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WARNING: Dangerous Levels of GAIN! ...EPIC Guitar Amp Conversion!

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In this vid, we'll convert a vintage Precision Electronics Grommes 50PG-3 PA amplifier into a high gain guitar amp with a Fender Princeton tone stack and 6V6 output. I left a lot in this one, so pull up a comfy chair and grab some popcorn. (Schematic used in this vid is for a model 55PG.)
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Опубликовано:

29 авг 2024

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Комментарии : 688

@heathbarnhart1092 6 лет назад

That's probably one of the best sounding amps I've ever heard.

@johnymartin5411 3 года назад

Ever hear a hovercraft?

@Buhhhhhh-xi4ju 3 года назад

@@johnymartin5411 lol every hear of a mace?

@johnymartin5411 3 года назад

@@Buhhhhhh-xi4ju nope , but hovercraft are some pretty awesome amps

@frankferriolo9212 3 года назад

Yes!!

@madmod 3 года назад

Peavey Festival 200w head biased so hot you're changing tubes between songs. Take that to the bank.

@mushkamusic 6 лет назад

Man this is one of the best sounding amps you've done. Nice job dude.

@joshuaweiner6378 6 лет назад

I find watching Brad's videos very meditative, even if I only can follow 1/4 of the tech stuff. Great sounding amp!

@russellhltn1396 6 лет назад

Re: Loudness. Very common on Hi-Fi systems. It adds bass boost at lower volume settings so that the sound doesn't go "tinny" because of the way our ears work. Look up Fletcher-Munson or equal-loudness contours for the details on the "why". Seems like this might be a nice thing to have in a practice amp.

@dwaynemcallister7231 6 месяцев назад

I recall the stereos systems of the '70's and they usually had a loudness button.

@TonySkiens 6 лет назад

i do believe what the client meant by "smooth" was the transition from clean to overdrive on the gain pot. A smoother transition from clean to distorted...

@Boogiemoose 6 лет назад

Another nice one Brad. I rather sit here for an hour and half and learn something than watching a stupid TVshow or movie. Sounds great.

@tubical71 6 лет назад

best answer ever! go build your own stuff, even if it won´t work first place, keep on doing it, and you end up with a unit that just will perform maximum right for you.

@jkhan337 4 года назад

i agree

@alainbrisebois8334 4 года назад

I spend hours and hours learning on you tube. I even learned to play guitar.

@erikvaldur3334 5 лет назад

this amp sounds fantastic. can't believe you played Pantera with this thing. Awesome job man

@matthewf1979 6 лет назад

Yes! A switchable NFB is my favorite mod. Tonally subtle but the amount of gain it frees up is crazy. It’s like an old school treble booster. This amp, with the Princeton tone stack, is far more Boogie Mk1 than Marshall. The bottom end and clean is great! No fizzy bullshit either!

@alainbrisebois8334 4 года назад

I was just picking my brain on what amp has that killer of tone.

@IAmKillEveryone 2 года назад

You're spot-on with the NFB analogy imo. If more people looked at it as an built-in treble boost pedal, they wouldn't be so apprehensive about them.

@ibanezleftyclub 6 лет назад

That is definitely one of the best amps you’ve done over. You really should design and sell your own brand, even if it’s limited runs. I would also love to hear these amps in a small rig with a right matching cab and some comp and delay with a tube screamer to really get the amp pushing.

@2dazetake 3 года назад

That's got to be the hardest job any musician could ever have,having to send the sweetest tones and vintages amps back to the owners, you always make great sounding circuits Brad,awesome skills bro.

@TempoDrift1480 5 лет назад

Man, that's the sort of amp I want right there.

@michaelkornet1227 6 лет назад

Yeah! Pantera from the little amp!! Awesome video as always, these are the videos I love watching from you. Don't ever think that your videos are too long, most RU-vid videos are too short love this style of vid. Keep up the great work

@valvenator 5 лет назад

yeah, most of his videos seem to long till you get past the 2 or 3 minute mark and than you're like 'wait, I just sat here for an hour watching this shit?' and than you look for another one :)))

@Atomic1710 4 года назад

Agreed .

@sparkeyjames 4 года назад

I'll bet that guy was pleased with that job. What a versatile amp that has turned out to be.

