Cyrus one amp and B&W speakers.

[Boyz001]

Why is my Cyrus one amp and B&W speakers humming ?
Just purchased.
Can anyone help I have a problem with hum but only when I select phono.
Aux, CD etc quite as a mouse.
This is when I have nothing connected to any RCA input. I also have a Thorens TD 150 and a Cyrus tuner but have these switched off and still hum from the speakers.
I took the amp to a company who looked over it and said they had no hum!
I have all my equipment plugged into a surge adapter into one wall socket and gave tried with just amp and speakers with nothing else connected or plugged in.
Any advice would be much appreciated as very frustrating.
Oh and the hum does increase in volume as I turn the volume up.
Thanks, John.

[Richardgr]

Is the earth lead connected from the record deck, or the deck connected at all?

[rontech]

I would try completely isolating the deck from the amp. Unplug the phono lead. Disconnect any power leads between the deck and amp including any earthing connection.

[Radio Wrangler]

I wouls start with the absolute minimum, just the amplifier and speakers. Completely disconnect (signal cables, mains cables, grounding wires, everything) from the record deck, tuner, and CD player. Physically remove those units, so you just have the amplifier and the speakers. Now try turning the volume up with each position of the amp'a input selector in turn.

If you still have excessive hum, then there's nothing other than the amp involved.

Are you using a moving coil cartridge, or a moving magnet one?

The output from moving coil cartridges is very low, and so amplifiers set up for them have to have especially high gain to make up for this, and so they are particularly prone to hum and also random thermal noise, so it's normal to hear random noise (shoosh sounding) as well as hum come up with higher settings of the volume control.

Even set for moving magnet cartridges, signal levels are much lower that you get from tuners and CD players. You can get hum induced into signal cables if they are routed next to mains cables. Electric motors and power transformers inside equipment also radiate magnetic fields at mains frequencies, so that's why I've suggested moving the things you're not using right away from the amp for the test.

The idea is to strip the system to the absolute minimum, look for hum and if it's OK, then slowly build things back up one piece at a time.

David

[Boyz001]

Thank you all for comments . I have taken everything out of the equation apart from amp and speakers and I only get hum when I select phono on the amp. CD, tuner, tape all silent?

I'm using mm but I have tried disconnecting everything but amp and speakers and just get hum when phono is selected on the amp.

Yes everything unplugged apart from amp and speakers. I only get hum when phono is selected on the amp.

[Radio Wrangler]

Have you moved the other stuff away from it?

Some things don't switch off everything when the power switch is off - they leave transformers running.... it makes the on/off switches cheaper and saves having high voltages wired around the place, but it wastes power.

It's now down to either the amp or to something near it making a strong mains frequency magnetic field. This is less likely, but worth checking to avoid risk of confusion. Certainty is a precious commodity!

Oh, do you get similar levels of hum from each speaker?

If you switch off the amp, how does the hum disappear, suddenly? or does it taper off? Some clues you have to go looking for.

David

[Craig Sawyers]

David's suggestions are absolutely solid (of course!)

But the other thing to try is shorting out the phono input. You might have to take a phono plug, and solder in a short circuit. When you do that does it still hum on phono?

Craig

[John Caswell]

I have had problems with the phono sockets breaking away from the tracks at the rear on the amps. I replace/overwire the tracks with tinned copper wire inside PTFE sleeving.

John

[G6ONEDave]

This might be a silly comment but the turntable appears to be sitting on top another piece of powered equipment, which makes me think the problem is due to magnetic induction between that piece of equipment and the mm cartridge on the turntable. If you have a table, stool etc, you could place the turntable onto it, so that it is not physically above any other parts of the system. It means that the wiring will be at full length stretch but may well solve the problem. If it does you will need to rethink the layout of the system components.
Dave

[Boyz001]

Originally Posted by Richardgr

Is the earth lead connected from the record deck, or the deck connected at all?

Originally Posted by Radio Wrangler

Have you moved the other stuff away from it?

Some things don't switch off everything when the power switch is off - they leave transformers running.... it makes the on/off switches cheaper and saves having high voltages wired around the place, but it wastes power.

It's now down to either the amp or to something near it making a strong mains frequency magnetic field. This is less likely, but worth checking to avoid risk of confusion. Certainty is a precious commodity!

Oh, do you get similar levels of hum from each speaker?

If you switch off the amp, how does the hum disappear, suddenly? or does it taper off? Some clues you have to go looking for.

David

Ok thanks I will give this a try and let you know the outcome. Really appreciate the advice !

Originally Posted by G6ONEDave

This might be a silly comment but the turntable appears to be sitting on top another piece of powered equipment, which makes me think the problem is due to magnetic induction between that piece of equipment and the mm cartridge on the turntable. If you have a table, stool etc, you could place the turntable onto it, so that it is not physically above any other parts of the system. It means that the wiring will be at full length stretch but may well solve the problem. If it does you will need to rethink the layout of the system components.
Dave

Thanks I have removed the eq underneath the turntable but still the same the turntable is on a separate shelf fixed to the wall over the top of sideboard unit .

Originally Posted by Craig Sawyers

David's suggestions are absolutely solid (of course!)

But the other thing to try is shorting out the phono input. You might have to take a phono plug, and solder in a short circuit. When you do that does it still hum on phono?

Craig

Thank you is there any directions anywhere were I could copy how to do this ?

[Boyz001]

Originally Posted by Radio Wrangler

Have you moved the other stuff away from it?

Some things don't switch off everything when the power switch is off - they leave transformers running.... it makes the on/off switches cheaper and saves having high voltages wired around the place, but it wastes power.

It's now down to either the amp or to something near it making a strong mains frequency magnetic field. This is less likely, but worth checking to avoid risk of confusion. Certainty is a precious commodity!

Oh, do you get similar levels of hum from each speaker?

If you switch off the amp, how does the hum disappear, suddenly? or does it taper off? Some clues you have to go looking for.

David

I will take the equipment away and see if that helps and yes the hum is equal in both speakers

[teetoon]

Hi. I remember there could be a problem with caps in the phono stage failing as they were under rated for the voltage.
It was a common problem with one of the versions of the Cyrus One.

David.

[Boyz001]

Hi so I have tried to follow advise.
I completely disconnected and moved all equipment away apart from amp and speakers .
No noise apart from hiss which I expect from phono selected.
Oh buy the way I purchased a new surge adapter just in case.
Then I connected rca and earth lead from the TT .
No noise .
Then connected power to TT.
Hum is now back .
Any ideas .
At least I know the amp is ok .

[Radio Wrangler]

That's good progress. And it fits with the report that the amp was OK.

Opinions differ on earthing in turntables.

My preference is to have the motor power cable provide a safety earth to the motor and turntable metalwork. To have the arm insulated from the turntable, and for the arm to have an earth wire back to the case of the amplifier and to have the four wires from the cartridge to go into two coaxes to the phono plugs into the amplifier.

David

[Boyz001]

Thank you for all your help . Changing the surge adapter and I changed the earthing lead and earthed it to another place. Voila !! I'm a happy man . These things are here to test us !