Toshiba ST-420 Tuner's Unusual Features

[cscottrun4it]

Hey, all. I'm pretty well versed in the world of vintage audio, but I'm not well versed in vintage tuners. I picked up a Toshiba ST-420 for a song. It has some interesting features/settings, two of which I'm not sure what to do with.

• The tuner has something called a 25/50/75µs de-emphasis switch. It's on the back of the tuner near the antenna connects. I think the symbol µs denotes microsecornds, right? Why would i want to de-emphasize time? The ST-420 doesnt seem to have a setting turn this feature off, so i get i have to de-emphasize something. What the heck should I "de-emphasize?"
• The tuner has an "air check level" toggle. What is this checking?

The tuner also has a dial to control its output. I assume this control is meant to support recording, but am I missing something here?

Thanks for any help anyone can offer.

 

[Punker X]

FM broadcasts have a pre-emphasis to the high end this helps eliminate the hiss that is inherent in the MPX decoding process. In the western hemisphere we us 75usec, the rest of the world uses 50usec. For a short time in the 70's there was a dolby broadcasts, and those were in 25usec. You would use the air check and level controls to record those broadcasts.

 

[cscottrun4it]

So which section should I use? The 75 setting?

 

[chazix]

Yes. 75 is the appropriate setting for CO and neighbors.

The idea of the "air check" is to set your recording deck for 0dB on the deck's VU meters. Usually, anyway, in the unlikely event that I remember correctly. In the extraordinarily unlikely event that this matters, it would be good to consult the tuner's owner's manual about it.

Cheers,

chazix

 

[cscottrun4it]

Thamks, chazix. I used that setting. It is really remarkable how that makes a difference in both reception and sound quality.

Back in the day, my parents bought a Marantz 2222b. It has the Dolby FM feature. My parents bought the receiver because of this feature, as they listened to broadcast music almost exclusively.

I remember the sound quality of FM when a station offered a Dolby signature: it was really good. Out here in Denver, FM KHOW never sounded so good, but the FM version of KHOW didn't last long. KHOW went back to AM and Allan Berg in the evenings. Allan was an entirely different experience for a 10 year old.