Worth the price of admission??
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0285835737
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0285835737
GA 77 RVT
- Thread starter BluesDan
- Start date
- Joined
- Jul 30, 2007
- Messages
- 13,637
- Reaction score
- 3,065
- Location
- Philly, or thereabouts
- Guild Total
- 11
Around the corner from me, but too big and too loud for my needs.
Hi Dan: Yes, but not much more; the minimum is about what it was worth at the beginning of the year. Among Gibson amps, only the venerable GA40 Les Pauls are holding their values. Some of these GA77s were fitted with a 15" speaker, you might want to confirm the size and ask him what make / model is in it now. It looks like the reverb and trem live on Channel 2 and this model pre-dates channel-switching.
Techno-jabber and assuming the amp matches the public domain schematic - Gibsons are notorious for not matching their schematics. The amp uses the poorly-understood 6EU7 in the preamp; except for Sovtek reissues, the tube is NOS/used only. It's a twin triode like a 12AX7 but the heaters are wired differently and the pinouts are different; that is, the 12AX7 tubes are not drop-in replacements for 6EU7s. Unlike the 12AX7s that come in flavors; RCA, Telefunken, JJ ... the 6EU7s don't; GE, National (Yugoslavian), and that's about it.
The 6EU7 is a reliable, sonically-neutral tube ... it just doesn't have the cachet of the 12AX7. But since this isn't a giant among vintage amps, re-wiring 6EU7 tube sockets to accept 12AX7s won't harm its value and, in fact, might increase it. 6EU7s run $12-$22, about what 12AX7s but there's no such thing as a 'killer' make/model of it. This amp also uses a 7199; I think it's functioning as a mixing amp but whatever it does, its a rugged but sort of expensive tube; $40-$50. The used models labeled 'Dynaco' out of Dynaco ST70s are $75-$100.
Speaker; the take-out, assuming it's 12", is a Jensen P12S; it wasn't the original but it was a poor substitution; it can't handle the power but would work fine in a single-ended / twin 6V6 / 15 watt amp. Seller says it has a generic higher power probably ceramic speaker; in other words, there's nothing in the choice of speaker to help justify or boost the asking price. So ... if you don't like it, you're going out of pocket for something that you do.
Blue boxes: bias supply at bottom, resulting negative bias voltage shown at the top. The amp has no bias pots or test points like the Guild Thunder Heads / Birds / Whoppers so it needs matched tubes - a little more expense and offers no direct means to piddle with the bias. Among ampistas with Obessive Compulsive Disorder, screwing with the bias amounts to something to do for an evening.
Green box/V5 - Red box/V4: this is the tremolo oscillator - it jerks DC voltage up and down and that flucutation is transmitted to V4. Worth mentioning is the 'Factory Adjustment' tag on a potentiometer between the V4 cathode and ground; I guess it's supposed to be adjusted to achieve 2.4v on the cathode but ... uh ... we here at Juanzampz get nervous when we see proprietary stuff ... same goes for the LDR above V4; a Light Dependent Resistor ... sort of a Gyro Gearloose design. In short, V4 and V5 make that little 'light bulb' go from bright to dim; doing so causes the resistor half of the gadget to decrease in resistance shunting power to ground and then increase in resistance as the light comes back on. The result is the dc power heading chart north to that 220K resistor goes up and down causing the line signal - heading left to right - to go: "...owawowawowa ..."
So.....wassa matta with that? One of the valuable features of the amp depends on a proprietary gadget and a semi-conductor that's approaching obselescence ... if it isn't already. Mad Dog's Ampeg Gemini and several Fender designs use an optical-coupler a/k/a 'roach' but the after-market is still supporting those amps ... without a part # or cross-reference, I can't say the same for this model Gibson.
Finally, the other half of V5 (upper center) is the phase splitter sending the positive half of the wave form to one half of V6 and the negative half to the other half of V6; that is, V6 acts like a true driver; a little more costly way to do it and likely to produce a good result. Otherwise, the amp looks great; tolex, control panel, knobs and so on. The smooth brown tolex a little easier on the eye than the tree-bark stuff seen on later models. Good luck! CJ
"Juanzampz"............I like that!
10-4 on the proprietary gadgets approaching obselescence, I thought I remembered something we discussed about that in a prior thread, wasn't a 77 though. So which Gibbys do and which don't? Is it only certain models, years, or "depends"......or how about I re-phrase that......."I have had my share of Fenders, I am intrigued by all the good reviews of older tube Gibby's here at LTG, if ya had to hunt down just one (single 12" or smaller.....the 77 would have been fun but not exactly practical for my use, I have Fender Twin if I want to take out windows in the den), which one would it be??
