And by some strange coincidence, a Gibson Maestro GA1RT shows up for sale on the site "Craigslist Sacramento" (California). The ad states "Good condition..." $800 US dollars. I had not seen one of these amps before. Good job Stuart and thanks for sharing this video!!
Wow that really IS amazing. The owner of this has the complete righ in mint condition. He's going to bring it over for me to do a short video of it in action. Quite rare.
I worked at a music store in Michigan USA in the late 60's and 70's. We had that amp in our inventory. The object of the amp is to add reverb to another amp creating a echo reverb effect. Turning on both amps, clip the brown wires from the maestro amp to the speaker leads of the other amp and plug the instrument into the second amp as the main amp, and it creates the reverb echo effect on the other amp. I have a catalog photo from the 1962 Gibson catalog. Cool piece of history. It retailed here in the states for $149.50. Not sure what happened to the amp when the store closed it's doors in 1980 but I think it was still in their inventory.
Skip Simmons from the Truth About Vintage Amps podcast is a huge fan of speaker driven reverb units, and has shared the schematic to make a freestanding unit that you can use to add reverb (via a slave amp) to any amp.
Man Stuart what a Jem, I remember these amps my uncle had one and my dad a a Gibson skylark amp these old amps are super cool,and simple,I live in Michigan so a lot of the old Gibson stuff I’ve seen a lot I. Pawn shop and people using them giging in blues bars
Amps with ECL82/ECL86/PCL86 were very popular in (at least) eastern europe. Many radios, TV, turntables and many more were equipped with power amps like this.
Hi Stuart. I got covid in 2019 before they new how to help with it. I'm glad your case is not bad. I was in the hospital for a week. Did not think I would recover for a few days.
Very interesting amplifier. Unusual reverb design. Still very cool, and I would love to work on something like that. I just picked up an estate sale of 1950's vintage test equipment (VTVM, cap tester, RF freq generator, frequency generator, and an oscilloscope) and 5 AA5 radios for $100. Nothing is as satisfying as fixing vintage gear with vintage tools. Needless to say, I've got a lot of cap replacing to do....
@@stuartukguitarampguy5830 one unit I got was a Sprague TO-4 Tel-Ohmike capacitor tester. Why don't modern cap testers have a "magic eye"? It's so cool!
@@tjsogmc , The vintage Sprague capacitor testers are useful and desirable nowadays because they can test high-voltage capacitors at working voltage. Be aware that you will likely have to partly recap it in order to be able to use it accurately and safely. Adding a grounded power cord would be a good idea as well. The other thing to be aware of is that the leads to the capacitor under test will have high voltage DC on them and so you have to be very careful not to shock yourself, as well as not accidentally reversing the polarity to an electrolytic capacitor and causing it to explode! It is also worth noting that oftentimes one will come across a vintage capacitor tester that has had the magic eye robbed from it and used to refurbish a collectible old radio. Some capacitor testers used the rarer and more valuable 6E5 or 6U5 eye tube, but if I remember correctly the tube used in the Sprague was a 1629 eye tube that is not a direct fit for most antique radios (different tube base and a 12 volt filament, not 6 volt).
@@goodun2974 sure thing! I plan on recapping and calibrating every test unit I got from the estate sale. Most of the ac cords are dry rotten and neeed replacing with modern polarized plugs. It's all untouched 1950's vintage gear. Surprisingly, I also got all the original operator manuals for all of it. Using proper test methods and precautions is definitely good advice! My workshop is very soon going to look like a mad scientist lab from one of those cheesy monster movies- and I'm perfectly fine with that 👌 🙂 I should probably get a lab coat and a set of welding goggles to complete the look.
The amp sounds amazing! The sound is such a familiar sound. I think that we have all heard that sound on 60's & 70's records before for sure. It's also a sound that the people born after the 60's & 70's are still chasing to this day.
Thanks for the runaway bias video on the Marshall jvm410h. I had the same problem and drilled out the pins with a 3/16" hole saw and an egg beater hand drill. The amp is back up and running after sitting 2 years. The bias has been stable playing it half a day on the bench.
