528hemi
191 posts
Mar 10, 2011
6:48 AM
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Are any of you familiar with aGibson GA-8 gibsonette? It has 2 6v6's with a 10 inch speaker. Is it a good harp amp?
I believe the Gibson might be abit louder according to the seller.
How does it compare to a Premier twin 8 in tone for harp?
They are both the same price and I can pick either up for about 450.00? Would you say that is a fair price if the amps both are working and sound good?
Regards,
528hemi
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chromaticblues
679 posts
Mar 10, 2011
7:22 AM
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The Premier is a more powerful amp and much more sought after! It really depends on what you want to do with it? If you are playing in a low volume setting and you play more of the traditional 1 thru 6 hole chicago blues. Then the Gibsonette is great amp for that. If your the type of player that doesn't get thru one song without playing scale type licks thru the upper register. Then I would say the premier. Oh and NO the Gibson is not louder unless something is wrong with the Premier. I'm not saying don't get the Gibson. I played a Gibson GA-20 from the late 50's for more than a decade that was a beutiful sounding amp! The Gibsonette is also a good sounding harp amp. Little rolled off on the highs and lows. Probably more on the highs. Very honky type sound. Its a wierd circuit. I've never seen or read about another being built like that!
I would say if the Gibson is something you want and it is mint for $450 then yes. If they are in idenical condition and you really don't care then the premier is the better amp and will be easier to sell at the price if you change your mind down the road!
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528hemi
192 posts
Mar 10, 2011
9:10 AM
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Thanks Chromaticblues!
I think everyone at some point sells thier amps to get others so the Premeir twin 8 sounds like the one that if I decide to flip it should sell faster.
It is in great shape except the back panel was missing and replaced with a painted brown wood panel.
How many watts is the twin 8 rated?
528hemi
Last Edited by on Mar 10, 2011 9:10 AM
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chromaticblues
681 posts
Mar 10, 2011
9:43 AM
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I don't remember! I think it was 8. It's been 10 to 15 years since I've thought about this stuff and without looking at the amp. I can't be sure of anything! Most of those amps are tweed and have the front baffle board tilted back a little. Some around 59' 60' were two tone brown. I know they all are documented as being 4 tube amps. Thats why its only 8 watts. Low pwered preamp. Some gibson amps made use of some cheaper TV tubes and this amp is one of them. Cheap meaning inexpensive! The preamp and driver are all one tube. Now most amps with one tube preamp would be designed with one half the tube being a sharp cutoff pentode (that being the preamp) and second half being a triod (that being the driver circuit). Which is what I believe this is. The odd thing about this amp is the driver circuit is not a cathodyne style inverter. I can't describe what it is because it didn't make sense to me years ago and no other company copied it! And that falls under my rule of thumb: If something is good enough other people will copy it! Some harp players fall in love with the Gibson amp sound. Its because the driver circuits they used in the fifties were different than almost every other manufacturer! Mid to late fifties Gibson amps are very unique! The only one worth an money is the GA-40. There is another Gibson amp thats worth money too. I think it was a GA-77. I'm not sure of the number and it was more of a early 60's amp. They weren't made long because they didn't sell well and were expensive to make. It was a stereo amp and had speakers on both sides. I think Joe Walsh used this amp when he first started out! Wow it hurts trying to remember this stuff.
No I didn't have an addiction to amplified harp!
Last Edited by on Mar 10, 2011 9:57 AM
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bluemoose
486 posts
Mar 10, 2011
12:30 PM
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"No I didn't have an addiction to amplified harp!"
Hummmm....denial? Isn't the first step to admit you have a problem. :)
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FerretCat Webbrain - Jason Ricci's vids (by hair colour!)
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htownfess
257 posts
Mar 10, 2011
6:19 PM
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The Gibsonettes didn't have the triode/pentode TV tube, that was yet another weird Gibson amp or two. The later Gibsonette is odd because it's a double SE amp: it has two 6V6s, but they're not push-pull, they're in parallel, it's a single-ended amp. A double-SE amp can be more powerful if designed correctly--see the Lone Wolf and Angela Instruments sites for examples--but the double-SE Gibsonette does not gain significant power from the design. It does gain harmonic complexity, it's even richer harmonically than a good SE amp, and the 6V6s don't have to be matched, so you can mix brands for even more harmonic/tonal complexity. It cost them a few dollars more to add another main tube and power is not the main reason, it's the tone. Great recording amp, fabulous TB-a-7-limit-JI-harp amp. No clean headroom, and pretty midrangy if stock, as chromaticblues observes; we reworked the '58 I sold to a friend, where I put in a 40 mfd main filter, 50 mfd bypass caps and 0.1 mfd coupler. Now it's got bottom end, sounds more like a HarpGear but with the additional harmonics, somewhat louder than stock. I don't know what they sound like with a permanent magnet speaker in place of the field coil one, probably less compressed would be my guess.
The early Gibsonette with a 6SJ7 preamp tube apparently is a push-pull twin-6V6, but is what is called a self-split design: it does not use a phase inverter, yet is a push-pull amp. 5F6-H has been doing some very interesting experiments with larger self-split amps lately; they tend not to produce the power you'd expect, but the responsiveness is distinctively good. I've got an early Gibsonette that I need to refurbish, never even played it because the speaker cone was tattered on arrival.
The late Premier Twin 8 w/ SS rectifier has unusually stout filtering and may have a 7591A or 6L6 main tube instead of a 6V6 (mine has the 7591A). I think the nominal 8 watts is pretty meaningless; in practical terms mine's not enough different from a Champ to notice, it's more the added speaker area of the pair of 8s and the tight note envelope's ability to push low end (with the SS recto) that make a volume difference. The volume is more than a typical Champ-type amp but probably not as much as you're hoping for. I haven't hopped mine up so I don't know how that turns out.
