Gibson Falcon GA-19RVT Question
Question:
I just recently acquired the Gibson GA-19RVT Falcon amp and I will need to do a couple of things to get it running well again (I will be taking it to a tech), but I was wondering if you guys could help a bit. The amp I have has a 6C4 tube and CTS speaker. 1) Without reverb, the amp is very clean with virtually no distortion, and is also pretty bright unless I run the tone control almost all the way down. When I kick in the reverb, the gain increases dramatically and produces a fatter, fuller sound, which provides a kick-ass sound. While the reverb sounds cool, I was wondering if I could get this amount of gain and type of EQ without the reverb by some kind of easy mod. 2) Is there a mod that could make the tone control more useable?? 3) The reverb hums a bit, is that normal?? Also when the reverb and volume are all dimed, the bass gets really farty and sometime the low notes produce a lower octave "ghost note" Is this normal, or can something be down about this??? Also, from what I’ve read, the reverb is suppossed to be very deep and 4) Would the amp benefit from a speaker change? I’ve heard that the CTS sux and that Weber makes a fine variety of replacement speakers. I like the sound now, but I’m wondering if it can be drastically improved. Thanx for all your help.
Response:
> I just recently acquired the Gibson GA-19RVT Falcon amp and I will need > to do a couple of things to get it running well again (I will be taking > it to a tech), but I was wondering if you guys could help a bit. The > amp I have has a 6C4 tube and CTS speaker. > 1) Without reverb, the amp is very clean with virtually no distortion, > and is also pretty bright unless I run the tone control almost all the > way down. When I kick in the reverb, the gain increases dramatically > and produces a fatter, fuller sound, which provides a kick-ass sound. > While the reverb sounds cool, I was wondering if I could get this > amount of gain and type of EQ without the reverb by some kind of easy > mod.
Unplug the tank and see what happens… the way the circuit is, you lose gain when the reverb is not on. Look at the schematic http://www.schematicheaven.com/gibsonamps/ga19rvt.pdf and see if you can tell why. (Anyone got an online schem for the tweed? I can’t find one to cite! It’s in the TABv4, pg506.) > 2) Is there a mod that could make the tone control more useable??
Now that I compare the tweed and Crestline schems… yes, there most certainly is! I’d rebuild it same as a tweed Falcon… there’s a volume pot bypass cap that makes all the difference… the funny network between V1 and the reverb pot is bound to suck tone away as well. I’d also move the reverb switch back to where God intended it to be… the output of the tank; this would cure the non-reverb tone suck. > 3) The reverb hums a bit, is that normal?? Also when the reverb and > volume are all dimed, the bass gets really farty and sometime the low > notes produce a lower octave "ghost note" Is this normal, or can > something be down about this??? Also, from what I’ve read, the reverb > is suppossed to be very deep.
Either experiment with it, or let a tech go to town… the tweed circuit has much to offer here. Hum in this case is normally due to ground loops, which take experience and intelligent guesswork to solve. > 4) Would the amp benefit from a speaker change? I’ve heard that the > CTS sux and that Weber makes a fine variety of replacement speakers. I > like the sound now, but I’m wondering if it can be drastically > improved.
Replacing the speaker is definitely recommended… how high up you go will determine how good it sounds. I recommend Alnico… I went with a Weber 12A1.5 or whatever it is… a 20watt alnico with a 1.5" voice coil. Of course, this amp is a great candidate for the $300 Celestion Blue… just about the right watts for it. The Weber costs less than half that, and gives more than half the bang for the buck IMO. I had to order mine without the bell cover… your Crestline will probably not have that worry. Talk to Ted, we always say. __ Steve .
