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Old 26th June 2012, 08:25 PM   #1
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Default Amplifier Issues....

The amplifiers are Rod Elliott's P3A
The preamp is Rod Elliott's P97

100W x 2 stereo amplifier, the power supply is a 300VA toroidal transformer with a 35A bridge rectifier and 2 15000uf, the preamp has Rod Elliott's P05 as its power supply and a small standard transformer for it (not toroidal)

Before I put it in the aluminum chassis it was working perfectly, low noise, high stability. After i put it in the chassis i get noise and the transistors seem to try to go into a thermal runaway when have an input connected but nothing playing and raise the volume high. i hook my ipod directly to the input of the amplifier, not through the preamp, and it works perfectly
I've checked for shorts there seems to be none

i notice i get more hum when i hook the house's earth to the chassis, and most of the noise goes away when i don't hook the house's earth to the chassis and hook just the amplifier's ground to the chassis

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Old 26th June 2012, 08:33 PM   #2
Did it Himself
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Location: Gloucestershire, England, UK
Are your RCA sockets isolated from the chassis?
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Old 26th June 2012, 08:36 PM   #3
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the ground of the RCAs are tied to the chassis and the positive is insulated, i disconnected the RCA and don't use them and i still have these issues
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Old 26th June 2012, 09:41 PM   #4
jaycee is offline jaycee  United Kingdom
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It's definitely a ground loop. Make sure signal ground is not connected to the chassis at all. Make sure you connect signal ground and power ground at only one place
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