Greetings, Stewart. I thoroughly enjoyed your tour and repair of the Gibson GA-1RT. I am in the process of scratch-building its slightly larger and infinitely rarer (quite possibly never built or sold by Gibson) brother, the GA-1RVT, which features an independent reverb effect (not slave) as well as the identical tremolo circuit as found in the RT. Please check out my video series if and when you get a chance. Meanwhile, thanks for the nice video and best regards from Sunny West Texas, USA :)
There were several Gretsch add-on reverb amplifiers (built by Valco) in the Sixties that worked in similar fashion, by clipping a pair of alligator clips onto the speaker of your existing amplifier and feeding the signal into the reverb amp. One model included instrument inputs and a guitar-signal preamp, as does the Gibson here, and the other did not. Neither had tremolo. Note from the Gibson schematic shown here that the speaker level signal from the main guitar amp was padded down with a 33 ohm resistor so as not to overdrive or damage the reverb tank. BTW, several Magnatone amps had semi-stereo two channel output, with the speaker-level signal of one amp feeding another seperate amp and speaker strictly for the "wet" reverb signal.
I'm a little surprised you didn't replace the "death" cap with a X/Y cap rated for across-the-line service, in case there was a noise issue. Could be added later if needed, I suppose. Good video, get well soon.
WOW! That 61' Gibson is a low-wattage tone machine! The final playthrough blew me away. It has a vintage growl with a pronounced midrange. I must admit that the overall design is unorthodox. But today's installment was worth the view. I'm very sorry the virus has invaded you, Stuart. I hope you're recovery is fast, with no lasting affects. This modern-day pestilence has to run its course and go away. Well done. Cheers!
So if the rectifier tube is replaced by ss diodes, you really can build a two tube tube amplifier featuring both reverb and tremolo. Pretty economic construction. Does the tremolo make LS cone to move because there is no push-pull output stage to cancel out that tremolo signal going through the output stage and OT? Well probably the OT cannot deliver much of tremolo signal because the very low frequency but it amplitudemodulates the sound as intended.
Yes I think that's how it works. On the 2-tube though rmember we don;t really have reverb recovery as well as tremelo. You only get reverb when the entire amp is being used as a reverb recover amp. Still pretty cool though! No tone control of course, that would need another tube.
so glad to see you are back with this wonderful new Sept. post. You are very unique and I always greedily enjoy watching your videos in the morning with a cup of coffee. This one in particular was great....love the old low wattage Gibson amps and their growling tone. I am sorry you got covid and hope that you recover quickly with absolutely no after effects. Thank you so much for sharing your talent worldwide! Oh....question....please explain “tuppence”😎
Thanks for the positive cimments. Ah yes, tuppence. It means Two Pence or Two Pennies. So not very much. The British expression "I wouldn;t give you tuppence for it!" means I wouldn;t give you anything much.
ECL82; E = 6.3V, C=Triode, L = Power Pentode. There's also a conceptually-similar 6GW8/ECL86 tube with a different pinout and different characteristics. Both of these types were often used in low-power hifi, radios, and guitar amps.The triode section was typically used to drive the output tube, and not for tremolo.
Yes, the gain of that triode of ECL82 is lower than gain of a triode of ECC83 so the tremolo oscillator triode needs for example a bit larger cathode bypass cap to make sure that the oscillator works well at lower frequencies. ECL82 was commonly used as a turntable amp because if you used a high output ceramic pickup, only one ECL82 was all you needed to build amp capable of creating a nice sound.
Stuart sorry to change the subject but it would be great every now and then to show us how repair or modify a Neumann u87 or repair like a neve 1073. I trust your skill more than Stuart . Cheers
Hi Joh, Woah! Serious stuff! Thnings like hi-end capacitor mics are quite specialist. Also I bet those Neve preamps are bristling with surface mount chips these days!
It may have been a normal flu or cold.. Hope that it didn’t linger! I’d turn it into just reverb.. Did the foot switch turn the Trem off and leave the reverb on? I own a GA19 RVT... an amazing little amp!
Never seen the inside of that particular amp before, although I had heard of it. I've seen and plugged into it's posh brother the GA-2RT which has 2X6V6's and 16 watts out. .. Anyway, great job as always and given it's condition , well worth saving ..
Fantastic video! This is an amazing little amp. I've never seen one before, but I agree with you it does sound bad with non adjustable tremolo. I find it entertaining to learn from your expertise. It seems you never run out of rare amps to work on. What is the model number of the megger you are using?
