aortizjr
Well-known member
In this thread:
http://www.groupdiy.com/index.php?topic=10417
There is a lot of talk about building a mic pre-amp with good EMI protection. With some of the nicer ones, they use Common Mode chokes/inductors to suppress EMI noise. Also with many of the designs available here, there are Ferrite beads and single inductors.
The problem is that theere are no values for these and I have had trouble sourcing parts. I lack the true understanding to really make decisions. And of course all companies have their different specs etc. etc.
So hopefully this will be a thread to clear this up for Mic pres.
The assumptions of the pre:
1. Already has some sort of Common Mode Rejection (CMRR)
2. Balanced Input (otherwise Common Mode would not be applicable). But I think the idea of the single inductor could apply to non-balanced applications.
3. Capactor shunts in place to ground. These are to roll off the higher (out of audio band) frequency ranges.
So looking at this schematic:
You see the inductors/ferrites and common mode choke. What would be ideal/available for these?
For good engineering and DIY, let's focus on stuff that is small, readily available, easily purchased in single quantities, and inexpensive.
There is some nice stuff out there, but having to E-mail companies, distributers, and dealing with high minimum quantities and ordering directly can be cumbersome. However, if we do go that route, perhaps provide information about purchasing these items.
In the next post I will post basically a summary of what I learned already with some additional questions.
http://www.groupdiy.com/index.php?topic=10417
There is a lot of talk about building a mic pre-amp with good EMI protection. With some of the nicer ones, they use Common Mode chokes/inductors to suppress EMI noise. Also with many of the designs available here, there are Ferrite beads and single inductors.
The problem is that theere are no values for these and I have had trouble sourcing parts. I lack the true understanding to really make decisions. And of course all companies have their different specs etc. etc.
So hopefully this will be a thread to clear this up for Mic pres.
The assumptions of the pre:
1. Already has some sort of Common Mode Rejection (CMRR)
2. Balanced Input (otherwise Common Mode would not be applicable). But I think the idea of the single inductor could apply to non-balanced applications.
3. Capactor shunts in place to ground. These are to roll off the higher (out of audio band) frequency ranges.
So looking at this schematic:
You see the inductors/ferrites and common mode choke. What would be ideal/available for these?
For good engineering and DIY, let's focus on stuff that is small, readily available, easily purchased in single quantities, and inexpensive.
There is some nice stuff out there, but having to E-mail companies, distributers, and dealing with high minimum quantities and ordering directly can be cumbersome. However, if we do go that route, perhaps provide information about purchasing these items.
In the next post I will post basically a summary of what I learned already with some additional questions.