[wonderwrench]

Hi Dave - and welcome!

The tweeters should not be really loud in a 38-690 - they should be noticeable, but not overpowering. This is unlike the 37-690, the tweeters of which are really TOO loud.

Just by shear luck I read your post in my Crosley Broadcasting Corporation thread.
http://philcoradio.com/phorum/showthread.php?tid=1245
I did some research on NRSC as you suggested.
http://www.nrscstandards.org/download.as...SC-1-A.pdf

I think I found the reason why the 37-690's tweeters are so bright. AM broadcasts have preemphasis in the high frequencies. This was never done in the old days. WLW was flat 20-20 KHz. My father was an engineer at KSTP for over 40 years and they were flat to 15 KHz even after the limit was changed to 10 KHz. When he retired about 18 years ago preemphasis on AM did not yet exist. Also note receivers today are required to have deemphasis. I'd guess this is done to cut down on interference and noise.
[Image: http://i156.photobucket.com/albums/t25/w...sc/Pre.jpg]

[Image: http://i156.photobucket.com/albums/t25/w...sc/Dee.jpg]

I did some looking at the spec's on my fathers SSTran AM transmitter and it has a treble boost function. I'll have to check to see if it is enabled.
I bet it is by default and I was to dumb to know any better. It would explain the bright treble on the 37-690 when using the SSTran.


Thanks everyone, I learned many things today.