Help! Replacing SUB5 preamp - Will a pre-EB schematic be an improvement?

[scotty89]

I am looking to replace my SUB5's preamp, because it is really weak sounding - not at all like I heard 'any' other musicman's sound like (SUB's or not)

I just bought the bass used off ebay, and I don't know why, but with all pots wide open, the bass sounds really really trebly. It is actually really harsh and unpleasant to listen to.

I asked the seller before bidding, and he said that it was the passive model SUB... then I picked it up and it turns out to have a battery compartment, and sure enough when I got it home and took the banana control plate off, there was a circuit board with the words "2 EQ" etched on it.

So I am confused... from what I can tell it is active (why else would it need a battery??), but the pots do not have centre points, they feel like regular volume pots. All the active preamp basses I have played previously had blend pots for the EQ controls, where the centre point (flat EQ) had a notch - is it a musicman thing to not have these? or are the controls on my bass really passive?

I can roll the treble off about 1/3 and it is a bit better, at least bearable for now, but the bass control... well, its useless. With the control wide open, the low-bass is quite weak, and with it rolled off, the bass only gets weaker.

I am thinking the problem is the preamp, and have been looking for a replacement - At the moment I am seriously unsure which way to go. I just spent $200 on an aguilar preamp for my other bass, and I don't want to spend that much again really (especially when it didn't seem to be all that special).

I then thought, I'll see if there are any schematics for building my own simple preamp... then I came across a schematic for a pre-EB stingray 2 band EQ, however there are mixed comments about this preamp, some saying that it is identical to the preamp used nowadays, just modified with a protection resistor... is this so?

If this is the case, will there be no audible difference if I do build one and replace my preamp?
What other options do I have? I don't really want to get something too expensive, and nothing that is going to take me further from the stingray tone I am trying to achieve... Can someone help me?

Thanks in advance.

 

[silverburst]

Since you just bought it, I would suggest sending it back to the seller. They misled you about it being an active bass.

Also, playing with all pots at maximum sounds pretty awful on most basses I have ever owned.

 

[Rod Trussbroken]

You have an active (not passive) SUB5 which comes with a 2EQ pre-amp from the factory. The 2EQ does not have center positions on the controls (only the 3EQ version does). The 2EQ is virtually the same as the Pre-EB preamp. It does now have a protection resistor.

The first thing I suggest you do is fit a fresh battery!

If that doesn't help things then I suggest you ask Ernie Ball for advice. The Customer Service email is:

[email protected]

 

[five7]

I had the same problem on a sub 5 and thought it was the battery. It turned out to be a bad solder point. Once it was fixed I had more than enough lows! And like Rod said, no center detents!

 

[scotty89]

I had the same problem on a sub 5 and thought it was the battery. It turned out to be a bad solder point. Once it was fixed I had more than enough lows! And like Rod said, no center detents!

Thanks, I think this may be my problem, I'll open it up and check over the circuit carefully. Are there any suspect components like caps or IC's that might have gone bad?

I have already replaced the battery with a fresh one, and noticed no change. Also put some new regular slinky's on it (which made it sound a whole heap better & clearer, but has done nothing for the low end).


And as for trying to return it to the seller; I would prefer the active SUB (if it worked like it should), I was going to put a preamp in it if it was indeed passive.

 

[five7]

An active sub5 should have plenty of low end. The two I had did. In fact I always had the lows rolled back from wide open.

 

[silverburst]

Ah. You are pretty far away, too. I temporarily have a SUB 5 and it is plenty bassy. Really a pretty darned nice bass.

 

[scotty89]

That's what I thought.... Only MM's I've ever heard were insanely fat and awesome - the sound that every bass strives for...

Only problem is that mine doesn't sound like the other MM's I've heard.

I did a forum search and found a couple of others with this problem, and everyone told them it was their amp, their cabinets, their playing style etc. as if the Musicman man could never be the problem.

I hate to say this but, it is the problem, I just want to know how to fix it. Don't get me wrong, I love the musicman sound (I wouldn't be on here otherwise), but mine just isn't quite a musicman at the moment.

Anyway, I'm not at home right now, so I'll take the control plate off and look over the preamp when I get home.
With it amped, the guitar is insanely trebly and barely any bass at all. Acoustically, when the bass isn't plugged in, it sounds fine/normal.
I'm pretty sure something in the preamp circuit is either shot or playing up at the moment.

 

[scotty89]

Just opened up the bass and tested the capacitors... all the electrolytic ones are reading their correct values, and the ceramic ones seem to be similar to that on the schematic....

I don't know what else it could be... the pickup maybe? Could the 4250 IC on the preamp be faulty?

 

[five7]

On mine it was the bass tone knob that needed to be resoldered to the board. One point.

 

[Ken Baker]

I really shouldn't do this, but...

I don't know what else it could be... the pickup maybe?

Probably not the pickup unless it's grievously messed up. Check the battery leads & contacts. The leads are quite fine and easily broken. You'll want to make sure the battery box contacts are clean and in good contact (with proper polarity) with the battery.

Could the 4250 IC on the preamp be faulty?

It is possible and your symptoms are fairly consistent with that. I won't court disaster by going any further.

Ken...

 

[scotty89]

I checked all the solder joints on the preamp board, all the joints were neat and solid. All the pots were firmly mounted, with good joints and measuring the correct resistances.

I also measured the voltage at the battery lead terminals on the board, they were fine and reading 9volts, so I think that the battery/power supply is ok.


Is it possible to source another 4250 IC from somewhere? I checked my local electronics store's online catalogue/database and they don't have a 4250 specifically.

Are there any similar IC's with a cross-referenced number or something that will function the same?

Thanks again for the help guys, much appreciated.

 

[five7]

Customer service.

 

[scotty89]

Still haven't heard from customer service

I sent a message on the 10th of September...

 

[r goldsmith]

Scotty, I suggest you take it to the Bass Centre in South Melbourne, plug it in and compare it to some of the EB's they carry there. I doubt they will have a SUB about the place but at least you can see if it's tonally in the ball park or whether you in fact have a fault. From your description it does sound faulty, but unless you have a yardstick it's a bit speculative.

 

[scotty89]

I'm heading over there on friday to have a look at an amp actually... I'll take my SUB along and see what they think...

 

[cellkirk74]

Maybe you should know that the 2-bamd EQ used to be boost only. This means by turning bass and treble up you already do boost the highs, whereas you have the passive Tone when you turn them fully counterclockwise. You should have this in mind when setting up your amp. The boost the bass alone does is huge, so there is no need to boost bass or treble on your amp.

If this does not help, adjust the pickup height. If Its too trebly, it may be too close or too far away from the strings. You will have to try a little, but this is likely to help a lot.

Did you check it with different strings? The wrong strings can make every bass sound terrible.

 

[scotty89]

I have set the pickup height, that was done when I first got the bass home.

I have installed a new set of Ernie Ball slinkies, read my posts. I doubt these are making the bass sound terrible.

I know the 2 band is boost only, hence the non-blend pots. I do not plan to run them wide open to achieve great tone either (as 57fender has already pointed out), my point is that with both pots opened right up, the tone should have an excessive treble AND bass presence. This is not the case, only the treble has a great amount of boost, the bass does not. The bass pot does change the sound, for sure, however with it completely boosted, it doesn't sound as fat as other Musicman's I've heard.

 

[cellkirk74]

well ok, if it is not an issue with the poti itself, it might be the pickup. I do not know which impendance it should have. Sorry and good luck.

 

[scotty89]

Each coil had ~4.1k ohms from memory when I had it open...