Response:
- Hide quoted text — Show quoted text -> I just recently acquired the Gibson GA-19RVT Falcon amp and I will need > to do a couple of things to get it running well again (I will be taking > it to a tech), but I was wondering if you guys could help a bit. The > amp I have has a 6C4 tube and CTS speaker. > 1) Without reverb, the amp is very clean with virtually no distortion, > and is also pretty bright unless I run the tone control almost all the > way down. When I kick in the reverb, the gain increases dramatically > and produces a fatter, fuller sound, which provides a kick-ass sound. > While the reverb sounds cool, I was wondering if I could get this > amount of gain and type of EQ without the reverb by some kind of easy > mod. > Unplug the tank and see what happens… the way the circuit is, > you lose gain when the reverb is not on. Look at the schematic > http://www.schematicheaven.com/gibsonamps/ga19rvt.pdf > and see if you can tell why. (Anyone got an online schem > for the tweed? I can’t find one to cite! It’s in the TABv4, > pg506.) > 2) Is there a mod that could make the tone control more useable?? > Now that I compare the tweed and Crestline schems… yes, there > most certainly is! I’d rebuild it same as a tweed Falcon… there’s > a volume pot bypass cap that makes all the difference… the > funny network between V1 and the reverb pot is bound to suck > tone away as well. I’d also move the reverb switch back to where > God intended it to be… the output of the tank; this would cure the > non-reverb tone suck. > 3) The reverb hums a bit, is that normal?? Also when the reverb and > volume are all dimed, the bass gets really farty and sometime the low > notes produce a lower octave "ghost note" Is this normal, or can > something be down about this??? Also, from what I’ve read, the reverb > is suppossed to be very deep. > Either experiment with it, or let a tech go to town… > the tweed circuit has much to offer here. Hum in > this case is normally due to ground loops, which > take experience and intelligent guesswork to solve. > 4) Would the amp benefit from a speaker change? I’ve heard that the > CTS sux and that Weber makes a fine variety of replacement speakers. I > like the sound now, but I’m wondering if it can be drastically > improved. > Replacing the speaker is definitely recommended… how > high up you go will determine how good it sounds. I > recommend Alnico… I went with a Weber 12A1.5 or > whatever it is… a 20watt alnico with a 1.5" voice coil. > Of course, this amp is a great candidate for the $300 > Celestion Blue… just about the right watts for it. The > Weber costs less than half that, and gives more than > half the bang for the buck IMO. I had to order mine > without the bell cover… your Crestline will probably > not have that worry. Talk to Ted, we always say. > __ > Steve > .
Of course, the day after I pull the Gibson MSM in both .pdf and .jpg formats off my site; because access logs say nobody ever looks at them… Along comes someone that wants to see one. Hint: Epi EA-28RVT with the 7199 tube is the same as the 1961 tweed Gibby. Steve’s advice all sounds good to me without taking a hard look. And speaking of looking: Behold before you one of the greatest unsung guitar amp circuits ever produced: http://www.catoosatrading.com/images/amps/schematics/tweed_ga19rvt.jpg The 1961 Tweed GA-19RVT Falcon. First amp series that I know of which included Hammond’s then recently developed spring reverb. A full three years ahead of any that Mr. Fender put out his back door. If it hadn’t shot several hundred dollar beyond my budget, I’d have bought this super clean example on eBay yesterday: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=008&item=180002820060 Ahh… looks like the cat is fully out of the bag on the old Gibson amps boys. Now all the rookies have to do is learn which are the good ones. Quite an expensive lesson if done by trial and error as I did it. 
OP: Print this thread off to hand to your tech. If he’s worth his salt, he’ll make things right. John King
Response:
… > If it hadn’t shot several hundred dollar beyond my budget, I’d have > bought this super clean example on eBay yesterday: > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=008&item=180002820060 > Ahh… looks like the cat is fully out of the bag on the old Gibson > amps boys. Now all the rookies have to do is learn which are the good > ones. Quite an expensive lesson if done by trial and error as I did it.
I was expecting that particular example to bust $1K, but it went all the way to $1131! Without original cover (got mine!)… still not tempted to unload, the Tweed is definitely a keeper. No reason the Crestline can’t be made to sound as good. OP, I forgot to mention filter caps… if they’re old, they should be replaced, general principles. __ Steve .
