-
Fishman Iris 1 Hum
Hallo electro people,
I have a Fishman Iris 1 Preamp with a piezo undersaddle pickup built into a taylor steel string.
The unit is quite noisy in general, and there is a ground hum. The same hum that you would have on an electric guitar. When I touch the output jack, it is significantly more quiet.
The guitar owner told me, that this is something new, that developped over time.
I already tried a new cable from preamp to jack.
Does anyone have an idea, or is this a common thing on older acoustic preamps?
Cheers and thank you very much
Jacob
-
6 Replies
-
I’m not familiar with that model, is it an Isys? Generally, that condition is from something grounding out. It could also be a faulty piezo. I would try disconnecting the piezo and if it goes away then you know it’s bad. You might want to open the preamp as well to make sure nothing is touching something it shouldn’t, sometimes there is some shielding in the form of a metallic sheet that could be touching the board.
-
I find that it usually is the piezo on the Fishmans. If the thin (red or golden) foil around the piezo has been scratched, only just a little bit, the electro-magnetic noise can find its way in. It seems to happen when strings are changed and the saddle is being moved a little. If there is a scratch, only just a little one, I tape some thin conductive foil under the saddle (all the way). When the saddle is back in place it covers the scratch, and the noise is gone.
-
<div>Yes it is the red one, and yes there is a scratch.</div>
Thanks for the idea with the copper foil!
In the meantime I have changed the electronics to another model. Time was an issue, the guy needed a working guitar. I have put the foil in, just for insurance 😉
I will order a new pieco, and see if the preamp becomes quiet. The inside of the preamp looked ok. If it works out with a new pieco, I will either build the old system back in the guitar or have something for the next guitar to come.
Thank you very much for your input!
-
Hi Jacob,
Ditto on the scratched lead and yes an ISYS. You can also try splitting ground from piezo directly to the jack bypassing the pre amp if it is a ground problem.
-
Forgot to mention……you can test the piezo by wiring directly to the jack, bypassing the pre amp. Hot to hot on jack and ground to ground. The piezo signal should be strong enough for amplifier to pick up. The pre amp and controls are mainly to filter (control) sound to amp. This way, you can isolate problem to piezo or pre amp.
-
<div>Thanks again for the input.</div>
My Bad, the Preamp is called Belcat Iris 1, apparantly only the piezo is by fishman. I think I will just buy a replacement piezo instead of spending too much time troubleshooting. It will come in handy for the next guitar 🙂
Log in to reply.