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.
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.
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.
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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?
Pics of one amp
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!
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!
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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.
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.
- 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.
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?
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.
NO NO, As I said in my last post I removed the resistor and capacitor and replaced with good wire connection. As per AndrewT´s instructions elsewhere. The chassis is indeed wood, but the bottom is lined with an aluminium sheet so there should be no problem here.
I have been looking again at other threads regarding same problem, should there be wiring from the PG points on the power supply boards to the star earth bolt? as the instructions I received were not very informative regarding this issue.
I have been looking again at other threads regarding same problem, should there be wiring from the PG points on the power supply boards to the star earth bolt? as the instructions I received were not very informative regarding this issue.
Hve a good look at the diagrams in the chip amp help section of this forum. The one set up by Peter Daniels it will help you get the earthing correct.
While I ran the input and output wires like this I got hum. I had to change the earth on the input and output plugs to earth directly to the star earth. This eliminated most of the hum.
http://www.diyaudio.com/forums/audi...cial-gainclone-kit-building-instructions.html
While I ran the input and output wires like this I got hum. I had to change the earth on the input and output plugs to earth directly to the star earth. This eliminated most of the hum.
http://www.diyaudio.com/forums/audi...cial-gainclone-kit-building-instructions.html
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There are a few ways hum can arise.
Some sources run better with or without the audio zero volt line connected to earth.
i.e. my ipod likes an earth on the zero volt line but my cd player (already earthed) doesnt.
It can arise from poor decoupling of the power supply.
The driver part of the amp should be decoupled with an RC filter in both + and - legs.
One of my early designs had a hum problem and it just needed a larger R in the RC supply filter to the driver stage.
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Returning to questions posed by Corben answers in order.
Yes Do both channels hum?
No - Does it hum when no source is connected?
Yes - Does it hum when there is no signal from a connected source?
No - Does the hum go away if the amp and the source are connected to the same power strip?
All my equipment is on the same power outlet.
When replaced with my Musical Fidelity P270-2 there is no hum.
Yes Do both channels hum?
No - Does it hum when no source is connected?
Yes - Does it hum when there is no signal from a connected source?
No - Does the hum go away if the amp and the source are connected to the same power strip?
All my equipment is on the same power outlet.
When replaced with my Musical Fidelity P270-2 there is no hum.
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