless definitely has really good master volumes. Great info, and thanks for bringing that up!

    RyanJ–for me, it was tone. I bought a Ho attenuator, which was supposedly the best money could buy, and a/b’d it with the ppimv. And it sounded good, but nowhere near as clear, smooth, and natural as the ppimv. (One of the guitarists on this board who has a great ear says that the Ho attenuators aren’t what they used to be; so that could be a factor. But most of my research has them supposed to be sounding still really good.) There’s just something real the ppimv captures that all the attenuators I’ve tried don’t. To my very, very humble and untrained ears.

    Also, it’s nice to not have to carry around an attenuator. hehe But that’s just laziness. :)

  4. This is funny… because this is the very reason I use the X3L….

    (Okay, maybe for reliability, tonal constancy regardless of temperature, versatility, etc……but that stuff just ruins my point. So I’m not going to mention it.)

    When giging alot it is also easy to pack in and out…

    The tone you are getting out of that amp is just wonderful. I would be satisfied with that tone for at least 6 months. ;-)

  5. good to know. i don’t have much attenuator experience, i had a badcat leash for awhile, i actually liked the sound of my amp turned down with pedals better than w/ the leash.
    you might be indirectly talking me into something.

  6. Sal–haha Ya, I give amp modelers and such a hard time, but I do recognize their purpose and significance. Every once in a while…we’re talking like, once a year…usually on those 117 degree July Sundays like this coming weekend, the thought of an X3L flashes into my brain. I then do my best to stuff it far, far away and hope nobody noticed. hehe :)

    And thanks for the kind tonal words. lol Six months would be pretty good for me, too! Cheers.

    RyanJ–I totally hear ya. Some attenuators sound worse than like, turning on an od pedal and turning the volume down on it. hehe Some are decent, but I’m just liking the ppimv.

    And if I indirectly help you spend more money on more gear and mods and such, then my purpose has been accomplished. hehe ;) That’s why guitarists hang out…to talk each other into more gear.

  7. I’ll pray for you guys. :-) I say this with affection and a smile: sounds like Porsche drivers who just have to have a Ferrari. I think I’m more in the Prius driver longing for a Mustang category.

    I played at a Christmas party for our company once with some co-workers. At that time I had an old Peavey Renown — 160 solid state watts into two 12 inch speakers. My bandmates complained that it was making their fillings loose. LOL So I miked my little Carvin Vintage 16 into the PA we used at the Radisson Hotel in Sacramento. Cheap stuff compared to the discussion here.

    Speaking of gear-heads, check out this guy
    http://www.youtube.com/user/Burgerman666

    Lastly, still on tone, a quote from the Foo Fighter’s Dave Grohl on Gibson RD Artist guitars:

    “RDs are awesome. It’s like holding a kitchen table over your chest and having it scream like a jet airplane. I like that they’re really heavy and can sound fat or bright. They’re kind of nasty guitars — played through a Boogie Rectifier, they sound completely insane.”

  8. Randy–as my amp tech says, ‘Better than drugs or gambling.’ :) But in all seriousness, I’m okay with having a lot of money go into something that is artistic, and is used for God. I drive an older car, have no boats, motorcycles, or other toys; no cable, live in an apartment, and I shop at Ross and snack on peanuts. hehe :) So I’m kinda proud that the one thing on which I actually spend 10% of what most people’s cars cost, is going towards bettering me artistically, hopefully bettering people around me, and helping to glorify God.

    But you have a point, brother. ;) And of course the answer to the Porsche/Ferrari or D13/Matchless question is……both. lol

    Sal–Nice! I’ve been looking at that guy’s stuff. There’s actually a link to his old Worship Musicians message board at the bottom of my links to the right. But I think it shut down. But Joe’s a great guy, and next time I don’t have money tied up in Divided by 13′s and Matchless’s I need to sell, hehe, I’ll definitely have to try some of his stuff. Are you a friend of his, or do you play one of his amps? :) Good times!

