250.2 power on hum

Hi, I am used to Naim amplifiers giving a little background hiss when powered up with no input signal.  I bought a 2015 250.2 and this is what it does.  It has a louder hiss than I am used to when turned on, after about 3 minutes the hiss gets louder, there is an audible click, and then it goes absolutely silent.  Is this normal?  I appreciate that many people will say to leave it on 24/7, but I am often away, we get power outages/storms, and I don’t want a risk of damage.  It sounds superb, and my only real concern is if an internal component is on the way out.  Any thoughts?

Original Post
Richard Dane posted:

Is the on/off button latching properly?

The power switch latches normally, it clicks positively. Like I say, it goes through this weird power up hum, click, silence routine and then sits quietly. I have never heard it make any other unexpected noises. I am wondering if a big capacitor is charging up and then, once it has charged, the circuit hits the design point and everything balances. 

NJB posted:
Richard Dane posted:

Is the on/off button latching properly?

The power switch latches normally, it clicks positively. Like I say, it goes through this weird power up hum, click, silence routine and then sits quietly. I have never heard it make any other unexpected noises. I am wondering if a big capacitor is charging up and then, once it has charged, the circuit hits the design point and everything balances. 

Need a bit more info -

When it's finished doing what it is doing, can you play music ok ?

Are you powering the 250 up after the preamp has been powered ?

What's the rest of the system - speakers and pre-amp / psu ?

Yes, music plays fine. I plug in the preamp, so the NAPSC comes on instantly, I then turn on the PSU (non Naim) for the audio channels in my 282. I count to 10 then turn on 250.2. Speakers are Dynaudio Focus 160, connected with 5m each channel of NACA5.  

For what it’s worth, never happened with my previous NAP200. I assumed was due to the internal regulation of the 250.2. Now, I am less convinced. 

Richard Dane posted:

It doesn't sound right. Of course, without actually hearing it, it's hard to say for sure. Best get your dealer involved.

Thanks Richard. I have emailed my local dealer but his English is minimal, as is my German!  One of the joys of being an expat. I have also emailed tech support at Naim, and will see their response. The distributor (Chektone in Switzerland) seems helpful and so once I have worked out the warranty issues then I am hoping that it can be checked by them. 

I seem to remember my 282 muting for longer than 10 seconds after first powering up. If you leave the pre-amp for a minute or so before powering the 250, does it still do this ?

The reason I ask, is that the 282 has a muting relay whilst it powers up and stabilises. The 250 has no relays (the only thing it does have is a thermal cut out) so I wonder if the issue is with the 282 / non naim PSU. When you had your 200 did you power the pre-amp from this or the non naim PSU ?

Edit - just checked the manual and it's 30 seconds of muting.

Hum for a few minutes at power on and then mechanically dead silent after that matches both my older 250.2 and current 250dr.

Hiss and then a click - yeah that sounds really odd. What sort of click is this? Like a furnace makes as it heats up or cools? Could it be that transformer bolt is making this sound against the resin core as temp changes due to a miniscule manufacturing irregularity? Probably, only a naim service centre can answer this.

feeling_zen posted:

Hum for a few minutes at power on and then mechanically dead silent after that matches both my older 250.2 and current 250dr.

Hiss and then a click - yeah that sounds really odd. What sort of click is this? Like a furnace makes as it heats up or cools? Could it be that transformer bolt is making this sound against the resin core as temp changes due to a miniscule manufacturing irregularity? Probably, only a naim service centre can answer this.

Reassuring that somebody else has a similar experience.  The click is just like a ticking furnace type noise, you described it perfectly.  To be honest, I have decided to live with it and see what happens.  It could be that it will not lead to a failure, and an expensive trip to the dealer is a complete waste of money!

NJB posted:
feeling_zen posted:

Hum for a few minutes at power on and then mechanically dead silent after that matches both my older 250.2 and current 250dr.

Hiss and then a click - yeah that sounds really odd. What sort of click is this? Like a furnace makes as it heats up or cools? Could it be that transformer bolt is making this sound against the resin core as temp changes due to a miniscule manufacturing irregularity? Probably, only a naim service centre can answer this.

Reassuring that somebody else has a similar experience.  The click is just like a ticking furnace type noise, you described it perfectly.  To be honest, I have decided to live with it and see what happens.  It could be that it will not lead to a failure, and an expensive trip to the dealer is a complete waste of money!

So it's the amp itself that is making the noise. Your first post mentioned hiss and a click

Hi, I am used to Naim amplifiers giving a little background hiss when powered up with no input signal.  I bought a 2015 250.2 and this is what it does.  It has a louder hiss than I am used to when turned on, after about 3 minutes the hiss gets louder, there is an audible click, and then it goes absolutely silent.  Is this normal?

which made it sound like it was coming through the speakers, hence the answers...

james n posted:
NJB posted:
feeling_zen posted:

Hum for a few minutes at power on and then mechanically dead silent after that matches both my older 250.2 and current 250dr.

Hiss and then a click - yeah that sounds really odd. What sort of click is this? Like a furnace makes as it heats up or cools? Could it be that transformer bolt is making this sound against the resin core as temp changes due to a miniscule manufacturing irregularity? Probably, only a naim service centre can answer this.

Reassuring that somebody else has a similar experience.  The click is just like a ticking furnace type noise, you described it perfectly.  To be honest, I have decided to live with it and see what happens.  It could be that it will not lead to a failure, and an expensive trip to the dealer is a complete waste of money!

So it's the amp itself that is making the noise. Your first post mentioned hiss and a click

Hi, I am used to Naim amplifiers giving a little background hiss when powered up with no input signal.  I bought a 2015 250.2 and this is what it does.  It has a louder hiss than I am used to when turned on, after about 3 minutes the hiss gets louder, there is an audible click, and then it goes absolutely silent.  Is this normal?

which made it sound like it was coming through the speakers, hence the answers...

Sorry if I confused you.  The amplifier makes no noise (from the box), what I am talking about is noise from the speakers.

You know how, when you turn off a Naim power amplifier, there is a good few seconds before the green logo goes off and there is a little pop, pop as the left and right channels power down .  Well, my noise is like that.  

Ahh no. My answer was based on mechanical noises from the physical unit, not via the speakers. I really would contact your dealer or Naim service and describe the problem as accurately as possible.

If it is coming through speakers at power on, I would not live with it. Could be a symptom of a more serious impending failure (could also be nothing).

So it is coming from the speakers then. The confusion came with the last few posts mentioning noise directly from the 250 itself which you agreed sounded like the same thing.

Personally i'd still get it checked out to be sure, or at least try replacing the non Naim psu with a Naim one to check there are no issues there 

feeling_zen posted:

Ahh no. My answer was based on mechanical noises from the physical unit, not via the speakers. I really would contact your dealer or Naim service and describe the problem as accurately as possible.

If it is coming through speakers at power on, I would not live with it. Could be a symptom of a more serious impending failure (could also be nothing).

Yes, but given that the problem lasts for around 3 minutes only, on first power up, then it is not bothering me during normal use.  If it was a permanent feature then it would be much more intrusive.  Naim has not screamed ‘get it fixed’ so I guess they are also not sure what is behind it.

james n posted:

So it is coming from the speakers then. The confusion came with the last few posts mentioning noise directly from the 250 itself which you agreed sounded like the same thing.

Personally i'd still get it checked out to be sure, or at least try replacing the non Naim psu with a Naim one to check there are no issues there 

Well, this appeared on the day that I replaced the old 200 with the 250.2. The chance of the PSU failing simultaneously must be pretty small.  I agree that it should be checked, but until I have money to burn, it stays!

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