Modifying and Comparing Gibson GA-19RVT Falcon Amps 

I just did this modification, along with a cap job. Second amp project, first being a tone circuit removal for a Fender Champion 600. Thanks for the detailed instructions, demos and explanations. I'm hooked!

I have a 1962. It is my go to amp. Celestion G12-65 speaker in it which is a perfect compliment. It stacks up against my blackface Princeton Reverb, Reverberocket and Matchless SC30. These are the best deals out there. Thanks for the great video.

Dude that 3 Rd Modified version sounds unbelievable!! I'd love to have one of these amps!!!

I have one and it's fantastic. I love it and can't believe how underatted they are. The one I have is the early brown Tolex. I bought a Falcon in 1962 and was really pleased with it then. When I found the one I have presently, it was in a warehouse basement and was going to be scrapped/garbaged. A friend of mine took it and re-conditioned it and it sounds great.

My 1964 Falcon sounds amazing after a recap and your mods. I'm using it in stereo with my 1976 Fender Deluxe Reverb. If you are ever in Portland, Oregon, stop in at my shop, East Side Guitar Repair. Thanks for the video.

Thanks for the info, going to dig into my '64 Falcon to smarten it up as soon as the caps come in. I've played it for years as-is, with the only change being a Weber Blue Dog 75w hemp cone, to help out with the highs. I'm playing more with single coils than humbuckers these days (namely my '63 Jaguar) and I really want to use this amp, without stabbing myself in the ear with treble!

I've done about 8 of these, going back to the tweed version. these amps really are amazing and if you turn the volume down all the way and the reverb up you get some really crazy surf tone. I love what you have done here. I rebuilt a 62 crestline version, probably one of the first, and it had a lot of the tweed specs still built into the circuit. It sounded so much better than the others I thought i'd convert them to match. The '62 also had a aluminum chassis!! Thanks for your work.

Great videos Brad.

Just got one for cheap that needs restoration, so your tips are perfect. Thanks!

The "Tone-Sucking" network you refer to is a Bridged T-Filter. In short, it's a midrange control. Rather than delete it, you can modify the values, and dial in a more interesting tone. I modded a Falcon. I used a 680pf works for the bridge, and 200k for the tops of the T, and 2200pf for the stem of the T. Reducing the value of the resistors, moves the center of the "V" to a higher frequency for a thicker tone, and vice-versa for higher value resistors. Reducing the value of the bridge cap makes the "V" deeper, as does increasing the value of the cap for the base of the T. Changing any values affects the shape of the EQ to some degree. Take a look at the schematic for the GA-30RVT. It used 150K resistors for the top of the T, and a .01 cap for the base of the T, but they also had a pot underneath it. Turning the pot CCW gets those too muddy very quickly, and too far CW makes them much too bright. In short, the Bridged T requires a knife edge balance to sound good. Increasing the value of the coupling cap preceding the Bridged T helps a lot, but your tip on increasing the value of the 500pf cap in front of the cathodyne phase inverter would be virtually inaudible. The input resistance of this cathodyne is north of 12M ohms, so even a small cap will pass all the frequencies you need, although it has been said that smaller caps will make the circuit more susceptible to picking up noise. In short. Increasing that first coupling cap value, getting a more robust speaker, and even a beefier O/T would help the most. After that, I would begin to have fun by dialing in the Bridged T. As you were....

Subscribed 😊 I absolutely love the detailed content on all of your videos Thanks......much appreciated

Awesome reviews and playing. I have a 1964 Falcon with the red grill and I found a review of your Hawk 25rvt which I sent to my amp tech which he is still working on. I didn't see these review until today. Very helpful. We are still having some trem and reverb problems with the Hawk but the tone is the real thing. After r&r the 2 speakers with jensen c 10 R, caps etc Oh I have read that the cabinets are made of red wood, maybe just in the Falcon but any way.Yep just looked at the Hawk it is different plywood. Thanks

man you get to mess with the coolest stuff. I have never even seen a gibson amp in person

I just bought my first Gibson amp, a very clean (cosmetically) Falcon like one of these. Has the original cover and manual, but somebody replaced the tube rectifier with S.S. and duct taped over it! Also has a 3 prong plug but a 2 wire cord.! Almost afraid to see what the chassis looks like inside. It works, but the volume is very low. Still sounds decent all things considered, but sure could use help. There is a lot of potential, I think. I bought a Variac recently and am getting a better Multi-Meter but I don't think I'm ready to get this thing squared away. Great video; these Gibby's need more love!

