weird pot behaviour...

[nuno1959]

Hi guys

just dropping by to ask a couple of things about my Squier Vintage Modified Fretless Jazz Bass, recently acquired 2nd hand for 200€..

the pickups are definitely NOT Duncan Designed - since they bear no markings whatsoever, i'll pull them out one of these days to check out if there are any clues under them...

they sound quite nice & are on the quiet side of things as far as hum & other ''afflictions''...

however it's the pot's behaviour that baffle me a bit :

1 - i have 1 Volume pot per PU & 1 tone pot for both PU. when i set BOTH vol. pots to their max, the sound kind of ''ducks'' a little !?
2 - if i back one or the other a tiny bit the overall level actually goes up
3 - if turn all the way down either of them & the remaining one to it's max i get a full sound as well, w/ good volume, punch, etc...

looking at the control plate & without having pulled it out, i can see the knobs are a bit further away from the plate than usual in these basses - could they have been replaced - ''upgraded'' !?.. - w/ what seems to be longer shaft ones & maybe even the wrong type ?

what would the original spec be ? perhaps even an original wiring diagram so i can compare what was & what's there ?

it's not like the bass DOESN'T sound good - it does & it's tone is actually quite nice but i never had anything such as this volume ducking happen to me before so i'm a bit baffled

last but not least : i think i'd like to make it active - what would be ''the right way to do it'' if there's such a thing...

now i can't but tomorrow i'll post some photos - any suggestions about what could be off would be most welcome

many thanks to all

Nuno

 

[JimmyM]

100% typical of Jazz basses.

 

[nuno1959]

well that explains it then - i NEVER played a Jazz Bass before !!...LOL...

i just took the whole thing apart & will post some photos, if you would be so kind as to have a peek later or tomorrow....

the pots are CTS which i suppose are not original Squier fare ?..

 

[bigmoosepi]

when both pickups are at full they hum cancel eachother and basically become a humbucker instead of two single coils. This is probably what you're hearing.

 

[Baird6869]

100% typical of Jazz basses.

+1

I almost always turn the neck PU down a tiny bit. Try it.... Put both PU on full then turn the neck PU down a tiny bit. You will hear the tone change (even boost) slightly and to me it sounds noticeably better.

In any case, I have a stock (except the bridge) VM fretless Jazz and it sounds killer.

My main gigging bass cost approx 20x what the Squier did and I still gig the Squier from time to time.

Fender did a great job with this bass.

 

[line6man]

1 - i have 1 Volume pot per PU & 1 tone pot for both PU. when i set BOTH vol. pots to their max, the sound kind of ''ducks'' a little !?
2 - if i back one or the other a tiny bit the overall level actually goes up
3 - if turn all the way down either of them & the remaining one to it's max i get a full sound as well, w/ good volume, punch, etc...

This is normal. When you roll down a volume pot, a resistance is introduced between the pickup and output. The resistance is lowest when both pots are up, and thus, the pickups are directly parallel, and the total output impedance is lowest. This is why there is a volume drop. Turning either volume down a bit increases the impedance of one pickup, thus, decreasing the load on the other. This decreased load allows that pickup to be louder. When one pot is all the way down, the output impedance for the other pickup is greatest, and thus, the highest output.

 

[Troph]

The first time I observed weird pot behavior was at a Pink Floyd concert long ago.

 

[nuno1959]

i'll be with you guys in a sec just uploading the pics to Flickr... :-b

 

[bobba66]

Just makes me hungry and sleepy these days. Not wierd anymore, sadly.

 

[nuno1959]

OK, here we go - if curious here are a few photos & no, sorry ! they are NOT about my rolling skills................. ;-)

Invalid Link Removed

the pots are CTS & as far as i can tell have this code written on them 013446 250K A 0626 CTS

the little green thingamajig is ....well green, & has this printed : K 42Y-2
160V
0,0047uF +/- 10%

all the soldering seems fine, i compared it's wiring to this one :

[Invalid or Expired Link Removed] & it all seems correct as well so between this & your answers i'm concluding it's all good & the behaviour is pretty ''standard'' so to speak

as Baird6869 & line6man say, rolling off slightly one pot kind of boosts the volume level

any ideas what the PU's on this bass could be ? besides having absolutely no identifying marks the only thing is that blue tape - typical of any manufacturer you guys might know ? not that it matters , as i said it DOES sound quite GOOD - i'm just curious..

now all this ''pot talk'' gave me the munchies : hey Troph, would you help me find a box of Hershey bars i KNOW i left here somewhere ? ;-)

thanks to all of you, this forum is one of the best - much appreciated

 

[nuno1959]

Bobba66

i feel you my friend, myself i feel like a car spinning it's wheels in a sand bog & not going anywhere !!...LOL...

 

[SquierJazz72]

Yeah, it's a Jazz bass thing. I too tend to like more the sound of backing off one or the other slightly, depending on which pickup I want to favor at the time. I don't care as much for the tone of both pickups on full.

 

[audioglenn]

This is normal. When you roll down a volume pot, a resistance is introduced between the pickup and output. The resistance is lowest when both pots are up, and thus, the pickups are directly parallel, and the total output impedance is lowest. This is why there is a volume drop. Turning either volume down a bit increases the impedance of one pickup, thus, decreasing the load on the other. This decreased load allows that pickup to be louder. When one pot is all the way down, the output impedance for the other pickup is greatest, and thus, the highest output.

+1 - Not because I knew it...because line6man knows guitar electronics REALLY REALLY well.

 

[Petethebassman]

Just makes me hungry and sleepy these days. Not wierd anymore, sadly.

LOL! But seriously, I know what you mean.

 

[kjpollo]

I dont own a Jazz right now but I have owned 3 or 4 over the years and I always ended up doing what most everyone is saying...turn both pickups up full and then back off ever so slightly on one pickup. In my case it was usually the neck picked that got backed off.

 

[SquierJazz72]

because line6man knows guitar electronics REALLY REALLY well.

I'll second that. Whenever I ask an electronics question, I do always hope he'll be one of the ones to see it.

 

[nuno1959]

well, not wanting to take advantage of you guys but since we're all here & considering you are a lot more knowledgeable than me in these matters...
even when i was only thinking about buying it, i've been toying with the idea of getting a preamp for it...
now on my Cort GB35 i got a Delano Sonar2 preamp & it sounds AWESOME but
1 - wouldn't it make this bass sound a bit like the Cort
2 - in your experience what would be a preamp that would bring the ''sonic signature'' of this instrument forth but still preserving it ?

if it brought a bit extra ooomph to the table i wouldn't mind either....

 

[FrednBass]

The first time I observed weird pot behavior was at a Pink Floyd concert long ago.

 

[lowphatbass]

well that explains it then - i NEVER played a Jazz Bass before !!...LOL...

i just took the whole thing apart & will post some photos, if you would be so kind as to have a peek later or tomorrow....

the pots are CTS which i suppose are not original Squier fare ?..

From the photos it looks like the electronics have been changed/upgraded along with some extra shielding.

 

[SquierJazz72]

Looks like a bit of upgrading to me too. And IME, Squiers generally come stock with 500k minipots, usually Alpha. At least all the ones I've seen, including my own did. CTS is not standard fare, but it's a fairly common upgrade.