BASF公司威廉先生关于chromium dioxide120磁带的部分谈话中文翻译

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本文，为2011年10月威廉先生在国外一论坛里面，反复应付大量前来咨询关于chromium dioxide120磁带相关问题的解答的中文翻译，威廉曾任BASF公司北美分部的高层干部，对chromium dioxide120磁带有着决定性的话语权威，在本文末，显然威廉的口气中已经透露出为了反复给不同网友解答同一问题的不耐烦情绪，显然西方人自己对这种奇怪磁带感到困惑和新鲜。在这个西方论坛的另一个帖子里威廉有些气恼甚至发一些小脾气。当然是针对那些扭曲了事实和歪曲了原本技术特性的各种奇葩“理解”。

Wilhem

10-26-2011, 08:56 AM

There are three settings that are getting confused: 1)bias; 2) record EQ; and 3) playback EQ. Bias is the high frequency signal addedto a tape during recording in order to bring enough magnetic energy to theparticles to get them to react to the lower, audible frequencies of therecording. Bias is only applied during recording, and the amount depends on thecoercivity of the magnetic material used. Chromium dioxide requires a higherbias setting than ferric oxided, and metal tapes require the most bias signal.The bias level is set to reduce distortion at a point that must be a compromisebetween low frequency sensitivity and high frequency sensitivity.

存在3种混乱的概念：1）偏磁；2）录音EQ；3）播放EQ。偏磁是磁带录音期间高频信号添加在磁带，带来足够的磁能量影响到磁颗粒的更下层来录音可以听到的频率。偏磁仅发生在录音过程中，并且偏磁量取决于使用的磁性材料的矫顽力。二氧化铬比铁氧化物需要更高的偏磁量，金属磁带需要最高的偏磁信号。偏磁电平要被设置在减少失真的一个位置，必须是低频灵敏度和高频灵敏度之间的折衷。

Playback EQ applies only to playback. It is either 120 microseconds (a termused to describe the circuitry used) or 70 microseconds. This is a fixedstandard. There is a difference in 4.5 dB of greater high frequency noise using120-microsecond EQ.

播放EQ仅用于播放，它可以是120微秒(用于描述所使用电路的术语)或者70微秒。这是固定标准。不同的是使用120微秒EQ会产生更大的4.5分贝的高频噪音。

Record EQ or preemphasis is a boost in high frequency signals used to flattenor to extend frequency response. A recorder is set up for a tape firstby assuring that its playback EQ is precise. Then the bias point isset to reduce distortion to a reasonable level. Then Record EQ is used to makesure the frequency response is flat.

录音均衡或者说是预加重是用来平坦化或者扩展频率响应的高频信号提升器。录音机设定磁带首先保证播放EQ是精确正确的，然后偏磁点设置到降低失真到一个合理的水平即可。这样录音EQ就可用来确保频率响应是平坦的了。

IEC settings are a combination of all three settings for recording only, but ofplayback EQ only for the playing of cassettes. This can cause confusion if onedoes not make the distinction and remember that bias is only used in the recordmode.

IEC设置了三个仅为录音而设置的组合，但是播放EQ仅用于盒式磁带的播放。如果不进行区别和记住偏磁仅仅用在录音模式，这可能会导致概念混乱。

When chromium dioxide was introduced in the late 1960's, it had lower noisethan ferric oxides and much higher coercivity with the concomitant greatercapacity for short wavelength, high frequency signals. Since the majorcomplaint about cassettes at the time was tape hiss, Philips and BASF thoughtthat a new, 70-microsecond playback EQ could be introduced to reduce tape hissby the 4.5 dB plus another few decibels because of chrome's lower noise floor.At almost the same time, Advent introduced the Model 200 with BOTH70-microsecond EQ for chrome tape and Dolby noise reduction, making it thefirst "high fidelity" cassette recorder. BASF engineers weresurprised. We would have preferred to keep the standard 120-microsecond EQ ifDolby NR was going to be used because it could reduce noise by 10 dB. Chromecould give up the 4.5 dB due to the different playback EQ, and that would allowbacking off the record EQ by the same amount in order to bring up SOL values--theamount of high frequency energy that a tape can take. Chrome was already a veryquiet cassette tape; and using 120-microsecond playback EQ, less record EQ, and increasing the bias point a bitwould have allowed cassette tape to show frequency responses at both high andlow levels that more closely approximated those of an open-reel recorder at 7.5ips.

