Phantom powered buffer/converter for passive Eq.

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Jean Clochet

Well-known member
Joined
Jun 25, 2011
Messages
387
Location
Currently taking a break to smell roses and the co
Hi,
here is a pdf of a phantom-powered buffer/impedance transformer circuit for use with something like posted here:

http://www.groupdiy.com/index.php?topic=43859.340

It allows to use a mic pre for making up the gain from a passive eq.  I speced the Jensen transformer but was told the Cinemag is the same but cheaper so, use that one  :)

Fig. 1 is the simplest version.

Fig. 2 has a few more parts to improve linearity and noise a little.

Fig. 3 shows the example of using a Neve output traffo instead of the Cinemag.  This version has a switched 12dB pad to put the output signal closer to mic level.

Thanks,
Jean.
 

Attachments

  • Phantom Powered Eq Buffers.pdf
    62 KB · Views: 75
Here's a version with a 'Blend-In' control to add back some of the uneq'ed signal.  I found that this can be useful on pultec eqs for instance:
You may be want to use maximum boosts and cuts to push the frequencys you eq'ed outwards (higher and lower frequency) and leave the middle alonr, but this can sometimes be too much actual eq.  If you add back in some uneq'ed signal, you are left with just the eq bumps at the bass and treble which might be nice.  You can get interesting effects anyway.
With the values I wrote, the amount you can add back in is from zero to 8dB above the eq'ed signal. I'll post some curves showing the 'blend' control in use later.

Thanks.

ps: The input traffo shown (10K:10K) is optional.
 

Attachments

  • EQ Buffer With Blend In Control.jpg
    EQ Buffer With Blend In Control.jpg
    240.1 KB · Views: 74
Back
Top