I finally bought an SSTran transmitter (best money I've spent so far other than my radios themselves.) Up until now all I've had was what I was lucky to tun in from Tampa, which was iffy at best. So, after restoring a set, I didn't have much to test it with fully.

I've got a Farnsworth set that I had my doubts about, but man can this thing belt out some sound. But after a total of a couple hours playing it, I'm noticing some distortion on S sounds. Anytime a someone sings a word with and S sound the S sounds like static. Also, "Nowhere to Run" By Martha Reeves just played - that's when I turned it off. The tambourines in that song really got lost in translation. I doubled checked the SSTran settings, and turned on my Philco, and no problem.

Here might be the tough part - the case is a Model ET-061, but I know that's not the chassis in it. The ET-061 had shortwave, and the chassis only has AM. So, some similar model that's AM only.

My guess is a tube getting weak, and I will have to pull them when I've had a bit more sleep, but they had all tested good during restoration.

By the way, this was a free table find radio at the Sarasota Antique radio meet a couple years ago.

Michael, I would check:
1)Source material for the SSTran (assuming you set it for flat response, no high
boost). Some of the stuff on the 'net especially can have too much high end,
giving the blasting sibilants, "or crushed glass" effect. However, if it sounds okay
on your Philco, it's probably okay.

2)Tuning of your Farnsworth right on the signal. Usually that's the "bassiest"
sound on AM. Some people actually tune slightly off to one side, to get more sideband
treble if their radio sounds like it's playing through a pillow. But it's hard to get just right.
The Farnsworth may have drifted just enough after a couple of hours to do that.

3)The alignment of the Farnsworth. If one or more IF primaries or secondaries are
slightly to one side or the other of the IF frequency, it will reduce the sensitivity AND
broaden the bandwidth to give you (possibly) too much treble. That's called "stagger
tuning" and is used intentionally in some circuits.

Now is the time for wiser heads to weigh in....

Nelson

I'll check the alignment and see. The source is my ipod, I'm sure that's not it. Also, the sound out of this thing is actually pretty good, otherwise. The Philco has that pillow sound a bit, but the Farnsworth did a lot better than I thought it would. In fact, other than this distortion that has started, I'd say it's every bit as good sounding as my car's AM radio.

I have noticed the exact same audio problem connecting my Sony-brand MP3 player to my SSTRAN.I was thinking that it may be caused by an impedance mis-match,but that really didn't make sense as my old Sony mp3 cd player sounds just fine through it(with audio cds).They both have 32 ohm headphone impedance.

Then...the other night I connected the MP3 player to my computer to recharge.As it was doing so,I decided to connect the headphones to the jack on the computer and listen to the files on the player.

I got a quick lesson on just how putrid MP3s really sound.I had ripped the audio cds to MP3 format at 192 kbps.With headphones on,they really sound bad.I had also previously attributed a rapidly fluctuating unsteadyness in the audio level to the SSTRAN.I soon discovered it was the MP3 player.

I recently posted about an impedance matching device I built using plans I found on the internet.It is nothing more than a couple of small Radio Shack audio output transformers .This device DOES clean-up the audio a fair amount and boost the signal level output of the connected portable device,but it can do nothing for poor sounding MP3 files.As they say,garbage in=garbage out.

I have been mentioning on several posts recently, that you need an iPod Dock Cable to get good sound. It has a 30 pin plug on one end, two RCA plugs on the other end, which you can combine with a Y-adapter. This cable gets the line-level output from the iPod instead of the headphone amplifier, and makes a very big improvement. Amazon.com has plenty to choose from.
Don

One 12SK7 and one 12SQ7 later and it's all better. The 50L6 was showing weak on the tester, but the thing blasts so I think in practical application it's just fine, at least for now. Martha and Vandellas sound as they should.

Good stuff, Michael. Seems your suspicion about the tubes was right on.
And it proves again the only real test of a tube is how it functions in a radio.
Nelson

a "virgin" MP3 file at 192Kb/s should sound as good as the original CD they were taken from. By "virgin", I mean a file that hasn't been through the compression/decompression process a few times, as is often the case with stuff you download from the 'net. Make sure the sample rate is 44KHz and bit rate is at least 192 Kb/s and I doubt you'll notice much difference.

If you've done it that way then I would suspect a problem with your encoder

Looky here....

http://www.lincomatic.com/mp3/mp3quality.html

I think that in many modern recordings that are digitally produced, a heck of a lot of degradation can occur when converting to mono for use in our antique radios. There is often a lot of "artificial" stereo effect applied through the use of comb filtering and special delay and phase shifting filters. When the channels are combined to mono, all this is lost and additionally phase cancellation can occur resulting in a very disappointing sound. It all depends on how the original was mastered.
I've noticed that most older recordings, made before the digital age, seem to transcribe to mono much better than many newer ones. Not always, of course.