Trying out a vintage '65 Ampeg Gemini I tomorrow

Armchair Bronco · Post by **Armchair Bronco** » Sun Jul 19, 2009 3:18 am

Hey guys,

Tomorrow evening, I'm trying out a Ampeg Gemini I amp that's for sale locally on CraigsList.

The guy was originally asking $950, then recently reduced the price to $850. This is still very expensive, but the amp is a genuine closet find in mint condish (at least cosmetically). The amp was serviced (for $250) back in April. I talked to the tech who did the work. He put in new caps in the power section, fabricated a new bracket for the chassis, and cleaned up all the pots & jacks. He also re-built the trem/reverb footswitch and shortened up its cord on both ends.

This amp still has the original 12" Jensen speaker, and the tubes are either Ampeg originals or vintage period originals. The tech said that the tubes alone would be worth some big bucks.

The tech also said the amp sounds great at lower volumes, but that once the volume starts to get up past 6 or 7, it starts to hum pretty significantly. Sadly, he said he didn't think I could gig with the amp on account of the hum. Now: I don't gig, but even so -- this is probably a deal-breaker for me, at least at the $850 price. Curiously, I asked about the power cord (which is still an ungrounded 2-pronger), and he didn't seem to think modding the amp for a properly-grounded 3-pronger would fix the hum...so maybe there's something more substantial going on.

I'm trying it tomorrow just to satisfy my curiosity, but I'm not taking along any money. Here's what the amp looks like. Too bad it seems to have some "issues" (although I'm sure most 45-year-old amps have "issues").

Do you guys have any advice for me?

Will · Post by **Will** » Sun Jul 19, 2009 3:55 am

HA! I saw this thread on TGP last night.

Anyway, a hum can have a variety of causes. Assuming it's a 120hz hum (which would make sense since I don't think you'd hear 60hz through the Jensen) it's probably a cathode bypass cap. That would be the knee-jerk answer.

You said the tech changed the caps, though - did he just do the filter caps, or all the electrolytics? The problem could be as simple as 1 more cap that needs changing. If it was in a closet, not running, for 40 years, I'd expect all the electrolytic caps to be dry and bad. They like to see voltage every now and then.

I also see in the schematic that there is AC current on the tube filaments (common hum source) with a hum-balance pot. It's possible this pot is simply in the wrong spot and a little adjustment will tune the hum right out. They also didn't have hum-canceling spiral would filaments back then, so a modern set of tubes with these filaments may remove the hum if that's the cause.

The thing to determine is if the hum is in both channels or just one. If it's in one, it's probably a tube or filament current problem in that channel. If it's in both, it's more likely to be a problem in the phase inverter or power amp.

Whatever the case, I don't think the hum should be a deal breaker. That's a great price on a great amp, and the problem should be easy to fix.

Armchair Bronco · Post by **Armchair Bronco** » Sun Jul 19, 2009 4:01 am

Great feedback.

What kind of tests can I / should I do tomorrow? Obviously, I play through all 4 inputs (guitar + accordian on each channel). I'm also planning to try out all of the jumpered combinations.

Are there any other tricks I can do to narrow down the number of things that *could* be wrong?

Oh: the tech did say that the cap upgrades were only to the power section, most the big silver ones, and maybe one or two other ones that were in need of obvious replacement. So presumably, there are still others that could be replaced. (But $250 for a partial cap job seems like a lot, doesn't it?)

Will · Post by **Will** » Sun Jul 19, 2009 4:30 am

Playing through it is about the most you can reasonably do (dude probably won't let you take it apart and multi-meter it!). It looks like it was hardly ever played, so the transformers and such should still be perfect. Look at the speaker as best you can and make sure there aren't any rips or holes. Rattles shouldn't be anything to worry about - it would probably be tubes that you'd replace anyway.

The 2-prong cord is a major safety hazard. Plug it in the wrong way (50/50 shot), touch your lips to a microphone on a separate amp, and expect 120v right into your face. Come to think of it, the 2-pronger might be the source of the hum. They used to put polarity switches on amps with 2-prong cords because they would hum in certain geographic areas, and switching the polarity could help. In any case, you should plan on replacing the cord.

$250 is a lot for a cap job. It's about $5 a piece for the bigger caps, and I could change them all in about 30 minutes on a PTP amp. That figure probably includes the bracket and stuff he made.

In any case, assume part of the cost in this amp is a new cord (actually an easy DIY job if you're handy) and replacing the rest of those caps. Some new tubes are probably in order as well.

If you have a soldering iron and want to tech it yourself, I can walk you through most of the stuff. It's actually pretty easy to diagnose most problems in tube amps - you look for the part that's black and charred!

Armchair Bronco · Post by **Armchair Bronco** » Sun Jul 19, 2009 4:40 am

DuoSonicBoy wrote:Playing through it is about the most you can reasonably do (dude probably won't let you take it apart and multi-meter it!). It looks like it was hardly ever played, so the transformers and such should still be perfect. Look at the speaker as best you can and make sure there aren't any rips or holes. Rattles shouldn't be anything to worry about - it would probably be tubes that you'd replace anyway.