This is very interesting. I would have liked to hear the comparison with humbuckers as well since the original amps seem to have been voiced for that.

Another really awesome vid!!! Very enjoyable to watch...and I always learn so much!! Quick question: you did the "same" mods to both the left- and right-most amps, correct? You attributed the difference in sound to the new, "tight" speaker (and wattage difference too)...is there a way the average person would be able to know/tell that the difference in sound is the speaker "only" and not a mod difference?

I have one.. .love it.. great tone......I have to take it in to the shop....blowing a fuse.. could be the rectifier

I have 2 of those brown ones like you have on the left. It is true they can sound a little shrill and thin stock. But they have a nice chime to them. I had my tech guy mod them to tame the high end and get a bit more gain out of them. I don't know if they are the same mods as you did here but they sound niiiiiiice. That brown one on the left sounds super great. I would love to have a schematic (which I can't read), take it to a builder and say "make me that". Also we need someone to start making good 6eu7 tubes again. Tungsol is doin it but they are not as nice as the old ones. Is go through them pretty good as I boost the signal at the front end of the amp hard. Great way to get distortion if you don't mind abusing your preamp tubes.

At 8:30, the plate resistors and bias resistors can be varied together along with a series 'coupling' capacitor with little change to the sound if proportional. On a triode amp circuit like this, the cathode/bias resistor will flow enough current to bring the cathode to a point of being above control grid to where there is an equilibrium condition. ie. with no input signal grid is pulled to zero volts nearly provided there is no leakage of coupling capacitor from a previous plate voltage . At about 1.5V for a lot of preamp tubes below cathode volts, they are curbing towards a pinch off state and so that tends to be the idle voltage you'll notice regardless of the size of the cathode resistor (within limits of the tubes ability to provide current). ie. if you use say a 1K resistor instead of 2.7K near 3X the current will flow to bring it up again near the pinch off voltage. So the different resistors used will mostly affect often the point at which the tube saturates/clips. Going with the 4.7K relatively low currents are going through the tube. Higher noise floor but wider signal range I'd guess there. Almost double the idle current with 2.7K so you have less headroom as the cathode can only supply electrons at a limited rate AND the Plate resistor and supply voltage will of course also present a limit. We have 280V or so and a 470K resistor even if grounded will flow 280/470000 amps or near 6mA so in this case that's maybe less significant of a limiting factor. THe 6EU7's max current is just a few mA I think? Anyway... Changing the PLATE resistor meanwhile will have another impact in the circuit though..well a couple. The higher the resistance the bigger the voltage gain since all the current is going through it save the small capacitive impedance in the circuit. ALSO though there is an RC time to be considered with coupling capacitance and any other circuitry in series/parallel. So for example we'd get a very similar sound if we used the 220K with the .02uf as we would with a 470K and a .01uf there. But twice the gain. So basically they double the voltage out of the chute there but then filter it in a more complex way rather than just a simple bass rolloff at 6dB/octave. So C12 in that circuit functions to stop DC primarily from leaking through the resistances to V2's grid, and it rolls off some bass at what appears about a 1M series load with the 100K, two 220K and 470K from the power supply's current source. Eg. say a square wave come in and suddenly turns the tube to pinch off state. Bam you go from max current sagging the voltage at plate to it's lowest point to 280V and the RC time of the high pass filter is 1M X .001uF and if that wave just stays high, the grid of V2 will experience an exponentially decaying pulse with a natural log point (about .39 isn't it as I recall?) at 1 millisecond roughly I'd think. So that's minimally where THAT cap starts diminishing things. a 500hz signal will pass fairly unaltered as you picture what that DC signal did that we just introduced. ie. 1 msecond is a half wave at 500hz... so that signal can form well within the confines revealed there since it's going from zero to peak to zero again. Rather than explaining using more complex math than some have taken you can get a concept by drawing these things out. But it begins to roll off the bass at some point at 6dB /octave getting ride of very lows we don't want over excursing the speaker etc. The filter circuit after the .001 (C12) then... has yes a high pass element in the 500pf. Coming into as much as a 1M load depending how pots are set there I suppose... but the 220K resistors are shorting highs to ground so you really have (to the high frequency component) an essentially 100K load on that part of the circuit since they will pass very efficiently through the .0033 or 3300pf capacitor. LOWS on the other hand (ie. frequencies outside the RC time domain of 220k X 3300pf = .007 seconds or so....1370 hz ish. so a few hundred hz will generally pass through lightly affected so those low frequencies essentially have a 440K resistance into the 1M drop or so. But at 1000 hz it's being attenuated significantly by the 3300pf cap to ground. Anyway maybe a good mod on those units would be install Anyway I appear to have an oddball amp...someone brought in here. It appears to have the older covering on the grill...a tweed (redone?) yellowish covering on the cabinet and the 6C4 (using the maestro schematic). Wood on the handle! hmm. Fairly nice shape from a guy in Helena, MT. I'm tired so hopefully I didn't confuse anyone too much :-)