  9. Yesterday I was changing out the speaker in my Carvin 16 from the stock cardboard made speaker to a Celestion V30 and had posted that on my facebook… my pastor saw it and sent me this link, he used to play with him at a church he planted. So I saw this and thought for a moment…”I gotta have one of these”, It was a fleeting thought… I came to my senses after I woke up this morning…

    I do like the sound of the Celestion in my V30, this speaker really smoothed it out. Cost so far…. Carvin16=Free, V30=Free…grand total=Free How sweet is that? Now I am looking to get the mod kit for it…gonna have to pay for that…;-)

  10. I heart master volume. I don’t know if mine’s ppimv but it sounds like what you’re describing. I set my gain where I want it and then just turn the master up and down for the room. Brilliant. The best part is if you turn the master to 10 it’s essentially bypassed and you have the original amp circuit at full power.

  11. I have a modeling amp and used it extensively during a two year period when I stepped back from recording and playing live because of a BAD experience I had playing in my first Christian band. Go Figure. I think I was paying penance.

    Anyway, it was a Line6 Flextone. I used it for teaching and annoying my children. It was pretty effective at both and overall it didn’t sound bad. I played it long enough that I totally forgot how a tube amp feels. Then a buddy of mine stopped by with his old Fender Princeton and left it at the house for me to play around with. He never got it back and I’ve got all my tube amps out of storage.

    There is just a certain something about the feel of tube amps. If you play one, you know what I mean. Is it possible to get the “tone” of a tube amp from modeling? Yes…you can. I spent a couple of weeks once programming my Flextone to sound pretty much exactly like my Orange, Fender and Frenzel tube amps. I got really close, but…it didn’t feel the same. And feel is as much a part of my tone as what comes out of the speakers.

    I know that Lincoln Brewster uses modeling when touring. I’ve seen him live and he’s a great player and sounded good coming out of the mains. In the same song, he could go from Fender clean in the verse to Marshall crunch in the refrain to Boogie scream for the lead. Setup time at the gig was probably 5 minutes. I’m happy for him. But…lets be honest here. He’s still just trying to copy tones that come out of a tube amp naturally. And he’s doing it for convenience sake.

    I don’t think I’ve ever met a guitar player that didn’t like the tone of a cranked tube amp. That’s because nothing sounds and feels like one. Would it be a pain to run a three amp setup with a switching system to manage it. Yes (I’ve done it.) it is a pain. Do I still use that three amp system outside of my house? No. Why? For convenience sake.

    My worship pastor at church uses the Line6 for times when he wants to lead with his electric and it sounds fine. It doesn’t cut through the mix like a tube amp will but….that’s what he’s got me for. 

    What does this have to do with anything about anything?

    Nothing.

  12. Mark,

    I couldn’t agree more. Even though I use an amp modeler, it is for making life easier when gigging a lot.

    Nothing can replace the feel of hot tubes. My favorite set up is still my guitar plugged direct to an amp. Any effects will have to come thru my finger tips. There is not a single one of us who read Karl’s post that would actually prefer modeling over the real thing.

    In our ultimate search for tone we not only want to satisfy our inner ear but like you wrote…

    “I’ve seen him live and he’s a great player and sounded good coming out of the mains.”

    We as guitar players also seek that recognition from other players to say such things as “it sounded good”.

    As for me…. I just hope to one day sound like Karl.

  13. “‘Better than drugs or gambling.’ But in all seriousness, I’m okay with having a lot of money go into something that is artistic, and is used for God. ”

    Absolutely ! I sure wouldn’t attempt to influence anyone else on how they spend their money. At least not here. I think I’ll try that “better than drugs or gambling” on my wife next time I “need” something in the way of gear. :-)

    Not likely to work on her though, she’ll walk across the street to pick up a dime. I count my blessings though, she won’t set foot in a store anything like Macy’s or Saks Fifth Avenue.

