Altec 9470A Mic Pre’s

Posted by DibS in DIY      2 comments

Jan
11

I got a pair of Altec Lansing 9470A mic preamps from a fellow on Prodigy. I racked them up with a power supply that was modded from a spare SSL9k PS board (omitting the neg voltage and increasing the LM7818 to an LM7824). I was told that they are similar to a Langevin AM-16. They were designed by the same guy, John Hall, presumably around the same time and share a class A push/pull design. The Altecs have a somewhat more “hi fi” sound than the Langevin largely in part to the Peerless transformers that are on these suckers. More info here.

Please excuse the iphone pics as my Elph seems to have bitten it today. I’ll upgrade the photos at a later date. The only caps that I replaced are the only electrolytics in the chain: two power filtering caps. Another trait that these have in common with the AM-16s are the lack of electrolytics in the audio path. The rest of this job was just wiring them up and staying out of their way.

Edit:  In response to many emails, here are some links that should help others:

Edge conncector:
http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=EDC307200-ND+

SSL9k Power Supply on page 5 (I omitted the negative rail parts and subbed an LM7824 for the LM7818)
http://www.studio21.ch/diy/neeno/ssl9k/DIY_9k_preamp.pdf

The board for which can be ordered from Gustav:
http://www.prodigy-pro.com/diy/index.php?topic=10776.0

The toroid I used was this:
http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=us&keywords=TE62085-ND+&x=0&y=0

How to calculate a pad:
http://www.uneeda-audio.com/pads/

Manual and Schematic:
http://www.audiomanuals.co.uk/docs/altec/Altec-9475A-MicPre.pdf