Never having built one of these, it appears that the string vibrations, on the saddle, are passed through the rod piezo, and to the body of the instrument. How effective is the rod at transmitting vibrations? Is it better to have the rod contact the bottom of the bridge or the top of the box directly? Would it be better to mount a disc piezo in the box?
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I like the clean look you keep with the rod pickup and yes they sound better then disc's and no they do not sound better the a mag.
Different than, not better or worse. It's all in the ear of the beholder IMHO. If one is seeking an "acoustic" tone but needs amplified volume then one will not get that from a magnetic pickup. If one wants a piezo disc to sound like a Strat with hot single coil pickups, one will not achieve that either.
I think you are all right! How about that. A disc is very easy and flexible for placement, hot, loud , cheap,whatever. A rod will give a more refined and individual sound to each string and be less of an issue with touch sensitivity of the box etc. I believe that some people have had poor performance from the rods due to inadequate string pressure on the rod. I have a 6 string classical guitar that I put a simple piezo disc in with a piece of velcro and wired straight to the jack, no volume or other controls. I play that out at open mics etc and have had nothing but compliments, especially from the guys running the PA, that the pickup sounds so smooth and pure and really holds the delicate sound of the nylon strings and I have never had any negative feedback at all. They are in disbelief when I tell them it is a one dollar piezo disc stuck in with tape. I also have a rod piezo in a cigar box bass with the fat poly strings and when plugged into a bass amp sounds like a full size acoustic bass. It took me more trial and effort to get great sound out of the rod but it was worth it. Thanks to Randy Bretz for help and advice on that project by the way. He is the Rod Piezo Guru! So if anyone thinks that a disc sucks or a rod sucks, you just ain't doin' it right!
I'll apologize now for the physics 101...
Piezoelectric crystals generate electricity when hit with a vibration. The more intense the vibration the stronger the voltage produced. The more crystal used the more amperage produced.
Because disk piezos have more crystal on them, they produce more amperage so you get less loss through the pots/wires/connectors. Because rods can easily be more easily placed between the bridge and the saddle where the vibrations are strongest, this can produce a higher voltage signal that has more fidelity.
Feedback has nothing to do with rod versus disk, it has to do with placement/shielding/dampening against unwanteed vibrations (another whole discussion itself)
I'll climb down from my podium and put away the mortarboard cap now...
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Thanks for the picture. That helps!
rods need to be under pressure to work effectively , i find slightly embeded in the bridge but still (sandwitched ) against the box top works a treat . letting the string pressure work for you .
rods are 10 steps up from a disk in sound quality and usability .
Is the rod sitting in a slot in the bridge that allows the rod to contact the box top, as well as the saddle?