The Twin 8 definitely has the hype in the harp community, if resale value is decisive. Can't go wrong with any Gibsonette for harp, but it's more of a home/recording amp.
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528hemi
194 posts
Mar 11, 2011
1:23 PM
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Thanks htownfess!
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strawwoodclaw
220 posts
Mar 11, 2011
4:59 PM
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Gibson GA 8 & the Premier twin 8 will make great little harp amps. I would buy the one which is in the best original condition. if its old & knacked looking or it has half the original parts changed I wouldn't bother buying it. If its in good original condition $450 is a reasonable price you might get double that on a good day. I think the twin 8 is around 8 watts with a single 6l6 power tube. both Multivox Premier & early Gibson make excellent harp amps where not much power is needed
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chromaticblues
688 posts
Mar 12, 2011
11:22 AM
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After reading htownfess I had to go back and look thru my stack of amp books in the basement. Ok this is really screwy. There is GA 8 Gibbsonette that has what he said there is a pretty standard model with same name that is a 5 tube amp. OK thats your answer Paul The 4 tube amp is the parralell champ type thing and the 5 tube amp (which I'm guessing is a 60's amp) is push pull 6v6 amp at about 14 watts. Now there is a Gibson GA-8T which has tremalo. This is the amp that I tried once and loved it!! So I looked to see what tubes it had. Because I have had an arsennal of RCA matched 6V6's from the fifties for years and love late fifties Gibsons set up a little brighter with more filtering in the power supply to tighten the bottomend up. So I was thinking Ah perfect. Just what I'm looking for. To my surprise it had 4 tubes and two of them were 6BM8's. Now I'm not affaid of wierd amps. The amp I practice with almost daily has a 6DG6 power tube. There was never a guitar amp made with that tube. Its a TV output tube. Its a low voltage amp I designed. But these 6BM8's are wierd! They are one half triode preamp and the other half power pentode. Everything I read about these tubes was bad! So I didn't buy the amp.
Back to the Premier amp I would only buy the one with 2 12ax7's and a tube recifier. This will sound much more harp friendly than the one with the SS rectifier and 3 12ax7's.
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5F6H
554 posts
Mar 12, 2011
12:07 PM
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Chromaticblues, the self split, push pull, Gibsonette and the parallel SE amp have the same number of tubes.
Last Edited by on Mar 12, 2011 12:08 PM
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chromaticblues
689 posts
Mar 12, 2011
1:59 PM
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5F6H
Yes I thought they all had four tubes also, but I have a pic and schematic of one with 2 12ax7's 2 6V6's and a 5y3. Thats 5! I don't know what year they started making them, but this is a tweed tilted baffle board and a fieldcoil 10" speaker. I'm guessing 57 58.
Oh I just realized I was looking at two different pics. This one is a Gibson GA-8, but not a Gibsonette. Must be they made these before the Gibsonette? This looks like a lower voltage version of the GA-20 I have.
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5F6H
555 posts
Mar 12, 2011
2:35 PM
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Chromaticblues - The self-split push-pull Gibsonette had 1x 6SJ7, 2x6V6, 1x5Y3 (this is the one to which Htownfess refers), I have been searching for a schematic of the 1x12AX7 version...but I may have dreamed that one?
Premier/Multivox, Magnatone also had push pull amps with just one preamp tube (& no interstage transformer), I have built 3 versions of this topology myself...as well as converting existing PP amps to push-pull, phase inverterless operation.
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528hemi
195 posts
Mar 12, 2011
2:36 PM
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So does that mean the Gibson is rated at more wattage then the Premier? It has a single 10" speaker
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5F6H
556 posts
Mar 12, 2011
2:46 PM
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Don't worry too much about rated power, volume of the amp is limited by how loud you can get it before feedback & may not be particularly relevant.
The 53 Gibsonette (self split) could potentially make more power, IF the 6SJ7 can deliver enough gain. There's no tone control, or treble cut cap, without those it's possible feedback could limit output (that's IF we are talking about the '53..."GA8" & "Gibsonette" refer to a series of amps, not one specific model).
Last Edited by on Mar 12, 2011 3:17 PM
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chromaticblues
691 posts
Mar 12, 2011
4:47 PM
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@ 5F6H No you weren't dreaming there is a Gibsoette that had one 12ax7. The book I have with that schematic doesn't say what year it is and there is pic. I can usually tell about what year a gibson is by the pic.
I have tried some old amps with 6SJ7's and loved them! The first Fender champ (Champion) was the best sounding champ I've tested! Well you know for harp. Guitar players consider that one to be the worst, but thats fine. I've tried to build some amps with 6SJ7's and have had no luck! I varied the plate resisters form 150K to 390K and just didn't like anything. tried it at different voltages and different supressor grid resisters 1M to 2.2M. I've tried it in SE amps and push pull and didn't like any combination!
I have built some amps with 6au6's and I had a dozen military low noise versions that sounded good, but didn't have great gain. I think the 6AU6 would work well in the first stage of a 5 tube amp.
OK enough of that! I don't have time to build amps anymore.
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htownfess
259 posts
Mar 13, 2011
3:59 AM
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@5F6H: I haven't looked very hard, but I've never seen a schematic for a self-split/single-12AX7 Gibsonette. If you need the schematic for the double-SE/single-12AX7 Gibsonette, I've got that.
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