@elit3darkness 4 года назад

Aesthetically Reminds me of a Sears Silvertone, or a Magnatone style. Really cool conversion!

@agtronic 5 лет назад

Amp sounds killer man! Thanks for your slow burning videos. Don't change a thing! It's nice to just sit back and observe your thought process. Also, it's a nice change of pace in the rush of every day life. Keep on truckin'!

@jegr3398 3 года назад

I see "dangerous levels of gain" I click.

@Th3F0nz 6 лет назад

PLEASE do another video on pimpin that Variac. I've looked into how to get those panels to read voltage all the way down to zero, but everyone's videos/explanations are no where close to as clear and thorough as you make yours. Cheers!

@phillipbainbridge9107 6 лет назад

I agree. I would enjoy to see how you did it.

@jasonjurczyk692 6 лет назад

Add me to this list

@phillipbainbridge9107 6 лет назад

Watched the video and ordered a panel. They're actually very simplistic in design. I too had noticed the incorrect meter value on my Chinese variac and just don't ever buy anything on Amazon so I never searched there.

@paladinjme 6 лет назад

Please let me know if this is in any way unclear...Thanks! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-wPFaEFEembc.html

@ctyragdoll 6 лет назад

Followed these instructions from paladinjme for my somewhat similar variac, works great.

@davidlejeune8764 3 года назад

I don't usually comment but I just have to say...Wow. This really cleared some mud for me. The amp sounds great. Big, bold, and honest. Much appreciate the inspiration you've given me for my own tube amp builds and conversions. BTW... I sure wish that could get my right hand to do finger picking magic that you do so easily. A pleasure watching and listening as always Brad. Thanks for sharing your wisdom and talent.

@TheGuitologist 3 года назад

That’s very kind of you to say. I did a video about fingerpicking tricks. You can search it out. Might help you.

@pdland4936 3 года назад

Dad was Army Air Corps radio repairman, 1945-46 Guam , I find your old amp fixes fascinating.

@davidstorm4015 5 лет назад

What a fantastic sounding amp, qudos to you Brad, you know how to make these circuits sing!

@NitroModelsAndComics 6 лет назад

What a straight up little beast that thing is.

@denniss2937 4 года назад

Thanks for the Vid. I went to school for electronics, a vocation I never used. Watching your vids is ringing a bell. I might just get back into it.

@ExitThirteen 6 лет назад

At 30:00, that can capacitor should have been soldered to the backing plate from factory, but it wasn't, also the fact they used pop rivets to mount the backing plate to the chassis is kinda cheap and cheezy... not a good way of getting a proper ground. If I utilized the original can caps I usually drill out the rivets and use screws/nuts with star washers, and then I solder all the ground posts on the can to the backing plate. Another awesome video! Keep 'em coming, Brad!!

@mikemartin6554 5 лет назад

love your videos! I just found your channel last week and I've been geeking out ever since! I subbed 10 minutes into the very 1st vid! Thanks for your knowledge,humor and ability to explain in a very entertaining and interesting manner!

@TheGuitologist 5 лет назад

Welcome aboard, Mike! Buckle your seatbelt.

@russellhltn1396 6 лет назад

Re: "AC on the DC" - I'm sure he's trying to say too much ripple on the DC power.

@tubical71 6 лет назад

yea, but the amp sounds ok, hum whise....;)

@themarcoharder 6 лет назад

That is massive gain!

@charlesbutts4303 3 года назад

I owned one of these around 1970 when I was a teen. An adult tech friend who recognized that there was a ‘tech inside that kid’, gave me a pile of mics, speakers and tube powered audio gear. I used the amp and an 18” speaker to add a homemade ‘subwoofer’ to my piece-meal stereo system. Eventually the output transformer failed and I could not get a replacement. Mine had a ‘loudness’ and ‘rumble cut’ circuit. Yes, there was a tech there. 40 great years and all I’ve ever wanted to do is “fix stuff”. Those of us with skills need to mentor kids just like Mr. Cecil did for me. The man believed in me... what a fantastic gift!

@EdgarsLS 4 года назад

can't watch it enough. your playing is just the best ever, at least I think so. and the amp sounds out of this world.

@jordanmayer5932 5 лет назад

Wow what a conversion, that thing sounds fantastic. Absolutely fantastic.

