Crown XLS- for the rest of us!

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Odal3

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Re: Crown XLS- for the rest of us!
« Reply #1620 on: 15 Feb 2017, 08:01 pm »
Could it be the internal fan?

dimedrol

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Re: Crown XLS- for the rest of us!
« Reply #1621 on: 15 Feb 2017, 09:51 pm »
no fan I have ever heard emits 15khz hiss. More sounds like electrical noise. But folks, could you check your own crown to see if there's any noise at all, or is everybody saying theirs are dead silent? That I can hardly believe, because every single switching power supply I've ever had hissed, some more, others less.

Panelhead1

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Re: Crown XLS- for the rest of us!
« Reply #1622 on: 16 Feb 2017, 04:46 pm »
  I misunderstood your issue. Thought you were getting noise from the speakers. Mine are at the bottom of a heavy wood rack. Will get down and listen.
  The chokes may be singing. Folsom recommended dampening them with a resistor to prevent this. Think a 2k, 5 watt was his choice here. He may contribute his thoughts.
   I have heard diodes make this noise in tube amps. Especially after replacing a one amp bridge with a three amp. Folsom replaced the stock diodes when he offered mods for the Crown units. Said the diodes was a lot of work.
  The flimsy chassis was a concern. Damped the lid and chassis. Snubbed the filter caps, and damped the chokes in both of my units. One or all these changes may lower the physical noise generated.

Panelhead1

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Re: Crown XLS- for the rest of us!
« Reply #1623 on: 17 Feb 2017, 04:30 am »
  Played a little music and turned volume off the listen to unit for mechanical noise. None.

seikosha

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Re: Crown XLS- for the rest of us!
« Reply #1624 on: 17 Feb 2017, 01:39 pm »
no fan I have ever heard emits 15khz hiss. More sounds like electrical noise. But folks, could you check your own crown to see if there's any noise at all, or is everybody saying theirs are dead silent? That I can hardly believe, because every single switching power supply I've ever had hissed, some more, others less.

Even if everyone's unit was emitting a 15khz hiss, most can't hear that high and would swear that their unit was dead silent.  I'd probably be one of them.  That's the upper limit of my hearing last time I checked.

dimedrol

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Re: Crown XLS- for the rest of us!
« Reply #1625 on: 17 Feb 2017, 08:01 pm »
I opened the cover and listened closely - it's the transformer that the noise is coming from. It is much more pronounced with the cover open. Since it's high pitched, those frequencies are easily absorbed with any kind of shield, so I just went ahead and duct-taped 50% of the front panel vent holes. That has significantly reduced the audible noise. Considering I'm only using 1/5 of the amp's power, I think it won't burn the house.

Armaegis

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Re: Crown XLS- for the rest of us!
« Reply #1626 on: 17 Feb 2017, 10:17 pm »
Maybe just put a small throw pillow in front of the amp?  That should absorb a good chunk of the sound and not block your ventilation.

dimedrol

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Re: Crown XLS- for the rest of us!
« Reply #1627 on: 21 Feb 2017, 01:49 pm »
so this one here sings pretty badly




I thought it was the transformer that hissed, but it wasn't. It's the choke. Any helpful ideas on how to tame it?

Panelhead1

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Re: Crown XLS- for the rest of us!
« Reply #1628 on: 22 Feb 2017, 02:47 am »
  Try mechanical dampening. A cork cabinet door bumper might be perfect. Look at Ace or another full service hardware store.

Armaegis

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Re: Crown XLS- for the rest of us!
« Reply #1629 on: 22 Feb 2017, 03:11 am »
If it doesn't have any heat, I'd be tempted to just glob hot glue over it.

dimedrol

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Re: Crown XLS- for the rest of us!
« Reply #1630 on: 22 Feb 2017, 10:00 am »
folks on diyaudio suggested that the hiss may be a consequence of an upstream problem, so it's worth to do some checks there before acoustically dampening the choke. I decided to sent it for repair to people with an oscilloscope. Hopefully it's just the choke that is faulty in which case a local fix will suffice.

Jazzaudio

Re: Crown XLS- for the rest of us!
« Reply #1631 on: 4 Mar 2017, 05:43 pm »
Is Salis Audio still around and cryoing amps?