| This article is based on a
message written by Simon Williams |
||
| After placing the keyboard on top of two
speaker cabinets used as a p.a., during the playback of
strong bass notes from the PSR I noticed some internal
feedback was occurring. It appeared that the microphone input circuitry for the harmoniser was picking up signals from the speakers, causing periodic low frequency sounds to come from the internal amplifier of the psr740. I moved the keyboard away from the p.a., but then every time I switched on the keyboard (even by itself) a periodic low frequency thumping would come from the speakers, even with the volume control set to zero. I was sure that the internal power amplifier was at fault since plugging a headphone jack into the phones socket to mute the onboard speakers would stop this interference. |
Anyway the strange thing is that I left
the keyboard disconnected overnight and this morning
decided to try it again. Guess what? The interference had
gone! It seemed that the internal audio amplifier chip had become saturated, possibly from the acoustic coupling between the p.a. and the input circuitry of the keyboard. After several hours though the circuitry had recovered and now the keyboard sounds fine. In summary, I recommend that you don't place your PSR 740 on top of speaker cabinets used as your p.a.! If the problem does happen and your psr begins to emit a periodic low frequency thumping from its internal speakers every time its turned on, leave it switched off for a day before trying it again. It seems that the internal amplifier takes a while to recover! |
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