@johnnyb3987 5 лет назад

Great job on this one. It sounds great all around, but it's really the clean sounds that are gorgeous on this one. I'm sure the owner was blown away by the end result.

@Crisdapari 6 лет назад

Beautiful point to point beast! Isolate and protect leads on this kind of circuit is laborious, but always needed.

@rebelcat420 6 лет назад

Always interesting to see how other techs approach a problem such as no output (this isn’t a criticism of you at all, just an observation of how we all do things differently). Your approach of the signal trace is one that I had not done before, but will do in the future as I’m sure it will help me at some point. I on the other hand always do things from the output working back, checking plate volts and lack of volts on the grids starting from output tubes working back toward V1, and use the audible “pop” as my leads hit the grids as my indicator that the stage is working. But there has been a time or 2 with PCB faults where my method had me scratching my head, but if I had used the signal trace like you did it would have saved me time (just as I’m sure if you used my method it could have saved you time at one point or another). In any case, always enjoy your videos as I always seem to learn something new (not always an easy task for someone my age! Lol). . P.s. Friends don’t let other friends ever use 220k plate resistors! Lol

@stevecooper3487 5 месяцев назад

Brother why are you not in a great band? You play awesome! Your channel is amazing and you showed me how to fix my Fender Champion 30 DSP! Thank you so much my brother keep up the good work . Coop

@danielwoll6917 5 лет назад

Standing ovation man. Great job. Always. fascinating to see where you end up and to watch a masters mind work. Thanks pal

@nomoniker7917 7 месяцев назад

You play surprisingly well. Impressed with your soldering skills too.

@outthereassociates7155 6 лет назад

Kept my attention the whole time Brad. I'm digging the cut aways, if that's what they're called. Amp sounds like what your client wanted.👍

@kronus513 6 лет назад

One of the nicest sounding amps in a while! Thanks, Brad!

@bjdenil 7 месяцев назад

Wow, it really sounds amazing by the time you are done with it! Sounds like it would cut through the mix, too.

@THEROLLINGROAD2010 2 года назад

You just can't beat valves / tubes, just can't. As soon as she went into overdrive it brought a great smile to my face, loved it.

@kurtweiand7086 8 месяцев назад

This is a real good amp, for some old school grind! Good job Brad!

@Lumby1 4 года назад

Amp customized by the Guitologist! Sounds pretty nice. Looks like a sleeper. Well designed tube amps are awesome.

@courier11sec 3 года назад

Holy shit that thing sounds fantastic for rock and roll. and the clean sounds really nice as well. Hell of a job you did here, friend.

@telecasteroil 6 лет назад

Best Video yet, an Hour and a half of entertainment

@JohnIainMcFarlanewaspfactor 5 лет назад

Had to come back and watch this again.Genius conversion ma man,sounds awesome!

@TempoDrift1480 5 лет назад

Anybody try to blow the smoke away when he's soldering something?

@guitarreman 4 года назад

I watched twice just do I could time it and freak out my granddaughter.

@jodichristensen9536 3 года назад

Indeed, I think that every time I watch Brads video’s...I personally run a ducted squirrel fan to pull off those poisonous leaded solder, and flux fumes, as I’m soldering up my stained glass projects. Brad is certainly a verifiable wizard with these vintage electronic circuits, but I fear those toxic lead fumes might end up cutting years off his life, and be the death of him?...The stained glass suppliers online, sell various ducted exhaust fans for this exact purpose, and yet certainly, someone of Brad electronic abilities, could very easily scavenge a old fan parts, and acquire a clothes dryer vent hose and cobble together some type of functional anti poison fume apparatus!!!...8)

@seansweeney3532 Год назад

Lead won't vaporize from the heat of soldering, but flux is bad to inhale.

@bullxtfpv8567 4 года назад

every time I watch your videos... at first I wanna pick up my soldering iron... then at the demo part I wanna pick up guitar... :D great videos and great playing.. tnx alot...

@kc6671 5 месяцев назад

You turned that thing into a rock beast. Love it.

@adamwaller5496 6 лет назад

🤘That's a lot of gain. Find someone who looks at you in the way Brad looks at a heavily overdriven custom guitar amp.

