Humming Gainclone Kits

[cln.white]

I have a problem with a gainclone kit bought some time ago and just now getting round to assembly. I am experiencing hum, I purchased two kits together and everything is identical right down to the cabinets.
It is not the source as I have tried different units and still it hums, the hum does not rise when the volume is turned up.

I have been using them to good effect with a Musical Fidelity P173, I have changed a lot of the components in it and it sounds great, I also have been blessed with ownership of a valve pre-amp that I built from a kit and they both still hum when connected to this. I built the two identical stereo amps to allow me to bi-amp my Vandersteen 2Ce´s but have since discovered on this forum that this is not possible. I was until now using a modified MF P270-2, which sounded great, but I would really require owning my own power station to run the thing!!
Any suggestions as to a solution will be greatly appreciated.

[hybridfiat]

Look closely at your grounding. Are you using a star ground?
I tried to use a straight forward earthing system with the first gainclone I built and the hum was loud and irritating. It is a feedback loop problem that can be fixed.
A search on this site will find you a wealth of info and diagrams to assist in fixing this very common problem with the gainclone amps.
If you have done all this try looking at the earthing in the house and make sure this is adequate too.
I did and amp that worked well inside but hummed like a bitch when plugged in in my shed, the fault was in the earthing wire in the shed.

[lanchile]

Originally Posted by cln.white

I have a problem with a gainclone kit bought some time ago and just now getting round to assembly. I am experiencing hum, I purchased two kits together and everything is identical right down to the cabinets.
It is not the source as I have tried different units and still it hums, the hum does not rise when the volume is turned up.

I have been using them to good effect with a Musical Fidelity P173, I have changed a lot of the components in it and it sounds great, I also have been blessed with ownership of a valve pre-amp that I built from a kit and they both still hum when connected to this. I built the two identical stereo amps to allow me to bi-amp my Vandersteen 2Ce´s but have since discovered on this forum that this is not possible. I was until now using a modified MF P270-2, which sounded great, but I would really require owning my own power station to run the thing!!
Any suggestions as to a solution will be greatly appreciated.

Can you post some pictures?

[cln.white]

Thanks for your response to my problem, I have taken previous advice and read all I can on the build and earthing of the gainclone. I am not new to building kits so am quite surprised at the outcome but anyone can make mistakes! I have now removed the resistor/cap in the mains earth conn. but everything else is as you see in the pic. I dont know as much as I should about electronics after a lot of years more or less changing components rather than designing and building amps etc. I changed my MF P270-2 to `star earthing`to great effect so I have done some fiddling that worked!

[tauro0221]

Do you have the AC ground wire connected to the chassis? I ran with a hum when building my LM3886 and I have to remove it.

[AndrewT]

Originally Posted by tauro0221

Do you have the AC ground wire connected to the chassis? I ran with a hum when building my LM3886 and I have to remove it.

the mains protective earth wire MUST be connected permanently to the chassis.
Some call this by different names, but third wire, Safety Earth, green wire, yellow/green wire.

[tauro0221]

I did not say removed permanently just remove it powered the amplifier and see if the problem goes away.

[Corben]

These questions might help locating the problem:
- Do both channels hum?
- Does it hum when no source is connected?
- Does it hum when there is no signal from a connected source?
- Does the hum go away if the amp and the source are connected to the same power strip?

Even though the enclosure is apparently wood, defeating Protection Earth is not advisable, since a fault in the device could perceivably electrocute someone via the RCA sockets or speaker connectors.

[lanchile]

Originally Posted by cln.white

Thanks for your response to my problem, I have taken previous advice and read all I can on the build and earthing of the gainclone. I am not new to building kits so am quite surprised at the outcome but anyone can make mistakes! I have now removed the resistor/cap in the mains earth conn. but everything else is as you see in the pic. I dont know as much as I should about electronics after a lot of years more or less changing components rather than designing and building amps etc. I changed my MF P270-2 to `star earthing`to great effect so I have done some fiddling that worked!

Ok, first is that a resistor connected to earth wire chassis? if that is a resistor. ELIMINATE that resistor and put a heavy wire bolted to chassis.
What kind of power supply is that with those "tiny" caps?

[lanchile]

Originally Posted by AndrewT

the mains protective earth wire MUST be connected permanently to the chassis.
Some call this by different names, but third wire, Safety Earth, green wire, yellow/green wire.

I second that AndrewT! The earth wire MUST be connected PERMANENLY to chassis with no other parts in line like resistors,caps etc, I say this because I see a black thing that looks like a resistor, but maybe my eyes are tricking me here.