[TenTec] 509 schematic - audio filter

[Brian]

Good that you have the Autek on hand.
Not to stir the pot, but I can recommend the Mi Per Mite filter from 4 States QRP. I think it is VERY good. I built one and find it extremely useful on older rigs lacking a CW filter or with a so-so  CW filter. For instance, the CW filter on my Drake TR7 is not good.. either old or not to my spec..who knows? Anyhow, the HiPerMite makes it useful. I have used it on my fave TR4Cw even though it already has a xtal filter which is fine. HPM filter makes it all better. Similarly for older boatanchor receivers... at the minimum having the HPM in line makes it easier on those old mechanical switches on the BAs by not having to use them.

Anyhow, the HPM is only one of the great audio filters out there, but it is great and not expensive. Also good and worth consideration are the NESCaf filter from New England QRP (when the kit is available from the volunteers), the CALF audio filter, and filters from SOTA Kits.
But you cannot go wrong with the HPM... not a lot of money and it does the job. A recent posting on the HPM is in Bill Meara's SolderSmoke daily blog.
http://soldersmoke.blogspot.com/2020/02/ph2lbs-homebrew-hi-per-mite-cw-filter.html


My Triton 544 has the MFJ CWF in it.. basically the same as the TT audio filter you were seeking.

Brian VE3VAW