    I may just have to rent a decent tube amp to see what everyone is talking about. My carvin Vintage 16 doesn’t move enough air for me to “get it.” Of course in our church the Vintage 16 is about as large as I could get away with. I did try a big “Eddie Van Halen” full stack once in an empty guitar center store. Something like a 100watt tube head sitting on two 4×12 cabinets. Now that was fun ! I’d like to hear more details on how you describe this tube “phenomenon.” Particularly when it’s a big enough rig to move air and interact with your guitar. I hear terms like sag, breath, etc.

  14. Sal–all for free? Man, you gotta get me to your guitar store!! hehe ;) But seriously, that’s totally awesome. I think the V30′s are the best mid-priced guitar speaker, hands down. Very underrated.

    And oddly enough, I knew exactly what ‘Celestion in my V30′ meant. lol

    Mike–right on! It might be ppimv; either that, or just a really well-designed master volume circuit. Isn’t it glorious to be able to get the same tones at all levels? Getting shivers just thinking about it.

    Mark–great info! And I agree with you that most amp modeler users are just doing it for convenience, and that it can definitely be more convenient. But what I just said isn’t nearly as eye-catching in a blog post as ‘solid state sucks’. So hence, solid state sucks! ;)

    But I hear ya. hehe

    Sal–I agree. There’s no replacement for hot tubes. But I do hear your point, that there are times when all the gear is just too much to lug around, yet you still need a Marshall, Vox, and Fender sound all at the same gig. :)

    I think I just have a complex. Because I would probably bring a Vox, Marshall, and Fender, and then get angry when the sound guy asked me to turn down. hehehe J/K…I hope. :)

    Randy–lol If that phrase works, you gotta let me know! hehe :) No, but in all seriousness, my wife’s really sweet about it.

    As for the tube thing, sometimes cheap or old tubes will cause you not to hear it. That’s how it was with me. Everyone was talking about that warm, huge tube sound. So I bought a friend’s old Peavey Classic 100 (which is a great and very underrated amp, by the way). But when I turned it on, I was like, what’s the big deal? Finally I changed out the preamp tubes (which were very old, and stock no name Chinese ones, too), and all of a sudden, the difference was huge! Bigger than going from the Crate solid state to the tube amp. So, old or cheap tubes can definitely kill the ability to get that, ‘Oh, that’s why everyone’s talking about tube amps’ feel.

  15. I got a hold of the guy who sells the mods… and it will cost me 40 bucks. so that will be the cost of the amp total…..YEEEEEHAAAAAAA!!!!!!!

  16. Hey Karl,
    Awesome article. I totally agree with what you are saying, and I feel your struggle. I too Hate to sacrifice tone, but recognize the need for balanced band sound.
    I don’t want to sound all snotty, but I think you gave a slightly wrong impression of what PPIMV is, but you did a great job of showing the improvement in sound it provides.

    The phase inverter is still often 12ax7 tube types and comes after the preamp/tonestack. The PPIMV however, does choke the signal before the power tubes still. You do get the benefit of the pushed phase inverter tube though, and it sure does add a lot to the tone. And, it might even get you the exact tone that you are after.
    However, the only way to get the actual pushed power tube sound is with what you described as a “Master Voltage”. Power-Scaling is the most famous one, and the one that I use in all my amps is called VVR (Variable Voltage Regulator). THis guy, Dana, sells the kits and knows his stuff when it comes to building amps:
    Check out Hall Amplification and click on products and KIts:
    http://www.hallamplification.com/main.html?src=%2F#2,2

    Matt

  17. Hey Matt,

    Thank you for the info! And I really appreciate your unassuming way of presenting it as well. :) You are right, and I’ll edit the article right now; I should have said, ‘comes after the preamp circuit.’
    I may have chosen my words poorly, as my tech describes his mod as sounding like a ppimv after the power amp. Seems more like power scaling, but I figured I’d take his word on it, as I am admittedly not as intelligent or learned as I’d like to be when it comes to the technical side of amps. But since you brought it up, I definitely do not want to be misleading. So consider it fixed, and my hat is off to you sir.
    Again, thank you. I make every effort to be accurate on this blog, but sometimes I’m just flat out wrong. And many times stupidly wrong, at that. hehe That’s probably due to buying gear when I should be studying actual music, and the parts that make it up. :)

    Cheers,
    Karl

  18. So Karl, I guess I am more confused than before, and my curiosity is really piqued.
    I understand that your tech’s mod is something that he developed himself a bit to sound really good. And, it really shouldn’t be your responsibility to have to fully understand it. You paid for it, you use it, and you love it.