The 2-prong cord is a major safety hazard. Plug it in the wrong way (50/50 shot), touch your lips to a microphone on a separate amp, and expect 120v right into your face. Come to think of it, the 2-pronger might be the source of the hum. They used to put polarity switches on amps with 2-prong cords because they would hum in certain geographic areas, and switching the polarity could help. In any case, you should plan on replacing the cord.

$250 is a lot for a cap job. It's about $5 a piece for the bigger caps, and I could change them all in about 30 minutes on a PTP amp. That figure probably includes the bracket and stuff he made.

In any case, assume part of the cost in this amp is a new cord (actually an easy DIY job if you're handy) and replacing the rest of those caps. Some new tubes are probably in order as well.

If you have a soldering iron and want to tech it yourself, I can walk you through most of the stuff. It's actually pretty easy to diagnose most problems in tube amps - you look for the part that's black and charred!

Thanks for the offer! I actually do know how to solder -- a few months ago, I built my first pedal: a GGG ProCo RAT clone with a NOS LM308N. However, building a pedal from a kit is one thing; recapping a 45-year-old amp is quite another. I really wish there were some kind of "hands on" class at a local community college I could take. If someone could walk me through the process just once in real time and in the same time/space continuum, then I'd be golden.

It's funny: the tech almost made it seem like fixing the hum was a hopeless endeavor unless I was willing to spend $300 or more. And, no, I don't think he was trying to drum up more business. I was surprised when I asked him about swapping out the 2-pronged plug. Not only did he *NOT* think this would help, but he didn't seem to think a 2-pronger was much of a safety hazard, either. From threads on TGP and elsewhere, it's clear to me that an ungrounded plug can be potentially lethal!

As far as new tubes go, everything this old amps needs is still available. Fliptops sells a $120 complete set for the Gemini I, and TubeDepot has everything I need, too for about the same price. So far, only the 7199 tube is getting hard to find.

Will · Post by **Will** » Sun Jul 19, 2009 4:52 am

Yikes - that 7199 is a weird one.

Amps are easy cause everything is BIG. You only need to worry about discharging the caps and keeping your leads neatly routed. I wouldn't call the hum hopeless. If I had to bet money, I'd say it's a $2 cap or a tweak to the hum-balance pot.

I used to have a Gerald Weber instructional video - let me see if I can track it down.

Armchair Bronco · Post by **Armchair Bronco** » Sun Jul 19, 2009 4:56 am

DuoSonicBoy wrote:Yikes - that 7199 is a weird one.

According to the TubeDepot website, the much less expensive 6U8A can be used in place of a 7199 with just a few simple mods, as outlined in this PDF file.

http://site.tubedepot.com/pdf/7199_6u8.pdf

Worldwide production of the 7199 has ceased, but Russian-made 7199's are still available for about $16 each.

Will · Post by **Will** » Sun Jul 19, 2009 5:06 am

Good deal.

It's weird to see a phase inverter like that. Usually you want the 2 halves of the tube balanced as closely as possible, with the 7199 they're not even the same type!

I can feel your excitement about this amp - if you feel sour about it when you plug in, there's no shame in passing. $850 is a good deal, but there are lots of great amps at that price. The Ampeg Jet reissue, which is similar but doesn't have reverb and only 1 channel, is around $470 on eBay. It's the same wattage, same speaker, and PTP. Basically, don't buy this just because it's a good deal.

Armchair Bronco · Post by **Armchair Bronco** » Sun Jul 19, 2009 5:24 am

DuoSonicBoy wrote:$850 is a good deal, but there are lots of great amps at that price. The Ampeg Jet reissue, which is similar but doesn't have reverb and only 1 channel, is around $470 on eBay.

More than anything else, I really want a lower-powered vintage Ampeg with a reverb tank.

My favorite band is The Wipers, and lead-guitarist Greg Sage used an Ampeg VT-22 on most of his recordings (paired up with an SG Classic, an EchoPlex, and some kind of Dallas Arbiter Fuzz Face pedal). A lot of his distortion just came from overdriving the amp, but with a VT-22 (or a V-4 head) this is impossible to do in a living room setting without killing small animals and breaking windows. So as much as I want a VT-22, it's just way too loud for me.

Sage also used an Ampeg Gemini I on the "Over the Edge" album, and when I researched this amp, I realized it was "The One"...at least on paper: 20 watts, a single 12" speaker, and that lush Ampeg reverb. The fact that the Gemini I also has tremolo is just icing on the cake. The 30-watt Gemini II with its 15" speaker is just too much amp for what I have in mind.

So it's the Ampeg Gemini I or nuttin'. Not sure if this specimen is "The One". If not, I'll just be patient waiting for one with fewer "issues". But I doubt I'll ever find one that looks as nice as this one. And if you're a collector of old things as I am (I also collect WWII guns and older trap shotguns) half the fun is owning something vintage that also looks killer. The gun should shoot straight, too, but it's no fun owning a straight shooter that was run over by a Sherman tank!

