Expert: Cleggsan - 1/10/2009

Question
I have rotel equiptment.. power amp, integrated amp, tuner all 15 years old. rotel cd player 5 disk changer 2 years old. Paradigm studio 60's  v 3
 the only thing wrong is a slurring of the s and t sounds.  They sound sharp and tinny.  the only 2 controls on the amp are bass and treble. Is it possible the amp lost it's ability in the mid range even though there is no way to control it? I have a pair of polk rti 6 that I hooked up to see if it was the paradigm's, but the same problem occurred. what should I do ?


Answer
If I could hear the sounds you were getting I could give you an intelligent guess, but since I can't I must just guess.

First guess would be damaged tweeters but you did the right thing and checked with another good (we hope) pair of speakers.  Also, it would be unlikely that both channels would sound the same if it were just one tweeter.  So, we must rule that out.  BUT: Check the channels carefully and see if there is a difference in sound quality between the left and the right.  If so, or any whatsoever, reverse the speakers and see if that tells anything.   This is just to make sure it is not a speaker problem - which would be my strongest suspicion.

Next, let's check the amplifier.  Do you have another cd player that you can temporarily replace the changer?  See if the sound quality is coming from the cd player.  Since it is quit old, it is several generations out of date and the DAC could be going south - or even the analog output stage within the cd player/changer.

Next, let's check the Rotel integrated amp.  Do you have an mp3 player or pocket radio you can use a a source other than a cd player?  That will help to isolate the problem to the amp.  Inside the amp there are a couple of power supply sections that could be causing a low voltage to one of the voltage amplifiers thus causing the sound problems you are hearing.  With the age being 15 years you could very easily have one or more lazy electrolytics in the power supply at the root cause.

Also, check the sound for level: If the sound is quite clear at low levels and as you increase the volume level you can hear the distortion sounds increase it is more reason to suspect a voltage problem in the amplifier.

So, I hope these checks will guide you to the right conclusion.  An aduio shop would not charge a lot of money to replace a bad lytic capacitor.  On the other hand, cd players and amplifiers are very inexpensive now days compared with what they were 15 years ago!

Best wishes,
C