当60年代末期推出了二氧化铬，拥有比铁氧化物更低的噪音以及更高的矫顽力附属的短波巨大容量，以及高频信号。由于关于磁带的主要抱怨是当时的磁带嘶嘶声，飞利浦和BASF认为，因为铬的低噪音下限，一个新的70微秒的播放EQ能带来降低磁带嘶嘶声4.5分贝以上那么多。几乎在同一时间，推出了型号名为200的，同时具备铬带70微秒EQ和杜比降噪系统的----使之成为第一台“高保真”的盒式录音机。BASF公司的工程师感到惊讶，如果杜比NR因为可以降低10分贝噪音而打算使用的话，我们本来就应该优先保留120微秒的均衡标准。铬材料可能会因为不相同的均衡而丢弃4.5分贝电平，这将使得退回了相同量的录音EQ，顺便带来的SOL数值----能为磁带带来的高频能量的总量。这种铬材料已经是非常安静的盒式磁带材料；并且使用120微秒播放EQ，和比较小的录音EQ，并且仅增加偏磁一丁点儿就让盒式磁带展现频响在高频和低频电平，这样估计更接近7.5ips开盘录音机的水准。

When we approached music labels to show them the advantages of chrome tape athigh-speed duplication, we got the chance to demonstrate the advantages ofchrome adjusted for 120-microsecond playback: a bit more bias for higher MOL,less record EQ for higher SOL, and a lower noise floor than ferric oxide.A&M was willing to try the chrome formulation with Supertramp's"Famous Last Words...," but they used 70-microsecond EQ. I produced anumber of chrome samples at 120-microsecond EQ and wrote up a white paperdescribing the advantages of using 120. Marvin Bornstein, the head of A&MQA, understood the concept; but he doubted that his upper management would. Irewrote the paper and ended with the note that using 120 microseconds wouldalso allow music labels to stock only one cassette shell, saving them money.(That was language music labels understood.) The next release was"Synchronicity" by the Police, which was such a big hit that BarbaraStreisand and Bruce Springsteen began to pester Columbia for chrome tape fortheir releases, too. It was far easier to convince classical music labels ofthe advantage of greater MOL/SOL because classical recordings required fargreater dynamic range than popular music recordings.

当我们接近唱片公司向他们展示在高速复制机上铬磁带的优势时，我们有机会展示这种调整到120微秒播放的铬材料的优势：仅需增加一丁点的偏磁获得更高的MOL，更少的录音EQ量获得更高的SOL，并且相比铁氧化物有更低的噪音下限。A&M唱片公司愿意尝试铬制剂材料发行磁带，用Supertramp乐队的“Famous Last Words”专辑，但是他们使用的是70微秒EQ。我生产了一些120微秒EQ的铬材料磁带样品，并且在一张白纸上写了使用120的优点的描述，马文·伯恩斯坦，A&M唱片公司的QA部门的头儿，明白了这个概念，但是他怀疑他的高层管理人员是否愿意，我重新写了张纸条，并且重点强调使用120微秒将也使唱片公司仅需采购一种盒带外壳，节省他们的钱。(这话唱片公司非常理解。)下个即将发行的专辑是警察乐队的“Synchronicity”，芭芭拉·史翠珊和布鲁斯·斯普林斯廷烦恼的是哥伦比亚公司也即将发行这种铬磁带，对于他们是个巨大的打击。对于更大的MOL/SOL的优势这更容易说服古典音乐唱片公司，因为古典音乐录音比流行音乐录音需要更大的动态范围。

