Trouble with long-threaded-barrel jack

[michaelandrew]

Has anyone else noticed this problem?

I have a Yamaha RBX 765A active bass that has a long threaded barrel stereo output jack. The problem is that when I use a cable with a straight plug, if the plug is bumped or pushed sideways somehow, there's sometimes a gut-wrenching pop similar to what happens if you - accidentally, of course - unplug without muting or switching off the amp first.

The jack looks similar to a Switchcraft #152B stereo jack, but I can't tell for sure. Most of my cables have Neutrik plugs, but the problem occurs with all types of plugs (including Switchcraft and "cheapies") and with different cables.

My solution, so far, is to use a right-angle plug, so it doesn't get hit, but I'm wondering whether the behavior is typical of long barrel jacks in general or whether it's a defect of some sort. Is there a better quality jack that might help?

Yamaha used the usual trick of wiring the pre-amp battery negative terminal to the ring terminal on the stereo jack so that the preamp gets power when a mono plug is inserted (an industry standard bad idea IMO). I'm guessing that, when the plug gets moved sideways, the jack tip and ring terminals are shorting internally - putting 9V on the tip and into the amp input.

The jack is installed in a hole that's drilled through to the pre-amp control cavity, so using a different type of jack really isn't an option; I'm stuck with the long-barrel type.

Thanks for reading - suggestions and advice welcome.

[walterw]

those jacks wear out, and just need to be periodically replaced.

the switchcraft #152B is what you want, it'll be an upgrade from the typical import jack. (it'll still need replacing down the road too, which is why i'm not a fan.)

[michaelandrew]

Nice short answer - thanks much.

[abemo]

Originally Posted by walterw

those jacks wear out, and just need to be periodically replaced.

the switchcraft #152B is what you want, it'll be an upgrade from the typical import jack. (it'll still need replacing down the road too, which is why i'm not a fan.)

This. And keep using the 90 degree cable, less bumps=less wear and tear

[walterw]

+1

90° cables are the right answer for any instrument that doesn't have some sort of weird recessed jack. (run them under the strap, of course.)

[michaelandrew]

Thanks. The RA cable connector works well. Now that I think about it, the long-barrel jacks must wear out faster than the open-frame style - the contacts shoe-horned inside there have to be lighter gauge and smaller. I have some Switchcraft #152Bs to order.

[walterw]

Originally Posted by michaelandrew

Now that I think about it, the long-barrel jacks must wear out faster than the open-frame style - the contacts shoe-horned inside there have to be lighter gauge and smaller.

oh yeah; think of all the dead-stock '50s and '60s fenders and gibsons going strong with their open-frame #11 jacks.

besides your (valid) point, the open-frames can be easily re-tensioned by bending them back, something you can't do with barrel jacks.

[michaelandrew]

Just to finish this off: I've built a short (2') adapter/extension cable using:

1. About 2 ft of Mogami W2582 low-Z mic cable (2 conductor w/shield)
2. Neutrik NJ3FC6-BAG "stereo" cable mounted TRS jack (locking)
3. Neutrik BP3RX-B "stereo" RA TRS plug

I connect the RA to the bass output jack and loop the cable under the strap, leaving the cable jack at a convenient spot to plug in any ordinary TS bass/guitar cable. I can leave the adapter cable plugged into the bass without running down the pre-amp battery, as long as the TS plug is disconnected from the cable jack. The cable jack has a lock (little red button) - so no danger of "fallout".

I don't know how bullet-proof this arrangement will turn out to be, but it solves a number of problems for me.

Total parts cost about $16 (US or Canada). If anyone is interested I can post more details - and now it's just occurred to me that, if I short the battery terminals, I can feed 9V power to the bass pre-amp through the ring terminal - next project.

[bumperbass]

You possibly could end this problem forever by drilling a hole big enough for an open frame jack, using a jack plate. That is, if your bass is thick enough to accept it, which I don't know.

[michaelandrew]

Don't think that'd work for this bass - maybe I need a new bass .

[michaelandrew]

I've replaced the the barrel jack with a Switchcraft 152A. Here's a pic of the stock Yamaha barrel jack after I "disassembled" it:



The inards are the two flimsy contact strips on the right, stuck through the end cap. No f___ing wonder this POS was causing trouble; it's designed to short tip-to-ring when bumped.

That's enough on barrel jacks - for now