Fishman F1 Aura & Martin GPCPA1

[Caseyxyz]

I own a few high end Martin guitars. One of my favorites is the Martin GPCPA1. I bought it before they simplified the preamp for those too lazy to learn how to use it, so essentially it is the same as the F1 Aura +, it just predates it.

A friend of mine also just bought the same guitar with the same preamp. the sound from these preamps is, by far, the most realistic acoustic sound I have ever heard from an acoustic electric, and I own, and have played, a lot of guitars.

The problem I have though is that I hear a 60Hz hum unless I touch the jack housing (then it goes away). My friend's guitar exhibits the exact same problem. It doesn't matter what amp or PA it is plugged in to or what cord I use.

If this was an electric guitar, I would suspect a ground problem, and I'd shield the pickup cavities with copper tape and solder it to ground, and then I'd look for cold ground solder joints.

However, this is an acoustic, and I have no reason to suspect that the preamp board has a faulty ground.

Has anyone else with this guitar had that problem, and if so, how did you fix it?

[jonfields45]

I would call Fishman tech support. They will know where to start on the problem and are in my experience very helpful. That said, I would be suspicious that the shield on the under saddle transducer is compromised. A fix might be as simple as giving the connection between the UST and the preamp board a little cleaning (disassemble, spray a VERY small amount of Deoxit on the terminals and pickup lead, reassemble).

[Side Man]

Originally Posted by Caseyxyz

If this was an electric guitar, I would suspect a ground problem, and I'd shield the pickup cavities with copper tape and solder it to ground, and then I'd look for cold ground solder joints.

However, this is an acoustic, and I have no reason to suspect that the preamp board has a faulty ground.

Has anyone else with this guitar had that problem, and if so, how did you fix it?

Let me beat Fishman Customer Service to the punch and suggest you loosen your strings remove the bridge pins, lift the string ends out of the bridge pin holes and then give your saddle a tug. If it's at all snug in the bridge slot, simply sand the sides and ends of the saddle on a piece of fine-grit sandpaper laid on a flat surface, until you have a "sliding" fit - the saddle should be able to drop into the bridge slot.

Once you've achieved the sliding fit, put the saddle back in the slot, reinsert the strings and bridge pins and tune the guitar back up to pitch.

Ground hum problem should then be solved...

[RockerDuck]

Originally Posted by Caseyxyz

I own a few high end Martin guitars. One of my favorites is the Martin GPCPA1. I bought it before they simplified the preamp for those too lazy to learn how to use it, so essentially it is the same as the F1 Aura +, it just predates it.

A friend of mine also just bought the same guitar with the same preamp. the sound from these preamps is, by far, the most realistic acoustic sound I have ever heard from an acoustic electric, and I own, and have played, a lot of guitars.

The problem I have though is that I hear a 60Hz hum unless I touch the jack housing (then it goes away). My friend's guitar exhibits the exact same problem. It doesn't matter what amp or PA it is plugged in to or what cord I use.

If this was an electric guitar, I would suspect a ground problem, and I'd shield the pickup cavities with copper tape and solder it to ground, and then I'd look for cold ground solder joints.

However, this is an acoustic, and I have no reason to suspect that the preamp board has a faulty ground.

Has anyone else with this guitar had that problem, and if so, how did you fix it?

You talk down to technically challenged people and then you are technically challenged with a problem? Just sayin'

[Caseyxyz]

Update:
I have not addressed the hum problem with my Martin GPCPA1 with the Fishman F1 Aura electronics yet because I have been playing my D45 and my Taylor PS, however, the friend that I mentioned that also had the same problem brought his guitar in to a Martin repair tech for repair of the same problem. His guitar is not covered under warrantee because he is not the original owner. The tech told him he had to replace the electronics and charged him $400. Sounded "Fishy" to me.

Thank you, Jonfields45 and Side Man for your replies. They were very helpful, and I think I will try them first. A while ago, I had an issue where the top was dipping at the end block and I brought it back to the Martin Factory in Nazareth. They said my guitar was over hydrated and showed me how the top was swelling and the action was rising, and they put me on track to restabilizing the humidity of my guitar. They changed the saddle to bring the action down and advised me that if I get a buzz when the top comes back down, to change the saddle back to the higher one. I never had to do that, but sometime after that saddle was changed was when I began experiencing the problem. So the advice from you guys may be right on.

RockerDuck, on the other end of the spectrum, your comment was totally useless. If you consider someone who is too lazy to read the manual and learn how their instrument functions "Technically challenged" then you must be one of those people, since I seem to have struck a dissonant chord with you. Personally, I call it lazy, and that is a statement of fact, not a way of talking down to someone. I am not technically challenged in any way, shape, or form, and I have been doing research to resolve a problem. I AM reading about it, I am putting in the work, and I have posted the issue on this forum for additional insight from people who may have experienced the same issue. If you have nothing intelligent to contribute, it is better to keep your mouth shut and appear as a fool than to open it and remove all doubt.
Just sayin.

[blacktr]

Originally Posted by Side Man

Let me beat Fishman Customer Service to the punch and suggest you loosen your strings remove the bridge pins, lift the string ends out of the bridge pin holes and then give your saddle a tug. If it's at all snug in the bridge slot, simply sand the sides and ends of the saddle on a piece of fine-grit sandpaper laid on a flat surface, until you have a "sliding" fit - the saddle should be able to drop into the bridge slot.

