Author Topic: Series I Electronics problem (Read 563 times)

brianm · « **on:** August 14, 2006, 11:39:08 AM »

I got my new short scale small body series I. It looks so much better in person than the pics that were on Ebay. Killer low action. Very light body weight, no neck dive. But there is a problem with the electronics.

The electronics do work, but I'm getting a pronounced overtone (kind of like a harmonic overtone but out of tune and a bit distorted), the higher up I play the more noticeable it is especially on the E and A strings (the D string in the second octave). I've also noticed that there is a setting on each one of the tone controls that creates a high frequency squeal similar to feed back. If you move the tone control up a nats hair in either direction you don't get the feed back. I've isolated each pick up and the problem is apparent regardless of which pick up is on. This happens with both of the tone controls, doesn't matter if only one or both pick ups are on. I'm taking the bass in to a local luthier this week, he's a bass player and does awesome work. But he has only worked on one other Alembic, I think there may be three or four Alembics here in town, I own two of them.

I talked to the previous owner about it and he said he never had that problem. I also researched the bass at the Alembic club board and read posts about it going back 3 owners. None of the posts mentioned any electronics problem. Possibly something happened during shipping??

Has anyone had this problem before? Any ideas on what the problem is?

cntrabssn · « **Reply #1 on:** August 14, 2006, 07:48:10 PM »

Brian,

I have a question about your overtone issue. You didn't mention hearing the strange overtones on your g-string. So, I was wondering if the strings exhibiting the strange behavior were taper or contact core. I've noticed this sort of behavior with taper/contact core strings, but I think you would hear the overtones even when unplugged.

- nate.

brianm · « **Reply #2 on:** August 14, 2006, 11:05:17 PM »

I solved the feedback/high frequency issue. I rotated the tone controls several hundred times each covering the full range of the pot. The previous owner did say he didn't play this bass very much so it was probably a build of crud in the pots causing the problem.

Still getting the overtone problem, though it's not as bad now. It's still quite pronounced on the E string and a bit on the A string. As far as strings, I'm using what was on the bass when I got it. I was told by the previous owner that they are Rotosound Swing Electric Bass 4 String Medium Scale, .040 - .090, RS66M
http://www.juststrings.com/rts-rs66m.html I purchased a set of GHS Bass Boomers (round wound, light guage). They didn't change the problem. I liked the Rotosounds better than the GHS so I boiled them and put them back on the bass.

One thing I suspect that may be contributing to my overtone problem is the tailpiece. When I got the bass I removed the tailpiece (for cleaning). When I put it back on the bass two of the three holes were stripped (in the wood of bass) on the E and A string side. I crammed tooth picks in the holes to temporarily secure the tailpiece till I could get the bass in to my luthier (it's going in tomorrow or the next day depending on his schedule).

effclef · « **Reply #3 on:** August 16, 2006, 01:46:11 PM »

Brian, I bet the noise is because the bridge is not totally secure. Your toothpicks may be OK but I'd suggest the luthier get the metal wood threaded inserts that Alembic uses to secure their hardware now. Call them and ask. Here is a picture of something similar (NOT tee nuts):

(www.mcmaster.com has them if you want to browse on knock-in inserts for wood)

Try hitting the low open E and feeling that side of the bridge, and see if it vibrates more than the G side.

Alembic may not have used the inserts on your vintage Series 1 but it should be simple to upgrade. The bridge screws will have to be changed to machine screws, if they're not.

I hope this helps. Nice score on the bass!

EffClef

David Houck · « **Reply #4 on:** August 16, 2006, 07:32:15 PM »

EffClef; I could be wrong, but I believe it is the case that Alembic still uses wood screws to attach the tailpiece directly to the body.

Brian; have you played the bass anywhere else other than your home? If so, are you having the same problem elsewhere? Are you certain this is not an RF noise problem? It doesn't sound like it from your description, but it would be worth checking out before taking the bass to the local luthier.

You could try two things. One, go here and run Mica's Humcancelling Procedure. Or two, if you haven't played the bass in more than one location, take it somewhere else and try it. I'm thinking there may be a possibility that it is a localized RF issue.

One other thing while I'm thinking of it. Are the strings touching the back rail of the bridge? Did you do anything else besides remove the tailpiece when you got the bass? Clean the nut or bridge?

dfung60 · « **Reply #5 on:** August 16, 2006, 08:49:58 PM »

First, unplug the bass, play it and see whether you hear any buzzing at all. Listen around all the hardware to see if a problem is localizable.

