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Old 20th October 2013, 10:19 AM   #1
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Default Creek amp,hum noise

Hello lads,

i recently purchased 2nd hand the Creek 4140 s2 and i can hear hum/buzz coming out from the speakers.
When i connect my headphones the hum is transfered through them stopping it from the speakers.
It's not very loud but you can hear it if you go close to the speakers.
There is also a Marantz AV receiver connected to the Creek but there is no hum from it (checked it already).
It's not a ground loop issue either, checked it through all the power sockets in the house.
The hum is present even with all interconects disconnected.
So i believe the problem is with the Creek.

Any ideas what should i check before sending it for service?
I've read about bad joints,capacitors but i cant find a schematic for that model.

Cheers
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Old 20th October 2013, 10:50 AM   #2
Mooly is offline Mooly  United Kingdom
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It depends how loud it is... it might be normal for that model and more noticeably with high efficiency speakers.

It is something that may benefit from recapping but its all guesswork without detailed tests (scope) to get an idea how bad the problem is.
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Old 20th October 2013, 11:14 AM   #3
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It's not loud at all,it's just there.
I have a scope,what can i check?
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Old 20th October 2013, 11:40 AM   #4
Mooly is offline Mooly  United Kingdom
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You could scope across the speaker output to get an idea of the amplitude of the hum and also across the rails to see if there is excessive ripple.
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Old 20th October 2013, 02:44 PM   #5
jaycee is offline jaycee  United Kingdom
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My gut feeling would be check the power supply rails and possibly renew the main supply capacitors if you found a lot of ripple there
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Old 20th October 2013, 02:50 PM   #6
Salas is offline Salas  Greece
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Or it could just be due to a field inside, like the transformer coupling to the PCBs or signal cables a little. Not all products show zero hum and buzz by default.
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Old 20th October 2013, 03:33 PM   #7
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Oddly Creek don't appear on the usual suspects when service diagrams come to mind. You might be fighting blind on this one.

I'd start by doing a Google search to see what reviews the Creek 4140 s2 had when it was new.

There would be no point in trying to mend something that was flawed from the beginning.

If it looks OK the start digging. Electrolytics all fail in time and power supply caps are a firm favourite. After that just work your way through all the 'lytics, unless someone can come up with a schematic and be more pragmatic.
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Old 20th October 2013, 04:27 PM   #8
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pm x-pro on here. He (Alex Nikitin) used to design for Creek.

He may well have access to schematics, even if he didn't design this one.
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Old 20th October 2013, 08:27 PM   #9
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I have the feeling that it will be tired capacitor fault. It could well be the reason the amplifier was on the market.

Is the noise at the same level and does it sound similar in either channel? If so, it's good odds that this is a power supply fault and since I don't recall the Creek 4040 or 4140 being noisy at all, I'd look to replacing the main power supply electrolytics. If you have large caps of more than about 40% marked capacitance and no less than the marked voltage rating, you can always tack solder these in parallel to verify that there is an improvement or not, without removing the originals. There are other caps that deteriorate too but they won't be in common.

FWIW, the original CAS 4140 shared the 4040 schematic. The series 2 though, may be another matter. Perhaps someone who has been through this before would care to speak...er..type up!
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Old 20th October 2013, 08:38 PM   #10
x-pro is offline x-pro  United Kingdom
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The CAS4140s2 uses a dual polarity power supply (unlike the 4140 and 4040 amps) and has a speaker protection circuit with a relay on the output. Most likely the hum is a result of a deteriorating power supply capacitor. I only have some old notes for that model, nothing on the power supply (and it may be the case that the full schematics did not survive).

Cheers

Alex
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