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Author
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Topic: Smart Mod VI alternative
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Bill Yacey
Film Handler
Posts: 23
From: St. Albert, Alberta, Canada
Registered: Feb 2011
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posted 06-16-2012 11:52 PM
I got the room up and running; I fed the reader head into a couple of balanced mic preamps and then to a 2 way active crossover, so I could drive the sub.
The reader is a BACP RSTR 2000. I noticed when setting the preamp gains there appears to be some high frequency distortion (fuzziness) in the audio, I was monitoring on headphones. I checked it with some different trailers and the feature that was scheduled to run in that room. I cleaned the reader head lens and the LED, adjusted focus for best high frequency response, but the distortion remains, both channels. I checked the lateral adjustment, but I didn't have my scope with me, so I just put it back to where it was, more or less centered, however it didn't improve in any way.
Any thoughts?
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Tony Bandiera Jr
Film God
![](/ubbmembers/2365e.jpg)
Posts: 3067
From: Moreland Idaho
Registered: Apr 2004
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posted 06-18-2012 12:26 AM
quote: The reader is a BACP RSTR 2000. I noticed when setting the preamp gains there appears to be some high frequency distortion (fuzziness) in the audio, I was monitoring on headphones. I checked it with some different trailers and the feature that was scheduled to run in that room. I cleaned the reader head lens and the LED, adjusted focus for best high frequency response, but the distortion remains, both channels. I checked the lateral adjustment, but I didn't have my scope with me, so I just put it back to where it was, more or less centered, however it didn't improve in any way.
I really cringe when I read about someone adjusting a reader without the proper test loops and without using a 'scope by "putting it back where it was, more or less".
Redo your reader adjustments properly, using a 'scope AND an RTA.
As for the HF "fuzziness" you need to make sure your reader's grounding is done EXACTLY as BACP instructs. The LED power supply is (and Sam will correct me if I am wrong) a HF "switch mode" type of supply and it can induce oscillation in the output of the reader if not grounded properly.
Or another (stronger) possibility: what you are hearing is HF artifacts because of the lack of proper Dolby NR decoding (most likely) or impedance/response mismatch because of using a non-standard preamp setup....or both.
Get a used CP55, 65 or 500 and do it right. Especially if this is a public venue. If it is for your personal screening room, no real harm in experimenting really.
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Bill Yacey
Film Handler
Posts: 23
From: St. Albert, Alberta, Canada
Registered: Feb 2011
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posted 06-19-2012 11:08 AM
I don't believe it's supply noise. It comes and goes consistent with the high frequency content in the audio track, so most likely it's Dolby pre-emphasis.
At the time, I didn't think I could make it any worse, even though I didn't have a test loop or my scope with me. The focus was out considerably, after adjusting I was getting audio considerably higher than 3Khz, which is about all it was reproducing before. After centering the lateral adjustment as best I could, I now have pretty even balance between L and R channels, even if there is a little bit of phase shift. After adjusting, at least the audio quality is 80% better than what it was.
When I get back on site to install a new processor, I'll do a proper alignment.
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