Help - I've changed part of my Strat's wiring and it now sounds different!

Gan_Ainm

Hi all

Hopefully some of you more knowledgeable types will be able to shed some light on this problem and stop me from going mad!

My main Strat is a vintage style partscaster. A couple of years ago I had the pickups changed by my local music shop's workshop, and at the same time I had them rewire it with new pots, as the original ones were always very stiff. A few weeks ago I took the scratchplate up, and saw that instead of being standard vintage correct wiring, it had a length of Gibson shielded wire. This wire took the positive from the middle lug of the volume pot, and then the outer shielding took the earth from the side of the neck tone pot, then it was soldered to the side of the other tone pot, before going to the jack socket in the usual way (with some insulation around it to stop any shorting). The earth to the trem claw came off the volume pot body as it should, as did an earth wire to the shielding paint in the cavity (strangely the volume pot didn't have an earth feed going to the jack, although it was probably using the aluminium shield OK)

So last weekend I decided to wire it back to vintage correct, using cloth push back wire. For now I left off the earth to the cavity paint, but otherwise it went back as per vintage spec - positive from middle lug on vol pot to jack, earth from vol pot body to jack, earth from vol pot body to trem claw. When I plugged in to test it afterwards I thought it sounded a little thinner than before, but thought I must have imagined it. However, at the band rehearsal today I found that it is definitely sounding thinner. With amp and pedals set the same as usual it is not as full sounding, and is not driving the drive pedals and amp as hard as before the change. It doesn't sound bad or wrong, and if you didn't know how it sounded before you probably wouldn't notice, but it really threw me at rehearsal!

Anyway, sorry for the long post. Can anyone shed some light on what might have occurred? I did wonder if I had managed to overheat one or more of the pots, despite trying to be careful (my wiring skills are not that developed, although I don't usually have any problems). Here is a photo of part of the wiring as it was previously:

https://i.imgur.com/b9KaBwn.jpg

Thanks

Mike

ICBM

Put the shielded cable back and re-connect the body shielding and all should be as it was.

There is no advantage to 'vintage correct' unshielded cable between the volume pot and the jack - it will do nothing other than increase noise - and shielding does take off a tiny bit of top-end by adding a little capacitance to the circuit.

The apparent loss of gain is probably because the resonant frequency has been altered slightly by the capacitance change and isn't in the right place to maximise output as it was before.

Funkfingers

Gan_Ainm said:

When I plugged in to test it afterwards, I thought it sounded a little thinner than before

How old were the strings that were on the guitar immediately before you worked on it?

Did you put the same strings back on just to test things or did you replace them with a brand new set? If you changed strings, were the new ones the same gauge as last time or did you go lighter this time?

Gan_Ainm

Funkfingers said:

Gan_Ainm said:

When I plugged in to test it afterwards, I thought it sounded a little thinner than before

How old were the strings that were on the guitar immediately before you worked on it?

Did you put the same strings back on just to test things or did you replace them with a brand new set? If you changed strings, were the new ones the same gauge as last time or did you go lighter this time?

The strings were not that old and so I kept them on the guitar, so nothing changed there

Gan_Ainm

ICBM said:

Put the shielded cable back and re-connect the body shielding and all should be as it was.

There is no advantage to 'vintage correct' unshielded cable between the volume pot and the jack - it will do nothing other than increase noise - and shielding does take off a tiny bit of top-end by adding a little capacitance to the circuit.

The apparent loss of gain is probably because the resonant frequency has been altered slightly by the capacitance change and isn't in the right place to maximise output as it was before.

I would never have thought such a change would make such a difference, otherwise I would’ve left it alone! However, what you say makes sense. Should I put it back exactly as it was before, with the earth to the jack only coming off the tone pots and not the volume? Just seems counterintuitive to me, although it was obviously working fine like that before. 

Annoyingly I cut the old shielded wire before unsoldering so I’ll have to get hold of some more before I tackle it. 

Thanks for for the help and wise words. 

ICBM

Gan_Ainm said:

I would never have thought such a change would make such a difference, otherwise I would’ve left it alone! However, what you say makes sense. Should I put it back exactly as it was before, with the earth to the jack only coming off the tone pots and not the volume? Just seems counterintuitive to me, although it was obviously working fine like that before.

You're correct, it's better to connect the cable shield to the volume pot if you can - that gives the lowest noise and no possibility of a bad ground connection via the pickguard shielding.

Shielding does make quite a difference to the tone. When I was first starting out with a cheap Strat-style guitar, I followed some advice in a book on how to thoroughly shield the whole thing to stop the noise, so I did - it took half a day since it was basically covering everything, including the insides of the pickup covers, with copper tape, and replacing all the wiring with shielded cable. Then feeling very satisfied I plugged in the guitar... no noise, but I thought the tone control had gone faulty because it sounded like it was turned halfway down even when it was full up. I took a lot of fruitless troubleshooting before I finally realised it was the shielding. I had to take about half of it back out before the tone was anything like normal.

Gan_Ainm

Well I’ve really learnt some things here. To save connecting the shielding of the wire to the jack to all three pot bodies, if I connect it to just the volume pot, but then connect the pots together with a separate length of bus wire, will it still have the same tone etc as it had originally (ie shielding of cable just to both tone pots)? I’m a bit cautious of doing something different that might stop it going fully back to how it was before. 

ICBM

Gan_Ainm said:

Well I’ve really learnt some things here. To save connecting the shielding of the wire to the jack to all three pot bodies, if I connect it to just the volume pot, but then connect the pots together with a separate length of bus wire, will it still have the same tone etc as it had originally (ie shielding of cable just to both tone pots)? I’m a bit cautious of doing something different that might stop it going fully back to how it was before. 

The vast majority of the tone change will be due to the cavity shielding. The cable to the jack barely adds any capacitance - it's actually effectively just an extension of the guitar cable, which is obviously far longer so it has much higher capacitance - but is one of the major sources of noise, so it's always worth using shielded cable here.

Yes, connecting a shielded cable from the volume pot to the jack and then a separate ground wire to the tone pots is fine. In fact, as long as the pickguard shield contacts to the pots are good you don't actually need the ground wire - at worst, if the contact fails al that will happen is that the tone control doesn't work.

Gan_Ainm

Brilliant, thanks for all the help. If leaving the cavity shielding connection has potentially made the biggest change, I might try reconnecting that and see how things are. I can then reinstate the shielded wire at a later stage if I want. 

Many thanks again - it’s much appreciated. 

Mike