    I’m more interested in backtracking and correcting any assumptions I may have made in error.

    So, does he mean to say that it is technically a type of PPIMV that SOUNDS LIKE it is after the power amp, or that it ACTUALLY IS after the Power Amp? I am 100% sure that your guy knows much more about amps than myself (not false modesty- he is a real tech).
    So, I am wondering what his mod his technically classified as. My first assumption is that it is a Post Phase Inverter Master Volume that he has designed quite well. But I don’t think (could be wrong) that it is possible to do it after the Power amp in the signal flow. Well, I guess you can dump power after the power amp, but that would just make it an attenuator, and no one would bother using the term PPIMV in regard to it and it would involve some pretty big components.

    I keep wondering if he is using some sort of Master Voltage or Variable Voltage Regulator and just trying to use a term that more people are familiar with in amp-using circles. I’ll often label my VVR knob as Master just because very simply, it acts like the uninitiated would dream that a Master volume should work-> all the same tone, but just quieter.

  19. hey karl, i tried something similar last night with my ycv40 setup. instead of using an attenuator (after the power-amp), i plugged in a volume pedal thru the fx-loop (after pre-amp). there is definitely a difference in sound.

    with the attenuator, i can really push the 5881′s to break-up even with the pre-amp volume at 4. with vp, no matter how much i push the volume on the pre-amp (tried it at 7), i can’t get the 12ax7 tubes to saturate/break-up. maybe i should get new pre-amp tubes.

    the nice thing without the attenuator, is that i can hear the low-end better. the problem is it sounds a little brittle on the high-end … so i might still come back to the attenuator.

    oh the choices … to think that the congregation probably doesn’t care! hehe :D

  20. BCMatt–haha Man, I wish I could understand what my tech was saying half the time! I believe the master is after the power amp, making it more of a power scaling thing…but when he saw the glazed over look in my eyes, he probably mentioned ppimv as what it most sounds like. That’s the best I can do for now; I’ll ask him to go into more detail next time I see him.

    Either way, I should have written ‘after the preamp’ in the original article; thank you so much for pointing that out! :) Cheers, my friend!

    Rhoy–Nice! I love hearing about experimenting like that. :) Ya, the volume pedal in the effects loop will definitely take a good deal away…strange that you can’t get the preamp tubes to break up, though. Maybe you do need new ones. Huh. Well, and from what I’ve read, Traynors have a very good amount of clean headroom. Of course, you’d know more than me, as I’ve never owned one.

    And that’s been my issue with attenuators, too…very brittle in the treble regions. Seriously…so many choices! haha If only they’d build the churches large enough to accommodate our amps!! lol

  21. Karl, just to clarify something:
    Most master volumes are after the preamp. A PPIMV is even later, after the last “preamp” tube, the phase inverter. There is a school of thought that says that most of the smooth drive we love comes from the phase inverter. And if that theory is correct, the PPIMV should allow the same amount of drive at lower levels because the phase inverter is being run full bore. The problem is this school of thought is wrong (because I said so). The beautiful drive comes from the power tubes, and a true PPIMV will still turn down the power going to those, and it will sound inferior to the amp being run all-out. So, yours might be different if it doesn’t turn the suck up when you turn the volume down.
    Also, have you ever tried the Weber MASS attenuators? They are supposed to be less brittle than the others, because they actually drive a voice coil as a resistor. [Good] Speakers naturally compress the highs a bit, smoothing out the upper end, and the Weber is supposed to use this as a way to get good tone at lower levels. I haven’t tried one yet, but I will be shortly. No one else at my church appreciates how good my amp can sound, even though it’s only running at 15 watts.

