Ampeg GS-12 Rocket 2

[mikhett]

ampeg reverbrocket

My ser# is018773 I had the same tubes as you 12ax7 6u10 7199 7591a(2). I changed the 7591as to 2 6v6s back in the early 90s. Still goin strong.But the blue diamond cloth has seen better days. Mike

[tvjr]

ampeg gs 12

My amp says g s 12 ,someone scratched off the wording a long time ago. Iv'e narrowed it down to a rocket 2.It has four tubes. 2-7591s and two small tubes . 7199 12ax7,or7199,6u10a or two 12ax7s ,witch is it ? thanks

[RWood]

The first tube is a 12AX7. Then a 7199.


I am curious - does your amp have a single tone control or bass & treble?

The only difference I've been able to find between Rocket 2 and Gemini IV, aside from the number of inputs, is that Rocket 2 has the single tone, Gemini IV has bass & treble.

RWood

[tvjr]

ampeg gs 12

The amp is layed out from left to right,two dials, speed and intensity with the word tremelo in between,then a guitar jack,a pilot light,and a accordian jack. Then seperate volume treble and bass dials. So if i understand you right the 12ax7 is the closest to the 7591s ,then the 7199.

[RWood]

No, the 12AX7 is the input tube, farthest away from the 7591s. The input jack is wired to this tube.

The 7199 is the driver/phase splitter, which sends the signal to the power tubes.

[tvjr]

gs 12

thanks. Hope the layout helped.

[rudutch]

I think this is a 1965 Rocket II

089-1.jpg picture by rudutch - Photobucket

Ampeg 1965 Rocket II picture by rudutch - Photobucket

Ampeg 1965 Rocket II picture by rudutch - Photobucket

Ampeg 1965 Rocket II picture by rudutch - Photobucket

[RWood]

Interesting. So a Rocket II does have a 12AX7 in V2, not a 7199 as Gemini IV has.

It is very similar to a J-12 Jet from that era.

TVJR, I may have steered you wrong - what ended up working in your amp?

RWood

[rudutch]

Ampeg 1965 Rocket II picture by rudutch - Photobucket

This, to the best of my knowledge, a factory changed label. The pics are from an amp I picked up this spring. I am guessing it sat in a closet somewhere for decades.. and I think (except the speaker) is 100% unmolested

[jimytheassassin]

I stumbled upon this when I was looking up a thread I participated in that yeilded a better Rocket 2 schematic Ampeg Rocket 2 Pix and Questions - The Gear Page

I also have a 1965 Rocket 2, and the ampeg above does appear to be stock, minus the speaker. It would have originally come with a (ceramic or alinco?) Jensen or an Alnico CTS (chicago telegraph supply) at that time "most likely". That was a period in time when Ampeg was switching to a new Factory so the components did vary in that regard, and perhaps more so but that's just my speculation. Infact this may be why they sub'd a 12ax7, if they had run out of 7199 tubes for some reason. I don't know what to say about the 7199 sub 12ax7 difference circuit wise, but even that looks legit. It's too late for me to rationalize it though. Indeed the 7199 was typical and you'll find that in the schematic in "thegearpage" link above

Cheers

[RWood]

Finally

JimyTA,

Thank you for linking to that schematic. Like you, I have been looking for it for a long, long time. I love the "print it on parchment and glue it inside the back panel" idea!

Nice work fixing up that 6U8 adapter - I would have been more inclined to rewire the tube socket, though, from the underside.

As for differences between the 12AX7 and the 7199 or 6U8, keep in mind that the 12AX7 is a twin triode while the 7199 has a pentode (driver) and a triode (phase splitter). The pentode is going to effect the tone differently than a triode would, as it drives the phase splitter harder. Just like a pentode input tube (EF86 for example) has a different sound compared to a triode input of a 12AX7.

Nice find,

RWood

[jimytheassassin]

JimyTA,

Thank you for linking to that schematic. Like you, I have been looking for it for a long, long time. I love the "print it on parchment and glue it inside the back panel" idea!

Nice work fixing up that 6U8 adapter - I would have been more inclined to rewire the tube socket, though, from the underside.

As for differences between the 12AX7 and the 7199 or 6U8, keep in mind that the 12AX7 is a twin triode while the 7199 has a pentode (driver) and a triode (phase splitter). The pentode is going to effect the tone differently than a triode would, as it drives the phase splitter harder. Just like a pentode input tube (EF86 for example) has a different sound compared to a triode input of a 12AX7.

Nice find,

RWood

i'm happy to oblige. I have worked some on a computer drawn version of this just for kicks, and now this thread has reminded me that it still needs to be finished. I do plan on updating the other thread if that comes to completion, so keep your eyes open on that if you're interested. Thanks for the compliment on the 6u8a adapter. I thought about reworking the socket, but decided against modifying it for posterity's sake. It didn't add any extra noise to the amp, so I'd say it was a smashing success. Their is a pre-made adapter at Tubesandmore.com, but it would never fit the bayonetted style socket. anyways, cheers, and enjoy. slowly but surely, the internet is acquiring even the hardest to find tid-bits of knowledge.

[rudutch]

Ampeg Rocket II 1965 pictures by rudutch - Photobucket

anything here helpful?

[RWood]

anything here helpful?

Well, that's definitive proof that they made the Rocket 2 both with and without the 7199 tube.

Nice shots.


RWood

[Rodip]

Hi,
New guy here. How do these amps sound? I am considering one... Presently I have a Marsh Tremolux replica... but I'm not quite convinced on the trem.

Much Thanks!