Another humming problem!

[alcarmichael]

A few weeks ago I posted in here regarding my power amp and its humming transformers. I rectified that issue with your help. Last night I turned my system on and there was a very loud buzzing/humming coming through the speakers. Initial assumption was the power amp again but this time it turns out to be my Croft 25R/RS pre amp. It does it with nothing connected to the inputs, I did quickly swap over the interconnects from pre to power but no change.

Nothing has changed in my system or even anywhere else in the house.

Please impart your wisdom on me once again....

[Bigman80]

Got any spare valves? Swap them out one at a time, Always worth taking them out and re inserting them too. Could just be a bit of grime on a contact.

[Stratmangler]

Any chance of recording 30 second or so of the noise and posting it up?
It'll give a better idea of what you're dealing with.

[Jazid]

Electric storms last night, could it be related to a power surge?
But for the timing I'd say as bigman above, also you could try shorting an input when selected to see if the hum goes. Just attach an RCA cable and stick the blade of an INSULATED screwdriver across the plug at the other end.

(normally it wouldn't need to be insulated but safety first...)

Sent from my BLA-L09 using Tapatalk

[alcarmichael]

I don’t have any spare valves. Will look into ordering some this evening.

I will take the pre back to work with me and connect it into my other system to enable me to try and get a sound clip.

To short the input am I connecting one rca cable and shorting the centre part to the outer part of the connector?

[YNWaN]

Yes.

[Jazid]

To short the input am I connecting one rca cable and shorting the centre part to the outer part of the connector?

Yup that's the thing, won't take a second and it eliminates one issue from the list.

[Bigman80]

Just get the cheapest new valve you can, it's only for checking the good ones.

What type you need?

I don’t have any spare valves. Will look into ordering some this evening.

I will take the pre back to work with me and connect it into my other system to enable me to try and get a sound clip.

To short the input am I connecting one rca cable and shorting the centre part to the outer part of the connector?

[337alant]

A loud buzzing at the speakers could be DC getting through I would check he output of your pre amp and power amp for DC
Disconnect your speaker as you could blow a driver

Alan

[Bigman80]

A loud buzzing at the speakers could be DC getting through I would check he output of your pre amp and power amp for DC
Disconnect your speaker as you could blow a driver

Alan

A quick step by step may help avoid a blown driver?