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Alembic Club » Owning an Alembic » Troubleshooting » Archive through November 30, 2011 » High-pitched squeal with 1977 Series I « Previous Next »

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Username: tomhug

Post Number: 68
Registered: 7-2008
Posted on Sunday, March 13, 2011 - 3:45 pm:   Edit Post

This is a great instrument, but given its age, I am thinking that the electronics might be in need of inspection/adjustment/overhaul. The primary symptoms are a high-pitched squeal (like microphone feedback) when switching to the bridge pickup when the q switch is at its highest setting. I also occasionally notice what sounds like motor noise when there are motors in the vicinity. This happens when using either the "blue-box" power supply and 5-pin cable or when using a standard guitar cable. I've tested this against several different amps as well as a DI box and the symptoms are the same.

It also seems like over time the overall timbre of the amplified sound has become somehow "thinner" and less beefy too. Not sure if it's related. Listening acoustically (i.e. not amplified) and by playing feel, it still seems like the same bass, but the results, when amplified, seem (and I hate to say this) disappointing. Not what I would expect from a Series I.

I've come to realize that I am avoiding playing this bass because of these problems, and leaving it sit in a corner is not what it's made for... Help ?!?!
Senior Member
Username: terryc

Post Number: 1525
Registered: 11-2004
Posted on Monday, March 14, 2011 - 6:20 am:   Edit Post

Not an expert but from what I have read on this forum it sounds like;-

a) Upgrade electronics package to stop RF interference

b) Pick up problem..going microphonic especially at boost levels(Q switch)

Could be expensive to sort
Advanced Member
Username: jimmyj

Post Number: 253
Registered: 8-2008
Posted on Monday, March 14, 2011 - 10:24 am:   Edit Post

I'm not an expert either but I've experienced the oscillation thing and the first thing to try is exercising all the pots. (Do this with the instrument off or you may attract whales!) Especially on an older instrument whose knobs have not been turned in a while you should spin them each back and forth through their entire sweep 50-100 times to bring them back into spec. The pots Alembic uses are sealed meaning there is no "spray cleaner" approach but they still need to be twisted now and then.

If by "motor noise" you mean the pickups are amplifying some electromagnetic interference then yes the electronics upgrade would make things quieter. This involves sending your instrument to Alembic HQ for a hand-tuning of its electronics package so it's time consuming and not cheep - but it is effective.

Good luck!
Jimmy J
Advanced Member
Username: gtrguy

Post Number: 353
Registered: 9-2004
Posted on Monday, March 14, 2011 - 1:06 pm:   Edit Post

Try pulling al the connectors and re-attaching them too. I would also pull the multipin connector to the board and carefully re-attach it. Switch the pickup leads to the board and see if it follows the pickup. I run a 9mm gun cleaning wire brush with some rubbing alchol on it into the output jack to remove any oxidation and if there are contact points in the output jack, I clean them with 600 grit wet/dry sandpaper (carefully). The blue box can be re-capped and the jacks cleaned too.

Good luck,
Senior Member
Username: dfung60

Post Number: 484
Registered: 5-2002
Posted on Monday, March 14, 2011 - 11:32 pm:   Edit Post

I'd try a couple of things to debug this.

First, have you changed anything else in your rig since the problems started? Amp? Amp settings? Effects? Cable (probably not if you're using the 5-pin cable!)?

Second, I would try another cable (at least in the 1/4") just to see if that's part of the problem.

Third, try another amp (even a guitar player's amp) and see if the problem doesn't go away. If it does, the problem is your amp or it's settings (too much high boost).

Fourth, clean the internal and external connectors. I'd see if you can find a Caig Labs DeOxit or ProGold cleaning pen. They're ridiculously expensive (over $20). It's a little metal pen-like container with a tiny amount of cleaning solution in it. The cleaning solution is good, but the really good part is that the pen has a special fiber tip that really does a good job cleaning connections. When you use it it applies the cleaning solution and lets you scrub the connector really clean. You'd want to use this on the molex pins on the EQ boards, the jack and plug and any other electrical contacts.

After this stuff, it will be more difficult and expensive to work on as you'll need to start swapping stuff around.

When you get this squeally noise, it's a combination of a lot of treble boost and some noise that's getting into the pickup circuit. Sometimes noise or a failed component can start injecting noise into the circuit at a frequency higher than the bass is producing. But the preamps in the bass will happily amplify it which can push them into overdrive or feedback.

Your description of things sounding thinner strikes me as a change that could be elsewhere in your chain, so I'd try to eliminate that possibility first. If you plug a different bass into your rig and it sound thin, then the problem is with the amp; if not, then the problem is in the bass.

Good luck,

David Fung
Username: tomhug

Post Number: 69
Registered: 7-2008
Posted on Thursday, March 17, 2011 - 3:02 pm:   Edit Post

Thanks for the ideas. I will try these if I can, and report back. Definitely need to find some weekend time for this project.
Username: strangeboy

Post Number: 1
Registered: 6-2011
Posted on Thursday, June 09, 2011 - 4:46 pm:   Edit Post

I have the EXACT same bass and problem... sans the "thinner sound" issue. I've learned to compensate for the squeal by flipping the Q switch to low just before turning the knob. I think it's a characteristic of the original electronics.

I'm afraid that the updated electronics solution is in our future tomhug! :-(

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