Mobile Fidelity Sound Lab was a different story. MFSL decided to record in realtime using JVC KD A77 recorders and BASF chrome tape originally loaded intoBASF housings selected for calibration tapes. The tape itself was batchselected on the basis of its higher output, and it was standard, single-coatchrome. Because the JVC recorders did not have all the adjustable settingsideal of modifying them, I used BASF 70-microsecond playback EQ alignment tapesfor equalization and adjusted the bias and sensitivity settings for BASF chrometape. I aligned the record gaps (not the playback gaps because the recordersused sandwich heads, and some of them were permanently out of alignment) forazimuth, again using BASF calibration tools. All the MFLS cassettes used70-microsecond EQ for this reason.

移动高保真唱片商则是一个不同的故事，MFSL决定使用JVC的KD A77录音机和BASF铬带来做实时录音，是最初装载选定的基准磁带到BASF外壳之中。磁带本身是从一批次当中筛选的较高输出的，并且它是标准的单涂层铬材料。由于JVC录音机没有调整修改任何他们的设置到理想状态，我使用BASF 70微秒播放EQ的基准磁带来均衡和调节了偏磁强度并且设置了BASF铬带的灵敏度。我校准录音缝隙方位角(不是播放缝隙，因为录音磁头是在三磁头上，并且他们当中一些是长年没有校准的)，再次使用了BASF校准工具。所有的MFLS盒式磁带使用了70微秒EQ就是因为这个原因。

Wilhem

10-26-2011, 01:01 PM

If there were no playback equalization, the sound outputwould be screechingly high. The change in flux patterns across a head gap iswhat creates the current from the head, and high frequency/short wavelengthschange more often than low frequency/long wavelengths. That would producelittle low frequency output but increasing output as the frequencies/fluxpattern changes increase--up to a point. That point is where the head can nolonger read the short wavelength changes as well, and that is where theequalization is removed. The point for 120 microseconds is 1,326 Hz and for 70microseconds it's 2,274 Hz. The output produced by the wavelength patternsbeyond those points is allowed to rise until the wavelength pattern is close totwice the width of the playback gap. Patterns narrower than 2X the width of theplayback gap cannot be resolved.

For record EQ, the result depends a lot on the characteristics of the tape. Without somepreemphasis, the high frequency output from the tape may not be able to be atthe same level as the output from lower frequencies below the playback EQturnover points of 1,326 and 2,274 Hz. The output above those frequencies mightdroop significantly. The ideal record EQ should be adjustable enough to takeinto account double-coated tapes that have a tendency to sag in the mid-rangewhere the coercivities of the lower and upper layers differ. That would offer afrequency response from double-coated tapes as flat as that from single-coattapes.

如果没有播放均衡的话，输出的声音将会非常高声尖利，磁印记波动流过磁头缝隙会在磁头产生电流，并且高频率/短波长的变换比低频率/长波长电流更大。这将产生少量的低频输出，但是相当与频率/磁印记波动的变换速度加快而增加了输出电流---直到增加到一个位置为止。该位置是磁头不能再读取短波长的变化，并且那里的均衡是开始下陷的。这个位置对于120微秒是1326Hz，对于70微秒是2274Hz。由磁印记波形产生的输出电流一直上升，直到磁印记波长接近两倍于播放缝隙宽度的位置为止。磁印记狭窄到播放磁头两倍宽度的时候不能被处理。

对于录音均衡，其结果在很大程度上取决于磁带的物理特性。没有一些预加重的话，磁带的高频信号输出可能不能象在播放EQ转折点1326或者2274Hz以下低频信号输出一样高的电平。以上这些频率的输出电平可能显著地下滑。理想的录音EQ应该有足够调节范围以促使双层磁带在中频有下陷的趋势，其中上层和下层的矫顽力不同，这将让双涂层磁带的频响如同单涂层磁带一样平坦。

Wilhem

10-27-2011, 12:06 PM

There are three low frequency EQ standards: the NAB 3180microsecond standard for open-reel and for cassette tape played back at 3.75ips and 1590 microsecond standard for audio cassette tape at 1.875 ips; the IECinfinite microsecond standard for open-reel; and the Philips/IEC 3180microsecond standard for audio cassette.

