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My attempts at a design of a 3 stage amplifier
My attempts at a design of a 3 stage amplifier
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Old Yesterday, 05:31 PM   #601
edbarx is offline edbarx  Malta
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Join Date: May 2018
I have not yet performed a Tian Test as I do not know what is the definition of variable 'u'. I also tried to do google searches to read about Tian testing but did not succeed to find anything. I would like to know what are the objectives of this test and why a theoretical constant current source and a voltage source are connected in series with the feedback resistance chain. As I may understand, the purpose is to inject some sort of frequency to evaluate the rejection effect of the feedback loop and Miller Capacitance.
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Old Yesterday, 06:08 PM   #602
mjona is offline mjona  New Zealand
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Join Date: Jul 2007
Location: Upper Hutt
Headphones used to come equipped with that sort of plug commonly referred to as a Jack abeit the socket on a domestic amplifier was an output.

I assumed that stage equipment had moved on to XLR connectors - I know this style of Jack was used for mixer and amplifier connectors back in the 70's. Stuff that old of passing interest only is not in my instant recall.
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Old Yesterday, 06:11 PM   #603
mjona is offline mjona  New Zealand
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Join Date: Jul 2007
Location: Upper Hutt
Headphones used to come equipped with that sort of plug commonly referred to as a Jack - albeit the socket on a domestic amplifier was an output.

I assumed that stage equipment had moved on to XLR connectors - I know this style of Jack was used for mixer and amplifier connectors back in the 70's. Stuff that old, of passing interest only, is not in my instant recall.
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Old Yesterday, 08:54 PM   #604
mjona is offline mjona  New Zealand
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Join Date: Jul 2007
Location: Upper Hutt
Quote:
Originally Posted by edbarx View Post
I have not yet performed a Tian Test as I do not know what is the definition of variable 'u'. I also tried to do google searches to read about Tian testing but did not succeed to find anything. I would like to know what are the objectives of this test and why a theoretical constant current source and a voltage source are connected in series with the feedback resistance chain. As I may understand, the purpose is to inject some sort of frequency to evaluate the rejection effect of the feedback loop and Miller Capacitance.
See Plotting Loop Gain Using the Tian Method - Spring 2011
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Old Today, 07:51 AM   #605
edbarx is offline edbarx  Malta
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Join Date: May 2018
Two Grounding Omissions Found!

a) two large current loops with areas exceeding 100 square centimeters were found. These are formed by the output conductors feeding the output PCB. One of them is almost touching the transformer! Both amplifier channels have these loops with the one having its loop almost touching the transformer exhibiting the loudest hum/buzz/noise.
b) the grounding of the amplifier modules is trough a large aluminium plate at the bottom of the amplifier box. Lifting this plate off the box's base, I found there is paint insulating it from the box. Checking with an Ohmmeter, I found it is completely isolated from ground! This means, the only ground path from the amplifier modules was through the capacitance formed by the amplifier box's base, paint and aluminium plate.

I have the intuitition, which can be wrong, that these omissions may have forced grounding currents to take strange abnormal paths, causing the hum/buzz/noise issues.

My not so efficient memory tells me the output conductors feeding loadspeakers are to be included in the elmination list of loop areas.

Last edited by edbarx; Today at 07:55 AM.
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