@stargatewv 5 лет назад

Well I'll be. Cut my legs off and call me Stumpy. That sounds damn nice. Wish I could have learnt that back many moons ago.

@camberwellcarrot420 5 лет назад

You fixed the cold solder joint and then you seemed to be leaning towards just fixing the obvious issues because it sounded good. Then you proceeded to rewire the whole amp! I think you're allergic to "good enough". 👌👍

@Ploobstill 4 года назад

I like the systematic way you attack problems. I think it makes me feel kinda safe. At least someone knows how to fix things.

@randyheath8566 3 года назад

Some of that doesn't look safe. Beautiful Paul Reed Smith ❤ The Amplifier sounds Awesome and quite quiet and Juicey TONEAGE. Great Job Brad

@jontallbacka9406 6 лет назад

Waow Brad! Cudos & hail to the Guitologist!!! Awsome conversion

@ziggylayneable 6 лет назад

Hey Brad, I live in Camden New Jersey. The original RCA Victor Ola building is down the street from my house. Next time I go there and walk close enough to the river because it's on the river although it's set back a couple hundred yards I will take a picture of the windows at the top of the building with the dog and his ear up to the gramophone. I know you would love to see a picture like this seeing as you have a giant RCA tapestry hanging behind you. Did you know they turned the building into very high-level expensive Condominiums. But the top of the building has not changed at all. Whoever bought the property and turned it into Apartments left the original top of the building there.

@TheGuitologist 6 лет назад

Cool. Yes, I'd like to see that.

@ctyragdoll 6 лет назад

In Albany, NY, the Nipper on top of the old RTA building now has surveillance cameras installed in it's eyes and listening devices in it's ears.

@valvenator 5 лет назад

@@TheGuitologist Same here. Nice to see folks that buy up property like this still hold a respect for the historical significance of it instead of tearing it all down and putting up another Wallyworld.

@Hue_Nery 5 лет назад

That thing sounds fantastic! I bet it would sound great with a Tele running into it.

@suavetrainwreck7300 6 лет назад

What a beautiful sounding amp. Incredible!

@thechannelforeverything2170 6 лет назад

That thing sounds badass, bet it would sound ferocious with a Telecaster

@valvenator 5 лет назад

Wha!!!???, no freakin' way! ...steps back and thinks "Led Zeppelin 1" ............................errr, nevermind that.

@CapeFearConstrictors910 5 лет назад

Man, I could watch these vids for hours....and I have been, lol. Thanks for allowing me to cancel my cable!

@kgedeongedon5933 4 года назад

neva like an amp video keo

@redbull8661 4 года назад

Holy crap! I bet that customer was very happy with that tone! Great job!

@tedvanmatje 5 лет назад

Mother of the gods. ...that amp sounds 'kin awesome! As an added bonus, a wee pantera lick for extra kudos. Thanks mate :)

@insanerotta5332 6 лет назад

How in hell did that Pantera riff part not have insane amounts of hiss and hum? I've never heard anyone have that kind of high gain tone and no hiss unless they had a noise gate somewhere. Gnarly as puck!

@DuoGlassix 6 лет назад

Not sure if you knew of this but a quick and simple trick to get an actual sort of cabinet sound from a plain speaker is to simply put a bucket over it (the way you have it sitting). So if you have a 12 inch speaker a 5 gallon bucket works perfectly. A 10 inch speaker can use a large plastic tub from ice cream, etc etc etc. Looking forward to hear your new cabinet tones from your test speaker!

@jonlennon3348 5 лет назад

That thing produces distortion extremely well. Man you do great work.

@metalhearted1 4 года назад

Commissioner: "What was the cause of death Detective?" Detective: "A cold solder joint sir." Commissioner: " Damn Hippie's."

@dougtaylor7724 3 года назад

From 34:00 to 39:00 I love when you tell the effects of each part on the sound. I learned a ton!

@normjacques6853 6 лет назад

Brad, you are very kind, generous, and diplomatic when it comes to the other guy's work! I have a few adjectives I might use....none of them complimentary. Bless your patient manner.