Thanks for all the info., as always greatly appreciated
D
10-4 on the proprietary gadgets approaching obselescence, I thought I remembered something we discussed about that in a prior thread, wasn't a 77 though. So which Gibbys do and which don't? Is it only certain models, years, or "depends"......or how about I re-phrase that......."I have had my share of Fenders, I am intrigued by all the good reviews of older tube Gibby's here at LTG, if ya had to hunt down just one (single 12" or smaller.....the 77 would have been fun but not exactly practical for my use, I have Fender Twin if I want to take out windows in the den), which one would it be??
Thanks for all the info., as always greatly appreciated
D
Hi Dan; thanks, missed the 15" speaker ID ... Offered for your consideration (Rod Serling) ..
Gibson GA19RVT: A Tweed GA19RVT on eBay Extremely good condition; seller says it's a '64 but I don't think it's any later than '62. Report of 'hum' likely caps; a $125 fix. Twin 6V6s, preamp tubes unknown because seller too dopey to remove tube shields and look. I had one of these threaded here; 3 X 6EU7s, 1 X 7199. 'Zilla has one, a 'Crest' model (dark tolex), 6EU7s, 6C4, twin 6V6s. They are 15 watt amps; the earlier 'tweed' models break up a little sooner, the 'Crest' models a little cleaner and break up a little later. To get a 12" alnico/belled speaker in my GA19, I had to re-cut the baffleboard for clearance but any 12" ceramic speaker will fit. Warm, throaty, versatile, punchy amps.
Gibson GA8T: on eBay for a lot of money Twin 6BM8s; near-mint condition. Maybe 12 watts, 6BM8 like the 6GW8 used by Guild but with better tone. Univox ripped the Gibson circuit off, produced the U45B, and Jimmy Page used a U45B/twin 6BM8 amp for recording. Seller doesn't say but its predecessor, the GA8, was fitted with a 10" speaker. Once again, to get a 12" belled/alnico in my GA8, I made a new baffle. Too much money but a killer amp. Another GA8T not so pristine but a good price.
Gibson GA18 Explorer: closed eBay auction Generically similar to a Fender Princeton; 2 X 12AX7, twin 6V6s, 10" speaker. Another closed GA18 auction and and another don't know why this one didn't sell. ... and I own one threaded here.
And just for fun, closed auction for a GA6 Lancer this and the GA14 the closest Gibson amps to a Fender Tweed Deluxe.
These are relatively simple amps, have tone to burn, rely on readily-available parts, and have ... well ... charm. They aren't Fenders ... and they aren't Fenders; they are cheaper for their age than Fenders and have a warm, distinctive sound. I personally draw the 'no-older-than' line at these Tweeds. Despite the extraordinary sound of the '50s two-tones, they are expensive and lean towards the fragile. The 'no newer than' line at the '63/'64 Crest-style GA19RVTs. Among Gibsons, the Tweeds are the trade-off among/between price, age, tone, mojo, and servicability. CJ
Gibson GA19RVT: A Tweed GA19RVT on eBay Extremely good condition; seller says it's a '64 but I don't think it's any later than '62. Report of 'hum' likely caps; a $125 fix. Twin 6V6s, preamp tubes unknown because seller too dopey to remove tube shields and look. I had one of these threaded here; 3 X 6EU7s, 1 X 7199. 'Zilla has one, a 'Crest' model (dark tolex), 6EU7s, 6C4, twin 6V6s. They are 15 watt amps; the earlier 'tweed' models break up a little sooner, the 'Crest' models a little cleaner and break up a little later. To get a 12" alnico/belled speaker in my GA19, I had to re-cut the baffleboard for clearance but any 12" ceramic speaker will fit. Warm, throaty, versatile, punchy amps.
Gibson GA8T: on eBay for a lot of money Twin 6BM8s; near-mint condition. Maybe 12 watts, 6BM8 like the 6GW8 used by Guild but with better tone. Univox ripped the Gibson circuit off, produced the U45B, and Jimmy Page used a U45B/twin 6BM8 amp for recording. Seller doesn't say but its predecessor, the GA8, was fitted with a 10" speaker. Once again, to get a 12" belled/alnico in my GA8, I made a new baffle. Too much money but a killer amp. Another GA8T not so pristine but a good price.
Gibson GA18 Explorer: closed eBay auction Generically similar to a Fender Princeton; 2 X 12AX7, twin 6V6s, 10" speaker. Another closed GA18 auction and and another don't know why this one didn't sell. ... and I own one threaded here.
And just for fun, closed auction for a GA6 Lancer this and the GA14 the closest Gibson amps to a Fender Tweed Deluxe.