Will · Post by **Will** » Sun Jul 19, 2009 5:38 am

If it's your dream amp, go for it. They don't come up often.

I could have modified a newer Dano, or just built a custom, for less than I payed for my U1. Heck, I even overpayed for a vintage one. Thing is I love it, it was my dream, and I was willing to pay the price. I haven't regretted it once. If a vintage Gemini is your "one", make it happen.

Armchair Bronco · Post by **Armchair Bronco** » Tue Jul 21, 2009 2:12 am

So, I tried out the '65 Ampeg Gemini I in person yesterday for about 30 minutes. Here's what I found: at very high volumes, the amp definitely has some hum, but it's nowhere near as bad as I was led to believe. In fact, if I crank up my Orange Tiny Terror at home with a guitar going straight in, my Tiny Terror has significantly *more* hum.

Not sure what this means: either cranked amps hum (some, perhaps, more than others), or my TT is messed up. I guess I need to go to GC next weekend and try out some more tube amps and crank 'em. Is there such as thing as a cranked up tube amp that's completely silent? Now I'm curious about what a grounded plug and a full-recap job [versus the partial one that it's had] would do...

I tried out both channels and both inputs (guitar & accordian) on each channel. Both of them exhibited the hum. I found I could reduce it measurably by turning the two tremolo knobs all the way down. I was also able to cut down on the hum measurably by jumpering channel 1 to channel 2. Channel jumpering, BTW, was very cool and gave me a lot of tonal options.

The reverb on this amp is very lush. I noticed that the reverb tank seems to be very sensitive to any jostling of the amp itself: as I was plugging and unplugging input & jumpering cables, I could hear the springs sloshing around, and this bled through to the speakers even with the volume pots at "0". And the bright switch (on the Treble knob for Channel 1) is freakishly bright. Very cool. The amp was responsive to the treble & bass pots on both channels

Anyway, I really liked this amp. The seller (who was a real nice guy) said that he could go as low as $800 -- this is his 'break even' cost. $800 is a lot of money for an Ampeg Gemini I, so I dunno. Gonna have to think about the whole package for a bit before I decide anything.

Will · Post by **Will** » Tue Jul 21, 2009 2:25 am

Sounds like normal hum than. The more you crank an amp, the more the speaker and circuit begin to impart compression to the sound. Thus, the natural hum of the amp becomes proportionally louder than the guitar signal. If you're not bothered by it, it's not a problem.

I'd buy it. $800 for a vintage handwired amp in great shape is a good deal no matter how you look at it.

stewart · Post by **stewart** » Tue Jul 21, 2009 7:51 am

just buy it and stop dithering. fuck sake, what more d'you need, a BJ thrown in gratis to seal the deal?

Armchair Bronco · Post by **Armchair Bronco** » Tue Jul 21, 2009 8:09 am

stewart wrote:just buy it and stop dithering. fuck sake, what more d'you need, a BJ thrown in gratis to seal the deal?

The trouble is: my Hungarian wife (who's out of the country right now with my kids for the summer) specifically told me before she left: "Don't buy anything crazy while I'm gone!"

So I really need to make sure that this amp is "The One". Besides, as that olde saying goes: Half the fun is the chase itself.

Post by **Mike** » Tue Jul 21, 2009 8:11 am

It sounds like you shouldn't buy it to me.

You already have an amp, an expensive vintage one is something I would class as "unnecessary" if not "crazy".
Constantly lusting after something you don't have isn't really healthy.

Armchair Bronco · Post by **Armchair Bronco** » Wed Jul 22, 2009 6:38 am

Mike wrote:It sounds like you shouldn't buy it to me.

You already have an amp, an expensive vintage one is something I would class as "unnecessary" if not "crazy".
Constantly lusting after something you don't have isn't really healthy.

I dunno. This is just a hobby for me. No more or less expensive than any of my other hobbies. It's no more crazy than buying a new bike or a vintage WWII gun.

Owning this amp would make me happy, and even if I overpay by $200, I figure I could still sell it for $600. One day of winter skiing with my family costs a lot more than $200.

Will · Post by **Will** » Wed Jul 22, 2009 7:00 am

Luxuries are at odds with Mike's working-class background.

If you have the money, do it. You could always sell something to offset the cost - it sounds like you have a lot of toys.

Armchair Bronco · Post by **Armchair Bronco** » Wed Jul 22, 2009 10:30 am

DuoSonicBoy wrote:Luxuries are at odds with Mike's working-class background.

If you have the money, do it. You could always sell something to offset the cost - it sounds like you have a lot of toys.

Thankfully, money isn't a problem...at least money AT THIS LEVEL ($750-$800) isn't a problem. I've reached a stage in my life where (thank God) I have some disposable income to work with. Rather, it's a question of yearning. My wife has East European sensibilities about such things (much like Mike's working class background), and she insists that I yearn for big-ticket items before buying them.

In this case, I've been freakin' yearning for several months for this specific amp and for at least 2 years for some kind of vintage Ampeg amp. I think I've yearned enough!