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Chip Amps Amplifiers based on integrated circuits

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Old 11th April 2011, 02:46 PM   #41
AndrewT is online now AndrewT  Scotland
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I believe that the volume pot should be near or at least accessible to the operator.

That leads directly to my adoption of never putting the volume pot inside a Power amp.

The only exception would be an integrated pre-power located centrally.

Putting a pot near (but not inside) the power amp is making life difficult for the electrons.

that grounding resistor across the RCA Hot to SG can be anywhere from 100k to 2M2. I tend towards the upper end.
I also add a 47pF across RCA Hot to SG.
regards Andrew T.
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Last edited by AndrewT; 11th April 2011 at 02:49 PM.
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Old 11th April 2011, 03:55 PM   #42
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Not sure I follow you, the pot will be on the front panel, well the knob will, then there is a shaft and then the stepped pot close to the inputs.... It is an integrated design with the following flow; RCA > input selector>pot> amp>DC protection> output.

Last edited by digits; 11th April 2011 at 03:59 PM.
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Old 16th April 2011, 05:31 PM   #43
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Originally Posted by AndrewT View Post
The diodes pass the fault current.
The resistor makes the voltage reference.

Quite different jobs.

The resistor alone or resistor//cap can never pass fault current. To say that one has never seen diodes (along with resistor) in these locations indicates that we have Member who does not read safety advice and is a danger to anyone around who may operate his/her badly assembled mains powered equipment.
The M Stereo Headphone Amplifier
uses the resistor and cap
Jonokuchi desktop amp
pete uses the diode method
Elliott uses both
Nelson Pass uses thermistors

All have the chassis directly tied to earth. All my stuff has chassis directly connected to earth. All my stuff has signal ground Connected to earth via a 35amp bridge rec.

Back to your scenario:
In the amp there is a 10 ohm lift resistor from power ground to audio ground, connected to the rcas outside shell.
Power ground is connected to chassis via a cap/resistor in parallel and a full wave rec.
Chassis is grounded to earth.

At the power entry the hot breaks loose and touches and rca.
Amp turns off.
10ohm resistor that goes from audio ground to power ground blows.
Rca is now hot.
What comes next?

I consider this a worse case, but i cant think of a safety. Even if the fuse is in the power entry, and the break is after the fuse. The rca is isolated from chassis. The rca is connected to ground via either a resistor, or a piece of 30 guage, or a small trace on the pcb. None of these are going to pass enough current to pop the slow blow fuse before they smoke.

Im not arguing, im asking for help. Or we are confused on my grounding methods.

Last edited by nightanole; 16th April 2011 at 05:37 PM.
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Old 16th April 2011, 06:09 PM   #44
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Solution, dont place long live wires close to RCA.... if it can touch, its too close.
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Old 17th April 2011, 09:32 AM   #45
AndrewT is online now AndrewT  Scotland
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All exposed conductive parts must be connected to Safety Earth.
regards Andrew T.
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