#1
Howdy.

I have a Jackson CMG Concert bass. It has 5 knobs on the front. (Tone pots? one is a volume. Is it still a tone pot or a volume pot? Am I calling these the right thing? I'm about to call them that a lot more, so lets hope.) According to Jackson's literature, they are a Master Volume, Blend, Treble, Mid and Bass. I'm inclined to believe Jackson. My issue is this; The pots have always been scratchy, with the exception of the volume. Also, if it matters, the four "tone" pots have a sort of... notch? in the middle of the knobs turn radius, but the volume knob does not. A quick Google search seems to indicate scratchy pots were a feature of the CMG from that era. Regardless, I would like to replace them.

I know enough to know that this is where my knowledge sort of stops being helpful.

The bass is stock, with EMG HZ35's and some active preamp. What sort of effort would be involved in changing pots, and what the hell pots do I need anyhow?

Any help in this matter would be appreciated.

Thanks
#2
The notch is also known as a centre indent. When the blend pot is sat at the notch, you have equal volume coming from each pickup. When you move away from the notch, the signal will favour one pickup over the other gradually. When you get to the extremes of the blend knob, you only get one pickup.

With the tone controls, that centre indent is the point where the knob has no affect on the signal. Move away from the centre indent, and you start either boosting the frequency the knob governs, or cutting the frequency, gradually.

In terms of replacing the pots, I think the CMG uses a Seymour Duncan BEQ 3 preamp. Contact SD for confirmation and see if they would supply replacement pots.
#3
You could try cleaning them first with some aerosol contact cleaner and another of compressed air.
#4
Quote by Deliriumbassist
The notch is also known as a centre indent. When the blend pot is sat at the notch, you have equal volume coming from each pickup. When you move away from the notch, the signal will favour one pickup over the other gradually. When you get to the extremes of the blend knob, you only get one pickup.

With the tone controls, that centre indent is the point where the knob has no affect on the signal. Move away from the centre indent, and you start either boosting the frequency the knob governs, or cutting the frequency, gradually.

In terms of replacing the pots, I think the CMG uses a Seymour Duncan BEQ 3 preamp. Contact SD for confirmation and see if they would supply replacement pots.


Correct about the Preamp. I emailed Seymour Duncan. The waiting game begins.

Quote by prowla
You could try cleaning them first with some aerosol contact cleaner and another of compressed air.


After ten years of scratch, I would be less than optimistic that this would work. Again, my cursory google search seemed to indicate this was an issue for the run of the bass near the years in which I bought mine. If I were 18 again, I would try this in a heart beat. A decade of work in the trades has lead me to a place in life where I find duct tape style solutions completely unacceptable. Not your issue though, mine. Thanks for the advice.
#5
Quote by SovietStar
After ten years of scratch, I would be less than optimistic that this would work. Again, my cursory google search seemed to indicate this was an issue for the run of the bass near the years in which I bought mine. If I were 18 again, I would try this in a heart beat. A decade of work in the trades has lead me to a place in life where I find duct tape style solutions completely unacceptable. Not your issue though, mine. Thanks for the advice.

Sure - it's probably not a lot less effort than surgery anyway.
I did it on one of my basses (a Status Graphite) and it worked on all but one pot; I'm going to try it again before I get my soldering iron out to it.
#6
In terms of wording, I've always heard "tone control" used to specifically refer to a passive tone control (Fender style tone pot, basically a low-pass filter), where-as the kind of controls you described (active EQ, usually 2 or 3 band) would be referred to as the bass/middle/treble controls.

A typical Fender Jazz would have volume/volume/tone, whereas I'd describe your bass as volume/blend/bass/middle/treble.
Spare a Cow
Eat a Vegan
#7
Quote by prowla
Sure - it's probably not a lot less effort than surgery anyway.
I did it on one of my basses (a Status Graphite) and it worked on all but one pot; I'm going to try it again before I get my soldering iron out to it.


My response from Seymour Duncan just said Contact cleaner too... That said, the response genuinely said little more than that and I am seriously nonplussed at the complete lack of customer service I just got out of SD. I asked for replacement specs. I get that recommending me the contact cleaner may save me time, money, whatever, but recommend that in conjunction with the info i asked for. Maybe? Missed opportunity to sell me something at any rate. Maybe the fact that I need the parts in Canada was part of the reason for such a weak response. Shame really.

in any case, you may be on to something here.

Thanks
#8
Maybe the SD person was doing that thinking and just had poor communication skills - who knows, eh?

A couple of cans of aerosol are probably worth a punt though.

I've been reworking a Precision and I've gone for CTS pots, as they seem to be the general recommendation.
#9
The values of each pot should be written on the case somewhere. Usually the pots are 20k or so, and once you have the value, you can order them. I'd still try contact cleaner first.
Dave @ Seymour Duncan
#10
Quote by Mincer
The values of each pot should be written on the case somewhere. Usually the pots are 20k or so, and once you have the value, you can order them. I'd still try contact cleaner first.


Good to know, thanks. Also, based on your signature, are you making up for a co-worker's lack of verbosity?
#11
I am sorry your question wasn't answered the way you had expected. Look on the pots, by the lugs (on the underside)...usually there is a value listed in white on a brown or green background. Pots are cheap and easy to replace, and you won't have to worry about them for a long time.
Dave @ Seymour Duncan
#12
Active preamps usually have pots that have a detent right in the middle. On all of my active setups, the detent at the "5" position corresponds to about where you'd be if you'd dimed a set of passive pots. They consider that a neutral position. Above that you're boosting the signal, below that you're actively cutting it. It's difficult to find those pots if you're not talking to the company that actually built it in the first place, and even then there's sometimes a lack of stock if the guitar is a bit old.

The contact cleaner (most of mine clear up with a shot of DeOxit) is usually the best idea. Spending some time rotating the pots back and forth is also a good idea (oxidation builds up on those).



You might also contact some of the small builders (like AC Guitars in the UK) who have a lot of contacts with folks who build custom active preamps; they may know exactly what the pots and knobs, etc., are. I have a feeling that SD simply bought them and sold them on.