Thanks for sharing Stuart . Maybe the rectifier marking 61-30 is a date code: 1961/30th week? I have a GA80 from the same era - sadly not in the same cosmetic condition! It also has some of the orginal Gibson branded valves. Hope you get over the bat-pox quickly.
I hope your COVID recovery continues. A few things: * Before you found the tremolo "off" position on the dial, I was thinking the foot switch controlled that. Did the foot switch control the reverb on / off? * Maybe next video could include an explanation of when to use flux and/or different types of solder? (Or maybe you already covered that in a previous video?). It mystifies me and I'm sure your explanation would be direct and helpful to many, including me. Keep up the good work!
Hi Jim. Yes the fooswitch was a simpke off/on reverb. It actually goes straight in to the reverb tank! If the connection wire etc is a bit tarnished I usually add a touch of flux. I also always use lead solder as I have done all my life. Can't stand the lead-free stuff!
And by some strange coincidence, a Gibson Maestro GA1RT shows up for sale on the site "Craigslist Sacramento" (California). The ad states "Good condition..." $800 US dollars. I had not seen one of these amps before. Good job Stuart and thanks for sharing this video!!
Wow that really IS amazing. The owner of this has the complete righ in mint condition. He's going to bring it over for me to do a short video of it in action. Quite rare.
I worked at a music store in Michigan USA in the late 60's and 70's. We had that amp in our inventory. The object of the amp is to add reverb to another amp creating a echo reverb effect. Turning on both amps, clip the brown wires from the maestro amp to the speaker leads of the other amp and plug the instrument into the second amp as the main amp, and it creates the reverb echo effect on the other amp. I have a catalog photo from the 1962 Gibson catalog. Cool piece of history. It retailed here in the states for $149.50. Not sure what happened to the amp when the store closed it's doors in 1980 but I think it was still in their inventory.
Hi Don. Yes that's exactly my understandoing of how this amp was supposed to be used. Shame you didn't buy a few and stash them away!
Skip Simmons from the Truth About Vintage Amps podcast is a huge fan of speaker driven reverb units, and has shared the schematic to make a freestanding unit that you can use to add reverb (via a slave amp) to any amp.
Interesting thanks Matt
Good catch and explanation on the death cap. Someone somewhere will appreciate that and they won't even know they appreciate it!
Interesting it was already leaking slightly!
Man Stuart what a Jem, I remember these amps my uncle had one and my dad a a Gibson skylark amp these old amps are super cool,and simple,I live in Michigan so a lot of the old Gibson stuff I’ve seen a lot I. Pawn shop and people using them giging in blues bars
Interesting! Worth quite a lot of money these days.
Amps with ECL82/ECL86/PCL86 were very popular in (at least) eastern europe. Many radios, TV, turntables and many more were equipped with power amps like this.
Wishing you a speedy recovery
Thanks Jeff!
Hi Stuart. I got covid in 2019 before they new how to help with it. I'm glad your case is not bad. I was in the hospital for a week. Did not think I would recover for a few days.
Hi Monty. Ooh, nasty! Yes I managed to avoid it in the early period. Mine is just like a bad cold really.
Very interesting amplifier. Unusual reverb design. Still very cool, and I would love to work on something like that. I just picked up an estate sale of 1950's vintage test equipment (VTVM, cap tester, RF freq generator, frequency generator, and an oscilloscope) and 5 AA5 radios for $100. Nothing is as satisfying as fixing vintage gear with vintage tools. Needless to say, I've got a lot of cap replacing to do....
Have fun!!
@@stuartukguitarampguy5830 one unit I got was a Sprague TO-4 Tel-Ohmike capacitor tester. Why don't modern cap testers have a "magic eye"? It's so cool!