Response:
- Hide quoted text — Show quoted text – > … > If it hadn’t shot several hundred dollar beyond my budget, I’d have > bought this super clean example on eBay yesterday: > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=008&item=180002820060 > Ahh… looks like the cat is fully out of the bag on the old Gibson > amps boys. Now all the rookies have to do is learn which are the good > ones. Quite an expensive lesson if done by trial and error as I did it. > > I was expecting that particular example to bust $1K, but it went all > the way to $1131! Without original cover (got mine!)… still not > tempted to unload, the Tweed is definitely a keeper. No reason the > Crestline can’t be made to sound as good. > OP, I forgot to mention filter caps… if they’re old, they > should be replaced, general principles. > __ > Steve > .
Yeah, even though it apparently needed a cap job, I had that one figured for the first I’d see pass the $1k mark; because of its appearance condition. I was right, but it went even higher than I expected. There was a really trashed one that went for around $280 not too long back, and I wish I’d picked it up. As I’ve now given up on the idea that I’ll ever be willing to spend the money to buy and keep a really nice one, I would have liked to have the funky one just to spec everything out for later cloning. In fact Steve, one of these days I might ask you to do considerable measuring, both physical and electronic, on your amp to give me a good starting place. I have my ‘61 EA-28RVT which is the exact same circuit, but I’d still like the cabinet measurements, and some circuit specs from yours to have on hand. Don’t bother right now, but I hope you don’t mind if I ask that favor at some point in the future. Thousands of people want to clone some Marshall, Vox, or Fender, but if I was going to make an "improved" clone of any amp, this Gibson would be very high on my list. Thanks, John
Response:
- Hide quoted text — Show quoted text ->> I just recently acquired the Gibson GA-19RVT Falcon amp and I will need >> to do a couple of things to get it running well again (I will be taking >> it to a tech), but I was wondering if you guys could help a bit. The >> amp I have has a 6C4 tube and CTS speaker. >> 1) Without reverb, the amp is very clean with virtually no distortion, >> and is also pretty bright unless I run the tone control almost all the >> way down. When I kick in the reverb, the gain increases dramatically >> and produces a fatter, fuller sound, which provides a kick-ass sound. >> While the reverb sounds cool, I was wondering if I could get this >> amount of gain and type of EQ without the reverb by some kind of easy >> mod. > Unplug the tank and see what happens… the way the circuit is, > you lose gain when the reverb is not on. Look at the schematic > http://www.schematicheaven.com/gibsonamps/ga19rvt.pdf > and see if you can tell why. (Anyone got an online schem > for the tweed? I can’t find one to cite! It’s in the TABv4, > pg506.) >> 2) Is there a mod that could make the tone control more useable?? > Now that I compare the tweed and Crestline schems… yes, there > most certainly is! I’d rebuild it same as a tweed Falcon… there’s > a volume pot bypass cap that makes all the difference… the > funny network between V1 and the reverb pot is bound to suck > tone away as well. I’d also move the reverb switch back to where > God intended it to be… the output of the tank; this would cure the > non-reverb tone suck. >> 3) The reverb hums a bit, is that normal?? Also when the reverb and >> volume are all dimed, the bass gets really farty and sometime the low >> notes produce a lower octave "ghost note" Is this normal, or can >> something be down about this??? Also, from what I’ve read, the reverb >> is suppossed to be very deep. > Either experiment with it, or let a tech go to town… > the tweed circuit has much to offer here. Hum in > this case is normally due to ground loops, which > take experience and intelligent guesswork to solve. >> 4) Would the amp benefit from a speaker change? I’ve heard that the >> CTS sux and that Weber makes a fine variety of replacement speakers. I >> like the sound now, but I’m wondering if it can be drastically >> improved. > Replacing the speaker is definitely recommended… how > high up you go will determine how good it sounds. I > recommend Alnico… I went with a Weber 12A1.5 or > whatever it is… a 20watt alnico with a 1.5" voice coil. > Of course, this amp is a great candidate for the $300 > Celestion Blue… just about the right watts for it. The > Weber costs less than half that, and gives more than > half the bang for the buck IMO. I had to order mine > without the bell cover… your Crestline will probably > not have that worry. Talk to Ted, we always say. > __ > Steve > . > Of course, the day after I pull the Gibson MSM in both > .pdf and .jpg formats off my site; because access logs > say nobody ever looks at them… Along comes someone > that wants to see one. > Hint: Epi EA-28RVT with the 7199 tube is the same as the > 1961 tweed Gibby. > Steve’s advice all sounds good to me without taking a > hard look. And speaking of looking: Behold before you > one of the greatest unsung guitar amp circuits ever produced: > http://www.catoosatrading.com/images/amps/schematics/tweed_ga19rvt.jpg > The 1961 Tweed GA-19RVT Falcon. First amp series that I know of which > included Hammond’s then recently developed spring reverb. A full > three years ahead of any that Mr. Fender put out his back door. > If it hadn’t shot several hundred dollar beyond my budget, I’d have > bought this super clean example on eBay yesterday: > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=008&item=180002820060 > Ahh… looks like the cat is fully out of the bag on the old Gibson > amps boys. Now all the rookies have to do is learn which are the good > ones. Quite an expensive lesson if done by trial and error as I did it. > OP: Print this thread off to hand to your tech. If he’s worth > his salt, he’ll make things right. > John King
Yeah, my dad bought me one in 1967…my first amp. He paid $35 for uit, but passed-up a chance for "a white Guild" for $75 (I had to make-do with my Silvertone…) Natureally I immediately painted it black…I KNOW, I KNOW! Found another one about 10 years ago (once painted black, but stripped)……and a brown-vinyl version (with the 6C4 a year later…there is NO comparison in sound, btw….THAT one’s tone just sux.
Response:
Thanx for all the great info guys. So if I bring the amp to my tech with crestline schematics and the tweed schematics, it shouldn’t be a big deal for the tech do do a tweed conversion?
Response:
… > OP, I forgot to mention filter caps… if they’re old, they > should be replaced, general principles. > __ > Steve > . > Yeah, even though it apparently needed a cap job, I had that > one figured for the first I’d see pass the $1k mark; because > of its appearance condition. I was right, but it went even > higher than I expected.
I watched it jump $300 in the last ten seconds… or so. Better than TV! > There was a really trashed one that went for around $280 not > too long back, and I wish I’d picked it up. As I’ve now given > up on the idea that I’ll ever be willing to spend the money > to buy and keep a really nice one, I would have liked to have > the funky one just to spec everything out for later cloning.
That poor beastie was flogged… stored in a leaky barn, flood victim, etc. I’ve got a Rhodes 54 with corrosion inside, tolex hanging in tatters… better shape than that poor tweed. > In fact Steve, one of these days I might ask you to do considerable > measuring, both physical and electronic, on your amp to give > me a good starting place. I have my ‘61 EA-28RVT which is the > exact same circuit, but I’d still like the cabinet measurements, > and some circuit specs from yours to have on hand. Don’t bother > right now, but I hope you don’t mind if I ask that favor at some > point in the future.
Hey, ‘blueprinting’ is a good thing… like sampling the DNA in order to do the Jurassic Park thing. I was amazed when I looked at the Crestline schem… no wonder the tweed blows it away, the preamp is designed for tone suck. Wait for a slow winter… : ) . __ Steve .
Response:
> Thanx for all the great info guys. So if I bring the amp to my tech > with crestline schematics and the tweed schematics, it shouldn’t be a > big deal for the tech do do a tweed conversion?