I know this is “old news” but it would be cool to hear the monitor out reverb through another amp. I don’t believe I’ve seen it demonstrated and it seems like a unique feature in this amp.That is if you still have one of these?

Just watched your demo on these 3 Falcon amps. The middle one sounds very "thin". Was it also modified? Maybe it's the speaker? Sounds like it has seen better days. The first one sounds good and the third one sounds not to bad for a replaced speaker. One thing I never liked about Gibson and their Epiphone amps was the construction layout technique used in placing the circuit components which made their amps kind of messy inside to begin with and even messier when repairs had to be done to them.

Do you happen to have a schematic of how the tremolo on there Crestline Falcons? I have one and it is wired very differently than what the two schematics I found online are drawn as.

Would you change the caps to 50 uF and coupling cap to .0047 on a Falcon tweed version as well? Thanks.

Mine is stamped on cab as inspected on April 19, 1963. Badger Wood Products. Racine, Wisconsin. Maybe thats just cab date. Serial on front plate starts with 48..has red arrows in knob tops. Supposedly a 63, from my findings. I dont see the tone sucking circuit, and looks like someone has made mods to cap cans. Havent played it in a few years. Came to me with a weber feromax.

Hello Sir . Love the channel. I'm giving a drum riser to a friend , and out of nowhere he tells me to take his Gibson Invader tube amp. It works great. 1x12 and 1x10. Are these worth keeping? Are they a Dog? I haven't got it home and set up yet. But it seemed to rock in his garage. Can't find info on it. Thanks , Anthony in Indy.

Hi Brad, Although I know nothing of the inner workings of amps, guitars, and other sweet electronics, I enjoy your your videos. I also have found hope that my Gibson Falcon might actually live again! Are you open to the prospect of modding it for me? I've not seen you address rather or not you offer service? Best

Very nice video.. I passed on buying one of those when I was younger as it sounded so thin, wish I didn't now. Can't believe the difference in tone between the two without the caps and the one with them still installed. They really come alive. I'm sure in person the amp with the new speaker is not as vibrant as the original, kinda hard to hear the difference after being compressed via RU-vid. But I don't think it ever will sound as good as it is never going to be pushed as hard with it's 75watt rating (just my opinion), still sounded very good. I think you were being very kind calling the person who was inside the customer's amplifier prior to yourself a "tech".... butcher comes to my mind. Keep em coming. Thanks, Tom

Greetings! I have a '62 Falcon Crestline GA 19 RVT(serial # beginning 774 ...) that has an RCA 6CU in the tube set. Somehow it has lost its tremolo capability. Is this a tube problem or some other component? Thanks.

I have a GA-5T that has been repaired, but NOT modified. The brightness is off the charts.... DO NOT plug in a single coil guitar unless you want treble searing your face off. I plugged a humbucker gibson into it... and with the tone knobs of the guitar at half... it sounds PERFECT. I find the tone knobs on the guitar generally useless, but with that AMP, they are very helpful.

Brad, how do I get in touch with you for amp work? I have the same early "brown" Gibson Falcon 19RVT The mods you did worked wonders for the amp. My computer speakers are pretty good and liked what I heard. I subscribed because your videos are great and easy to follow, good job.

..the newer stock is cleaner and more jangly which is good for certain styles.It could be made a bit fuller just by replacing c12 with say a .01 or .022uf to let more lows through to make for an intermediate between the newer and older version.Coupled with a decent mid boost pedal you could get a fuller jangly/cutting tone (with a bit of hair) that kicks into thick crunchy mode with the mids booster on.By that time the volume boost should be present but not insane since everything will be compressing nicely.

I love my ga-19rvt it's the best amp I've ever play cleans through. I built a clone so I can preserve my gibson amp. It sounds close but not exact. I wouldn't take 10 grand for it. It sounds that beautiful.

thanks for this

I'm about to acquire one of these. Can you tell me in a nutshell exactly what mods were performed on the one to the left?

well crap! I just started a video like this.. with one thats been modified and one that hadn't... but this is cool!!!

