ST-10 Hisses

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amarsicola

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ST-10 Hisses
« on: 22 Apr 2019, 06:58 pm »
I just bought an ST-10 and after few days my wife reported a headache when sitting on the chair near the amplifier.
We discovered a strange hiss when the amp is plugged but switched off, the hiss shifts to a higher frequency when the amp is switched on.
I also measured it with a phone phonometer app, the first hiss is around 8khz, the second (more disturbing) around 15khz.
The amplifier has been running 40+ hours, is it a normal behaviour of the oscillator in the first days or should i contact the distributor for assistance?

Regards
Antonio



rustydoglim

Re: ST-10 Hisses
« Reply #1 on: 22 Apr 2019, 09:03 pm »
This is the transformer noise. Google "transformer noise" and you will find that this is a natural occuring phenomenal but it shouldn't be so loud that you can hear it.  It could be a loose transformer (a tiny bit of vibration can produce higher freq noise) due to shipping.
This might fix it and save you the trouble of contacting the dealer to replace it - open the cover, there is a hex nut on top of the big copper coil transformer. Just tighten it. The transformer is very heavy and sometimes the box gets thrown around during shipping and we have a few cases of the screw becomes slightly loose.


seikosha

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Re: ST-10 Hisses
« Reply #2 on: 22 Apr 2019, 09:47 pm »
Does transformer noise actually occur at high frequencies?  I always thought that transformer noise was low in frequency.

rustydoglim

Re: ST-10 Hisses
« Reply #3 on: 23 Apr 2019, 04:18 pm »
by itself it is low freq, I don't know if vibration will result in higher freq.  But that's the only logical deduction.

RafaPolit

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Re: ST-10 Hisses
« Reply #4 on: 25 Apr 2019, 01:41 am »
Something is not right in your ST.

I can hear that high freq pitch on mine, if I rest my head against the unit (literally putting my ear 1" away).  But to be hearable from a sitting position shouldn't happen.

Hope you resolve this,
Rafa.

kaka89

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Re: ST-10 Hisses
« Reply #5 on: 27 Apr 2019, 12:52 pm »
My ST-10 also has high freq transformer noise.

Not audible from the listening position tho.

RDavidson

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Re: ST-10 Hisses
« Reply #6 on: 27 Apr 2019, 05:32 pm »
Hmmmm......maybe try other outlets around the house and see if results change :scratch:

seagreen

  • Newbie
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Re: ST-10 Hisses
« Reply #7 on: 8 May 2019, 03:07 pm »
I have an ST-10 that had the exact same issue with an ST-10 I bought used. I heard that high-piched noise immediately after plugging it in. Previous owner claimed not to hear it, so I recorded the output into a scope and verified 2 bands of noise at 8kHz and 14.5kHz. Had to send it to TDSS (authorized repair) to get both amp modules replaced. The unit was out of warranty, so it cost me $450. Good news is that I just got the unit back a few days ago and it's now dead silent and sounds great.

In short, you're not hearing things and unfortunately your unit is defective. Bob (great guy) at TDSS said the amp modules have been revised and suspects the older units were prone to this issue.

Feel free to reach out with any questions, I've spent the last couple months tracking down this issue, so happy to help.

John


I.Greyhound Fan

Re: ST-10 Hisses
« Reply #8 on: 8 May 2019, 04:11 pm »
A friend of mine had the same thing happen with his Nuforce Model 9se v3.  Paid $450, fixed the problem and then it returned.  I heard it.  It makes a high pitched whistling sound when not it use.

amarsicola

  • Jr. Member
  • Posts: 3
Re: ST-10 Hisses
« Reply #9 on: 18 May 2019, 11:35 pm »
Now the right channel only (!?!) hisses very noticeably through the speaker when amp is switched on.
Very very disappointed, I am returning it to Audiograffiti (italian distributor) next Saturday.
This was supposed to be a masterpiece of audio engineering...

rustydoglim

Re: ST-10 Hisses
« Reply #10 on: 21 May 2019, 09:50 pm »
This is probably not related to the amp board, the power supply probably come loose just a little during shipping.
You didn't try to tighten the screw on top of the transformer?

JackD

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Re: ST-10 Hisses
« Reply #11 on: 21 May 2019, 10:16 pm »
When you had a problem with a brand new product the dealer is the first place you should have gone.  People guessing about a problem over the internet is not going to resolve your issue.  My ST-10 has been dead quiet and flawless for over three years but shipping damage from common carriers is a regular occurrence even if the box looks fine.