Rotel amp - high pitch whistle after powering down

[ExPerfectionist]

I just purchased a used Rotel RB-1070 power amplifier over the weekend and have it hooked up to a Denon 3700h, connected with a 12v trigger cable, powering my mains (Ascend Sierra-LX). The amp is plugged into the same power strip as the Denon, TV, etc.

I have noticed that a couple of times (not every time/use) when I turn off the Denon, and the 1070 powers down, there's a high pitch whistle / slide whistle sound. I am not sure if it's coming from the amp or through the speaker/s. EDIT > The sound is coming from the right speaker only.

Upon doing some research, it sounds like it's probably the capacitors draining. And might or might not be an issue? Could be caps aging or another issue? Or might be normal for an amp like this because it stores up some power reserves?

Should I be worried about the longevity or about my speakers? Or is this normal for an amp like this?
This is my first external amp for home theater paring with an AVR.

 

[Oddball]

I have 5 of 1070's and none of them exhibit this behaviour. They are powering up and down pretty silent and are about 15 years old.

Perhaps try to open the amp and clean dust as a first step. Also, what is your power down sequence? If you power down Denon first, is there still this sound? If the problem persists perhaps best for some repair shop to take a look. RB 1070 is not that complex in design.

BTW if you could share with us how much did you pay for the unit that would be helpful.

 

[ExPerfectionist]

I have 5 of 1070's and none of them exhibit this behaviour. They are powering up and down pretty silent and are about 15 years old.

Perhaps try to open the amp and clean dust as a first step. Also, what is your power down sequence? If you power down Denon first, is there still this sound? If the problem persists perhaps best for some repair shop to take a look. RB 1070 is not that complex in design.

BTW if you could share with us how much did you pay for the unit that would be helpful.

Thank you! Good to know you haven't noticed the issue with your amps.

I paid $400, bought it from someone on Facebook Marketplace.

Power down sequence is turning off the Denon with the remote, which sends a trigger signal to the 1070 to shut down after the Denon is off.


I do have the amp plugged into a power strip that supports the Denon, TV, etc. as well, if that matters.

 

[Oddball]

Probably not a matter of power strip, would likely manifest with hum or some other issues. Can you try without the trigger and see it still persists? Trigger unit is a separate small cube-ish thing so perhaps something could have gone wrong in there. If that does not work, sorry but amp insides are way out of my depth. Double checking the cabling and making sure all is OK is also an obvious advice.

Not a bad price, I have seen people asking much more. I have treated my 1070s pretty good (except occasional party modes) so expect them to last for next 10 years at least.

 

[ExPerfectionist]

Thank you!

Will give those tests a try, and I've found a few repair shops in my area that I can reach out to if needed as well. EDIT > (welp - I called what looks like the most legit one and they have a 3-month backlog for repairs, drop off the unit and wait)

The RCA cables are from very old component video cables. I have a new set of cables coming tomorrow just to have higher quality and in case there's any degradation/rot in the old cables. But I don't think that would be the source of the sometimes whistle through the right channel.

 

[Gregss]

I just purchased a used Rotel RB-1070 power amplifier over the weekend and have it hooked up to a Denon 3700h, connected with a 12v trigger cable, powering my mains (Ascend Sierra-LX). The amp is plugged into the same power strip as the Denon, TV, etc.

I have noticed that a couple of times (not every time/use) when I turn off the Denon, and the 1070 powers down, there's a high pitch whistle / slide whistle sound. I am not sure if it's coming from the amp or through the speaker/s. EDIT > The sound is coming from the right speaker only.

Upon doing some research, it sounds like it's probably the capacitors draining. And might or might not be an issue? Could be caps aging or another issue? Or might be normal for an amp like this because it stores up some power reserves?

Should I be worried about the longevity or about my speakers? Or is this normal for an amp like this?
This is my first external amp for home theater paring with an AVR.

Hello, Sounds like the speaker output relay (one for each channel) is not working and disconnecting the speaker when powering off.
Best guess. Most fairly modern amps have these relays, at least for non class D amps.

