Author Topic: Tech questions regarding pot values and pickup buzz (Read 14184 times)

Tinus · « **on:** April 20, 2005, 10:54:29 AM »

Hi there y'all,

Just two things I was wondering about:
1) Is it possible to use different pot values for tone and volume pots (for example 300k for tones, 500k for volumes)? Would this make any tonal difference? Any serious disadvantages? The reason I ask is that, although I love the PU's w/300k pots, I'd like to add just a bit of clarity, as my other most used guitars (epi riviera's with miniHB's) are very bright and I'd like to switch between them during gigs without adjusting my amp. As I love the travel and effect of the tones like they are I considered just switching the volumes to 500k.

2) When I had fitted BKP P90's to my Casino I found out that when I turn a volume down to zero and don't touch any strings there's a pretty strong buzz/hum coming from the guitar. When I do the same with all volumes opened up this buzz is non-existent. Also, this effect is strongest at home, in other environments it varies from the same to virtually none. Could this be caused by something like maybe bad earthing at home or did I muck up the wiring somewhere?

Looking forward to your added wisdom :idea:

Regards,
Martijn

aisuru · « **Reply #1 on:** April 20, 2005, 05:15:25 PM »

i've noticed a certain buzz with my BKs - caused by my PC's monitor... so i just sit further away while recording :D

Tinus · « **Reply #2 on:** April 20, 2005, 05:57:42 PM »

Quote from: aisuru

i've noticed a certain buzz with my BKs - caused by my PC's monitor... so i just sit further away while recording :D

Thx Aisuru, I'm familiar with EMR buzz/hum from TV sets, PC's etc. but it was a first for me to actually get more of it when the volumes turned to zero... :?

HJM · « **Reply #3 on:** April 20, 2005, 09:32:06 PM »

Quote from: Tinus

Quote from: aisuru
i've noticed a certain buzz with my BKs - caused by my PC's monitor... so i just sit further away while recording :D

Thx Aisuru, I'm familiar with EMR buzz/hum from TV sets, PC's etc. but it was a first for me to actually get more of it when the volumes turned to zero... :?

Does the noise go if you touch a string with the volume down?

Tinus · « **Reply #4 on:** April 20, 2005, 11:42:34 PM »

That's correct HJM. Any Idea's?

HJM · « **Reply #5 on:** April 21, 2005, 06:51:23 AM »

Check that the output jack is grounded, and then work back to the pots and the bridge. 99% chance you'll find a problem there!

HTH AMPS · « **Reply #6 on:** April 24, 2005, 11:02:37 PM »

btw, to answer your original question - 500k volume pots will give you a brighter tone. I think P90s are supposed to have 250k volume pots (from memory) but there is no reason why you can't have 500k or even 1M volume pots if it gets the tone you're after.

:twisted:

Tinus · « **Reply #7 on:** April 25, 2005, 09:31:41 AM »

Thanx HJM and HthH for replying.

I checked the output ground and it was working ok. As the guitar is a thinline hollowbody the electronics aren't accessible without major surgery so I'll leave it for now and try it out in different environments. In trying to resolve this matter I rewired this guitar three times already so I am reluctant to jump in once again without a definite idea what to look for. Maybe lack of effective screening in hollowbodies is causing this; I used shielded wire but maybe it's just not enough to keep out EMR in my appartment building. I'll tell my neighbours they can't watch the telly anymore :twisted:

Regarding my question about pot values: my question really was if it's OK to mix pot values in the same system, for example 500k for volumes and 300k for tones.

Regards,
Martijn

HJM · « **Reply #8 on:** April 25, 2005, 12:51:47 PM »

You need a decent connection to the bridge to sort out the grounding. Somewhere there'll be a weak ground connection! It's just getting to it, I hate dealling with semis.... :roll:

Often thought it can be a ground issue with the house or incoming supply.......

Mixing values is fine, I've used 500k vol and 250k tone before, just alters the way the the tone control works a touch.

Tinus · « **Reply #9 on:** April 26, 2005, 03:25:08 PM »

Cheers HJM for clearing up the mixed-value Q. I'll just do some more testing outside my house before I start prying through f-holes again.

Regards,
Martijn

Baxter · « **Reply #10 on:** May 04, 2005, 01:06:56 PM »

Hello Everybody,

Im new this my first post

I was an Electrical / Electronic Engineer, here is my opinion.

Volume and Tone pots have an entirely different function (obviously !). If a 500Kor 250K volume pot are used, this can really effect the tone of the guitar, a higher value should make the sound brighter. The value of volume pot is a more complex subject, and effects can vary from PU to PU. You can always turn down a 500k pots to give a 250k value, so 500K is a safe bet.

Tone pots are usually used with a series connected capacitor which then acts as a high pass filter. The higher the value of tone pot the less treble you will loose from your pickup signal, but the cap value has the same effect, so the lower the value of the cap the less treble you will loose. I use no-load tone pots - these switch off at position 10, so no high pass filter is in the circuit. So this means max treble. Then as you wind down the pot the filter circuit is switched on as normal. A 1M tone cap is a good choice as it can be set to 250k, 500k or higher. As far as cap values go, I think these are achieved by trail and error. Also I have been told that the type of cap used can effect the tone, and some types of cap are not suitable.