Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Willabe on July 01, 2011, 04:04:18 pm
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I have a copy of the Gibson Amp. book by Wallace Marx Jr. which is a very good book IMHO. In it he goes thru a lot of if not most of the Gibson amp line. Has some nice pics. also.
Anyway he covers this amp and says that " while the main speaker (12") up front would broadcast signal, the side speakers would be able to --fire (4x8") in sequence--, a true stereo experience".
Anybody here ever play one? How's it sound?
Production totals from Gibson that are listed in the book say only 279 were made.
Pre-amp here; http://www.el34world.com/charts/Schematics/files/gibson/GA-83S_STEREO-VIB_(PREAMP).pdf (http://www.el34world.com/charts/Schematics/files/gibson/GA-83S_STEREO-VIB_(PREAMP).pdf)
Power amp and vibrato here; http://www.el34world.com/charts/Schematics/files/gibson/GA-83S_STEREO-VIB_(PWR_AMP).pdf (http://www.el34world.com/charts/Schematics/files/gibson/GA-83S_STEREO-VIB_(PWR_AMP).pdf)
and here; http://www.el34world.com/charts/Schematics/files/gibson/GA-83S_STEREO_VIB.pdf (http://www.el34world.com/charts/Schematics/files/gibson/GA-83S_STEREO_VIB.pdf)
Thanks, Brad :dontknow:
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responding to your question, NO.
But, I have built a solid state version of the Gibson stereo vibrato circuit (using scaled versions of the Gibson phase shift circuits) and dual VCAs. It's a pleasant, Leslie-ish sort of sound... a bit of slight pitch bend and side to side panning. I'm not really a guitarist, and I don't have a ton of experience with pedals, so I can't say "oh, it sounds like a Uni-vibe only...."
IMO, it does have more depth and pitch bend than say the Fender "harmonic vibrato."
The Vox AC-30 uses a very similar circuit, only mono. You can find sound clips of the vox vibrato on You tube.
Nathan
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The circuit looks like the GA-79. It is also stereo vibrato. The 79 is a combo. I had one on my bench and it sounds really cool.
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Hey Dan,
Look at V4, V5, V6 in the GA-83. Phase shifter? And where V5, V6 tie into V12. Looks like sluckey's "Warbler". The PI and power amp look very close.
I've heard many times thru the years the GA-79's sound great. Joe Walsh said he sold his to Aspen Pittman and could'nt find another one. :dontknow:
Thanks, Brad :icon_biggrin:
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But, I have built a solid state version of the Gibson stereo vibrato circuit (using scaled versions of the Gibson phase shift circuits) and dual VCAs. It's a pleasant, Leslie-ish sort of sound... a bit of slight pitch bend and side to side panning. I'm not really a guitarist, and I don't have a ton of experience with pedals, so I can't say "oh, it sounds like a Uni-vibe only...."
IMO, it does have more depth and pitch bend than say the Fender "harmonic vibrato."
Hi octal,
Thanks for the info. I belive it does sound good. Have you ever heard the "Warbler" that sluckey made? It's realy great sounding. There's a 4 page post on it here, with sound bits posted with it. I wonder what you think about the way the 2 sound like side by side?
Here's the link; http://www.el34world.com/Forum/index.php?topic=10681.0 (http://www.el34world.com/Forum/index.php?topic=10681.0)
Do you have a schematic that you would'nt mind sharing?
Thanks, Brad :icon_biggrin:
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A friend in high school I played with occasionally's dad played with Lonnie Mack at that time. He used a GA-79. I played through it a couple times. I loved it, although only in mono. The '59 Les Paul Jr I used didn't have much capability to produce stereo. I'm pretty sure I had the amp set on mono so it was 40 watts, + or - (4 - EL84's). I'll take it over a Vox any day!
Dave
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So you played through it with the vibrato on? What I'd really like to know is how the vibrato sounds in that amp.
Man Dave, 59 LP Jr. with 59 P90's through that amp, I'll bet it sounded great.
And your friends dad played for Lonnie Mack? Wasn't he based in south Ohio/Indiana. Is that where your from?
Gotta tell ya, I love Lonnie Mack.
(Hmmm.... What other stories you got left up your sleeve?:think1:)
Thanks, Brad :icon_biggrin:
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I grew up in Hamilton, OH. Lonnie was our hometown hero, even though he was actually from Indiana. I borrowed his bass player's equipment a couple times when I first started playing bass. Nothing like getting a phone call from a buddy saying, "We have a job tonight and you're gonna play bass." I'd never touched a bass in my life! Lonnie played in local bars (The Halfway House, The King of Clubs, etc) back then. God, I loved the '60's!