Once you've achieved the sliding fit, put the saddle back in the slot, reinsert the strings and bridge pins and tune the guitar back up to pitch.

Ground hum problem should then be solved...

Side Man-thank you thank you. I took my Martin OMCPA1 to a guitar tech and he could not figure out what the problem was. The hum was not as loud in the store. Once I got back home it was very apparent. I tried a DI box, conditioner, new cables, etc. I was about to give up and call Martin and was expecting to pay a lot of money when I came across this thread. I tried the steps you detailed and it is very quiet. My saddle is very low and I think it is time for a new one. My headacke is gone. Thanks again.

[Side Man]

Originally Posted by blacktr

Side Man-thank you thank you. I took my Martin OMCPA1 to a guitar tech and he could not figure out what the problem was. The hum was not as loud in the store. Once I got back home it was very apparent. I tried a DI box, conditioner, new cables, etc. I was about to give up and call Martin and was expecting to pay a lot of money when I came across this thread. I tried the steps you detailed and it is very quiet. My saddle is very low and I think it is time for a new one. My headacke is gone. Thanks again.

So kind of you to send your thanks, blacktr. It's greatly appreciated and I hope my old post has been helpful to others, also. This time of year is especially tough on under saddle pickup-equipped guitars...

[Mourner]

Hey Side Man, just wanted to tell you that you've made my day. I've been plagued by this problem with my Martin GPCPA1 on and off for years! Stumbled upon your message by chance and hurried up home to try it out. Discovered some subtle dirt in the bridge slot, cleaned up everything thoroughly (didn't even need to sand the bridge), put everything back, restrung and voila — no hum! This made me SO HAPPY!!! Thank you from the bottom of my heart!

[Side Man]

Glad to have been of service, Mourner. Nice to know the ol' trick still works!

S.M.

[John Bartus]

I had this happen with one of my Martin Auras -- turns out that it was a broken shield in the UST pickup and not the electronics. Got a new Fishman UST, had my repair guy install it, and good to go. Hope this helps.

[Lesterlee]

Originally Posted by John Bartus

I had this happen with one of my Martin Auras -- turns out that it was a broken shield in the UST pickup and not the electronics. Got a new Fishman UST, had my repair guy install it, and good to go. Hope this helps.

I think this is a common issue for Fishman f1 aura+ owner, I had exactly the same problem as everyone did here. Thank you Bartus, replacing the UST is the final solution to me.

Also I would suggest other people having the same issue to try what @Side Man said, as it worked for me intermittently.

I would conclude that it has possibly two causes:
1. The shielding of your UST is just broken, the only solution is to replace it (lots of people already complain about how fragile the red UST is)
2. The contact between your UST and preamp is not good, you can try to reconnect them and see if it can be improved

Also what other people didn't mention is, it is really hard to replace the UST, but there is a definitely a way and you just need to be more patient, I finally ended up with inserting the two wires into the preamp's input without being able to look at it, but I still succeeded. Ask a tech guy to do this if you find it too difficult by doing it yourself. DON'T detach the whole preamp unless you have to replace the whole unit.

[jonfields45]

In my experience the Matrix UST is fragile. If you replace/modify your saddle, over/under humidify cycle your guitar, etc. the shield can get compromised. The Baggs Element is in comparison indestructible (it can short at the bend where it enters the saddle slot but that is really rare).

The good news is a Matrix is installed from the top of the guitar which means its contacts to the preamp are never soldered and it is a simple DIY project to replace a Matrix. An Element is sometimes soldered and sometimes socketed into the preamp since it is installed from the inside of the guitar.

IMO the Matrix sounds a little better. In the opinion of others the Matrix has less impact on acoustic tone. IMO both make no detectable change (and many big guitar manufacturers must agree too).

[Mbroady]

Originally Posted by Side Man

Let me beat Fishman Customer Service to the punch and suggest you loosen your strings remove the bridge pins, lift the string ends out of the bridge pin holes and then give your saddle a tug. If it's at all snug in the bridge slot, simply sand the sides and ends of the saddle on a piece of fine-grit sandpaper laid on a flat surface, until you have a "sliding" fit - the saddle should be able to drop into the bridge slot.

Once you've achieved the sliding fit, put the saddle back in the slot, reinsert the strings and bridge pins and tune the guitar back up to pitch.

Ground hum problem should then be solved...

Can you explain in layman’s terms how a tight saddle fit would cause the hum. Inquiring minds want to know

[jonfields45]

Originally Posted by Mbroady

Can you explain in layman’s terms how a tight saddle fit would cause the hum. Inquiring minds want to know

The shield on a Matrix is carefully wrapped foil and is also the ground side contact to the high impedance piezo material (you want a clean low impedance contact across the entire polymer piezo strip). The saddle and saddle slot keep a marginal Matrix shield properly in-place making good contact along the entire piezo strip (assuming the saddle can seat firmly on the UST which a binding saddle might not).

In our atmosphere oxygen and water work to make that shield a less than perfect electrical contact to the piezo strip and uniform pressure helps.

IMO, if the Matrix was 100% perfect it would not make any difference.

[Mourner]

Quick update — the hum reappeared after a while, and this time I discovered that the Matrix shield is slightly damaged with some kind of a scratch. I put a strip of tinfoil underneath the element, and the hum went away, while the sound seems unaffected. Not sure whether I should try finding a replacement (heard they're pretty hard to find since it's a discontinued product), but this temp solution worked for over a year now with many gigs played.