That's probably not your problem though. More likely, you're getting electromagnetic interference from something in the vicinity of your rig. You want to debug this by trying your entire rig somewhere else (not just the other side of the room) first. You should also try plugging into a different amp.

When you hear high-frequency grit or distortion, this is usually a byproduct of electronic noise that's outside the range of what you can hear or what your amp can reproduce (by the time you're through the speakers, a regular bass amp has output over less than 1/3 the full range of your hearing). You might be picking up noise from lighting, computers, cell phones, radio, or something else electronic in your vicinity. The preamps in the bass have very wide frequency response, well beyond what you can hear. They will happily amplify ultrasonic signals and do so until the preamp is totally overdriven. The effect of that overdrive is that the audible parts of the signal, especially the treble becomes distorted as well. The problem you describe with a feedback point on the tone controls is also a symptom of the preamp being overdriven by something you can't hear.

This can also be caused by a bad interaction between your amplifier's front end and your bass. Trying a different amp and different EQ settings may make the problem go away. If that's the case, then you really will probably need to switch amps to solve this problem. The Q switches can generate a LOT of boost at their frequency centers when the Q switch is in the high position. It would be surprising that you'd get feedback like this with a normal bass amp unless you were playing really loud or in physical contact with the amp.

If you still have the problem with a different amp and different location, then something really may be wrong inside the bass. You might look for a dirty connector (you can fix this by plugging and unplugging the molex connectors on the EQ boards) or possibly a short. A dirty connector changes the impedance of the connection and may cause feedback type effects. I doubt this is the problem too as a Series bass has independent preamps for each pickup and the humcancelling coil. You'd need to have developed dirty connectors on all there connections to have the problem on both pickups.

Good luck

effclef · « **Reply #6 on:** August 17, 2006, 10:16:17 AM »

Whoops, Dave is probably right...in any case we should refer direct to Alembic as to what is standard hardware!

EffClef

brianm · « **Reply #7 on:** August 18, 2006, 01:33:53 AM »

The high frequency squeal similar to feedback is not happening any more. Valentino suggested that I rotate each of the tone controls 50 to 100 times each. I did this, actually it took several hundred rotations of the bridge tone control before the problem went away. The previous owner told me that he hardly played the bass. Valentino told me that gunk can build up in the pots if the bass isn't used much and that Almebic uses self cleaning pots so rotating them actually cleans them.

I am still getting the overtone problem. It's not as bad as it was when I also had the feedback problem. The overtones are mainly on the E string and a bit on the A string, the higher you play the worse it gets. I can hear the overtones even when the bass is not plugged in. This makes me think that it isn't an electronics problem. I currently have Rotosound strings on the bass, I've tried GHS strings and still get the overtones.

I didn't remove the bridge, I only removed the tailpiece. I like the idea of the metal wood threaded inserts.

I have done the hum canceling procedure, the bass is very quiet when plugged in and not being played. I suspect it may be a combination of the bridge and tailpiece. To raise or lower the bridge there is a screw on each side of the bridge. There is a nut threaded on each of the two screws under the bridge. The nut is supposed to turn when you turn the screw which is supposed to raise or lower the bridge. The nut(s) doesn't always turn when adjusting the bridge height by turning the screw. I wondering if there is a better system that I could use that would replace the two screws and two nuts on the bridge?

I love this bass, if I can just get this overtone problem fixed I'd be very happy.

Manfred · « **Reply #8 on:** August 18, 2006, 02:24:20 AM »

Hey Brian,

I've owned your bass some time ago but I didn't had the overtone problem you are describing. I try to understand the problem you have, but I can't remember anything bad about this bass. When I bought it, it needed a major cleaning and neck adjustment which was done by Ellio Martina here in The Netherlands. Who, as always, did a good job. When I picked up the bass he mentioned this one has such a great tone. I've played it several times without any problems.

Manfred

dfung60 · « **Reply #9 on:** August 18, 2006, 01:19:11 PM »

Glad that the squeal is gone now. It's that darn high-impedance dirt film!

OK, now you know the other problem is mechanical. Check to make sure everything on the entire instrument is snug and doesn't rattle. I had this sort of a problem on Fender once due to a bent decorative washer that goes on under the big tuning machine locknut, but it never sounded like it was coming from the headstock. You often also get problems like this when one of the trussrods is loose. At a minimum, they should be firmly set even if not providing any tension to the neck.

