amp hummmmmmm

[boomtheroom]

Well the issue is not if somebody can repair it the issue is that finding the right person is the tricky part here. @restorer-john is in Australia and maybe you would get lucky and he might take on your unit for repair. Try him and see what happens. The major issue with finding a good tech is that most of them are dead or retired. So they are in short supply.

 

[boomtheroom]

Just the sides. Forgot to describe to also cover the "mu-metal belt" with electrical tape so it does not touch and short circuit anything.

this do?
https://www.3m.com/3M/en_US/p/d/b00041317/ or similar?

 

[RayDunzl]

That's a nasty little noise.

audible only form a few inches away

Don't break it trying to fix it...

 

[Matias]

this do?
https://www.3m.com/3M/en_US/p/d/b00041317/ or similar?

More like a sheet.

Ultraperm 80 Metal Shield; MuMetal Mu Metal Alloy Shielding Sheet Audio HiFi USA | eBay

Ultraperm 80 shielding sheet commonly used to reduce EMI (interference) in all sorts of DIY projects. Very popular for RF and audio applications. 5.4% Molybdenum. Unlike sheets sold from other vendors, these custom sheets are fully annealed to increase the EMI shielding properties and increase...

www.ebay.com

 

[boomtheroom]

More like a sheet.

Ultraperm 80 Metal Shield; MuMetal Mu Metal Alloy Shielding Sheet Audio HiFi USA | eBay

Ultraperm 80 shielding sheet commonly used to reduce EMI (interference) in all sorts of DIY projects. Very popular for RF and audio applications. 5.4% Molybdenum. Unlike sheets sold from other vendors, these custom sheets are fully annealed to increase the EMI shielding properties and increase...

www.ebay.com

is there a easy way to test if it will make a difference before i buy it?

 

[restorer-john]

You don't want to be shipping an amplifier of that weight to Australia and back- just wouldn't be sensible. Apart from cost, there is damage potential.

If you can hear the hum in your midrange, it's most likely not hum, but a buzz and >100Hz, which means it's post rectification. There's also an additional toroid likely for the preamp/switching and its associated PSUs.

Actually, looked at the file and that's 50Hz alright.

 

[boomtheroom]

You don't want to be shipping an amplifier of that weight to Australia and back- just wouldn't be sensible. Apart from cost, there is damage potential.

If you can hear the hum in your midrange, it's most likely not hum, but a buzz and >100Hz, which means it's post rectification. There's also an additional toroid likely for the preamp/switching and its associated PSUs.

Actually, looked at the file and that's 50Hz alright.

View attachment 288062

yah would cost hundreds just to ship.. defiantly coming form midrange ..and also identical to the noise coming from the transformers inside the amp.. any suggestions?

 

[egellings]

I would be annoyed if my quality integrated power amp where making a buzz, fuzz, hum etc. So there is a issue.

If it hums with the music, then teach it the words.

 

[boomtheroom]

If it hums with the music, then teach it the words.

 

[boomtheroom]

You don't want to be shipping an amplifier of that weight to Australia and back- just wouldn't be sensible. Apart from cost, there is damage potential.

If you can hear the hum in your midrange, it's most likely not hum, but a buzz and >100Hz, which means it's post rectification. There's also an additional toroid likely for the preamp/switching and its associated PSUs.

Actually, looked at the file and that's 50Hz alright.

View attachment 288062

What is it most likely to be if At 50hz any ideas?

 

[Chrispy]

Unaffected by volume control , source selection ,or source connection high quality caps replaced 6 years ago but have been told they may be the problem attached is a recording from my iphone at 1 cm away from the speaker.. ignore the wind noise picked up..

What happened to need to have this work done? This person no longer available?

 

[boomtheroom]

What happened to need to have this work done? This person no longer available?

previous owner of the company...new owners dont want a Bar of it

 

[restorer-john]

previous owner of the company...new owners dont want a Bar of it

You need to get the amplifier on the bench of a very experienced audio technician, to quantify the severity of the noise/hum and determine if it is in spec or not. Surely there's someone in NZ left? There used to be a good range of HiFi stores in Christchurch, but they're probably all dead and buried by now.

Perrreaux amplifiers have never been renowned for being hum free, right from their earliest models. Neither were their preamplifiers. Lots of power, nicely made but never state of the art in S/N.

 

[egellings]

What is it most likely to be if At 50hz any ideas?

Could be heavy AC current carrying conductors placed near sensitive input signal ones in high impedance amplifier circuits. Could be caused by not using star-grounding techniques, resulting in possible ground loops. Could also be caused by magnetic leakage from a line-frequency operated power transformer radiating magnetic field that intersects small signal carrying wires, inducing a hum signal in them.

 

[boomtheroom]

just a update i sent it to a repair person who recapped both channel amp module caps... but no change .....
has suggested maybe replacing the power supply filter caps now.. whats the chances they might be the problem?

 

[Trell]

If it hums with the music, then teach it the words.

Then there is this at claimed 432 Hz, but that is not the case when looking at the spectral content.

 

[boomtheroom]

You don't want to be shipping an amplifier of that weight to Australia and back- just wouldn't be sensible. Apart from cost, there is damage potential.

If you can hear the hum in your midrange, it's most likely not hum, but a buzz and >100Hz, which means it's post rectification. There's also an additional toroid likely for the preamp/switching and its associated PSUs.

Actually, looked at the file and that's 50Hz alright.

View attachment 288062

so post rectification would mean?

 

[egellings]

just a update i sent it to a repair person who recapped both channel amp module caps... but no change .....
has suggested maybe replacing the power supply filter caps now.. whats the chances they might be the problem?

Maybe the supply in the amp isn't the problem. If the big 'lytics are bad but not shorted, you'd hear a gawdawful loud 120Hz or 100Hz depending on whether your power is 60 or 50 Hz. Disconnect the inputs to the amp and use shorting RCA plugs to ground the inputs for testing purposes. Power up the amp. If there's no hum when you do this, then the source of the hum is in the signal fed to the amp, or you could have a really nasty ground loop somewhere in the system.

 

[boomtheroom]

Maybe the supply in the amp isn't the problem. If the big 'lytics are bad but not shorted, you'd hear a gawdawful loud 120Hz or 100Hz depending on whether your power is 60 or 50 Hz. Disconnect the inputs to the amp and use shorting RCA plugs to ground the inputs for testing purposes. Power up the amp. If there's no hum when you do this, then the source of the hum is in the signal fed to the amp, or you could have a really nasty ground loop somewhere in the system.

Hey
Nothing is connected to the amp..the noise is quiet until a few inches away form the mid driver. Doesnt change with volume or input selection

 

[egellings]

Hey
Nothing is connected to the amp..the noise is quiet until a few inches away form the mid driver. Doesnt change with volume or input selection

Is it 60Hz or 50Hz, whichever you have, hum, or is it 100Hz or 120Hz, again whatever your AC power frequency is?