Noise-reduction messes with phase information in QS?

[ChopperCharles]

So, I have a quad receiver, and a Pioneer RT-707 reel to reel.

Between the reel to reel and the receiver, I have a Phase Linear 1000 Auto-correlator, which is a REALLY effective noise reduction system. It completely removes tape hiss, but leaves all the highs intact. And it's adjustable, so you can tune out specific noise. The auto-correlator is meant to be installed on the tape loop, but I'm using it in-line between the tape deck and the receiver, because I really don't need it for CD or vinyl sources. (While it can remove some surface noise, I don't see that as a huge problem)

However, I think something it does is stripping out matrix decoding information. I'm playing back recordings of non-quadraphonic albums, and using the SQ processor just because it's pleasant to have the sound... more full. Well, when A/Bing the setup with the correlator in-line, or removed from the signal path.... the music doesn't sound as rich and full with the correlator installed. Sound is missing from the speakers, it sounds noticeably better with the correlator removed. HOWEVER, if I put it in 2-channel stereo mode, it sounds considerably better WITH the correlator in-circuit.

All I really know about the auto-correlator is that it buffers the signal somehow. Even with the correlation and dynamic range expansion turned off, it was still stripping quad out of the mix.

I suppose I could get two of these and put them both on the tape loop, since that will be after the signal is split into quad by the receiver.

I'm going to make a recording of my Dark Side Of The Moon SQ album, and see how badly it strips quad info when I play it back on the R2R.


So I guess the purpose of this post is:
1. Outboard noise canceling hardware can mess with the quad signal
2. Why? What causes this particular unit to strip quad out? Phase inversion? Something else?

Charles.

 

[proufo]

However, I think something it does is stripping out matrix decoding information. I'm playing back recordings of non-quadraphonic albums, and using the SQ processor just because it's pleasant to have the sound... more full. Well, when A/Bing the setup with the correlator in-line, or removed from the signal path.... the music doesn't sound as rich and full with the correlator installed. Sound is missing from the speakers, it sounds noticeably better with the correlator removed. HOWEVER, if I put it in 2-channel stereo mode, it sounds considerably better WITH the correlator in-circuit.

All I really know about the auto-correlator is that it buffers the signal somehow. Even with the correlation and dynamic range expansion turned off, it was still stripping quad out of the mix.

Hello CC.

I had one decades ago, daisy chained with a SAE click remover on the tape monitor loop.

All these units, perhaps all units, produce phase shift that could mess with matrix decoding.

I believe that improvements with the scripts have to do with preprocessing the stereo recording before decoding, and it's probably phase-related.