Inverse RIAA Filter

[sl-15]

I would like to get a inverse RIAA filter to measure and figure out channel imbalance in my vinyl system. I would use a test tone CD and then connect only one channel from my CD player to only one channel of the inverse RIAA filter. Then connect to the Eros and measure the output voltage one channel at a time. I found one inverse filter sold by hagerman for a reasonable price. I am wondering if there are other options out there and if anybody here has tried such a network for this kind of trouble shooting. I am also wondering if it will even make sense to measure the output voltage directly at the Eros without a load. Thanks, Best, Stefan

[Paul Birkeland]

The inverse filter isn't necessary here.  You can play tones into your Eros from a phone or tablet with an 1/8" headphone jack, just turn the volume so it's one click above mute.  Yes, the EQ will make the frequency response non-linear, but a channel imbalance is still measurable. 

[ccmccull]

I agree with PB.

See
  https://forum.bottlehead.com/index.php?topic=14214.0
for my work along the same lines, including a link to my google sheet!

You can do the inverse RIAA filter in math, see column I. LMK if I can clarify anything I did there.

[sl-15]

Ah, very cool. Thanks Paul for the tip. And I will check out the link to the other thread.

[sl-15]

What would be a good input voltage to test the Foreplay 3 extended or soon the BeePre2?

[Paul Birkeland]

I find that it's easiest to put 1V into the input, then your gain is just 20*log(output).