Regards,
Greg

 

[ExPerfectionist]

Hello, Sounds like the speaker output relay (one for each channel) is not working and disconnecting the speaker when powering off.
Best guess. Most fairly modern amps have these relays, at least for non class D amps.

Regards,
Greg

Thank you!

Is that an issue that could damage the speaker? Fail completely and need to be repaired in order to function properly? Or just a quirk with the whistle sound?

 

[Gregss]

Thank you!

Is that an issue that could damage the speaker? Fail completely and need to be repaired in order to function properly? Or just a quirk with the whistle sound?

If it is the relay not operating correctly, just an annoyance, not likely to damage anything. Usual is the relays keep music from going to the speakers until things stabilize. And then shutting off the music to the speakers while power drifts down to zero. Best guess, I have seen this in real life.

 

[ExPerfectionist]

If it is the relay not operating correctly, just an annoyance, not likely to damage anything. Usual is the relays keep music from going to the speakers until things stabilize. And then shutting off the music to the speakers while power drifts down to zero. Best guess, I have seen this in real life.

Thank you!

 

[LTig]

Thank you!

Is that an issue that could damage the speaker? Fail completely and need to be repaired in order to function properly? Or just a quirk with the whistle sound?

The task of the relay is to protect the speaker while powering the amp and down, and also if the amp fails and outputs DC voltage. You should have it fixed.

 

[Oddball]

The task of the relay is to protect the speaker while powering the amp and down, and also if the amp fails and outputs DC voltage. You should have it fixed.

Agree completely - should have it repaired. As noted, not too complicated so local shop will probably do well.

 

[ExPerfectionist]

Thank you!

I'll see if I can find a repair shop. The first one I called said they have a 3mo backlog.

 

[Oddball]

Thank you!

I'll see if I can find a repair shop. The first one I called said they have a 3mo backlog.

Well they are a dying breed. We will soon run out of such shops and electronics will go straight to dumpster. But keep trying. This is not a complex job. They will be able to figure it out in hour or less and then fix easily.

 

[Extreme_Boky]

Thank you!

I'll see if I can find a repair shop. The first one I called said they have a 3mo backlog.

That amp does not have speaker protection relays... just the overtemperature protection. Even then (overtemperature condition), the relay shorts input signals to ground... still no protection at the output at all. So... if you have expensive speakers, make a decision if you'll keep the amp or sell.

 

[Oddball]

That amp does not have speaker protection relays... just the overtemperature protection. Even then (overtemperature condition), the relay shorts input signals to ground... still no protection at the output at all. So... if you have expensive speakers, make a decision if you'll keep the amp or sell.

As I said, the amp should be looked at by a shop that will understand what's wrong.

On my part, I can say that my 5 1070s have been performing admirably over the 15 years and have not damaged any of the expensive speakers. They were at times forced into clipping and thermal shutdown as the occasion called for extreme SPL, but they never damaged the speakers and went up as soon as they cooled down a bit. We are talking about full tilt volume that at that time was +18dB to reference.

 

[ExPerfectionist]

I took it to the repair shop today. Their backlog is about 2~3 months but hopefully will be a simple-ish fix, once it's up in the queue.

 

[LTig]

 

[Whiskey the Cat]

Just a thought, but are you sure that the problem does not lie with the Dennon? It could be producing the right channel signal rather than the Rotel, during the power down process. It would seem that somewhere in the right channel, as the voltage level drops, one component or another is ceasing to amplify and becoming an oscillator instead. Can you hand in the Dennon as well so that the repair person has a good chance to isolate the problem?

 

[Chrispy]

Seems your amp has issues. Just use the avr, the difference in amplification is trivial.

 

[Hiten]

This looks like power supply capacitors drying out. (As I had same problem of an old amplifier. It stopped playing music with screeching sound.) I guess its too late to visually inspect the inside of the amplifier as it is already in the repair shop.