  22. Lol! I love it. Oh how I wish things were true because I said so! hehe In my humble opinion, it all depends on what sound you’re going for. I’ve heard some guys sound fantastic with just preamp drive…others, like say Jimmy Page, seem to rely on power tube breakup. In which case, yes, master voltage, power scaling, or attenuators can be good options.

    I’ve tried one of the smaller Weber attenuators, and it was very decent…sounded just as good to my humble ears as the Ho. However, I just have never been able to find the smoothness I’m looking for out of an attenuator. But that’s just me. And it could very possibly be operator error. ;) hehe

  23. An ID 10 T error? I personally have never used one, either. I just run my amp at 15 watts, and its quiet enough. Usually the drummer is louder than me anyway.

  24. Karl,
    I’m kinda lost. What’s the difference between a PPIMV and a cheapo “suck knob” from ebay to attenuate via FX loop?
    I always thought the “suck knob” was ripoff… but the hole thing about pushing the phase inverter tube sounds awesome! I’ll give it a try with a pedal or something…
    Even if it doesn’t do wonders to the tone it will probably help since my JCM900 master fader starts abruptly at 1.5 – more precise volume control.

    Just so you don’t hate me for using a JCM 900: I also have a 1965 Blackface Fender Vibrochamp ;)

    I love you site and I’m catching up reading all your posts!

  25. Hey,

    Recently came across your blog… some great insights for the most part. Just wanted to make a comment on the PPIMV. It works well in a lot of amps, but not all…

    Depends where the gain is coming from, basically. I’ve built a few amps myself, and gotten into circuit design lately.

    In Vox type of amps, a lot of the grind comes from the preamp and how it hits the phase inverter (which, in that amp clips really hard). So a PPIMV really gives you something other master volumes don’t – hence sounding more like the cranked amp.

    However, in something like an 18 watt marshall, the vast majority of the overdrive comes from a really clean pre-amp/phase inveter hitting the power tubes hard. Putting in a PPIMV only cleans up the sound of the amp – rather than getting it to sound overdriven at a lower volume level. Kind of the opposite of what one wants!

    In larger fender & marshall types of amps, a master volume after the phase inverter may or may not sound better than one before the phase inverter… some designs seem to work better in different amps. Just know the PPIMV doesn’t universally sound better.

    Something after the power tubes, like you described, though, would allow the power tubes to do their thing still… you’d need some pretty hefty parts to handle the voltage/current in that part of the amp though, if that is what is really being done…

  26. Hey there guys, love the discussions on this page. I build amps, infact we are currently building for Avatar Speakers may be building for Xits and Naylor as well. here are some thinigs I have to say about PPIMV’s, one like patrick says they sound absolutlely horrible in certain amp circuts, the actual 1974 18 watt circut is horrible with a PPI…..yet a TMB modded 1974 circut sounds great. Headroom of the power section plays a great deal into this, if you already have a great, fat punchy power section you will have a great sounding PPIMV. If you have a really brite snarly power section it tends to sound brittle. The amps we have installed them on and that I have owned include the new Avatar 45 amp, a 1983 JCM 800 (still had brutal volume at 126db out of a 50 watt head), Splawn Quickrod, 18 watt Marshall TMB built by us. We did a lot of work designing the Avatar 45′s PPIMV but the other thing we did is change it to a single input but left the bright/normal channels in the circut with the ability to switch between them or cascade them all the while still allowing you the ability to use the PPIMV. With all PPIMV the presence control is affected at lower master volume settings. David Bray who is the absolute master of building PPIMV amps plain and simple (as well as Paul Reed Smith Customs LOL) explains it best. Most people think they getting a overdriven and saturated power section when the amp is cranked but it is actually the pre amp section that clips the most. Also adding a Global control makes a you more able to dial in your tone with a PPIMV. Remember Transformers also play a huge role, using an underrated transformer can give you the “sag” that we hear when the power section is crying for more voltage. Bias also plays a role. If I can ever be of any help to anyone please let me know, the Lord is blessing us abundantly in our buisness right now and we love to pass that on.

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