Mic Preamp Schematic Collection

[opacheco]

You might want to experiment with a few parts and see what you get.

It looks like the 3391A may be a low noise part (or lowest of that series) The 3390 is higher beta tho..But specifying NF at a few hundred ohms and using it at tens of K makes NF academic.  They are a 500mA part (good for low Rbb) but clearly a lower current part could be used.

From looking at the impedances around that circuit I would suggest a decent low noise JFET (for at least Q1, but you would need to revisit the DC biasing scheme.

JR

I made some electronic analysis and the ICQ1 + ICQ2 =210 Microamperes aprox. when power supply is 40 volts aprox. Which ones transistor will be good in order to start this experiment process???.....I can do a biasing change for JFET or Mosfet but Which ones will be a good parts for start???

Thanks a lot for your interesting comments!!!!
Opacheco.

 

[JohnRoberts]

I'd try a 2sk117  nice low noise JFET but it may be better than you need.

JR

PS: This should probably be in a new thread rather than Hijack and add noise to Sam's preamp collection

 

[opacheco]

I'd try a 2sk117  nice low noise JFET but it may be better than you need.

JR

PS: This should probably be in a new thread rather than Hijack and add noise to Sam's preamp collection

Really???......I will do a test with this Jfet.

Sorry for my incistence but I would like to know What Transistor BJT will be better than 2N3391A and 2N3417?

Thanks for your comments and advises, that is very important for me!!!
Opacheco.

 

[speakercoil]

Why is it when I try to download these I get an error message...

-Grant

 

[JohnRoberts]

Why is it when I try to download these I get an error message...

-Grant

Perhaps Because they changed the BB software between when those links were created... so the old adresses don't work..

This was discussed already probably in this thread, but if you are web handy you can figure it out from looking at the old links and some new ones.

old    http://www.groupdiy.com/www.sg-acoustics.ch/analogue_audio/microphone_preamplifiers/pdf/A_r1.pdf

new-  http://www.sg-acoustics.ch/analogue_audio/microphone_preamplifiers/pdf/A_r1.pdf

JR