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Some good decks have markers to where to set the record level to for maximum output. On my decks type 1 was the least and metal was the most. I think metal went to 8 db, while normal was 2 db. Anyway I read a review on an Aiwa deck and the tester noticed that the deck was over rated with chrome and metal tapes in terms of the maximum setting, while under rated for normal tapes. Basically he was able to record on a premium normal tape to 9db, while chrome could only go to 6db and metal 8 db. I have read elsewhere someone saying good normal tapes can take louder levels then the upper two tapes, but this was the first time I've read it in a review. I can't say where regular normal tapes stand. Has anyone else noticed this? Im aware the high end would drop off if recorded at a high level, so maybe thats part of the deck's manufacturers settings?
Follow Ups:
contact me off site and I'll be happy to educate... it's really all sort of simple as it's all analog...
cheers,
Danny
That's a very good question. Here is what I've learned over many years.
First, we must establish what reference magnetic flux level on the tape corresponds to "0 dB" as indicated on the meters. A reference tape is needed for this. My deck (Tandberg TCD3014A) is calibrated so that 0 dB corresponds to a 250 nanoweber/meter (nwb/m) flux level. This is the IEC standard for tape types 1 & 2. This is +2 dB above the Dolby reference level, which is 200 nwb/m. On my deck, the "double D" Dolby logo is at -2 dB. Again, this is for types 1 & 2. Some decks from the far East use Dolby level as 0 dB (200 nwb/m), and some use 160 nwb/m. Thus there can be a 4 dB difference as to what actual flux level is recorded onto the tape when the meters indicate 0 dB.
To further complicate matters, most decks have meters which display the signal strength *before* equalization, or "pre-equalized" meters. Since all signals inputted to the record amp undergo a large treble boost, necessary with the cassette format, the actual signal hitting the tape is stronger than the meter indication. This could result in hf saturation if the program material is rich in hf. Otherwise, all could be well. The actual upper limit on recording level will vary according to the hf content of the program material.
The deck I use features *post-equalized* metering. The signal strength displayed by the meters is taken after equalization has already taken place giving a true indication of the actual signal strength hitting the tape. The recording level can be optimized without fear of hf saturation. Thus, for program material very rich in hf content, a post-eq meter will indicate higher readings than a pre-eq meter.
To complicate things more, metal tape, aka type 4, can accept around 4 dB more signal at all frequencies, and also accepts more hf as well. My deck, as well as some others feature a second metering display calibrated for metal. The 0 dB point is at 400 nwb/m, a full 4 dB above 250 nwb/m. This allows the user to fully utilize the extra headroom offered by metal tape.
Now regarding the question about whether type 1 tape has more hf headroom than types 2/4, here is my educated guess. Type 1 utilizes 120 us (microsecond) eq vs. type 2/4 at 70 us. The type 1 eq of 120 us uses less record treble boost and more playback treble boost as opposed to 70 us. This means that all being equal, 120 us offers more hf headroom, i.e. less chance of hf saturation, but 70 us offers higher SNR (signal to noise ratio). It's a classic tradeoff. But, all is seldom equal. Type 2 tape has more hf headroom to start with than type 1. The use of 70 us w/ type 2 vs. 120 us w/ type 1 may end up being a wash regarding hf headroom, or pretty darn close either way. A premium type 1 tape has less raw hf headroom than an average type 2, but the 120 us eq vs. the 70 us may make a difference, tipping the scales in favor of the type 1. The tradeoff is SNR, which is better for type 2 due to the 70 us eq.
With type 4, I strongly doubt that type 1 will surpass it. Even with the 120 us eq used for type 1, type 4 tape has so much more maximum recording level across the full frequency range, and more hf level to boot, that type 1 should not surpass type 4 despite the eq difference.
In a nutshell, types 1 and 2 are pretty close, with type 2 having more hf headroom, but sacrificing it due to the 70 us eq vs. 120 us for type 1. The type 2 provides higher SNR on playback due to 70 us eq. Type 4 offers the best hf headroom and best SNR. With either type, how far you can push the meters into the red zone depends on the calibration of the meters, whether they read the pre-eq or post-eq signal, the adjustmant of the tape deck regarding record sensitivity and bias level, and of course the tape properties.
I hope I've helped. BR.
Claude
The reason I ask is because I've read a review on the Aiwa deck I have. They said with it they could record to the 9db level on the decks meters before saturation. On metal tapes it was at 8db and 6db for chromes. This is what I was getting at. Apparently my deck is really good at making type 1 tapes.
I think the discrepancy here could be in your deck itself. In other words the meter average should be around 0db, while the meter peak can spike a lot higher. If your deck can do it, flip back and forth from the two to get the best recording and tape saturation. On my two machines, I push the peak meters/signal a lot higher on chrome and metal-maybe I'm stating the obvious. And of course there's the bias.....
I've always found that very odd - that the record level (as shown on the VU meters) should be different for different tape types. The recording alignment adjustments inside should compensate for the tape formulation sensitivity, so that optimum record level is always "0dB", no matter what tape type is used.
Optimum record level is usually defined as the point where a specific distortion is reached (1.55 or 3% I think). To gauge this by ear is almost impossible.
Setting record level for maximum output - I'd not recommend that ; set for best signal to noise ratio, and acceptable distortion.
Further, very few decks that I've seen actually correlate meter reading with the actual recorded flux density - so what you are seeing on the meters is a rather arbitrary level - you never know what the 'real' level on the tape is.
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