how is this possible?

I may not be getting this at all but the first thing I thought of was delay due to digital latency in the sound card.
 
I may not be getting this at all but the first thing I thought of was delay due to digital latency in the sound card.
how could that be if it doesn't show up in any of the baseline tests? i'm not being a jerk, i want to know, as i can't explain why one channel of the revox is trailing.

anyway i have graphs. oh boy do i have graphs.

first, baseline frequency response, left and right. i used a white noise file and then let the response graph settle. this is obtained by switching the dbx200's tape 3 (the sound card device) to line.
baseline left.jpg baseline right.jpg
i'm going to consider this as my 'target' for the curve, assuming it's flat - not that i am under the impression that my electronics are perfect, but rather, this is as good as things get....i'm sure some of this is due to limitations of the sound card, the software, the white noise file i used, etc.....and some is my gear.

at the very least, whatever is going on, it's going on equally in both channels.

i took graphs of both decks, with all the various noise reduction schemes in place, but in the interest of not boring everyone to death, i won't post them all.

so first off is the ReVOX A77 - first just through the deck's electronics:
revox monitor left.jpg revox monitor right.jpg
these curves are not symetrical like the baselines, most especially in the low end.

next the A77 monitoring it's recording:
revox record no nr left.jpgrevox record no nr right.jpg
yeegawds. Don't worry Mr. Studer, she will live again, i swear it.

next up is the Yamaha. here's the response just monitoring the signal through the deck's electronics:
yamaha monitor left.jpg yamaha monitor right.jpg
well, it's not perfect, but a lot more symmetrical than the ol' A77. it's really a neat tape deck too. when you press record it plays some tape, calibrates iteself, and rewinds back to where it started and puts itself in pause. then it lights up "tuned". anyway, here's the response recording to a CRO2 tape:
yamaha record no nr left.jpg yamaha record no nr right.jpg
hmm, i guess not a lot of HF response here either, although i'm listening to it recording right now, and it sounds truly excellent, whereas the A77 needs some work clearly, just from listening to it, without doing all this graphing.
 
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and for those that thought maybe this time lag was due to my setup, and not the A77....here's the Yamaha with the same setup and the same 1khz tone file.

1khz monitor k2000.jpg
this is playing through the decks electronics, no recording just yet. clearly the left and right channels are identical just on source monitor, as one would expect....not time-shifted as in my A77's case.

here's the record monitor of the same thing on chrome tape:
1khz record k2000 no nr.jpg
there's a bit of delay and a difference in amplitude, but just playing with the controls it's easy to see that i have a few pots to clean in the Yamaha.

anyone have any tips for cleaning slide-pots?
 
i feel like an idiot. I have discovered that i had the matheq filter running on my white noise generator the whole time.

here's what an actual baseline looks like for my sound system:
ana.gif
considerably flatter
 
Cassettes (and reels, to a lesser extent) tend to roll off in the highest frequencies at 0 dB and higher levels (the high level of signal at a high frequency applies a bit of "self-erasure" signal; this is what Dolby HX Pro was designed to address in the recording stage).

You might try a similar recording test, but do it at a -20 dB recording level, rather than 0 dB. Tape deck response is almost always spec'ed at -20 dB. I expect that you'll see a much flatter response from the Yamaha
 
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