John Curl's Blowtorch preamplifier part II

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#73,843
john curl said:
Dolby? We tried it, no way. Burwen? A joke with rock material. DBX, not too bad
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If I remember well, Dolby (A = pro) was not so bad in itself, but the Dolby units get awry constantly. Need to be tuned everyday. And, as it was a multi-band system, this affected the tonal response of little signals.
DBX was violent, and, this time the slightest non linearity of the recorder in record/playback (levels and response curves errors was multiplied). With DBX, it was more the dynamic to be affected, and, as I am sensible to this, i dunno liked-it.

At the beginning, like most of us, I was very happy with the noise reduction. With time, I preferred more noise and more "natural" musical instruments... without those artifacts.
Agree ?
After this, we tried 76cm/s, with the problems in the basses you know... Then Digital arrived: Thanks, Lord !
(Burwen ? you teased my curiosity, never heard about this)
 
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#73,849
Well I just got my 30 seconds of semi-fame. A local TV interview on the noise level in the local ballpark. Actual clips were ok but they got a few facts wrong. Biggie was listing it as one of my sound systems. It is not and it just doesn't work the way it should. Ah well they pronounced my name correctly.
 
#73,858
Hi dvv,
So I lined up 5 decks of interest to me from Denon, Technics, Nakamichi and Sony, all 3 head machines.
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The Nakamichi would have left the others in the dust had it been calibrated properly. Not the auto-cal. The factory tape is TDK SA-60, the Nakamichi tapes are center cut from SA and SAX tapes. Maxell will usually be about +5 dB at 10 KHz, so it wants a hotter bias level.

We discovered that the high frequency azimuth tape was way off spec. When we mentioned this to Nakamichi they told us that very few shops had discovered this problem. 🙂 So the azimuth should be set to a lower freq cal tape, or the Teac test tape. The proper mechanical alignment takes a little time because the tape path is very close to that of an open reel machine. No pressure pad (pushed back) and two capstan design that sets up the tape tension the same way a R-R does. Back tension should be around 12 gr / cm (I think) and take up tension is set to 50 gr/cm. The record, erase and playback heads are all completely adjustable in free space - just like a R-R.

It sounds as if the tape path was out mechanically and maybe electrically too. The tape head electronics was a proper low noise setup and they used a form of sendust head. Very low tape hiss and a clear, open sound is normal for a Nak in alignment. There is no way that machine was properly adjusted. That's too bad, because you missed out on an amazing machine. I have a BX-300 and a Dragon (rather have a 1000ZXL). I do know the auto-calibration works very well as long as the machine is in tolerance. When it isn't .. yuck by comparison. I also have a Teac V-800x that is hand tuned. It seems that the dolby C and dBx can't co-exist on that machine, so I picked dBx. It worked properly with a calibration that was normal. The Nak was also hand tuned (both by me) and the Nak is very clearly a better machine. I was a Teac believer until I finished my first Nakamichi calibration on a three head machine.
Both dBx and Dolby C amplify any differences between record and play calibration. They can both be very brutal if they aren't working properly.

Metal tapes! :yikes: That stuff is really abrasive. It's almost as bad as Memorex (real Chromium Dioxide !! more like lapping tape).

-Chris
 
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