Impedance/Load Questions - Ampex, Millennia preamps, etc.

[laoded]

hi everyone and happy holidays! first time poster here.

i've started working at a new studio, and have gotten some strange results with mics and preamps. wasn't sure with what was going on, so i did some research...i think what i've been experiencing are impedance mismatching.

the Ampex MX-10 and Millennia HV3 were used for some tracking. I ended up going with a couple Earthworks mics into the MX-10 for some Toy Piano stuff. got some interesting tones. then, using the same mics, i tried tracking some glockenspiel into the mx-10 in mono, and all i got were a-little-too-interesting, ring modulating-type sounds. so, we used the millennia pre and got more "standard" sounds (not that the ampex sounded bad).

just looking at the royer cheat sheet says that royers work best with a preamp that has at least a 1500 ohm impedance or else the signal will lose low end and body. and the earthworks are at 600 (meaning 3000 impedance is best?)

how can i change these loads so the ampex pre (200 ohm rating) can handle these mics better?

perhaps a -20 pad would have helped with the ring-modulating and distorting of the ampex pre, but would these impedance mismatchings also be a cause for harsh sounds?

thanks!
gene

[brianroth]

It's possible that the Ampex was being overdriven. An input pad might be in order, and with a lossy pad, it's also possible to do better impedance matching.

Bri

[laoded]

thanks for the reply! what are some ways to adjust impedance mismatches (asides from trying a different mic or preamp)?

[brianroth]

If you can accept the signal ooss, a pad can be designed to have differetn input and output impedances. Typically, you would use a pad with, say, 1500 Ohms input impedance to appear like a typical input stage, and a 200 Ohm output impedance so the transformer "thinks" it is seeing a mic's output. My friend Rick Chinn has written a general paper about pads:

http://www.uneeda-audio.com/pads/

Bri