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Capacitors

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Graham Slee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2019 at 2:56pm
Thank you for your suggestion but I need the references which fit my hearing; room etc, and without them I would not have been able to develop the products that you currently enjoy. This is not a dig.
Not simple enough for Google-Bot to understand...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DogBox Quote  Post ReplyReply Direct Link To This Post Posted: 28 Mar 2019 at 3:57am
Back on page 3:  Once you have your Genera built and run-in a few weeks, tag a 0.1 - 1.0 uF film cap across C9 (under the board) and tell us what you found? Give it a week to bed-in though. 

Graham, should (per the Genera Phono Preamp Part 1:) a definite change be audible where "The op-amp reference voltage is set by a simple resistor potential divider R11 and R12, and bias current is provided by R2, with a capacitor C9 to ground which provides power supply noise rejection for the inputs...a large value to prevent 'motor-boating' - the power supply could cause oscillation by feeding back into the inputs."  

So the 'biasing capacitor' under the board should make the 'circuit noise' even quieter?  

Also, from page 2 of the Phono Preamp Project forum you put up a Simplified Active RIAA filter courtesy of Walt Jung and I looked at the filter and how it was structured with R1 then C1 and R2 in series paralleled over R1 and further C2 paralleled over R2... 
 Are there different ways of doing this but a way that is arranged such that the phase and filter will work together and not compete and throw the other out? 

I am sure you will tell me how far wrong I am but please... be gentle. 

My copy of The Art Of Elect. came - Hardcover and weighing in at 10 pounds!...well, it IS heavy!  
So very grateful for your Help! 
[I'll get to the MC side of things next...!] 
Grateful, 
DogBox 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 28 Mar 2019 at 11:14am
1. It is more about unintended signal feedback and its effect on the sound. The image on this page may help? https://www.murata.com/en-eu/products/emiconfun/capacitor/2013/02/14/en-20130214-p2

2. There are a number of "best fit" equations for obtaining the "right" curve, as well as a number of configurations which essentially achieve the same thing. But having tried just about all of them in my lifetime (so far), my hearing tells me they all have subtle differences, and I have chosen the configuration which suited my hearing best.

When using the "best fit" equations we soon find that at some gains they don't fit at all, but in mathematical modelling domains are taught (which illustrates this fact), and so if you look at some switched-gain (MM/MC) circuits you will notice the apparent lack of education!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 28 Mar 2019 at 4:21pm
You might also wish to read the article by J.L. LINSLEY HOOD starting on page 261 (page 57 in Acrobat viewer) https://www.americanradiohistory.com/Archive-Wireless-World/80s/Wireless-World-1989-03.pdf

It also gives us a clue as to why the liberal use of little red Wima polypropylene capacitors in high-end products might not lead to the expected results... Shocked

He should know his stuff (that should be past tense as he died in 2004) having been an engineer in "plastic films".


Edited by Graham Slee - 28 Mar 2019 at 4:23pm
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