Partial coil split resistor values

grappagreen

Hi all,

Shortly fitting a push/pull for coil splitting a Suhr Aldrich (bridge) and SD Hot Rails (neck). Any idea what size resistors I should be using for this?

Regards,

Si

ICBM

1K for the neck and 2.2K for the bridge is a good starting point - that seems to work with most humbuckers, although I've never tried a partial split with a rails-type one.

If you want to experiment more than that, it's probably better to fit a couple of trimmers rather than keep changing the resistors. 10K trimmers should be OK, or maybe 5K for the neck - the values aren't likely to be larger than this.

grappagreen

ICBM said:

1K for the neck and 2.2K for the bridge is a good starting point - that seems to work with most humbuckers, although I've never tried a partial split with a rails-type one.

If you want to experiment more than that, it's probably better to fit a couple of trimmers rather than keep changing the resistors. 10K trimmers should be OK, or maybe 5K for the neck - the values aren't likely to be larger than this.

Brill - thanks John..

Winny_Pooh

I prefer much higher 3-5K

Dave_Mc

What @ICBM said- it's very dependent on the pickup so a trimmer allows you to get more or less exactly the right value (and if you can't get anything you like you know that's as good as it's going to get rather than worrying you haven't got the right value!). 10k gives you a bit more room on the bridge (some bridge pickups are fine with quite a bit less than 5k but some aren't) and the neck doesn't usually need as much as 5k anyway so a 5k trimmer gives you finer control.

(I haven't tried it on a rails either)

TimmyO

I recently downloaded the pdf for the newer style DGT wiring from PRS (I want to get my older DGT modded to match) and as concurs with what @ICBM says the values on that are 1.1k and 2.2k 

Trimmer sounds like a good idea though. 

BigPaulie

Are these resistors a good idea for all split HBs, including hotter ones?

I thought they were only required in low output HBs...

ICBM

BigPaulie said:

Are these resistors a good idea for all split HBs, including hotter ones?

I thought they were only required in low output HBs...

They work well on hotter ones, even though possibly less needed. I have them on PRS Dragon IIs and even the bridge is better with the resistor (2.2K) than without.

normula1

I use trimmers and tune by ear. I once measured the results with a pair of Burstbuckers in a PRS. Guess what they came out at........ pretty much 1k and 2k2

BigPaulie

Wonder why Fralin recommend 7k....?

https://www.fralinpickups.com/product/resistors/

normula1

It really does depend on the pickup and the guitar. I have a BK Mule in a Strat and that one sounded best around 4.5k which is why the trimmers are the way to go. 

steamabacus

normula1 said:

I use trimmers and tune by ear. I once measured the results with a pair of Burstbuckers in a PRS. Guess what they came out at........ pretty much 1k and 2k2

I've not used trimmers, just flying leads and crocodile clips to try out different values, and have come to the conclusion the PRS values are pretty well judged. I once opted for a 1k8 (next value down from a 2k2 that I have in my box of resistors) on a Seymour Duncan Screamin' Demon in a 'superstrat' style HSS bridge position but, other than that, have found 1k and 2.2k to be pretty much spot on for the vintage wind humbuckers I gravitate towards.

Dave_Mc

TimmyO said:

I recently downloaded the pdf for the newer style DGT wiring from PRS (I want to get my older DGT modded to match) and as concurs with what @ICBM says the values on that are 1.1k and 2.2k 

Trimmer sounds like a good idea though. 

I definitely think that PRS is onto something with its component values- I like its treble bleed (180pF) value, too. Not saying you can't do better for a specific instance or anything like that- but if you want to pick a value which will probably work without a ton of faffing about, the PRS values are usually a pretty decent place to start.

But yeah a trimmer does give you a lot more tweakability.

ICBM said:

BigPaulie said:

Are these resistors a good idea for all split HBs, including hotter ones?

I thought they were only required in low output HBs...

They work well on hotter ones, even though possibly less needed. I have them on PRS Dragon IIs and even the bridge is better with the resistor (2.2K) than without.

Yeah agreed. You probably need them less, but they can still be helpful. Again, as usual, it's very dependent on the exact pickup.

BigPaulie said:

Wonder why Fralin recommend 7k....?

https://www.fralinpickups.com/product/resistors/

Maybe that sounds best with his pickups? Or maybe he did some maths and came up with that value as getting closest within range of a proper single coil's resistance... except that's not necessarily how it works! A humbucker is different enough that I'm not sure the resistances are exactly comparable, and that's if you're even using the same wire gauges for the winds...

normula1 said:

It really does depend on the pickup and the guitar. I have a BK Mule in a Strat and that one sounded best around 4.5k which is why the trimmers are the way to go. 

I've had a range of values... I've had some where I only had a few hundred ohms which sounded best. I ran out of room with a 5k trimmer on a bridge pickup, too- I was too lazy to wire in a 10k, but since that I started using 10k on the bridge pickup as @ICBM said! Up till then I'd been using 5k since I hadn't needed more than that before (or even anywhere close to that!), and 5k gives a bit more fine control. (Also it probably doesn't help that I constantly change my mind!)

It didn't always necessarily be completely proportionate to output, either. I'd say the tone of the pickup is more important than the output- a darker and/or thicker humbucker usually needs a lower value of resistor, if it even needs one at all. Those things tend to go hand-in-hand (hotter tends to be darker), but not always.

grappagreen

Thanks for the posts all.

Going to highlight my lack of electrical understanding here but I've looked at 10k trim pots and they all seem to have 3 pins. Given that a resister has two ends how is the trim pot connected?

Can anyone point me to the ideal component and I'll grab a couple and wire it up..

Regards,

Simon

Dave_Mc

You wire the middle leg to ground and one of the other ones* to the DPDT switch contact. You ignore the third one, I guess to be really safe you should probably insulate it in case it comes into contact with something it shouldn't.

And (no prizes for guessing how I know this) make sure the actual trimmer bit is accessible once it's soldered in! It may well be easier to solder wires to the DPDT and/or ground and solder the appropriate trimmer legs to the wires if the trimmer is quite small. (Also it's a bit easier to solder wires to the DPDT and ground than the trimmer.)

I just got some Bourns ones on CPC which seemed to work fine. 

Trimmer, 10K - Bourns | CPC UK (farnell.com)

Trimmer, 5K - Bourns | CPC UK (farnell.com)

But the problem with them is that you have to get over £21 or something like that (and that might not include VAT) to avoid paying a £5 handling fee and also postage. EDIT: Ooof, I just noticed, apparently you also have to buy a minimum of 5 of the 10k ones.

*Hopefully someone else can help with which one, if it matters- I forget! I had to google it myself to find out how to do it, lol (and the info I found, which I saved, doesn't specify which one- I suspect I had to do the following test with a multimeter to figure it out!). You can test it if you have a multimeter, though, you just attach the multimeter to the middle lug and one of the end ones and turn the trimmer and make a note of the resistance- if it goes from 0 to (roughly) the 10k then I think that should be ok. But someone will be along presently to say I'm wrong, I'm sure! 

normula1

https://www.amazon.co.uk/sourcingmap-Multiturn-Potentiometer-Variable-Resistor/dp/B01ARJE6ZS/ref=sr_1_6?crid=70ZSKK4BOU07&keywords=10k+cermet&qid=1668770187&sprefix=10k+cermet,aps,65&sr=8-6

I usually connect the spare leg to the centre, I tend to use the CTS push pulls and solder the trimmer directly to it and then a blob of hot melt glue to keep it in place.