Fishman/Taylor guitar pre electret mic repair

[ebartlet]

Hi everyone, I have a taylor guitar with a fishman preamp that uses an uni-directional electret mic that has failed. I managed to match up a mic from mouser made by Horn that is physically identical. One thing that I noticed is the Horn spec sheet states the normal operating voltage is 1.5 volts. The preamp bias is 4.5 volts! Horn doesn't make any cardioids that run on 4.5 volts, and I am almost certain that they were the orignal supplier of these mikes.

It seems to be working fine, and I will leave it on for a while before giving the guitar back to the customer. Should I have anything to worry about? I would rather not modify their preamp if I don't have to.

 

[dayvel]

Shouldn't be a problem. Panasonic capsules sound better than the Horn electrets, though.

 

[ebartlet]

[quote author="dayvel"]Shouldn't be a problem. Panasonic capsules sound better than the Horn electrets, though.[/quote]

Thanks :guinness:

 

[Guest]

[quote author="ebartlet"]
The preamp bias is 4.5 volts! Horn doesn't make any cardioids that run on 4.5 volts, and
It seems to be working fine, [/quote]

FET in the electret MICs is in saturation for
all voltages over 1.5 V
4.5 or 9 V can be little more optimal. Some gain 1.5 dB over 1.5 V power.
These fets are low-noise and every low 1/f noise device have big
Vdsmax. The FET can normally go up to 30 V. They have 300 uA saturation
current and power is not limit.

xvlk