You might check the relief too to make sure you don't have a high fret. Normally, I'd start diagnosing this by changing strings, but it sounds like you did that already.

Good luck,

David Fung

cntrabssn · « **Reply #10 on:** August 18, 2006, 02:07:38 PM »

Brian,

Also be sure to follow David's advice from before; listen around the instrument to try to localize the noise. If you suspect hardware, sometimes you can try touching the part while letting one of those buzz triggering notes ring.

Now, a brief story... I had a similar problem with a Series instrument. Playing certain notes resulted in a strange mechanical buzz.

By listening around, I was able to localize the the noise to somewhere around my electronics cavity. This is a newer instrument that has two cavities. I found that the noise disappeared when I played the instrument with the preamp card cavity open. I ultimately found out that the noise was caused by vibrating trim pots (I know, sounds weird). I actually had to disconnect the preamp and mount the card/backplate assembly inside-out to allow me to find the offending part. I added a piece of foam, which solved my problem. This took me more than a week to isolate and troubleshoot.

Anyway, keep working at it bit by bit, and I'm sure you'll eventually solve the problem.

- nate.

brianm · « **Reply #11 on:** August 19, 2006, 12:16:43 PM »

Hi Manfred, I was wondering why you sold the bass? I'm glad you did :-) I love that bass (except for the overtone problem). Tim, who I purchased the bass from also said he didn't have the overtone problem. I'm wondering if my bass was dropped during shipping which may have loosed something thus causing the overtone problem. Between my superfilter and preamps, I'm getting a lot of awesome sounds from the bass. I doubt if I'll ever sell it.

Hi David, I did adjust the trusrods, there is tension on both of them and they seems to be working properly. The previous owner did have the bass refretted. The frets seem fine, but to be honest I'm not all that great at the tech side of things. Something I really need to improve on.

Nate, thanks for the story about your Series problem. I would have never thought of parts in the electronics cavity causing the problem, till you mentioned it.

I've tried to listen around my bass to localize the problem, no luck so far. I haven't taken off the electronics back plate.......yet. I'm still waiting to get the bass in to my luthier. He does awesome work and is extremely busy. Most of the serious players here in town take their instruments to him, so it takes time to get in to see him. Plus he is a bass player who has been playing over 30 years and really knows the deal.

Thank you everyone, you have given me some great ideas to check out. I'll let you know what is causing the problem, as soon as I figure it out. I'll keep you posted.

Take care and have fun
Brian

effclef · « **Reply #12 on:** August 19, 2006, 12:40:39 PM »

Brian, can you post a close up picture of the bridge/tailpiece?

If the overtones get stronger the higher up you play -- and there's one strike against me in this thread so far for possibly incorrect advice, LOL -- I wonder if there is an issue with the bridge.

The rounded end of the saddles should face the tailpiece. What you're describing could be almost a sitar-effect, and a sitar bridge has a sort of parabolic curve to the bridge, facing the fingerboard. But that's too wacky to really consider. Something's definitely odd, but definitely FIXABLE, too.

Can you touch different parts of the bridge and make the overtones go away?

That loose nut underneath could be an issue. I believe that's a locknut which should be tight against the bridge rail, and turn as the adjustment screw turns.

Effclef (probably wrong about the sitar effect LOL)

Manfred · « **Reply #13 on:** August 21, 2006, 04:23:32 AM »

A closeup of the bridge can be seen here: http://club.alembic.com/Images/411/10842.html?1100699372
I took those pictures myself. Maybe you can compare it with newer pictures. On my picture, the saddles are facing the right direction.
Tension on the trussrods can't be the problem since my luthier solved that problem.

Brian, I sold the bass simply because I was looking for another bass, another look. I wanted a maple top. That's all. I recently bought the Series I (my mysterious pawn shop bass) which you can see in the Showcase section.

Batteries maybe? I once had an Alembic which created a funny sound, played acoustic, that bass had four 9v batteries which were rattling against eachother, I took a piece of paper to solve that part.
Another problem I had was in the five-pin connector, there's a small screw which I had turned in the wrong direction. The whole connector was rattling before it disappeared in the body.
All kinds of small stupid things but they affected the sound in one way or another. But not while played through my amp.
So, to be honest, I don't know. Just check every part to see what happens.

Manfred

David Houck · « **Reply #14 on:** August 21, 2006, 05:01:55 PM »

In another thread in this section, a similar problem was found to be caused by a loose bridge rail screw. Make sure these screws are snug; they are the screws that attach the front and rear rails to the side barrels.