@@tjsogmc , The vintage Sprague capacitor testers are useful and desirable nowadays because they can test high-voltage capacitors at working voltage. Be aware that you will likely have to partly recap it in order to be able to use it accurately and safely. Adding a grounded power cord would be a good idea as well. The other thing to be aware of is that the leads to the capacitor under test will have high voltage DC on them and so you have to be very careful not to shock yourself, as well as not accidentally reversing the polarity to an electrolytic capacitor and causing it to explode! It is also worth noting that oftentimes one will come across a vintage capacitor tester that has had the magic eye robbed from it and used to refurbish a collectible old radio. Some capacitor testers used the rarer and more valuable 6E5 or 6U5 eye tube, but if I remember correctly the tube used in the Sprague was a 1629 eye tube that is not a direct fit for most antique radios (different tube base and a 12 volt filament, not 6 volt).
@@goodun2974 sure thing! I plan on recapping and calibrating every test unit I got from the estate sale. Most of the ac cords are dry rotten and neeed replacing with modern polarized plugs. It's all untouched 1950's vintage gear. Surprisingly, I also got all the original operator manuals for all of it. Using proper test methods and precautions is definitely good advice!
My workshop is very soon going to look like a mad scientist lab from one of those cheesy monster movies- and I'm perfectly fine with that 👌 🙂 I should probably get a lab coat and a set of welding goggles to complete the look.
@@tjsogmc I remember the old magic eye from my first tape recorder - a Grundig!
The amp sounds amazing! The sound is such a familiar sound. I think that we have all heard that sound on 60's & 70's records before for sure. It's also a sound that the people born after the 60's & 70's are still chasing to this day.
Hi Matthew glad you enjoyed it!
Sounds perfect for playing any Creedence Clearwater Revival song. Perfect job, Stuart.
I hear the bad Moo-Hoon risin'.....
Thanks for the runaway bias video on the Marshall jvm410h. I had the same problem and drilled out the pins with a 3/16" hole saw and an egg beater hand drill. The amp is back up and running after sitting 2 years. The bias has been stable playing it half a day on the bench.
Nice, well done!
Nice one Young Stuart!!
Glad you enjoyed it.
Greetings, Stewart. I thoroughly enjoyed your tour and repair of the Gibson GA-1RT. I am in the process of scratch-building its slightly larger and infinitely rarer (quite possibly never built or sold by Gibson) brother, the GA-1RVT, which features an independent reverb effect (not slave) as well as the identical tremolo circuit as found in the RT. Please check out my video series if and when you get a chance. Meanwhile, thanks for the nice video and best regards from Sunny West Texas, USA :)
Thanks Doug I'm a great fan of your channel. STuart
@@stuartukguitarampguy5830 That's great to hear, Stuart. Thanks so much :)
Hey Stuart, never seen one of those before..! Unusual amp to say the least...Interesting info as usual..Ed..uk..😀
There were several Gretsch add-on reverb amplifiers (built by Valco) in the Sixties that worked in similar fashion, by clipping a pair of alligator clips onto the speaker of your existing amplifier and feeding the signal into the reverb amp. One model included instrument inputs and a guitar-signal preamp, as does the Gibson here, and the other did not. Neither had tremolo. Note from the Gibson schematic shown here that the speaker level signal from the main guitar amp was padded down with a 33 ohm resistor so as not to overdrive or damage the reverb tank. BTW, several Magnatone amps had semi-stereo two channel output, with the speaker-level signal of one amp feeding another seperate amp and speaker strictly for the "wet" reverb signal.
Interesting info thanks.
I'm a little surprised you didn't replace the "death" cap with a X/Y cap rated for across-the-line service, in case there was a noise issue. Could be added later if needed, I suppose. Good video, get well soon.
WOW! That 61' Gibson is a low-wattage tone machine! The final playthrough blew me away. It has a vintage growl with a pronounced midrange. I must admit that the overall design is unorthodox. But today's installment was worth the view. I'm very sorry the virus has invaded you, Stuart. I hope you're recovery is fast, with no lasting affects. This modern-day pestilence has to run its course and go away. Well done. Cheers!
Thanks Alex - hanging on in there!
So if the rectifier tube is replaced by ss diodes, you really can build a two tube tube amplifier featuring both reverb and tremolo. Pretty economic construction.
Does the tremolo make LS cone to move because there is no push-pull output stage to cancel out that tremolo signal going through the output stage and OT? Well probably the OT cannot deliver much of tremolo signal because the very low frequency but it amplitudemodulates the sound as intended.
