Hmm.But if that is so then whats the purpose of Dolby as an extra option?
Recording in a Nakamichi
- Thread starter jayants
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Hmm.But if that is so then whats the purpose of Dolby as an extra option?
greenhorn
Well-Known Member
Can you explain?
As you said that DOLBY helps them to prevent getting drowned from the tape noise,but while playback if Dolby is kept on the treble sounds subdued.But if its put off it sounds much much better.But if that is put off while playback a recorded stuff (which is recorded with Dolby on) u said the reverse happens.
greenhorn
Well-Known Member
When I said reverse, I meant the reverse of what happens during playback. let me illustrate - please note these values are NOT accurate, and are merely representative.
Suppose you have a loud signal at 10W power, and a faint signal at .01W power. Because of the tape medium there will always be hiss, which has say, .01W power which makes the .01W signal not very audible. When you record it with dolby encoding, the .01W signal gets boosted 100 times to 1W (but the 10W signal stays the same) .
When you listen to the Dobly recorded cassette, without enabling the dolby decoding you are listening to the faint signal at 1W and the loud signal at 10W. This is not the original signal you had, but a treble boosted one. If you like turning up the treble, then this will sound a bit better, but on recordings which already have a lot of treble, this will sound horrible (too much treble).
Now why should you enable dolby decoding on when playing back tapes?
If you are playing the tape back without turning on dolby, you are listening to the original loud signal at 10W, the boosted faint signal at 1W, and the tape noise at .01W
If you turn on Dolby, because of the volume reduction applied at the high frequency band, both the .01W noise and the 1W signal get reduced by 100, ie they become .01W for the signal, and .0001W for the noise, thus the noise has become much less than original. While this makes it duller than with dolby turned off, it should be accurate to the original input. If not, you need to get your deck checked (a small loss is acceptable. This is analog, after all)
Now, you say you like the higher treble. In that case, you should turn the dolby on, and then increase the treble on your stereo, so that the treble boost is applied uniformly to both quiet and loud signals (dolby boosts treble for only the quieter signals) so that you retain the full dynamics and impact of the recording. thus the .0001W noise will become .01W again, the .01W small signal will be boosted back to 1W, So far this is the same as the undecoded Dolby recording. But now, the 10W signal will get boosted to 1000W now, giving you full impact of the treble, which would otherwise sound compressed and lacking if you had been listening to the undecoded version.
how exactly the boosting happens
http://hyperphysics.phy-astr.gsu.edu/hbase/audio/tape5.html#c5
Suppose you have a loud signal at 10W power, and a faint signal at .01W power. Because of the tape medium there will always be hiss, which has say, .01W power which makes the .01W signal not very audible. When you record it with dolby encoding, the .01W signal gets boosted 100 times to 1W (but the 10W signal stays the same) .
When you listen to the Dobly recorded cassette, without enabling the dolby decoding you are listening to the faint signal at 1W and the loud signal at 10W. This is not the original signal you had, but a treble boosted one. If you like turning up the treble, then this will sound a bit better, but on recordings which already have a lot of treble, this will sound horrible (too much treble).
Now why should you enable dolby decoding on when playing back tapes?
If you are playing the tape back without turning on dolby, you are listening to the original loud signal at 10W, the boosted faint signal at 1W, and the tape noise at .01W
If you turn on Dolby, because of the volume reduction applied at the high frequency band, both the .01W noise and the 1W signal get reduced by 100, ie they become .01W for the signal, and .0001W for the noise, thus the noise has become much less than original. While this makes it duller than with dolby turned off, it should be accurate to the original input. If not, you need to get your deck checked (a small loss is acceptable. This is analog, after all)
Now, you say you like the higher treble. In that case, you should turn the dolby on, and then increase the treble on your stereo, so that the treble boost is applied uniformly to both quiet and loud signals (dolby boosts treble for only the quieter signals) so that you retain the full dynamics and impact of the recording. thus the .0001W noise will become .01W again, the .01W small signal will be boosted back to 1W, So far this is the same as the undecoded Dolby recording. But now, the 10W signal will get boosted to 1000W now, giving you full impact of the treble, which would otherwise sound compressed and lacking if you had been listening to the undecoded version.
how exactly the boosting happens
http://hyperphysics.phy-astr.gsu.edu/hbase/audio/tape5.html#c5
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greenhorn
Well-Known Member
as I said before, the numbers are representative, Dolby B boosts by 10dB = 10X boost. Dolby C does 20dB = 100X boost for power. The actual values you can figure out from the graph in the link at the bottom of that post
Funny story. When I was being interviewed for MBA at IIT Delhi, i was asked to explain exactly this to the prof. I did, and I was told that I was wasting myself in Management, and should continue in Engineering. A few years later, after I had dumbed myself down sufficiently, I managed to get into a better B school, but it's glad to know that I've still got it
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greenhorn
Well-Known Member
So you mean to say that Dolby boosts up 100 times lower frequencies during recordings and reduces the same during playback in the same ratio.
Why didn't it boost the .01 power while recording? If it didn't boost it then why during playback you divide .01 power (hiss sound) by 100?
greenhorn
Well-Known Member
Please read my posts again. LOW POWER, HIGH FREQUENCY.
The .01W noise is already there on the tape, and does not come from the source or the equipment. Dolby is applied to the input signal while recording, but to both the signal + noise during playback, because the noise is now part of the playback signal
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Now understood. As Dolby affects only the input or source signal so it will not affect the sound where source is getting recorded(here it's tape) during time of recording. Whereas during playback it affects the playback signal and as the noise is now part of the recorded tape so it will get affected. Correct?
greenhorn
Well-Known Member
I mean to say that Dolby only will boost the source signals. It will not boost any thing that is there already in the tape(noise) as it's not a source signal.
greenhorn
Well-Known Member
correct. You got it
reubensm
Well-Known Member
Sometimes while recording, I saturate the tape a bit (without distorting it) to reduce the tape hiss feel during playback. This technique works when recording on NAKs but other decks cannot handle this saturation aspect. I could never succeed at this while recording on Denon, Akai and Technics decks.
as a matter of fact ruben sir i was able to achieve no hiss sound while recording on my technics deck model rs m 20 . it is a very simple deck . so i what i do is i dont record tapes on my nakamichi i record using the technics deck and play back on nakamichi . in this way even though i saturate my tape a little bit there is absolutely no hiss while playback on my nakamichi .
ps : i do not use dolby noise reduction .
ps : i do not use dolby noise reduction .
greenhorn
Well-Known Member
My guess is because Nak used a non standard eq/re eq curve which attentuated the signal a bit more aggresively than the reference design during record
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But if the PUNDITS are to be believed what you get out of a NAK while recording isn't available from other Decks.So if the hiss is less or no hiss by recording in a different deck,still its not a NAK recording.Isn't it?
How is this done? I mean the saturation part.
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