Audio Sampling

A friend is looking to buy an A-70 Pioneer amplifier. Don't get me wrong - I like Pioneer stuff. But why does it have a 192 kHz/32-bit DAC?

I was relieved to find a sane, comprehensive article that clarifies all.

Ultrasonics - and a relevant story

A relevant and also a true story...
A long time ago a friend, Rod, built an audio amplifier. (We're talking 1974!) This was his own custom design, with large homemade chipboard speakers. Rod connected the amp to a television sound circuit. (FM discriminator - removing those nasty capacitors that would affect the treble.)

He was enjoying the "Old Grey Whistle Test", a music late night programme where the production team really cared about high quality sound. 

His amplifier was at a generous volume... nice and loud!

The programme ended. BBC2 signs off: "That's all for today - goodnight!"

BBC2 closed down for the night...Rod's tweeters blew up when the transmitter began to close down... A 19 kHz sub-carrier was used to control transmitter shut-down.

This link explains all. An extract follows...

"A low-level 19-kHz continuous tone is inserted at the  input of the sound transmitter and detected at the output. Standby arrangements are brought into service if this tone fails. At stations receiving signals off-air, the incoming 19-kHz tone is used to control the changeover to the reserve receiver. Incoming tones are removed from the signal before the station's own tones are added.

Some parent transmitting stations use a dependent relay station as an alternative programme source. When the parent station loses its incoming programme, the 19-kHz tone at its output is pulsed, causing a detector at the dependent station to change over to a reserve feed. A few seconds later, the parent station automatically changes over to the dependent station. As soon as programme is available at the parent station from its normal source, it automatically reverts to that source and restores continuous transmission of the 19-kHz tone. The dependent station then returns to its normal source the parent station.

In addition to the executive 19-kHz tone, a 23-kHz phase- modulated subcarrier is also used for providing monitoring information to a remote centre."

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