consequence

请问四友兄如何评价benz micro lp 唱头,个人感觉其两端延伸并非非常充足,动态感觉也梢弱..不知道是否这样?

tty123

整个帖子看完花了断断续续2天时间，非常有诱惑力啊！等我下决心上黑胶系统的时候一定得拜访四友大侠！

无难

原帖由 四友 于 2009-6-26 12:43 发表
在正式评论之前，我请徐兄自我介绍



簡介

............到現在已差不多10個年頭,經過長年的不斷改良,它巳是很精練的器材. 本公司一向以合理的設計達成自然中性反影訊源的音色和極佳3D表現見稱. Concerto Ver2以三支12AX7真空管構成左右聲道放大部份,6X4真空管作整流, 並具有EQ曲線撰擇, 曲線種類有四種, #一為RIAA對應大部份LP唱片所用的曲線, #二和#三是1955年前LP唱片未统一前的兩種曲線,分別是London ffrr和Columbia , London對應London ffrr LP唱片, Columbia 對應Columbia和old NAB LP唱片,  #四是SP對應78轉SP唱片. 本唱放是為對應MM唱頭而設計, 具53dB放大率從而達到高S/N比的好處(接low output時是48dB).
...

四友兄好，一直关注这个帖子并学习了很多有益的东西，看到这几个曲线心里痒痒的，请问有相关的线路图吗？很想试试这些不同的效果，特别是SP的曲线，我现在用中华206来播放SP唱片，因为是老的压电唱头不需要唱放，如果换用其他普通的粗纹唱头就要这个曲线及唱放对吧？

四友

原帖由 无难 于 2009-7-15 23:35 发表

四友兄好，一直关注这个帖子并学习了很多有益的东西，看到这几个曲线心里痒痒的，请问有相关的线路图吗？很想试试这些不同的效果，特别是SP的曲线，我现在用中华206来播放SP唱片，因为是老的压电唱头不需要唱放，如 ...

我沒有用过中华206，所以我也不了解

不过我不懂老的压电唱头不需要唱放是否正确，什么是老的压电唱头，如果是古老的78转唱机自带唱头

我另外一个帖子有一些曲线的资料，也有线路图

RIAA制定以前各家唱片公司有自己的曲线，对于喜欢这些经典录音的朋友这曲线的重要性

市面上把这些曲线放进唱头放大除了我曾介绍的香港土炮价格算是可以接受，其他像FM，EMT等为了那些曲线可是得花大钱的

找到这个网站

http://members.myactv.net/~je205d/mono.htm


有许多资料可以参考

其中

http://geocities.com/midimagic@sbcglobal.net/mixphono.htm

HOW TO EQ OLD RECORDSPLAYING OLD RECORDSBefore delving into record equalization, we should first look at all of the variables found when playing records of undetermined type:

• Rotation speed: Ranges from 8.66 to 120 RPM.
  • Common speeds are 16.67, 33.33, 45.00, 78.26, 80.00)
• Groove size:
  • 7 mil, 3 mil, 2.5 mil, and .7 mil were used.
• Groove modulation direction:
  • Vertical, lateral, diagonal, and stereo were used.
• Recording curve (see below)
• Groove cutting direction:
  • Most records are rim start, but some are center start.
• Center hole size:
  • The usual sizes are 5/16" or 1.5", but there are some oddballs, including 1/2", 1", and 2".
• Surface material:
  • Most 33 and 45 RPM records are vinyl or filled vinylite.
  • Most 78 RPM records are shellac.
  • Some are more fragile and need lighter tracking forces.
  • Other materials are Bakelite, hard rubber, cellulose, and styrene.
  • Records made during World War II rationing were made of substitute materials, including cardboard, sawdust, hide glue, and glass.
• The thickness of the record:
  • The standard thickness at the center hole is 3/32 inches.
  • 12-inch 78s are 1/8" thick.
  • Edison records are 1/4" thick.
  • Odd thicknesses can prevent play, or foul a record changer.
• Record diameter:
  • This is important only if automatic play is being used, or if the record is very large or very small.
  • 12-inch, 10-inch, and 7-inch records are industry-standard sizes.
  • 8-inch, 6 inch, and 4-inch records were also made in larger quantities.
• Closest groove to spindle:
  • Some players have limit stops on arm movement.

Be aware that the materials in records made between 1939 and 1946 are substandard, due to shortages, caused by Japan holding the world's primary sources of shellac. You will encounter the fragile binder-filled shellac, and records with cardboard or glass cores and shellac surfaces. Do not use these records with record changers, and be careful not to bump the edges or let them get wet beyond a quick cleaning.
THE HISTORY OF EQUALIZATIONThe recording curve for phonograph records was not standardized until 1958, and was not universally accepted until 1975. Before that, each company selected the curve that they thought would provide the best possible recording. Because of this disagreement between record companies, you must know how to equalize records made before 1958, and some re-issues and foreign records made after that. This article will show you how.
There are several phases in the history of recording phonograph records. Each phase has its own set of recording characteristics. The phases are:
THE ACOUSTIC ERA - 1877-1926: During this period, all recordings were made by collecting sound in a horn and funneling it to a mechanical groove cutter. Most of these cutters produced a constant amplitude cut, where the groove excursion is proportional to volume. The curves produced vary widely, and are certainly not matched to other recording curves. But they are similar enough to them to allow the same switchable reproducing pre-amp to handle them.
Note that record speeds were not standardized during this period. The direction the modulation moves the stylus was also not standardized, with some companies using vertical modulation (moving the stylus up and down) and some choosing lateral modulation (moving the stylus toward and away from the center spindle). One company used a 45 degree modulation so its records could play on any player. In a few cases, the stylus was a radically different size from the normal steel needle. Also, although all records turned clockwise, some were cut outward, starting at the center of the disc and ending at the rim.

