Lr Baggs X-bridge Electronics Parts Question

[Stew]

I have two LR Baggs piezo X-bridge systems in my parts bin. Well, I can't find the pot. I recently substituted a mini 5K for a system and misplaced the original pot (5 Megaohm pot).

Along with this pot is the original capacitor that came pre soldered. LR Baggs support will not help me. I need to know:

1. Where can I find a standard 5 Megaohm pot

2. What is the value of the cap used.

The cap is very small and I think it was electrolytic polyester, not ceramic. LR Baggs will not disclose this information in any of their literature. Any help would be great. Thanks.

[thegarehanman]

I just bought a t-bridge, but I bought the active preamp for it too. So I don't even need that pot and output jack. I will sell you the parts that come with the bridge(pot, capacitor, and output jack) for a few bucks plus shipping. Do you live in the US?

Edited July 20, 2005 by thegarehanman

[marksound]

This may or may not help, but I came across this bit of info on the Fishman site in the Powerbridge Installation Manual:

Passive Volume for the Powerbridge™

This circuit that is easily assembled from "stock" guitar pots and components available

at any electronics parts retailer.

You will need:

• 250 k audio taper pot

• 330k resistor

• 820 pF capacitor

• 1500 pF capacitor

This network will attenuate the Powerbridge™ so that it better matches levels

between magnetic and piezo pickups. You can expect a 14 dB (nominal) decrease in

Powerbridge™ output with this circuit.

[transient]

I think the 5M pot is used because of the very high impedance of the piezo pickups, so using a lower value pot will probably result in a loss in tone.

I recently have bought Graphtech's Ghost piezo saddles, but did not get their preamp, nor the passive wiring kit (which consists of a 5M pot and a 330pf cap).

What i did was, to build a simple piezo-preamp and connect it directly to the saddles. It handles the impedance part, and you can use a regular pot after the preamp without the tone-loss.

This is the preamp i've built:

http://www.scotthelmke.com/Mint-box-buffer.html

But you can also use this one if you want more boost, it also has a volume control by itself:

http://www.muzique.com/schem/mosfet.htm

...

emre

[Pr3Va1L]

does those acually bffer it to the same as mags??

I plan on using the mimf preamp (wich does)

[transient]

There's a difference. While magnetic pickups have high impedance, it's not as high as piezo pickups. This means that you can't use all magnetic buffer circuits for piezo's.

The circuit should have around 5-10 Megs of input impedance for the piezo pickups to sound "right". Those two circuits i've linked both have high enough input impedance. Most magnetic preamp circuits have around 1M input impedance, which wouldn't be enough for piezo pickups. I don't know about the MIMF preamp, but you can use it if its input impedance is high enough (>3M).

...

emre

Edited July 20, 2005 by transient

[Stew]

All I want to do is use the existing setup with original pot and cap values. I don't want to build something, I just wanted to know if anyone knows the cap value that's used in the LR Baggs X-Bridge system.

thegarhanman: I'll be contacting you very soon, I'm interested. (Yes I'm in the US).

[thegarehanman]

Just pm me. I think $3 is fair for the pot, capacitor and jack(especially considering the $162 I paid for the bridge). If you're willing to ship ground with USPS, you could probably get away with spending less than $10.