At 2:30 PM -0500 2/10/05, Walter Knapp wrote:
>From: Rob Danielson <>
>
> > I did a quick, subjective comparison of the 744T's pre and the MP2's
>> this morning. The mp2's signal is compromised by the additional line
>> out and in transformers in its path. Some difference can also be
>> attributed to the mics. I wanted to use some matched mkh's for this
>> but my mbho603/100D omni mics (14dBA self noise) will have to do. Rob
>> D.
>
>I'm not sure about your conclusion on the line out/line in. Only if
>there is a mismatch between the two pieces of equipment, the 744's own
>mic inputs have a line out/line in point going from the pre, even if
>it's not brought out as a connector.
>
>In any case, I did the big download and set it up in SparkXL where I can
>have a realtime sonogram as well as listening. Spark's sonogram allows
>me to click back and forth between right and left while playing for a
>seamless transition in the sonogram. Any difference will be obvious in
>the moving display. Much better than the spectrum snapshot in Firium at
>telling differences.
>
>There was no obvious difference in the sonograms, it was, in fact hard
>to spot the transition point switching channels. Biggest small
>difference I saw was that very high frequency spike was stronger in the
>MP2 side. And the accelerating car in the middle of the piece was also
>reproduced slightly better on the MP2 side. Both of those could be mic
>positioning.
>
>I did the switch test many times at all the various settings available
>for the sonogram and throughout the sample. Same conclusion at all settings.
>
>It's also possible you had a very slight difference in gain between the
>two channels. Peak indicates the top sound level of the right channel is
>0.1 dB higher than the left. That's not a average, but is a indicator.
>That agrees with that spike being stronger on the MP2 side.
>
>Listening the MP2 channel also sounded very slightly louder, and maybe
>more detail. Again this could be mics.
>
>You might get a more accurate test splitting the output of a single mic,
>no matter how you do it two mics are sampling slightly different sound.
>
>My own conclusion just from this sample is there is no difference
>between the 744 and MP2 pre's in this piece.
Sorry, I missed this post earlier in the week. I agree, there's
little I could point to and say with confidence was result of a
difference in the 744 and MP2 preamps.
I figured out what prompted the impression of greater transparency
with the 744 pre. I had by-passed the bi-amplification on my rear
speakers and forgot about it. The 744's signals were getting bi-amp'd
and the MP-2s' signals were not (creating additional load on the full
range speaker's subwoofers). Comparing the pres calibrated, I'm
getting similar results between two MKH 30's I had commented upon
earlier-- like the mbho test. Sorry about this! The test is still
informative, I guess. Amazing to me that the pres sound so similar
given that one design uses transformers and the other doesn't.
Plenty of field experience ahead as I'll likely keep the MP2 on the
rear mics now. There might be more difference with a quieter setting
and flatter mics, but its not likely to be profound.
Here's another reassuring feature of the 744: Yesterday, I
interrupted the external DC power supply when it was recording. There
was no Sony battery installed so it shut-down instantly without
closing-out the data/sound files files. When I re-started the 744 on
AC, a menu prompt informed me the unit had not been shut-off
correctly and asked if I wanted to repair the audio files. The
repair took about 7 minutes and all four, 1GB files were fully
restorted and accessible. Rob D.
> They are very closely
>matched. It is possible that there could be extremely small differences
>that are masked by using two separate mics. But you cannot draw that
>conclusion from this sample.
>
>Walt
>
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