Not for a tech worth his salt… I wouldn’t try to go with the 7199 tube, just stay with the current complement, but change the other circuits to tweed. __ Steve .
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Does anyone know approximately what the conversion should cost if I take it to a tech??
Response:
> Does anyone know approximately what the conversion should cost if I > take it to a tech??
That’s really tough to guess. Some Fender/Marshall centric toob techs resent working on anything else. OTOH, some curious and ingenious folks appreciate the occasional challenge and brain exercise. Leave out the 7199 as Steve suggests, and it shouldn’t put too deep of a hole in your pocket. If the tech is good, his improvements, and a better speaker should be worth every penny ‘tone-wise’ but don’t expect to recoup everything on a resale. John King
Response:
> Does anyone know approximately what the conversion should cost if I > take it to a tech?? > That’s really tough to guess. Some Fender/Marshall centric toob techs > resent working on anything else. OTOH, some curious and ingenious folks > appreciate the occasional challenge and brain exercise. > Leave out the 7199 as Steve suggests, and it shouldn’t put too deep of > a hole in your pocket. If the tech is good, his improvements, and a > better speaker should be worth every penny ‘tone-wise’ but don’t expect > to recoup everything on a resale.
If the Crestline has the same forked-turret board construction as the tweed, those things are a pain to work on… on the other hand, a lot of what has to happen is removing stuff, with the addition of one 500pF cap and moving the reverb footswitch over to the grid of the recovery tube. If I did it, and had to guarantee it, I’d want near $80 for the job.. would include a general bench tune up, plus parts. By the time you figure in new speaker, etc you’ve spent several hundred dollars… money you won’t recoup upon sale, that amp will never be worth more than $300, too many of them made. Things to think about… __ Steve .
Response:
I’m not too concerned with resale value as I really dig the amp and think it has a lot of potential. I’m thinking of keeping this one (gasp!!) I actually saw the crestline falcon sell on ebay recently for $550, but it was in perfect condition. Now comes the question (thanx again btw, you guys have been a tremendous help) should I take it to a tech in the bay area, San Francisco/Berkeley (where I live) or ship it out to a tech who knows the Falcon amp well. Can anyone here recommend a Bay Area tech, or perhaps a tech in another state who does excellent work?
Response:
> I’m not too concerned with resale value as I really dig the amp and > think it has a lot of potential. I’m thinking of keeping this one > (gasp!!) > I actually saw the crestline falcon sell on ebay recently for $550, but > it was in perfect condition. > Now comes the question (thanx again btw, you guys have been a > tremendous help) should I take it to a tech in the bay area, San > Francisco/Berkeley (where I live) or ship it out to a tech who knows > the Falcon amp well. Can anyone here recommend a Bay Area tech, or > perhaps a tech in another state who does excellent work?
IMO, you probably need a relationship with a local tech… there ought to be a good one in your area… try the AGA tech ref pages: http://aga.rru.com/b2g/ if you haven’t already. The FAQ is highly recommended as well… hell, read the whole site while you’re at it. Use one that posts here… it’s a guarantee that your tech will be available, and subject to peer review. __ Steve .
Response:
- Hide quoted text — Show quoted text ->>Does anyone know approximately what the conversion should cost if I >>take it to a tech?? >That’s really tough to guess. Some Fender/Marshall centric toob techs >resent working on anything else. OTOH, some curious and ingenious folks >appreciate the occasional challenge and brain exercise. >Leave out the 7199 as Steve suggests, and it shouldn’t put too deep of >a hole in your pocket. If the tech is good, his improvements, and a >better speaker should be worth every penny ‘tone-wise’ but don’t expect >to recoup everything on a resale. > If the Crestline has the same forked-turret board > construction as the tweed, those things are a pain > to work on… on the other hand, a lot of what has > to happen is removing stuff, with the addition of > one 500pF cap and moving the reverb footswitch > over to the grid of the recovery tube. If I did it, > and had to guarantee it, I’d want near $80 for the > job.. would include a general bench tune up, plus > parts. > By the time you figure in new speaker, etc you’ve > spent several hundred dollars… money you won’t > recoup upon sale, that amp will never be worth more > than $300, too many of them made. Things to think > about… > __ > Steve > .
