ROTEL RC-1590 PREAMP phono input noise

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VideoVic

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A good friend bought a ROTEL RA-1592 integrated amp (not the new MKII version) based on my recommendation of how satisfied I was with my ROTEL RC-1590 preamp / ROTEL RB-1582MKII amp combo. He has a turntable connected and recently discovered there was "noise" coming from his speakers when the phono input was selected and the volume level approached "60" when no music was playing.

I do not have a turntable connected to my system. However since the RC-1590 preamp is basically the "front end" of his integrated amp and the RB-1582MkII amp is the"back end" I was curious and wanted to find out if my phono section was also noisy. Sure enough, I get a "hash" type noise (similar to FM radio inter-station type "pink" noise) that is audible thru my ESL-X speakers when the volume level approached "60" even though no turntable is connected.

Seems to me this noise is internally generated by the preamp and is possibly a warranty repair issue but Rotel tech support tells me they will not even trouble shoot my problem or issue an RA until I get a turntable connected. My friend says he has reached out to Rotel to tell them about his problem but they have not responded.

I realize I can use an external phono preamp to overcome this problem but it sure stings to know that I have to do that if I want to playback vinyl after spending almost $2K for a preamp !

Just wondering if this has occurred to anyone else with Rotel products out there?
 

Leporello

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Too many variables here for this to be meaningful. You hear noise with the volume at 6 o'clock, but how loud would the music be? What is the manufacturer's spec for the SNR of the phono section? Is it meeting it? You would probably have to determine it's not before they would consider a warranty repair. Things like amp power, speaker sensitivity, room size, how close to the speakers you are, all come into play. Also, is it moving magnet only or moving coil/moving magnet? Is the right one selected?

You would need to back up your claim with measurements. Measure the noise at the output at the speaker, with the input terminated (it does make a difference) in 47,000 ohms for a mm, or a few hundred ohms for a mc (the better ones are adjustable), preferably with a true RMS meter. Then measure the output, without adjusting the volume, using a signal generator, with an input of 1 millivolt, or 5 millivolts, or whatever the spec says. 20 times the base 10 log of the ratio of those two values is your SNR. BTW if the reference level is too loud for your ears, clips the amp or threatens to blow up your speakers, that's your problem. You should actually do that measurement first, starting with the volume at zero and working up to a comfortable level, or 6 o'clock, whichever comes first. If you can't hear the hiss at the comfortable level that's another indicator.
 
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