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New member
Username: Phreddiet

Post Number: 5
Registered: 3-2005
Posted on Tuesday, April 12, 2005 - 4:50 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I have a jb-12 and several other larger amps. I was wondering the best wat to use the little jb-12 modulator. i have heard some who have used it to excite another amp like a maverick xl-600. Some others have said the second amp wouldn't hold up in that condition. I'm trying to benefit from the monster swing of the jb-12??
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Intermediate Member
Username: Hotwire

Post Number: 293
Registered: 1-2005

Posted on Wednesday, April 13, 2005 - 7:55 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Back when I was a youngster (1987-88) I drove a Maverick Kicker 500 with a JB12 curtisy of my dear ol dad. Without turning anything up to much I averaged about 1000 to 1200 watts peak. Thats just to much juice for a 13 year old!! BTW I was very responsible kid and never was a trouble maker with all that power. Lots of jealous adults I might add. LOL
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Advanced Member
Username: 2600

Post Number: 542
Registered: 7-2002

Posted on Thursday, April 14, 2005 - 5:09 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Hmmm. Most popular use for a JB-12 is to drive another amplifier meant for only radio drive. For most 'radio-drive' amplifiers, this is like putting a nitrous tank on your daily driver. You can race it on the weekends, but if you keep that nitrous button pressed for too long, it'll be tow-truck time. If you want to drive it to work Monday morning, you have to be careful. When sweep tubes were $6.00 each, it wasn't all that expensive a bad habit. Times have changed.

The knob in the rear will permit you to reduce the carrier, and keep the forward modulated "swing". If nothing is broke or out of whack, anyway. The little 6BQ5 tube isn't good for more than 2 or 3 Watts carrier. All that swing adds up to a lot of heat for such a small tube. Too much carrier and the tube will "cherry" and die. Usually with a "Snap" or a "POW!".

Some newer dual-final radios will swing every bit as much as the JB-12. Older base amplifiers designed 30 years ago were meant to match radios that would key at most 3 and swing maybe 12. A 2517 (for example) that has been cut loose can hurt an old amplifier this way, too.

The one, single feature that made it useful as a driver was to eliminate the need to put a variable carrier control in the radio. Newer solid-state radios are made with most (or all) of the "variable" circuit built-in. Tube radios don't. That little "carrier" knob on the rear of the JB-12 would do the same job without spending $100 to put 'variable key' on a tube base radio.

Oh, and BTW a solid-state linear meant for radio drive will NOT like the extra drive from a JB-12. It may impress the wattmeter, but if you hear the audio, you'll be disappointed. A wattmeter is NOT an audio meter.

The one old tube-factory box that would match it okay was the old Palomar 300A. On "low" side, this model fed your drive directly to the four final tubes. Took the two drivers completely out of the picture. A common "freight-train" setup 20 years ago was a tube base radio, a jb-12, a 300A on 'low', driving a ham-type "2kw" like the Drake L4, Heath SB-220/221 or a Henry. The JB-12 was essential since nobody had 'variable' for a tube radio 20 years ago.

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Junior Member
Username: Pogo12

Post Number: 20
Registered: 3-2005
Posted on Sunday, June 04, 2006 - 4:36 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Let it deadkey 4watts and swing but if the amp behind it cant handle 40 watts input you will fry something.Most cb amps cant handle it.The palomar 300a can if you put it on low because on low it bypasses the driver tubes.
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New member
Username: Jimmyd

Post Number: 5
Registered: 11-2005
Posted on Friday, June 13, 2008 - 7:36 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

the best thing to do with that jb12 is to sale it to me. boy o boy do i love that black cat

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