Yes I think that's how it works. On the 2-tube though rmember we don;t really have reverb recovery as well as tremelo. You only get reverb when the entire amp is being used as a reverb recover amp. Still pretty cool though! No tone control of course, that would need another tube.
so glad to see you are back with this wonderful new Sept. post. You are very unique and I always greedily enjoy watching your videos in the morning with a cup of coffee. This one in particular was great....love the old low wattage Gibson amps and their growling tone. I am sorry you got covid and hope that you recover quickly with absolutely no after effects. Thank you so much for sharing your talent worldwide! Oh....question....please explain “tuppence”😎
Thanks for the positive cimments. Ah yes, tuppence. It means Two Pence or Two Pennies. So not very much. The British expression "I wouldn;t give you tuppence for it!" means I wouldn;t give you anything much.
Dude, the tremolo speed pot will click OFF if rotated fully left. These are GREAT amps. Needs some finesse to get the sound dialed in.
Aha! Thanks, didn;t notice that!
ECL82; E = 6.3V, C=Triode, L = Power Pentode. There's also a conceptually-similar 6GW8/ECL86 tube with a different pinout and different characteristics. Both of these types were often used in low-power hifi, radios, and guitar amps.The triode section was typically used to drive the output tube, and not for tremolo.
Yes, the gain of that triode of ECL82 is lower than gain of a triode of ECC83 so the tremolo oscillator triode needs for example a bit larger cathode bypass cap to make sure that the oscillator works well at lower frequencies.
ECL82 was commonly used as a turntable amp because if you used a high output ceramic pickup, only one ECL82 was all you needed to build amp capable of creating a nice sound.
Stuart sorry to change the subject but it would be great every now and then to show us how repair or modify a Neumann u87 or repair like a neve 1073. I trust your skill more than Stuart . Cheers
Hi Joh, Woah! Serious stuff! Thnings like hi-end capacitor mics are quite specialist. Also I bet those Neve preamps are bristling with surface mount chips these days!
It may have been a normal flu or cold..
Hope that it didn’t linger!
I’d turn it into just reverb..
Did the foot switch turn the Trem off and leave the reverb on?
I own a GA19 RVT... an amazing little amp!
Never seen the inside of that particular amp before, although I had heard of it. I've seen and plugged into it's posh brother the GA-2RT which has 2X6V6's and 16 watts out. .. Anyway, great job as always and given it's condition , well worth saving ..
Fantastic video! This is an amazing little amp. I've never seen one before, but I agree with you it does sound bad with non adjustable tremolo. I find it entertaining to learn from your expertise. It seems you never run out of rare amps to work on. What is the model number of the megger you are using?
Thanks for sharing Stuart . Maybe the rectifier marking 61-30 is a date code: 1961/30th week? I have a GA80 from the same era - sadly not in the same cosmetic condition! It also has some of the orginal Gibson branded valves.
Hope you get over the bat-pox quickly.
Thanks Andrew, yes that might be ewhat those numbers were. Odd not to have the valve type written on it though!
Hi Stuart. Nice Video. Is the asymmetrical clipping as you show at 32,24min, normal for a class A amplifier? What is causing it?
Hi William YEs that's perfectly nrmal, just the valve running out of volts at one end!
I hope your COVID recovery continues. A few things:
* Before you found the tremolo "off" position on the dial, I was thinking the foot switch controlled that. Did the foot switch control the reverb on / off?
* Maybe next video could include an explanation of when to use flux and/or different types of solder? (Or maybe you already covered that in a previous video?). It mystifies me and I'm sure your explanation would be direct and helpful to many, including me.
Keep up the good work!
Hi Jim. Yes the fooswitch was a simpke off/on reverb. It actually goes straight in to the reverb tank! If the connection wire etc is a bit tarnished I usually add a touch of flux. I also always use lead solder as I have done all my life. Can't stand the lead-free stuff!
I would have enjoyed it more if you had taken the trouble to align the fuse holder correctly after re-fitting it.
Call me fussy, if you wish!!
That costs extra...
@@stuartukguitarampguy5830 🤣
Does the owner live in the U.K.?
Yes he does.
@@stuartukguitarampguy5830 awesome you don’t see these amps over here in England all that often
@@memygtar No, SUPER rare.
@@stuartukguitarampguy5830 I’ll have to keep an eye out for one