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Old 18th February 2011, 12:36 AM   #1
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Default ZEN V4 PLEASE HELP

ok so i just finished the build of a dual mono z4 using smps regulated supplies for the 50v power source. after running both channels for about 1.5 hour with nothing connected to speaker outs and rca the heatsinks stabilize at @58 c.
now my real problem starts. when speakers are connected all is well, no noise heard from ripple or other wise. BUT when rca's are connected things get crazy! weird crackle sounds and such that are obvious that something is very wrong. now when i just insert the rca so just the center pin is making contact then no crazy noises and i can hear the audio as intended except at a very low level. now i have not installed the resistor from the earth ground to the rca ground yet. could this be causing all my problems? i dont see how it could but then again im on here looking for help. im a novice for sure although i have built a zen v1 that is working awsome. please any advice will be greatly appreciated as i dont have a clue as to where to start right now.
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Old 18th February 2011, 12:47 AM   #2
flg is offline flg  United States
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Let's see, yes it could. Could be the imfamous ground loop?
Very nice looking by the way.
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Old 18th February 2011, 12:51 AM   #3
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really? could the lack of having a ground from the rca jacket to earth be causing all my problems? why is it when the center pin is the only part of the rca connected i do hear some audio but at a very low level? will this also be corrected when the ground is resolved? im all ears.....
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Old 18th February 2011, 01:01 AM   #4
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i forgot to add when the rca is completely plugged in there is no sound out of the amplifier at all except the hidious crackles and such
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Old 18th February 2011, 01:07 AM   #5
flg is offline flg  United States
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When the center pin is connected you have some sort of ground connection. Possibly only capacitive?
When the connector is all the way in??? Do you have a coupling (DC Blocking) capacitor in the input or the output of your source? Do you have a resistor to ground on the gate of your input FET?
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Old 18th February 2011, 01:10 AM   #6
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Nice, Nichicon and Orange Drops? Looking good.
Please clarify: You take the 'hot' signal from your source, but not the ground? In other words, are the ground of the source and the ground of the amp meeting somewhere?
What is the source? Is the source's ground connected to earth (safety) ground?
Is the amp's input ground connected to the circuit ground?
Is the circuit ground connected to the earth (safety) ground?

Too many questions, and too many Budvar...
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Old 18th February 2011, 01:17 AM   #7
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Nice, Nichicon and Orange Drops? Looking good.
Please clarify: You take the 'hot' signal from your source, but not the ground? In other words, are the ground of the source and the ground of the amp meeting somewhere?
What is the source? Is the source's ground connected to earth (safety) ground?
Is the amp's input ground connected to the circuit ground?
Is the circuit ground connected to the earth (safety) ground?

Too many questions, and too many Budvar...
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Old 18th February 2011, 01:22 AM   #8
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first the source ground and the amp ground are not connected in any way when i do get some sort of audio. second, the source is a b&k cs-117 preamp and is grounded through the ac line with a 3 prong plug. third, the amps rails are in no way connected to the earth unless the regulated supplies are doing that for me internally. the earth is connected to the input of the power supplies and thats it.
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Old 18th February 2011, 02:47 AM   #9
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lol, it got quiet here. i have found that the case of the smps's are conducting in some sort. my dvom is at work so i wont know in what way till tomorrow night. what i did do is dismount the power supplies and isolate them from the chassi then tried to plug everything in again. now the rca's can be plugged in and all is well on one channel(explain after). but still the gain of the amp is very poor. my preamp has a 9vrms out and at full crank the sound is barely above a whisper.
now one of my channels is down, no sound and the regulated supply bleeds down on power off almost instant. so ive got an excessive load somewhere on the board now. im not to concerned about that right now as i can just replace some common parts that would fail under conditions such as mine. so now my main question is why is the gain so low? any ideas why i would have to pump so much voltage to hear anything on the output?
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Old 18th February 2011, 07:32 AM   #10
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you must give us either proper schematic of wiring , including chassis safety gnd , or several decent macro pictures
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