@normjacques6853 6 лет назад

BTW, if you're forced, by design and space, to live with an output transformer adjacent to a power transformer, simply turning one 90 degrees (so that the cores are perpendicular to one another) will cut down *some* of your mutual inductance problems. I suspect you knew that....but you didn't mention it, so..... :-)

@normjacques6853 6 лет назад

Also, where those gain adjustments send the amp into oscillation - try adjusting the pot(s) to just below osc. then measure the pot resistance...then insert a like-valued resistor in the wiper circuit so that that circuit can never fall below a minimum resistance...and get rid of the possibility of driving it into osc.....or just switch to a 12 AT7, 12 AU7, etc....but sacrifice gain.

@richardturk7162 6 лет назад

Great sounding amp Brad nice work.I do like the fact you made it non idiot proof.I have a 30 watt 1X12 combo amp a friend (Kevin Knapp Irmo SC) built for me and has a gain 1 and 2 that cascades and you can get to a point where it oscillates its a super dirty 30 watt amp.

@Smurf431 2 года назад

Nice playing, f'n GREAT tone, and a OUTSTANDING tutorial video of tweaking a tube amp.......I don't care how old the vid is.......THANK YOU for this!

@GigglePantsMcGee Год назад

This is my new favorite channel

@78tag 4 года назад

BTW - I have watched a couple of your posts before but this one grabbed me. I know nothing about working on amps yet I watched the whole thing. You have a new sub. All I can say about the 28 thumbs down is - screw 'em if they can't take a joke!

@vinn.5215 4 года назад

Wow. that thing really sings with some gain, so warm and clear but its got some bite. Nice.

@jagtone 5 лет назад

.02 coupling caps to .1 - that's a lot more bass, couldn't that be causing the motorboating? (Not the same issue, but a fairly universal recommendation for smaller silverface amps is to switch the coupling cap into the PI from .1 back to the blackface value of .01--clears up muddiness/flub quite amazingly.) Anyway, the amp sounds great, and the whole video was really enjoyable.

@w.rustylane5650 4 года назад

I think the power transformer being so close to the audio output transformer causes eddy currents in the output transformer. Those eddy currents induced are causing the hum. I would think all the output transformer connections should be shielded. It also sounds like the pots need cleaning. You can use tuner cleaner to clean pots if you can still find tuner cleaner. Or you can replace the pots. He ought to be happy with that amp. It sounds great!

@jeremiahfiek5495 5 месяцев назад

You're a fkn badass, dude! This is the coolest thing i've seen in a LONG time.

@brpadington 4 года назад

That thing had a surprising amount of gain. Killer little amp.

@martinreid1740 6 лет назад

Your best video yet. I've watched this three times, great amp Brad. Thanks.

@justinpridham7919 4 года назад

Stayed long enough to hear "I'm Broken" Dime lick. Appreciate the references you throw into the demo. Thx Brad!!!

@gnatiu 3 года назад

Unbelievable to me. This sounds just perfect. Without any effects, not even reverb.

@jordanmartinez2432 2 года назад

You sir have the coolest job in the world!!!!👍😊🤘 Excellent content!!!

@kengihepworth5761 6 лет назад

I jealous! ( I'm Gona tell my self that it was that green shirt) Love that red PRS.

@johnbecker8768 4 года назад

Dude, your amp skill are amazing. That thing sounds awesome. Nice chops too! Thank you!

@giulioluzzardi7632 8 месяцев назад

Great job, I noticed that "Mic/phono" switch at the begining and thought maybe "That" could be causing the crazy oscillations. It sounds nice and crunchy but smooth at the same time. That amp does'nt need any FX not even Reverb, it's almost like Vox meets Fender for tone but better!! If I could get a sound like that in a pedal it would be cool, like a Valve pre-amp.

@bigfootingermany 6 лет назад

Wow! That PRS and little amp sounds epic together and definitely some beautiful Fender tones without being too clean!!! Great job Brad and great playing!!! Bob in Germany

@sidneysnottley6414 6 лет назад

A long one, but as always, informative - Keep 'em coming. Thoroughly enjoyed.

@alveydoug 4 года назад

Love the closeups at 25 minutes in! I’ve made point to point connections that were all rosin too. You’ve got an experienced eye!

@rickyleeengle 6 лет назад

You could totally build these and sell them, I'd buy one. Btw, love the chuck levins guitar cable...

