Ampeg Gemini I and II info

[Stevem]

Hi all!
I would like to post up some info about these two amps that I did not know about them for a good while when I first started to work on them ages ago without the aid of a owners manual in hand, and if fact in all of the many of these two model amps I have worked on only 1 of the second hand owners new about these features I will talk about here.

This is in part due to how rusty these amps chrome faceplates get with age and how much of the lettering comes off when they are cleaned the wrong way!


Anyway, here’s the low down.

The big guy the Gemini II with its 15” driver is fixed bias and uses 7591a output tubes as does the smaller model.

The Gemini I with it’s 12” driver is cathode biased with smaller transformers, although both amps have the same preamp sections.
The model I has no standby switch.

Channel one which is on the left side of the amp and is the only channel of the two with reverb has its reverb pot all the way over the hell over on the extreme right side of the amp!

Next up in terms once again of the left channel the tremolo intensity pot has a star at the end of it’s max range , this is telling you there is a on/ off switch there.
When you click it you now have Vibrato, not tremolo any more.

Next over on channel 2 there is a start at that same spot, but this time it’s set up as a brite switch at the end of the treble control.

Note that channel 2 does bleed into the reverb circuit some and many times owners think that the amp has a issue because channel 1 has tons of reverb and channel
2 is 95% down on reverb level, but sorry to say only channel 1 has reverb!

Well that’s the story and hopefully these great amps will still be around for the next era of tube amp tech’s to recap and tube once again and then can reference this info when there is nothing legible left on the faceplate’s of these amps, lol!

[sluckey]

I bought a Gemini II-15 brand new in the late '60s for $350. Wish I still had it.

[Stevem]

The model I and .II are some of the best amps for cleans that one can have in terms of amps under 50 watts.

A decade ago or so I restored a guys model II and it had the optional Altec 418 driver in it and it was just breathtaking to play thru!!
It responded to your touch as if your fingers them selves where pushing the electrons around in side the circuit!

I have always wondered what that amp with its Altec driver would have sounded like with a interleaved output transformer.

Gez! I have 2 of those 418 drivers... Um maybe it’s time to build another amp during the winter here!

[didit]

Hello -

Been assured the output transformer on my '64 B15 is interleaved. Given Everett Hull's reputation would be plausible that those Gemini had one too. Regardless, great sounding amps if a pain to source valves for repairs. Puzzle why none of the usual current production sources have no 7199.

Best .. Ian

[FUCHSAUDIO]

Hello -

Been assured the output transformer on my '64 B15 is interleaved. Given Everett Hull's reputation would be plausible that those Gemini had one too. Regardless, great sounding amps if a pain to source valves for repairs. Puzzle why none of the usual current production sources have no 7199.

Best .. Ian

FWIW: I don't think Hull really did any engineering, that would be Jess Oliver.

[didit]

Hmm -

Hello -

Been assured the output transformer on my '64 B15 is interleaved. Given Everett Hull's reputation would be plausible that those Gemini had one too. Regardless, great sounding amps if a pain to source valves for repairs. Puzzle why none of the usual current production sources have no 7199.

Best .. Ian

FWIW: I don't think Hull really did any engineering, that would be Jess Oliver.

Yes--quite correct Andy. Everett was the boss and didn't necessarily need to get into any of the engineering. He did have a reputation though regarding how his would products sound. And absolutely, any understanding on amp designs I have comes mostly from comments attributed to Jess Oliver. Somewhere here there's an Ampeg history on PDF with various of the product design details.

Best .. Ian

[Stevem]

Can you provide some tangible proof that the output transformer in these amps are interleaved?

I ask because both Mercury magnetics and fliptops offer direct reproduction replacements, and neither one is stated as being interleaved !

I have wondered this same thing about my Oliver B200, but I guess unfortunately we will never know the easy answer on that one !

I have a failed OT from a Gemini II and if during the week I can not get a answer from these two companies I will endeavor to unwind it some to see!

[didit]

Will look around for definitive references. I came to this conclusion a long time back when first wanting to understand what I had, and so could be lost to some sloppy archiving.

Best .. Ian