I encounter a Falcon which I believe is a late 60's 1061 model, is this a good amp to have for clean sound alone? I intended to use the amp for jazz only.

I enjoy your videos !! I love the tone of these old Falcons. How about an ext. speaker. Do you recommend or not ?? I do use the line / monitor out and its very quite.

When changing the cap values for the bypass caps and decoupling caps, do you do this one by one because technically I would think you would need 4 to 6 capacitor decade boxes to be switching all of them for all the stages at the same time or its going to be a domino effect when changing only one cap value leaving the rest the same and when you change the next cap value that is going affect the others so you get this domino effect? This process is called Amplifiers Tuning

Are Gibson emblems available anywhere? For the Invader?

Hey man - I’ve got one of these, and it sounds quiet and a little thin - Would be curious if you could work your magic on it

Love your videos. You know your shit!

I have a Gibson gss50 any none tube amps good or collectable?

I have a Falcon sn 774934 like the one on the far left . Is it a 61?

Hey Guys, I found a 1963 Falcon GA-19RVT next to the dumpster at my building today. It fires up but there is no sound coming out of it at all. All of the tubes are heating up. The 6v6GT tubes are all black. I'm not sure if they are supposed to be that way. They are Peavey 6v6GT made in china. Before I buys a set of tubes for it is there anything else I should look at before drop the cash on the tubes? I'm handy with a volt meter if there are some measurements I need to take. Let me know. Thanks a bunch.

A weber 12a125-A sounds great in mine.

Thanks for the videos on these old Gibson amps. Just picked up a non-functional Falcon 19rvt. Mid-1964. Needed a fuse. Works great except the tremolo is not working. I've swapped tubes. Tested the foot switch. Any advice on what typically causes the trem to not work? I have installed a grounded plug. Removed the death cap. Removed the weird square tone cap as well. Thanks!

Mine is 776 beginning serial #, tolex is tree bark like first on left + bluish and wheat grill. So cosmetically not in alignment with your progression. Maybe ‘used’ what they had.

What a difference with modification

Brad, a local person is selling one of these for just under 400 clams- is that a decent price?

I just did that mod to my Falcon....and it became a TON bigger and warmer....but it seemed to have lost its mojo. I swapped the .02 for a .01 and it got back its crunchy awesomeness without being the thin amp it was at first. I think the .02 lets too much bass through. And when you change the other cap from a 500pf to .0047 I think its just too warm. Even the original had the 500pf coupling cap IIRC. I kept the .0047 but swapped the first coupling cap to a .01

the particul bored backing is for light weight

Interesting plate resistor fact: 470 K instead of 220 K gives more second order harmonics.

I enjoy your videos a lot, Brad, but I think that calling the tone stack in the later amp a 'tone-sucker' is a bit harsh. It's called a 'Bridged-T' and it does not filter bass or treble - it is a mid-cut circuit (with the given component values). It actually has a very low insertion loss and cuts about 13db centered on 550hz. This is a very Fender-like mid-cut without the huge insertion loss. To reduce the effect, you can put in a resistor (or pot) to ground to vary the amount of cut. Put in a SPST switch to ground and you can bypass the effect. It's also a bit misleading to say that a 1nf cap lets 'more highs' pass than a 20nf cap. It actually lets 'less lows' pass; but, you can't look at the coupling cap in isolation - the coupling caps form a high pass filter with the grid leak resistor of the following stage. In this case, the cutoff freq after V1 with the 1nf cap should be 79hz. Increasing to 20nf will lower the cutoff to about 4hz.

Brad, looking to retube my falcon. any recommendations? mine is the model with 6eu7 pre's. '62, I believe?

I use one for m electric fluglehorn

Do these weigh about 30 lbs?

Have two of the "tweed" model version of this amp...also too much twang. and not enough volume. Anything I should look at on these?

Came upon this while recapping a 1965 version and found the 10/10/10 uf lytic at the side had two legs of the cap wired together to apparently deliver 20uf rather than 10 at one point. The other 20/20 was wired as on the schematic, Wondering if you encountered this as well and why they diverged from the schematic.

2:07 this camera angle is killing me. Lol 😅 I know they're small amps but dang.

For me the mod + new speaker is the best. The original is awful compared to both of the others though.

Brad, Great vid, but please stop spreading this around...the prices of these will shoot up tomorrow! ;)

I’ve lost the reverb and trem. Any thoughts? Thx