The turn over points for 3180 microseconds is 50 Hz, and this was chosen toreduce the effects of rumble from transports or overload from recording fromturntables that had low frequency rumble problems. The infinite microsecondselected by the IEC means no roll off is applied in the equalization curve atlow frequencies. The odd 1590 NAB standard selected in 1972 may have been toavoid transmitter overload from low frequency energy from a cassette, but it isan odd idea to ignore the Philips international standard and apply"new" standards to Philips's invention. I have no idea if 1590microsecond EQ was typically used in the broadcast industry. I believe theymostly used larger tape cartridges rather than the compact cassette format.

有三种低频EQ标准：NAB3180微秒标准是3.75ips开盘机和盒式磁带机的，1590微秒标准是1.875ips盒式磁带标准；IEC无限微秒标准是开盘机的；飞利浦/IEC 3180微秒标准是音频盒式磁带的。转折点3180微秒是50HZ，并且它被选择来降低来自变压器或者唱盘的录音过载造成的隆隆声的影响之类的这些低频影响的问题。IEC的无限制微秒选项的方法，是应用在低频曲线的均衡上无滚降的处理。这个怪异的1590 NAB标准选项在1972年可能是用来避免传送来自盒式磁带的低频能量的过载，但是它是一个奇怪的想法来忽略飞利浦国际标准并且应用飞利浦发明的“新”标准。如果1590微秒EQ通常用在广播行业的话我没有意见，我相信他们大多会使用大盒卡带而不是小型盒式磁带格式。

Wilhem

12-14-2011, 08:58 AM

"Equalization" can be signal modificationsbefore recording, signal modifications after recording, record preemphasis, orequalization of the signal from the head. I refer to "playbackequalization" to distinguish it from the other three types.

“均衡”能修改录音前的信号，修改录音后的信号，录制预加重，或者均衡来自磁头的信号。我所指的是“播放均衡”来区别其它三种类型。

Wilhem

12-14-2011, 01:44 PM

Equalization is a process, not a device. The devices youmention are used in the first two processes I listed.

“均衡”是一个处理，而不是设备，你提到的设备用在我列出的前两个处理过程。

Wilhem

03-24-2014, 09:10 AM

This document explains tape equalization. It is a simpleintroduction for anyone interested in the time constants, R-C networks, and themeanings of the terms. Perhaps those with an EQ fetish will pick up enoughknowledge to reduce or even eliminate the odd comments and statements repeatedon multiple boards.

本文介绍了磁带均衡，这是为感兴趣的人做的简单的介绍，有时间常数，R-C网络和术语的含义。或许那些EQ的求知者将得到足够的知识来减少甚至消除奇奇怪怪的评论和在多个版面的反复陈述。

Link: http://www.ant-audio.co.uk/Tape_Recording/Library/EQ.pdf

I noticed that in the PDF file linked above, the formulae that explain whyequalization ends up in time did not appear. The formulae are:

我看到PDF链接文件，解释均衡的时间公式没出现，这个公式是

Frequency=1/2πT=159,155/(Time Constant Value)
where T is the time constant in microseconds and the Time Constant Value is anintegral number such as 70 or 120.

其中的T是用微秒表示的时间常数，时间常数的值是整数，比如70或120。

R = ohm = (Mass x Length^2)/(Time x Charge^2 )

C = Farad = (Time^2 x Charge^2)/(Mass x Length^2 )

R x C = Time in seconds
because all the other multiplicands and divisors cancel each other out.

因为所有其它的被乘数和除数相互抵消。