Loud hum in sustainiac mod

[lespaul1964]

I am still finishing a sustainiac install in a very small bodied guitar. Since I did not have space for two batteries (one to handle the emg's), i had a four pin xlr plug installed, one pin carries the power. I bought all the parts from the manufacturer of the sustainiac. The thing is that from time to time I get this very loud hum in my signal for a while, then it goes away. It comes and goes. I have the power connected in a furman power conditioner where I connect all my other equipment. Any ideas?

[WRGKMC]

I'm guess you send DC voltage through the 4 pin cable. Is the DC supply designed for the Sustaniac or is this some DC supply you rigged up?

 

The reason I ask is because the DC supplies must be zero Hum. Any old wall wart will not do. There's only a few out there that will be as quiet as

a battery and you should avoid unknown generics because their smoothing of AC ripple is poor.

 

Second question might be are you running both the pickups and Sustaniac off the same DC power supply or are you running each on a separate supply?

The coming and going of the hum can be a sign of a power supply circuit overheating and letting more AC through. Or it may be the sustaniac which is

current hungry is robbing the pickups of enough current to operate.

 

The issue may also be a cold ground contact in the wiring. Wiring up a 4 pin XLR is tricky business and they can easily be damaged soldering easily

or have leftover solder resin and make bad contacts.

 

I'm not sure why you had to run a 4 conductor unless you do have two power supplies. In most phantom systems you only need a mic cable with three conductors.

The Positive voltage is sent on the third core wire and the negative supply shares the ground shield with the guitars ground. In any case the power supply being insufficient may be causing the supply to overheat and sending AC ripple through the DC conductor and its generating EMF in the guitars signal wire or circuits. The Furman has no real use at all other than protecting your gear from spikes.

 

What you have to do is troubleshoot the cause if the hum. One thing to do is to test the cable and make sure it has no intermittent connections. You can use an ohm meter connected to pairs of connections on one end then short the other end with a jumper. Then flex the cable and see if the ohms varies. The cable may not be designed to be flexed like mic or guitar cables do and it may be the cable itself that has an issue loosing conductivity. Careful inspection and testing of the instruments wiring is another issue. It may be the cavity needs shielding or the wire that goes to your bridge is not making a good ground to the strings. Your body is what helps to shield the cavity from stray EMF when you touch the grounded strings.

 

The sustaniac Coil is an EMF generator. Making sure its not bleeding over to the pickups or guitar signal may require ground shielding as well.

 

Don't know if any of those suggestions help. I'd definitely start by checking the current draw of the pickups and sustaniac, and see if the milliamp draw of the power supply is sufficient to drive units. If its right at the limit, the cable run between the guitar and power supply does add resistance and capacitance and it may be overloading/overheating the power supply making it flake out.

[lespaul1964]

Thanks, wow, that is a lot to digest. The adaptos was the specific model recommended by the manufacturer. I plugged in yesterday with another pedalboard, connected outside my usual chain and got no hum. Everything looks right, except that the volume/sustain engage knob gets loose every now and then. The only thing I can say for sure is that it is an intermittent hum, it comes and goes. The cable is sort of home made as per the instructions of the manufacturer, but the hum does not sound like a connection problem. It is not like a scratchy type sound, it is a loud hum, barely masked by a live band, very loud without music. It goes down with volume down. Thanks.

[WRGKMC]

A loose ground can cause a loud hum. Its like touching the tip of a guitar cord. I'd use an ohm meter and check all my ground connections.

You likely have a cold solder joint some place.

[tedmich]

Alan Hoover is a cool guy, you might as well take advantage of buying your unit from the inventor/patent holder and ask him directly, no offense but he's forgotten more about sustainers than WRGKMC will even know.

 

[WRGKMC]

^^^ You don't seem to realize its one of 4 possibilities. The sustainer is only one of those 4, and the least likely to cause a hum.

 

Your advice is he should have bought from someone else and my advice couldn't possibly be accurate as the guy who sells them?

Well Ted, it does seem you have a weed up your butt today and no desire to help the OP fix his problem. If that's the best advice you got I'd say its no advice at all. .