Concentric Volume/Blend pot w/new Bart preamp?

[fat-bottom]

I have an early 1990's Fender P Bass special with P/J pickups and a two band/two knob preamp. The first knob is a concentric volume/blend and the second is a concentric bass/treble boost and cut. I need to replace the preamp and I think I'm going with a Bartolini NTBT-918 2-band Preamp/Tone Control Module, which comes with only the concentric bass/treble pot.

My question is, can I use this pre with my stock volume/blend pot which is a 50k/100K, and if not where can I find a compatible new one? Will a standard 250k/500k concentric pot do the trick? Should I contact Bartolini?

Thanks,
Tony

[The Penguin]

Is the old volume/blend a triple or a double pot?

[fat-bottom]

I think it's called a dual concentric. It only does two things.

[The Penguin]

I was asking since a "normal" blend pot has 2 pots on one shaft so one with an additional volume function should have 3. I haven't seen that.

I have seen some hack setups that blend with a single pot but that never can have both at full volume. I'm just curious to how you have blend and volume in one knob since that would be cool

If you do have pots in the 25-100 region in a pickup the are usually doing something to a buffered signal, swapping that for a 250/500 won't work well. Is it a stock Fender preamp you have now?

[fat-bottom]

Thanks P,

The outer ring is blend and the inner knob is master volume, and yes it's a stock Fender preamp for that bass. I just opened up the bass and the vol/blend is two pots, one stacked upon the other.

I had my repair guy look at this assembly a few weeks ago and he said the vol/blend pot was 50k volume and 100k tone. The bass/treble is a 100k dual concentric.

Hope this helps.

Thanks,
Tony

[fat-bottom]

Sorry, I meant 50k volume and 100k blend.

[The Penguin]

I think the Bart takes a 25k volume so you're probably fine there. A single pot being a blend implies it works with something in the preamp circuit instead of the more common 2 pots that are full on in the center so I don't know what you have there.

A blend for your particular Bart will be a 250 or 500 dual and will be a passive blend before it gets to the preamp so your 100k pot won't work.

[fat-bottom]

Thanks P,

Any suggestions? I'm ready to scrap the whole thing and start new.

Thanks,
Tony

[fat-bottom]

Just to add,

The bass has only two knob holes and I'd like to not have to drill another.

Thanks again,
Tony

[Mika]

Hi,

If you want volume and blend controls on a concentric pot, you'll need something like this MEC pot:

http://www.banzaieffects.com/MEC-M-8...-pr-13695.html

- 500 kohm log (volume)
- 220 kohm log / 220 kohm reverse log (blend)
- DPDT push-pull switch (this you could wire for preamp bypass)

If you're unable to get a hold of one, PM me and let's work something out. I have one of these lying around (it's from my '89 Warwick Streamer Ltd. Edition), but the switch is only SPDT... Supposedly half of the switch prongs have been removed at the factory. You can wire the SPDT for preamp bypass, but it will not be true bypass.

[The Penguin]

Originally Posted by Mika

Hi,

If you want volume and blend controls on a concentric pot, you'll need something like this MEC pot:

http://www.banzaieffects.com/MEC-M-8...-pr-13695.html

So with this Tony could wire up his 2 knob bass with a passive blend and volume and use the second knob for a passive tone or maybe a 2 band stacked eq. Very cool

[Rano Bass]

I recommend going with a stacked vol/vol pot, it's easier to find and to wire.
If you are using stock Fender pickups you need a stacked 250k pot.

[fat-bottom]

Thanks Rano,

Any suggestions on where I could find one?

Thanks,
Tony

[Mika]

Originally Posted by Tony Conroy

Thanks Rano,

Any suggestions on where I could find one?

Thanks,
Tony

http://www.allparts.com/categories.p...me=250K%20POTS

The first item on the list is a 250 kohm log / 250 kohm log concentric. Make sure the shafts are the same size as your current concentric or otherwise you'll need to find appropriate knobs. The CTS concentrics sold at Allparts have shaft diameters of 3/16" for the knob and 1/4" for the lower knob.

[fat-bottom]

Thanks to all you fine folks who have participated in this thread. I've decided to drill a third hole in the bass and install a Bart 3.3 preamp harness, which is vol-blend-bass/treble with an active defeat pull-up on the volume knob.

I could not have come to this conclusion without your contributions.

Thanks Again,

Tony

[NewGuy]

I think you will be happy with your decision. Don't forget to let us know how things turn out.

[luknfur]

FWIW:

interesting sounding pot. Never seen a stacked vol/blend only two pots. I would pull the whole pre and put it in safe keeping. Pull the replacement and stick it back in come sell time. You can re-transplant the transplant or resell it.

The Bart NTBT hard copy I've got says 250K audio/dc50kBcd stack tone. The tone is a bit of a hard find.

If you buy the NTBT used you'll get the tone pot but you'll probably have to buy the stacked volume cause typically they're either v/v or v/b harnesses.

Being active, I'm guessing the bass has more room than the usual Fender. The NTBT takes up a chunk of space. If that's an issue, you might consider the EMG BTC (or the Aggie OBP for that matter). But the BTC is just a dual concentric pot with a 1"pcb attached so doesn't take up any space per se'. I've had all 3 and the there's no tone difference of any consequence to them. The plus on the NTBT is usually they have a gain trim pot which could come in handy although I never found application for it in some dozen Bart pre's and literally dozens of pup swaps.

Oh yeh, an issue to watch out for is Fender usually has those HUGE fat diameter short shaft pots cause of the pickguard. The preamps mentioned I have had come with the small diameter long shaft mini pots. You can shim the holes but the knobs will probably stick up goofy looking off the pickguard if they fit at all.

See FAQ Dimento's Trouble Shooting Guide 1st paragraph for the Bass Modification Guide if want a more thorough list of impending trauma.

Anyway, don't expect this to be a drop-in/no glitches. Even the only drop-in I ever had wasn't a drop in cause I screwed up the jack wiring.

[Callused Finger]

I'm stacked concentrics on my passive fretless P bass. Was kind of odd how 250/250k pots are a lot harder to find than 250/500k.

The Barto passive P/J setup requires 250/250k concentric pots. I'm using 1 pot per pickup: volume on top, tone on the bottom.