RB1080 strange sound after shutdown

[Jj157]

Hi,

I have the RB1080 that makes a strange sound a couple of seconds after shutdown.
It sounds like a high frequency whistle and is no longer then a second. It comes through the speakers. It is like pfffieeewwwt

Hope someone knows the problem or can give me some tips ;x(

[madmac]

Well........Rotel's are known for their strange (or shall I say different from other brands) sounds at start up and shutdown!! All I can recommend is that you check all your wiring and power connections. Make sure the power connection is properly grounded. Also, does the unit make this sound only with a specific source choice selected (ie...CD) or does it happen regardless of what source you were listening to before shutdown?

[Glen B]

That model Rotel amp has no output relay to disconnect the speakers. What you're hearing is the sound of the power supply main filter caps discharging. It's nothing to be concerned about, just an annoying sound.

[Jj157]

Thank you both for taking the time to reply!i discovered that the sound comes only from the right speaker and only after i used the amp for more then 1 hour. Does this still mean it is related to the powersupply? I have someone in my family that is good with electronics. Is there something i can have him adjust or replace?

[Glen B]

One channel or two channels, same issue of power supply discharge. An output relay solves the problem of hearing amplifier turn-on/turn-off noises. Manufacturers may emit relays in the interest of sonic "purity" or to reduce costs. Most such amps rely on DC rail fuses and output fuses as the only protection. If the output stage suffers a catastrophic failure, it is possible for the entire DC power rail voltage to be dumped into one's speakers.

At least with properly working DC detection/overload circuity and output relays for each channel, there is a greater chance they will open instantaneously, and disconnect the speakers. To retrofit output relays into an amp, the job has to be done properly, so as not to look like a hack job.

I have retrofitted DC protection circuitry into amps that didn't have output relays, including my 1970s Phase Linear amp (popularly known back in the day as "flame linear"). Power to operate the circuitry in this case was obtained from the amp main power supply rail, through a voltage divider network (tiny PC board to the right of the two main caps),

[wkhanna]

OMG, that PL is gorgeous!