Earthing of Amplifiers And Hum.

[Audioman]

An interesting problem and one that may interest the techies on the forum.

On introducing a Denon Universal player into my system I had peristent buzz/hum problems when switched on. This is worse when switched to outputs other than those to which the Denon is connected.

The amp is a Pioneer 400X. The amp is earthed through 3 core IEC and the Denon has a unearthed 2 core IEC. Other similarly unearthed components have never caused a problem.

Now the Pioneer does have a noisy volume pot which I thought may be contributing to the problem. Have taken it out to clean and service the vol pot. In meantime I have an inherited Rotel 840BX3 which has been hardly used for years. Put this in the system and the hum/buzz is gone. Has a captive lead with no earth.

Conclusion is earthing regime causing the problem or clash of earth arrangements between Denon and Pioneer. Interestingly though there is no path to mains earth now (except the QC power supply from the Gyro?) There is no issue with deck/arm earthing. The amp has an earth terminal for a record deck which is not used at present due to the Rega arm wiring and separate phono stage.

Would like some technical insight that may aid solving the 'incompatability' with the Pioneer amp. Or could any internal mod on the Pioneer solve the problem. Leaving it unearthed is likely a dangerous option.

BTW the Rotel is rather good and superior to the Pioneer in some respects especially bass and timing. Still in effect burning in after a 17 year rest.

[Reffc]

An interesting problem and one that may interest the techies on the forum.

On introducing a Denon Universal player into my system I had peristent buzz/hum problems when switched on. This is worse when switched to outputs other than those to which the Denon is connected.

The amp is a Pioneer 400X. The amp is earthed through 3 core IEC and the Denon has a unearthed 2 core IEC. Other similarly unearthed components have never caused a problem.

Now the Pioneer does have a noisy volume pot which I thought may be contributing to the problem. Have taken it out to clean and service the vol pot. In meantime I have an inherited Rotel 840BX3 which has been hardly used for years. Put this in the system and the hum/buzz is gone. Has a captive lead with no earth.

Conclusion is earthing regime causing the problem or clash of earth arrangements between Denon and Pioneer. Interestingly though there is no path to mains earth now (except the QC power supply from the Gyro?) There is no issue with deck/arm earthing. The amp has an earth terminal for a record deck which is not used at present due to the Rega arm wiring and separate phono stage.

Would like some technical insight that may aid solving the 'incompatability' with the Pioneer amp. Or could any internal mod on the Pioneer solve the problem. Leaving it unearthed is likely a dangerous option.

BTW the Rotel is rather good and superior to the Pioneer in some respects especially bass and timing. Still in effect burning in after a 17 year rest.

Just written an article on this very thing which you can find HERE (http://referencefidelitycomponents.co.uk/hum-a-merry-tune-the-dreaded-earth-loop-hum/)

It sounds like the problem may be an earth ground loop whereby the mains earth and signal ground are intermingled and the signal earth is carrying mains noise and capacitively coupling this to the signal, hence the 50Hz hum.

It can be cured by installing an earth lift circuit between the signal star earth and chassis earth of the amp, or you could try earthing the interior chassis of the (double insulated) universal player if that's easy enough for you to do (and if that doesn't work, install an earth lift on the amp). The alternative is to use a full bandwidth 1:1 transformer between the universal player and amp.

[Audioman]

Just written an article on this very thing which you can find HERE (http://referencefidelitycomponents.co.uk/hum-a-merry-tune-the-dreaded-earth-loop-hum/)

It sounds like the problem may be an earth ground loop whereby the mains earth and signal ground are intermingled and the signal earth is carrying mains noise and capacitively coupling this to the signal, hence the 50Hz hum.

It can be cured by installing an earth lift circuit between the signal star earth and chassis earth of the amp, or you could try earthing the interior chassis of the (double insulated) universal player if that's easy enough for you to do (and if that doesn't work, install an earth lift on the amp). The alternative is to use a full bandwidth 1:1 transformer between the universal player and amp.

Thanks Paul. Looks like the earth lift is the best option. I have looked into transformers and though a useful tool they are very pricey. Cheaper to move the amp on. A small circuit diagram would be a useful addition to that article. The strange thing is I assumed other components to be double insulated as well but no issues. Do most current amp designs include an earth lift to avoid such problems as it appears to be the more modern AV orientated stuff that causes these issues to arise?

Paul.

[Reffc]

Thanks Paul. Looks like the earth lift is the best option. I have looked into transformers and though a useful tool they are very pricey. Cheaper to move the amp on. A small circuit diagram would be a useful addition to that article. The strange thing is I assumed other components to be double insulated as well but no issues. Do most current amp designs include an earth lift to avoid such problems as it appears to be the more modern AV orientated stuff that causes these issues to arise?

Paul.

Some do and some don't. Of those that do, many, rather surprisingly do not include the very necessary bridge rectifiers there to allow a robust and safe path to mains earth. If you pm me your email details, I'll provide details of a circuit that I use which is pictured below. The white lead coming from the left os from "signal earth" and the one disappearing off shot to the right from the rectifier (small square device bolted to the chassis) is the connection to the IEC mains earth:

http://i1140.photobucket.com/albums/n577/24pacman/Hifi/_MG_6359_zps6bdc118b.jpg