Author Topic: Intermittent loss of treble (Read 150 times)

karl · « **on:** December 10, 2007, 01:45:35 PM »

Hi guys,

Looking for advice on this: I have a 1993 SC deluxe. Since owning it, I've occasionally noticed that when I first plug it in, there's a noticeably non-Alembic lack of top end. However, this is very quickly remedied by a quick 'twang' on the G-string - almost as if the treble only comes into play when it's needed. And then it's fine for the rest of the gig/rehearsal/whatever.

My first thought was that it might be the battery, but I've had it happen even with a brand new battery, so I'm pretty sure it's not that.

The problem is that it only happens very occasionally - most of the time I plug in and it's fine. I took the bass into the Bass Gallery in Camden to have the guys there check it out. And they couldn't find anything - they disconnected and reconnected everything in case it was a bad connection, but it all seemed fine. In fact, while the bass was there, it behaved itself (typical!) and the problem never manifested.

But it's happened a few more times since I've had her back. Has anybody had anything similar or know what the problem might be? As I said, it's never been critical, but I'm concerned it might be a sign that some component is failing, and that I might turn up for a gig sometime soon and the old 'twanging' might not bring the treble back . . .

Any help appreciated!

Karl
www.myspace.com/harambe
www.myspace.com/karlclews

jbybj · « **Reply #1 on:** December 10, 2007, 03:47:22 PM »

It could be the early stage of corrosion on the input jack or the instrument cable. Do you always use the same cable when the problem occurs? Corrosion will interfere with the conductivity and can cause overall level or high freq loss as you describe. Try burnishing the input jack, or steel wooling the instrument jack. Good luck. JBY

jazzyvee · « **Reply #2 on:** December 11, 2007, 01:03:20 AM »

Are you using the planetwaves cables with their so called compression spring that is supposed to keep them firmly into the instrument?

I had a similar experience when using it with my SC they slowly push themselves out of the jack socket. It's not apparent straight away buy eventually the sound goes crackly/intermittent and then all sound is lost but the jack still looks like it is plugged in properly.

However it is only a couple of millimetres out which is enough to break the sound signal connection but not enough to get the loud hum you would get if it unplugged completely.

It took me a while to find this out but since then I don't use these cables on my alembics. Standard jack sockets on my Strats they are fine.

Just my 50p worth.
Jazzyvee

karl · « **Reply #3 on:** December 11, 2007, 04:50:33 AM »

Thanks for your input, guys!

Jazzyvee - heh, I used to use one of those planetwaves cables a while back and had exactly the same experience as you, so I don't use it any more! But that was a very different problem to what I've got now - it's difficult to explain clearly, but the cable is securely in the jack socket and the volume is there, no crackles etc - but there's no top end in the sound - it sounds like an old P-bass with flats - until I 'twang' a string, at which point, the treble comes through loud and clear and it's back to sounding like an Alembic again. It feels like there's some kind of 'gate' on the upper frequencies, until I play an upper frequency sound loud enough to 'open' the gate and it then stays open. It's very weird.

JBY - you might be right: I use the same cable all the time. But that said, I use the same cable with all my basses, and only the Alembic does this. But there again, I use the Alembic much more than the others . . . and maybe it's the combination of a dirty jack socket and dirty cable . . . so I'll take at look at both and see if I can fix anything there.

Cheers,

K.

jacko · « **Reply #4 on:** December 11, 2007, 05:05:52 AM »

it sounds like an intermittent circuit problem to me, maybe as simple as a loose connector inside that's getting moved when you 'twang'?

graeme

David Houck · « **Reply #5 on:** December 11, 2007, 03:14:20 PM »

I'm not an electronics person, but my first thought is a leaking capacitor. I have no idea what that means as far as the electronics in your bass; but the behaviour you described seemed to suggest it.

How often does the problem occur?

One thing you could try, since it only occurs when you first start playing, is to move the pan all the way to the neck position before playing the first note, and do that regularly for a while and see what happens. You could then try starting with the pan all the way in the bridge position for a while and see if anything happens there as well. That might isolate the problem to one or the other circuit. A variation on this would be to start with the Q switch in the off position, etc.

karl · « **Reply #6 on:** December 12, 2007, 03:15:53 AM »

Hello again, and thanks for the continued input.

Graeme - I don't think there's anything loose inside - the guys at the Bass Gallery pulled the circuit board to bits, checked all the connectors for me, and couldn't find anything loose.

Dave - the problem occurs maybe once a week, with me plugging in once or twice a day. That said, the week I left the bass with the Bass Gallery, it didn't happen at all! I don't know the first thing about electronics, so a leaky capacitor at least sounds plausible to me. I'm dropping by the Bass Gallery again this weekend (picking up a new amp!), so I may ask the guys if they can test the capacitors while I'm there.

Cheers,

K.

jbybj · « **Reply #7 on:** December 12, 2007, 08:06:31 AM »

Karl,

I think you need to send me your bass for a year or two, let me troubleshoot it properly.

Always glad to help out, James

terryc · « **Reply #8 on:** December 13, 2007, 02:19:06 AM »

If all else fails you could send it back to Alembic..a pain and it may cost a bit but it may be worth it the long term.
Those spring loaded cables, once did a jam session and used another guys rig with them..damn thing kept popping out of my Mk..don't like them at all!!