Help with Hum please

Penny Nelson September 12, 2011 at 9:00am

okay! Thanks for all your help seems like its sorted now. Solution shielded both pick up and pot separately. ran earth wire from shielding to back of pot ran earth wire to jack.

Thanks again everyone - now I can move on to the next error in judgement acoustic bridge with no tailpiece for strings - box bowed and strings to high at 12 fret so am going to get a hinge or something for tail piece to take teh stress of the soundboard and reinforce the base of the box....tomorrow night after work...lol

Penny Nelson September 12, 2011 at 7:37am

we are okay then :D on that count anyway

Wes "Moaning Mule" Yates said:

K. So long as what we are seeing is like:

you're ok.

-WY

Penny Nelson September 12, 2011 at 3:42am

oh okay I have them all to the pot but not back to the jack will try that as well.
Dan Sleep said:

A ground loop is created any time the signal can take multiple paths to the ground on the jack.

Typically you will attach all ground wires to the case of one of the pots, then run a wire from the case where all the grounds are to the ground on the jack. The ground can only have one route to take.

If you run multiple ground wires to multiple locations, you can inadvertently cause a ground loop, which could cause a hum.

Penny Nelson said:

Grounding the pot to the jack wouldnt cause a ground loop?

Artist Formerly Known as Matt said:
I would shield the pup. Just for info, the first thing I always do with new basses is too remove the pick guard and add shielding.

I assume you have a ground going to the case of the pot?

Since you have what looks like a stacked pot, the volume part needs to be grounded to the case.

You might also want to ground the pot case to the jack , in fact , might wanna try that first.

AFKAM

Penny Nelson September 12, 2011 at 3:41am

Yes, it is my dodgey grounding apparatus. Yep I put the piezo under the bridge like real acoustic/electric guitars. with a camel bone compensated bridge. It has all the bells and whistles... and a hum lol. Going to build a box for the pot & pick up tonight and shield it. Failing that I will run the ground back to the equaliser and see if that sorts it.. because whilst its not bad now it does lessen more if I touch the strings... will keep you all posted on the results... cant wait till I can make a sound file for you all. Appart from the hum it sounds awesome!!

Ron "Oily" Sprague September 11, 2011 at 4:46pm

Penny,

Further to my last, I now suspect that what I'm seeing in your pic #1 is your metal skewer grounding apparatus. Rats...

Oily

Ron "Oily" Sprague September 11, 2011 at 4:39pm

Penny,

One question about your first pic in the sequence: is that the rod piezo, sitting behind the saddle, and next to the strings? If so, it appears from the pic that all your strings are actually touching it. You may already know this, but the best placement for a rod piezo ( I have installed two of these on classical guitars over the years, my Ovations are set up the same way - actually, the rod piezo is molded directly into the saddles on the Ovations - and my newish Yamaha FGX720SCA is exactly like what I am about to describe) is directly underneath the saddle. In many commercial guitars, the rod is set in a shallow slot in the bridge, and the saddle slots in directly atop that.

If that is indeed the piezo rod just behind the saddle and touching the strings, you need to put it beneath the saddle, not touching the strings. This may be the source of your hum. However, in looking at your wiring, I also think Wes may be right: it just somehow looks like there might be a ground loop in there as well.

Hope this helps,

Oily

Dan Sleep September 11, 2011 at 4:23pm

A ground loop is created any time the signal can take multiple paths to the ground on the jack.

Typically you will attach all ground wires to the case of one of the pots, then run a wire from the case where all the grounds are to the ground on the jack. The ground can only have one route to take.

If you run multiple ground wires to multiple locations, you can inadvertently cause a ground loop, which could cause a hum.

Penny Nelson said:

Grounding the pot to the jack wouldnt cause a ground loop?

Artist Formerly Known as Matt said:

I would shield the pup. Just for info, the first thing I always do with new basses is too remove the pick guard and add shielding.

I assume you have a ground going to the case of the pot?

Since you have what looks like a stacked pot, the volume part needs to be grounded to the case.

You might also want to ground the pot case to the jack , in fact , might wanna try that first.

AFKAM

Wes "I'm Baaaaack" Yates September 11, 2011 at 4:22pm

Nah if you connect to the 'ring' or 'sleeve' part of the jack -- not the part that touches the tip end.

-WY

Penny Nelson said:

Grounding the pot to the jack wouldnt cause a ground loop?

Artist Formerly Known as Matt said:

I would shield the pup. Just for info, the first thing I always do with new basses is too remove the pick guard and add shielding.

I assume you have a ground going to the case of the pot?

Since you have what looks like a stacked pot, the volume part needs to be grounded to the case.

You might also want to ground the pot case to the jack , in fact , might wanna try that first.

AFKAM

Wes "I'm Baaaaack" Yates September 11, 2011 at 4:19pm

K. So long as what we are seeing is like:

you're ok.

-WY

Penny Nelson September 11, 2011 at 4:08pm

Grounding the pot to the jack wouldnt cause a ground loop?

Artist Formerly Known as Matt said:

I would shield the pup. Just for info, the first thing I always do with new basses is too remove the pick guard and add shielding.

I assume you have a ground going to the case of the pot?

Since you have what looks like a stacked pot, the volume part needs to be grounded to the case.

You might also want to ground the pot case to the jack , in fact , might wanna try that first.

AFKAM

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Help with Hum please

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