@Clmkxoxo 3 года назад

Loved this video !! It's awesome to hear the reason for changes and see the changes! Playing later AWESOM !!! Loved hearing you play !!!

@nicwilson89 3 года назад

This amp sounds fucking incredible, absolutely stellar job here. Good lord. I imagine if you stick a Tubescreamer infront of it or perhaps something even sillier, it'd get absolutely ridiculous.

@neuk01642 6 лет назад

I know fuck all about electrical engineering/electronics. I get the raging fear re wiring a plug. I play a little guitar (not particularly well, but I'm learning). For some inexplicable reason I love this channel. I have no clue what half of the stuff you're talking about means, it sounds like the teacher from Peanuts most of the time, but I can't get enough... Thanks for providing hours of weirdly addictive entertainment dude! Matt

@TheGuitologist 6 лет назад

I get this a lot. Maybe I just have one of those voices or something.

@tomasotreasaigh111 3 года назад

You got that thing sounding creamy and smooth as hell when needed and plenty of snarl and groan when needed! I would absolutely love to own that amp. Fantastic job Brad, peace and respect from Ireland mo chara x.

@ericwilliams7374 6 лет назад

Even though I can understand a damn thing going on in your videos, I love watching them!!! I truly wish I had your skills to be able to make my own high gain amps!!! Love your videos!!! I try to study them to get a better understanding.

@bucyruserie1211 6 лет назад

Cool amp Brad, You should do the mod on the variac meter. Others have video's posted on how to do it.. As I recall you just need to open up the meter and clip one leg of the large capacitor inside. It can than measure down to zero..

@frankferriolo9212 3 года назад

I really liked the riff you played when you tested the amps tone before beginning the modification......I thought it was a solid rhythm! The amp sounds great too.

@ferna182 Год назад

damn, this is honestly one of the best amps I've ever heard

@danw1955 5 лет назад

WOW! That little sh*t has some serious punch when you cranked in the drive!! Well done Brad.. between the Princeton tone stack and moving your main volume to just before the phase inverter really livened it up, and even though the transformers are still too close together, I'm really impressed you got it so quiet with a little other internal magic to alleviate the power hum. You're right about the theory of possibly driving the finals to the point of *just under* oscillation to get some cool effects that you could only hope to achieve on a transistor amp with a bunch of pedals. I know you were getting that just by fiddling with the gain and main vol. and going straight in with your guitar! Even on your 'shop' speaker it sounds pretty badass, so I can imagine what it will be like in a cabinet with a 12" Black Widow or similar. Nice work man, really enjoy watching the process from beginning to end!😍🎸 🤘😎🤘 Rock on!!

@alexkennedy7671 2 года назад

Hey Brad Just watched this and I couldn't help thinking that this wee beastie in full rip mode on the edge of oscillation sounds not unlike one of the hi-gain stages in John Petrucci's latest Mesa Boogie Amp Head that he demonstrated on Rob Anderton's RU-vid channel not too long ago. It is super vicious and dirty - I like it! Great job man, what an analysis and modification process you went through there - Hat's off to you big time - So Cool! All the best from Alex the K in Scotland

@peteroditis2156 4 года назад

show off!! sounds great. been checking you out since the knight km15 amp

@JC-11111 3 года назад

This is pretty funny. When I first started learning to play guitar this January, I tried watching some of your vids, Brad, and just, couldn't do it. Here I am 10 months later binging Guitologist vids 😆❤️👍🎸 I guess because I much more clearly understand what you're saying and what I'm looking at.

@klcbsoft 6 лет назад

1:16:40 - turns knob for "really greasy overdrive tones" ... paper flies off amp ... hi-gain mod officially certified :) What a beast! Excellent sounding amp; true, gritty, no-nonsense. A well done service.

@dan_perry 6 лет назад

You're motoring! da da daaaa! The first 4 stage cascading preamp I made motorboated wide open too . I left it be cuz I thought it was cool.

@tubical71 6 лет назад

you can easily overcome this with some little math....motorboating happens when the overall phase caused by the feedback loop is summed up to any positive degree and beyond. So just calc any RC-filters inside and the gain loop in that stage and you pretty much the low end frequency where thw shift to positive feedback (feedforeward) occurs. Then increase the resistor or decrease the capcacitor until you reach at least unity. No more motorboating.