Noise Measurement Amplifier

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#42
Hi Jesper,

The whole idea of providing a link is that you do not have to go through the effort of typing/copy in every part number.
Project:SG LN preamp has 56 parts in it, so that's a lot of duplicate work.
Well I was lucky this time, as I had the parts list in two places on Mouser, in projects and in shopping carts.
I realize now, that folks with the shopping cart link can go in and change quantities, so if one changes it to "0" it deletes the item from the cart.

There is no way to make a shopping cart "read-only". You can make a project "read-only", so that is what I have done.
From now on, I will never post links to a Mouser shopping cart or even a project list, so others can't mess with them and "f" them up.
I am not sure if is the way it happened but can you imagine that someone purposely did this, does this forum contain one or more a$$holes?
If someone requires a link, they will now have to PM me from now on, so I know who I am dealing with.

Rick
 
#43
Hi Rick,

Yes, I can understand that it may be "dissatisfying" to have things altered or outright erased ... However, my thought about the BOM relates to the ability on Mouser to fully import a spreadsheet's content, and thus in this case all 56 components in one fell swoop. In this way the BOM spreadsheet could be attached to a post here and then you didn't really have to think about it ...

You may of course already know about this - otherwise I can say that in my experience this feature works quite well 😉

Again - just a thought ... Cheers, Jesper
 
#45
There were substitutes in my shopping cart that’s now erased by the unknown a$$hole member.
After this last experience, I do wonder why I should help anyone in this forum.

Jesper , thanks for your suggestions, I am aware of and use Mouser’s methods to import BOMs, the correct data has to be put in the BOM to begin with, so it can become a chicken and egg situation.
 
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#46
As I mentioned before I think you are barking the wrong tree by putting your efforts on extra low noise measurement.
With the EMU USB soundcard I measured the 7818 linear regulator (left input channel)
 

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#49
So I tweaked it with the help of this measurement setup.
As a result the switching regulator now outperforms by far the linear regulator in the most audible mid range
 

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#52
for the PNP, maybe BC860C. If present, ",215" denotes only the original wheel size IIRC.
I don't know if the 120V are important. I don't want to delve into the schematics,
I have enough to do with the n+1. version of my own amplifier.

< https://www.digikey.de/de/products/detail/nexperia-usa-inc/BC860C-215/1232367 >

For the FET, I have no idea. With a cutoff voltage between 1.8 and 9 V
and Idss between 4 and 16 mA I wonder if they guaranty anything other
than that it does hit the barn door when thrown from a 1 meter distance.

< https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/1167/MMBF5460-62.pdf >
 
#57
the noise equivalent bandwidth (brick wall effecive bandwidth) is not specified , and depends on the low pass slope. if I remember correctly a 6db/oct LP has a 1.67 times the 3dB bandwidth effectively. assuming white noise you then can calculate the noise density.
 
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