Odd Dolby signal level problem (or maybe not!)

[Blue Jinn]

Hello,

I was just calibrating a Dolby 362 with an Otari 5050BXII-2. Used the on board osc to calibrate playback. No problem. Then while calibrating record, which is supposed to be done, well recording, before I hit REC-PLAY I am painting 0VU on both channels. As soon as I hit record, the left channel drops a good 5-6 dB. But if I re-adjust the output trimmer on the 362, I can bring it back up to 0 VU while actually recording tone. It then works OK while actually recording program material.

I just went through the same process on a pair of 360's and 0 VU with dolby tone was the same whether or not recording was engaged or monitoring from "source." Also, it isn't the CAT-22 modules, because I swapped them and the phenonmenon stayed in the left channel. It doesn't **seem** to be a problem, because I'm not going to send tone to the tape unless it is recording, but if I am not actually spinning tape, and monitor from source rather than tape, I get way over on the left channel. Mind you this was just around midnight a few nights ago... but I'm completely baffled. I haven't pulled the manual to see if there is some quirky dolby tone adjustment on the box somewhere. I had thought the tone was generated from the CAT modules...

 

[Blue Jinn]

Well,

Looked at the 360 manual which has information on the CAT-22 card, and the dolby tone oscillator is on the card. Dunno. It appears to work OK, so the signal discrepancy doesn't make any sense. This isn't how the 360's acted when I went through the same process the night before.

I haven't actually mastered with the thing, just ran some music through and could tell a higher freq content on playback with NR engaged. Tape really does make a difference. I used Ampex 632 with the 360s and tried that and Quantegy 031 with the 362 and could really hear the difference.

I had low level selected by mistake at first on the Otari, the 360's would get there, but had to really really turn the trimmer. So I think they prefer the +4 operating level, which is a quandary, because the rest of my gear is primarily -10.



Can't wait to try the 365 w/ SR....