Double bass transducer problem

"N_Cook" wrote in news:kcm5ca$hfd$ snipped-for-privacy@dont-email.me:

Input dependend oscillations? for retain freguencies and /or source impedances oscillations at certain parts of the waveform. Sounds just like you described. And a change of source will make it appear/disappear. Remedy: carefully changing the HF bandwidth a bit, and improve dc power decoupling. A small cap across inputs also is worth trying.

What is the likely cause of this problem. Just as well I keep repair records as I met this amp 5 years ago with the same untraceable fault. Owner and me had forgotten it re-appeared when he used the bass with a different bass amp. Previously reported as a fuzzy sound when he used the bass E string. This time just playing the F on the bass E string , a rattly buzz, like a spiral wound guitar string vibrating against a fret and loss of the actual F note. I've not seen the bass or transducer , assuming its a piezo element - make Ashworth transducers, what could cause this symptom, disappearing for 4 years? Both bass and amp have been around the world a few times on cruise ships so perhaps excessive heat or humidity

I would imagine the piezo pickup is not securely attached to the body. This would no doubt cause it to rattle at a resonant frequency determined by its mass and the properties of whatever fixing arrangement is partly (and long term intermittently) securing it to the Bass.

Or alternatively, the pickup might be insecurely contained within some sort of housing, and the rattling is the pickup in such a housing.

Or more alternatively, there is a battery powered pre-amp installed between pickup and outside world. When the battery runs down, you can get all sorts of weird stuff happening that you wouldn't immediately associate with a flat battery.

Gareth.

Can he try another bass guitar?

Can he try another bass guitar?

Er, I've been assuming this is about a Double Bass, i.e. an acoustic upright bass.

Maybe I'm mistaken?

Gareth.

What is the likely cause of this problem. Just as well I keep repair records as I met this amp 5 years ago with the same untraceable fault. Owner and me had forgotten it re-appeared when he used the bass with a different bass amp. Previously reported as a fuzzy sound when he used the bass E string. This time just playing the F on the bass E string , a rattly buzz, like a spiral wound guitar string vibrating against a fret and loss of the actual F note. I've not seen the bass or transducer , assuming its a piezo element - make Ashworth transducers, what could cause this symptom, disappearing for 4 years? Both bass and amp have been around the world a few times on cruise ships so perhaps excessive heat or humidity

On reflection, and assuming this is an acoustic Bass with a piezo pickup, the most likely scenario is the Bass was feeding back through the PA.

Whatever, you seem to have no first hand evidence of this problem whatsoever, and appear to be simply relaying what your customer has told you is the problem.

In my experience, customers will cite all sorts of reasons for their reported symptoms, almost all of which will be complete rubbish, because they are simply not capable of making any sort of informed diagnosis. That's your job.

Gareth.

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I'll give him a rubbber doorstop to place under the spike , worth a try

I'm trying to work out what HF means in terms of 44 to 44 Hz, but as the amp is only used with an acoustic bass then a permanent adaption at the input is possible

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He was swapping pickup for a gig last night and also another amp and should report back today

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I'll ask about battery, my only experience with piezo was a violin transducer and no battery with that one

a&c

It looks as though it was due to owner sticking a bit of plastic tape between transducer and the body of the bass, to stop the bridge moving - so much for electronic repair