These are relatively simple amps, have tone to burn, rely on readily-available parts, and have ... well ... charm. They aren't Fenders ... and they aren't Fenders; they are cheaper for their age than Fenders and have a warm, distinctive sound. I personally draw the 'no-older-than' line at these Tweeds. Despite the extraordinary sound of the '50s two-tones, they are expensive and lean towards the fragile. The 'no newer than' line at the '63/'64 Crest-style GA19RVTs. Among Gibsons, the Tweeds are the trade-off among/between price, age, tone, mojo, and servicability. CJ
Cap,
Thanks again for the rundown on the various Gibby models and specs, very helpful and greatly appreciated. GA18 it is ! :wink:
Quick question regarding the GA18. I noticed that yours has a trem but no "T" designation. In a quick google sweep of the net I came up with info that suggested Gibby made GA18's without the "T" designation, yet Trem equipped" during the '59 / '60 time frame before changing it to a GA18T. Is that accurate? If so, then yours is "pre T" and from that "59/'60 time frame? Or is yours actually a GA18T?
Dan
Thanks again for the rundown on the various Gibby models and specs, very helpful and greatly appreciated. GA18 it is ! :wink:
Quick question regarding the GA18. I noticed that yours has a trem but no "T" designation. In a quick google sweep of the net I came up with info that suggested Gibby made GA18's without the "T" designation, yet Trem equipped" during the '59 / '60 time frame before changing it to a GA18T. Is that accurate? If so, then yours is "pre T" and from that "59/'60 time frame? Or is yours actually a GA18T?
Dan
Hi Dan and welcome to the wacky world of Gibson ... mine has GA18 silk-screened on the control panel but the GA18 Owner's Manual adds a 'T'. The folks at HarpAmps who have on-line copies of Gibson Owner's Manuals; the info they have for a GA18T, page 4, shows a GA18T with 6EU7s in the preamp and 6BQ5/EL84 outputs. I have never seen a tweed GA18 (with or with a T) with EL84s ... although there could have been one in the 'Crest' format.
I know ... none of this is very clear ... but for the sake of muddying the waters a little further, this is a Maestro GA16T Viscount a rare model and this one is in nice condition; the common domain schematic typically tagged GA16 or GA18(with or with T) on the outside, when opened, has GA16T in the upper right hand corner ... :shock: :? The short of it is that the GA16(T) schematic applies to any GA18 with 6V6s ... and, oh yeah, the GA6 and the GA14 share the same schematic - the difference is 8 ... Schematic sources of interest:
Free Information Society Warning; sponsors have some unusual political ideas
Schematic Heaven Very good with the lesser makes and models in their Bargain Bin
HarpAmps Schematics are included as individual pages in each Manual.
I know this doesn't help much so I won't say; 'hope this helps' :lol: J
I know ... none of this is very clear ... but for the sake of muddying the waters a little further, this is a Maestro GA16T Viscount a rare model and this one is in nice condition; the common domain schematic typically tagged GA16 or GA18(with or with T) on the outside, when opened, has GA16T in the upper right hand corner ... :shock: :? The short of it is that the GA16(T) schematic applies to any GA18 with 6V6s ... and, oh yeah, the GA6 and the GA14 share the same schematic - the difference is 8 ... Schematic sources of interest:
Free Information Society Warning; sponsors have some unusual political ideas
Schematic Heaven Very good with the lesser makes and models in their Bargain Bin
HarpAmps Schematics are included as individual pages in each Manual.
I know this doesn't help much so I won't say; 'hope this helps' :lol: J
Delisted then Relisted w/ different item #BluesDan said:
Thanks Dan; an intriguing thought. What with the books on Ampeg and Fender, I'm surprised no one has approached Backbeat Books or Hal Leonard about writing one ... Reading the Ampeg and Fender stuff, you get an appreciation about how much work Hans Moust must have put it in .... not to mention the personality and political issues; Jess Oliver and Everitt Hull ... Leo Fender not going quietly into the night ...
Maybe Juanzampz should try and reach Orville Gibson on the Ouija Board :wink: J
Maybe Juanzampz should try and reach Orville Gibson on the Ouija Board :wink: J
Bump: Gibson amps getting props here in PremierGuitar.com. Mentions the prominence of Mad Dog's GA40 but omits reference to the 5879 tubes in both channels of the preamp which are the electronic foundation of the re-issue Victoria GA40s.
Jes me but I think Gibson amps come closer to being worth what's paid for them in the same way that Guild guitars, compared to Martins, are worth what's paid for them. The incremental price; Fender/Gibson or Martin/Guild difference isn't matched by incremental value ... at least I think so anyway 