Gibson A bridge "hot rod"

[Charlieshafer]

Brought my A2-Z into George Youngblood's place the other day for a tuneup, and as the bridge adjusters were extended a little to get the right action, he installed little shims under the wheels to get it back to a more solid transmission of vibration. The result was superb, all the sustain you could ever expect. The shims are essentially invisible, and completely removeable if someone should want to, or if the adjusters ever need to be moved again. Highly recommended, as it really stiffens up the bridge. Here's a photo, I hope....

[woodwizard]

Under the wheels? I can't even see them. Nice job.

[Charlieshafer]

whoops. On top of the wheels. Still invisible, though. George does great work. I believe he was along for the ride with Roger Siminoff when Gibson first was trying to recreate the Master model. He's also done some killer work on a couple of presentation-grade fretless banjos I have.

[Rob Gerety]

Charlie, could you explain a bit more? Why not just turn the adjusters up a bit to raise the action if needed?

[Ivan Kelsall]

I don't doubt your word re.the sound difference,but the bridge saddle should have already been sitting firmly on top of the wheels.There would be bare screw thread under the wheels,so if the shims were placed underneath the wheels,coupling them more firmly to the base,then i could understand it more. Obviously,whatever was done it works ,
Ivan:confused:

[mandroid]

Studs Are already tight in the base of the bridge .. I've never sweated the minutiae to that extent ..

Have to see the oscilloscope printouts to detect any difference.

[Bill Baldock]

More than one old mandolin mechanic has preached about the magic of getting an adjustable bridge set just right. The wheels should just barely lift the saddle off the base. Set the action by adjusting the base and saddle material. Some say it keeps the bridge's center of gravity lower, others say the bridge is better able to oscillate in all directions while having less post exposed which can act as a frequency filter of sorts. How's that for a first post?

[Charlieshafer]

Charlie, could you explain a bit more? Why not just turn the adjusters up a bit to raise the action if needed?


The wheels were turned up, but in this case, there was a good 1/8th inch of free post exposed. This resulted in a little extra "slop" where the force of the strings was reduced somewhat by losing that direct connection of bridge to feet to soundboard. The gap was simply filled with small bits of ebony to provide a very solid transmission from the strings straight through to the top.
Sometimes, you'll also see an extended bridge tilt slightly, and the force there is really lost. That was the case in this bridge (and on a couple of other newer mandolins I have too, come to think of it...)

[Rob Gerety]

How's that for a first post?

Hit the nail right on the head.

[Kevin K]

I measured my height between bridge base and saddle, removed thumb wheels and replaced with ivory, sorta a one piece in a way. Big improvement.

[Darryl Wolfe]

OK, here is my two cents worth after building and installing hundreds of repro Gibson bridges. I, like IVAN sort of doubt the difference occured just because there is zero gap in the stud/wheel/wood set-up. But, I do highly believe that the taller the bridge top is above the adjusting wheel, the more dark and complex the tone becomes. So in this case, the bridge top has essentially modified to be taller, increasing the amount of wood between the string and the wheel.

When you have to modify the bridge wheel notches in the bridge top to lower the action on a mando with a shallow neck set, the result is almost always reduction in tone. So my point is stressing the opposite here.

In conjunction with all of the above, the heavier/taller the base the better I like it too.

So, MAYBE complete contact is adding something, but I generally associate the tonal difference simply with more mass and not the transmission qualities of the studs

[Bill Baldock]

I measured my height between bridge base and saddle, removed thumb wheels and replaced with ivory, sorta a one piece in a way. Big improvement.

It's a lot of fun making spacers like that, saddles and bridges of different materials-bone, ivory, brass, carbon graphite, aluminum, ebony, maple, etc. Each change gives a different flavor to the sound, some minor, some major.

End result for me: nothing sounds more like a Loar than a Loar style bridge. Seems like all the experimenting I could come up with just led me back to Loar. Go figure.

[Charlieshafer]

In conjunction with all of the above, the heavier/taller the base the better I like it too.

So, MAYBE complete contact is adding something, but I generally associate the tonal difference simply with more mass and not the transmission qualities of the studs[/QUOTE]


Well THAT makes a lot of sense, too. The higher angle would put more downward force on the soundboard, and the added mass would also help to transmit a more complete vibration.

It would be fun to try to figure this out with some sort of scientific method, using oscilloscopes and other neat looking devices (a neat old reel-to-reel tape recorder, with all the VU meters would be great just for that Frankenstein lab look) but I think that with all the differences in wood grain, build techniques, and so on, you're back to the point where while there may be generalities, each instrument will need slightly different tweaking in string angle, etc, to bring out it's best.

[Charlieshafer]

I don't doubt your word re.the sound difference,but the bridge saddle should have already been sitting firmly on top of the wheels.There would be bare screw thread under the wheels,so if the shims were placed underneath the wheels,coupling them more firmly to the base,then i could understand it more. Obviously,whatever was done it works ,
Ivan:confused:

I believe the method George used was to raise the bridge (after flattening it) to where he got the best tone/playability, and then measured the bridge height. He then relieved the pressure on the strings so he could bottom out the wheels, thus exposing the threads above the wheel, but below the bridge, then inserting the shims there, so they could be less visible, and easier to remove if someone wanted to go back to completely original.