I never tried the vibrato. Of course, I tried the vibrato on Lonnie's amp! It was a sweet and strange setup. Magnatone preamp run into the input of a Bandmaster. I have no clue how it was done. I was 15 back then. A few years later, I got to play bass with him a couple times when Bil coundn't be there. Another buddy, Darrel Wayne Perry was his drummer back then. He had a whole wall full of gold records when he died a few years ago. Google THAT name if you want to read some weird stuff! Typical Hamilton! I'm going there tomorrow.
Dave
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WOW! Played a few times with Lonnie Mack! Very cool. :icon_biggrin: Your a lucky man Dave.
Lonnie was well known for that Maggi Vibrato, way cool. SRV and his brother Jimmy loved him, so did Rick Derringer.
I played for a while, for a Chgo. blues man named Son Seals. His -- oldest -- stuff is great, "Live at Wise Fools Pub". Anyway, his sax man, Red and I got to talkin about LM and he says he got a live tape from the sound man at a club we played at in Neb. with Son. He gave it to me and it was killer. Lonnie did some acoustic songs on it too that were great. I thought he was a very good writer.
Thanks, Brad :icon_biggrin:
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What most people miss is that Lonnie is the greatest white blues singer ever... especially for such a country boy. If I ever tried to do what he did on "Why", I'd never be able to speak again.
Son Seals is a hero of mine, too. Being from Chicago and playing with guys like Son Seals, Matt Murphy, Charlie Musselwhite, etc, was like being from around here and playing with guys like Lonnie, Chuck Sullivan (Bo Dollar and the Coins, The Casinos), Billie Joe Royal, etc. No matter how big they get, they're still local boys at home.
Dave
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What most people miss is that Lonnie is the greatest white blues singer ever... especially for such a country boy.
Thats what the acoustic stuff was, country/blues.
No matter how big they get, they're still local boys at home.
Yup. They were just hangin out. Have a drink, talk with the other players who were hangin out, maybe get up and play a little. I sat in as much as they'ed let me.
Learned a lot doin that. One guy, Magic Slim, used to let me do the whole 3'rd set with him a lot of the time. Man that guy could tear it up.
Ya know, Son, early on played for Hound Dog Taylor. So he liked the sound of slide and would play Sadie and have me play slide on it. Not that I played like Hound Dog. He just liked the sound in the mix. I thought he was a very good band leader on stage. And he used horns all the time and got a lot of punch out of them on stage.
Son was realy pretty much a shy, quiet guy, if you can belive that. Diabetes took him in the end. :sad:
Thanks, Brad :icon_biggrin:
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Wow! Lonnie Mack. No telling how many times me and my old high school side kick Charlie use to sit and play Memphis Lonnie Mack Style. We were playing cheap guitars both through a single ss amp with a 8" speaker. You can imagine what we sounded like. :dontknow: Lonnie was way ahead of his time the way he made the flying V scream with his outlandish vibroto. You got me having flash backs of those old 60's tv vidios of Lonnie. Kind of stuff dreams are made of!!! Platefire
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But, I have built a solid state version of the Gibson stereo vibrato circuit (using scaled versions of the Gibson phase shift circuits) and dual VCAs. It's a pleasant, Leslie-ish sort of sound... a bit of slight pitch bend and side to side panning. I'm not really a guitarist, and I don't have a ton of experience with pedals, so I can't say "oh, it sounds like a Uni-vibe only...."
IMO, it does have more depth and pitch bend than say the Fender "harmonic vibrato."
Hi octal,
Thanks for the info. I belive it does sound good. Have you ever heard the "Warbler" that sluckey made? It's realy great sounding. There's a 4 page post on it here, with sound bits posted with it. I wonder what you think about the way the 2 sound like side by side?
Here's the link; http://www.el34world.com/Forum/index.php?topic=10681.0 (http://www.el34world.com/Forum/index.php?topic=10681.0)
Do you have a schematic that you would'nt mind sharing?
Thanks, Brad :icon_biggrin:
I built the SS version of the Gibson vibe almost a decade ago, I don't have a schematic and the VCA chips I used are long discontinued. The VCA was a Philips stereo volume control IC used in '80s Bang and Olufsen stereo gear. Basically, what I did was to feed the audio into an op amp phase inverter circuit (one inverting gain stage with its output fed into a unity gain inverting stage) I then scaled all the parts values around V4 in the original circuit by a factor of ten (Multiply the capacitor values by 10, divide the resistor values by ten.) The output of that network went into stereo VCAs and was followed by a buffer. For modulation, I used an LF op amp sine wave generator which drove another op amp phase inverter circuit so I had two out of phase LFO outputs to drive the VCAs. There are probably much more elegant ways to get the same sound. It does sound similar to the "Warbler" -perhaps a little deeper 'wobble'? If you're really interested, I can dig up some more details for you, but it might take a while.
Nathan