Hello Everyone,

I have moved this post to a separate thread in the hope that other folks with Onkyo AV Receivers will conduct similar tests to determine whether or not this is an endemic problem with Onkyo AV Receivers.

After extensive testing, I have determined that my Onkyo NR 3009 AV Receiver cannot handle monaural recordings for correct surround-sound processing. When I play a monaural recording of any type through the Onkyo and select any of the surround-sound processing options (Dolby, NEC, etc.), the resultant surround-sound from all surround speakers is very low in volume and highly distorted. However, when I play a stereo recording of any type, the surround-sound is fully clear and of normal volume.

I have tested this issue as follows:

1. Mono and stereo LPs played through the Phono input on the Onkyo.

2. Mono and stereo CDs played through the Onkyo Auxiliary (Front) audio inputs and the Auxiliary Optical input.

3. FLAC mono and stereo files converted to analog via an external DAC and played through the Onkyo BD/DVD audio inputs.

In every test case, when the source was a stereo recording, the surround-sound selections functioned normally. But, in every case, when the source was a monaural recording, the surround-sound processing was highly distorted and of very low volume.

It is interesting to note that, when the receiver is placed in either the Mono, Stereo, or All Channel Stereo Modes, the receiver will properly handle the sound from monaural recordings. It is only the surround-sound processing which is affected by monaural recordings.

I am going to attempt to speak directly with Onkyo technical people to determine whether or not this is a normal condition for this receiver. Based upon a rather curious comment in the Receiver's Owners Manual, I believe that this situation is normal for this receiver. If so, that is a very unfortunate design flaw - particularly for a receiver with a phono input through which the owner might very well play a monaural record. There are also a fair number of CD reissues available of historic monaural recordings, none of which will function properly with this receiver.

If I am successful in reaching the proper technical people at Onkyo, I will report upon my findings.

I have older SONY 5.1 and 7.1 channel AV Receivers which do not have this issue.

If any of you own Onkyo AV Receivers and are willing to repeat these tests, I would be most pleased to learn about your results.

Regards to all,

Art

Here is an update to my previous post regarding Mono Sound processing issues in my Onkyo NR 3009 AV Receiver:

When I created the initial post, I was using a speaker configuration which included Surrounds, Surround Backs and Subs, but no Center speaker. It did not occur to me that having the Center Speaker set to NO SPEAKER might be a factor with the Mono Sound issue - but it appears that the absence of a Center Speaker was perhaps the main cause.

I added a Center Speaker for reasons not connected with the Mono Sound issue and found, to my surprise that, with the Center Speaker setting turned ON, the distortion in the Mono sound disappeared from all of the speakers.

My speculation is that the receiver processes Mono signals in such a way that the absence of a Center speaker caused the problem because the Center channel plays a more important role when Mono sounds are present.

So, for now, the problem is resolved.

Happy Listening,

Art