Erik's pre for measuring mic

[MethMan]

I'm pretty sure that lots of you are very familiar with EW's preamp2 design.
I've got into troubles with availability of LM6134 and LM4040 shunt reference. Only easily available shunt reference seems to be LM336Z 2,5 and TL074 opamp.
Is it interchangeable without additional changes or the resistors values R1-R4 must be changed? I'm very incompetent in these things. Can anyone help me?
Tomas

[soongsc]

There are some kits from Madaboutsound that is the EW pre.

[Henrik Juhl]

Had the same problem with availability of parts in Denmark. Ended up buying a kit from H.E.L.

https://securewsch01.websitecomplete...t.asp?dept=629

12$ for the PCB additional 25$ for the components. Assemblied but not yet tested

[soongsc]

http://www.madaboutsound.com/prod.asp?pname=MPK

[jbateman]

There was an older version that didn't require any specialized components. It's what I built years ago and it works fine:
http://www.akustyk.com/pomiary/hardw...%20preamp1.htm

[MethMan]

Thank for your responses.
I know Madaboutsound. If I compare price of the complete kit + sound card M Audio Transit vs. M Audio MobilePre USB without necessary interconnects etc., it's very similar.

jbateman, thanks for link. I'll probably do it this way. I´ve already soldered all parts on universal PCB and finished with 32x62mm. I will have to put the triple diode in air. Isn't two of them enough? Or can I use any kind of zener diode instead of them?

[jbateman]

I think the very earliest version of this circuit showed it could be either 2 or 3 diodes. I don't know what the reasoning was for this indecision, though. I'm pretty sure I made mine with just 2 1N914's...they're tiny.

With 2 diodes they would supply about 4.5vdc bias to the mic element. With 3 diodes they would supply about 6.7vdc to it. I can't imagine it mattering a whole lot in this application.

If you were to use a zener, you might need to change R1 in order to get the zener to operate. If you use 2 1N914's, just stand them vertically...no big deal. Leave enough space between them so that you could add a third one horizontally if you later decide you need it.