Crestline is actually more "point-to-point"…..
Response:
… > If the Crestline has the same forked-turret board > construction as the tweed, those things are a pain > to work on…
… > Crestline is actually more "point-to-point"…..
Very cool, much easier to work on… I had fun fixing up a Kalamazoo Reverb 12 that had ground loop issues in the reverb circuit… got it very quiet. Those are true P2P. __ Steve .
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- Hide quoted text — Show quoted text – > … >>If the Crestline has the same forked-turret board >>construction as the tweed, those things are a pain >>to work on… > … >Crestline is actually more "point-to-point"….. > Very cool, much easier to work on… I had fun > fixing up a Kalamazoo Reverb 12 that had ground > loop issues in the reverb circuit… got it very quiet. > Those are true P2P. > __ > Steve > .
Oops…I was a bit off…I just popped mine open, and altough there is a lot more room in the chassis, but it still uses that turret-type board that the tweed version used. I’ve been looking at the schem provided earlier and it is NOT the correct one, even though it shows the use of a 6C4 vice 7199. The values I’ve looked at so far mirror the tweed components……only diff looks like the 6C4….
Response:
… > Oops…I was a bit off…I just popped mine open, and altough there is a > lot more room in the chassis, but it still uses that turret-type board > that the tweed version used. I’ve been looking at the schem provided > earlier and it is NOT the correct one, even though it shows the use of a > 6C4 vice 7199. The values I’ve looked at so far mirror the tweed > components……only diff looks like the 6C4….
The biggie for me is that volume control bypass… this is what allows you to dial in the sweet spot, just dime the tone and crank the volume until it gets how you like it. Sounds like it conforms to the Gibson amp norm… none, that is! __ Steve .
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The amp is cathode-biased right??? Does that mean I can put in a different set of 6V6’s without rebiasing. I have a set of hytrons I want to try out.
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- Hide quoted text — Show quoted text – > … >Oops…I was a bit off…I just popped mine open, and altough there is a >lot more room in the chassis, but it still uses that turret-type board >that the tweed version used. I’ve been looking at the schem provided >earlier and it is NOT the correct one, even though it shows the use of a >6C4 vice 7199. The values I’ve looked at so far mirror the tweed >components……only diff looks like the 6C4…. > The biggie for me is that volume control bypass… this > is what allows you to dial in the sweet spot, just dime > the tone and crank the volume until it gets how you like > it. > Sounds like it conforms to the Gibson amp norm… > none, that is! > __ > Steve > .
Well, the ‘64 Jensen C12R in there was pretty tired…I replaced it with a Weber 12F125…a little more crisp, but by no means much treble, even dimed. A little better with a 5V4 rectifier. Volume control bypass? What’s that?
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> The amp is cathode-biased right??? Does that mean I can put in a > different set of 6V6’s without rebiasing. I have a set of hytrons I > want to try out.
yep
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… > Well, the ‘64 Jensen C12R in there was pretty tired…I replaced it with > a Weber 12F125…a little more crisp, but by no means much treble, even > dimed. A little better with a 5V4 rectifier. > Volume control bypass? What’s that?
Refer to the tweed schematic… the more you turn up the volume, the more the top part of the pot is bypassed by the 500uuF (500pF) cap… same trick as used in guitars, to try and mitigate cord capacitance that steals highs as the volume pot is rolled off. The further down you turn the pot, the more the ‘bright cap’ takes over… in order to use it properly, you dime the tone control (turn it all the way up), then start bringing up the volume… at some point, you’ll have your favorite tone, the ’sweet’ spot. It does the same thing as the Fender bright switch cap… bypasses the Volume pot for treble signal. __ Steve .
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