THE EARLY ELECTRICAL ERA - 1926-1937: The development of the audio amplifier and the electric cutter produced a different basic cut, the constant velocity cut. In this type, the velocity of the stylus excursion is proportional to volume. This means that bass notes produce wider swings of the cutter stylus than treble notes of the same volume. The result was a very short playing time, because the groove spacing had to be increased.
To counteract this, the record companies rolled off the bass at 6 dB/octave below a selected frequency, called the turnover frequency. This frequency was selected to produce what the company thought was the best playback on an average acoustic machine. Each company selected its own turnover frequency, and it was considered a trade secret, so the average consumer didn't know what frequency to use, even if his set had a turnover control. This led to the introduction of the tone control on phonographs.
Records were also standardized to operate record changers during this period. By 1932, broadcast transcription discs were the only records still made by cutting outward. Many broadcasters alternated inward and outward cuts on long programs, so the radio listener could not tell that a new record had been started from sudden changes in quality. For voice broadcasts, the speed of 33.33 RPM became standard. In addition, all records for home use were modulated laterally after 1929, with vertical modulation used only for broadcast purposes.

THE MATURE 78 ERA - 1937-1947: Record companies found out that they could reduce surface noise by boosting the treble by 3 dB/octave or 6 dB/octave above a certain frequency. A corresponding reduction in treble (and surface noise) occurs on playback. This produced better sound than was ever possible before.
But again, they could not agree on how much to strengthen the treble. For some reason, instead of specifying a second turnover frequency for the boost, the treble boost was measured in dB at 10 KHz. Some of the records made with this method are as good as early LP records. This development also produced the first wide variation in recording curves, especially since most European companies did not strengthen the treble until after World War II. This new characteristic is called treble roll off. Again, the precise amount of treble rolloff to use for each brand of record was kept secret from the public. Some phonographs made during this period had treble and bass controls for the first time, others had a switch with "American" and "European" on it - the first switchable record compensators.

THE BIRTH OF THE LP - 1947-1958: With the new slower rotation speed and a new material (vinyl) to make records out of, a new set of recording curves emerged. The first two, LP and NAB, were derived from the National Association of (Radio and Television) Broadcasters (NAB, or NARTB) curve, which was used to make acetate radio program transcriptions.
The Columbia LP curve adds the rumble shelf, to reduce the effect of turntable rumble. Turntable rumble increased with slow rotation speeds and smaller grooves. But the treble boost from these curves was so much that it caused mistracking in cheaper cartridges. This caused some record companies to adopt more gentle recording curves.
One was designed by the Audio Engineering Society (AES), but the surface noise on records cut with that curve was excessive. Then RCA stuck its nose into the mix with the 45 RPM record, with an entirely new curve as well as a new speed and center hole size. As a result, several different curves were adopted by different record companies.
By this time, hi-fi enthusiasts clamored for the record companies to publish this information, so the user could adjust his set to handle each curve correctly. Most 33 RPM records made after 1951 have information on which curve to use printed on the label or the jacket, and most 45 and 78 RPM records didn't.

THE RIAA YEARS - 1952-present: Hi-fi enthusiasts called for a single curve that all records would be made in. In 1952, RCA developed the New Orthophonic curve with all of the solutions to problems listed above compounded into one set of record and reproduce curves. Within a year, the Recording Industry Association of America (RIAA) adopted this curve. By 1955, most American labels had adopted the RIAA standard.
The only changes to the curve were definitions adopted in 1974 to set the ultrasonic and infrasonic characteristics of records and playback pre-amps. This change was prompted by the introduction of the CD-4 quadraphonic disc system with its ultrasonic carrier. Note that some European companies did not make the change to RIAA until the 1960s, and some Russian and Asian companies didn't standardize until 1975.

STEREO - 1958-present: When stereo was introduced, many different ways of putting two audio tracks on the same record were discussed. Cook developed a disc with two sets of grooves, played with a forked tonearm. Minter tried to put a radio-frequency carrier into the record groove, a process that failed just as badly back then as it did with CD-4 in the 1970s. A worn record sounded like sandpaper. The Zenith system finally chosen records the left channel at a 45 degree angle from horizontal in one direction, and the right channel at a 45 degree angle in the other direction, in the same groove. A sound centered between the speakers is recorded laterally. And sounds to the back of the room in quadraphonic and Dolby Surround systems are recorded vertically.

ELEMENTS OF PHONO EQUALIZATIONNow let's look at the actual components of the RIAA curve and other curves used for reproducing records:

At some point (undefined until 1974, where it was set at 15 Hz) is the low-frequency cutoff of the system. Usually it was defined by the limits of the cutter, amplifiers, and loudspeaker, until extended low frequency response became available with the use of transistors.	The flat midrange section comes next, between the turnover frequencies of the bass boost and the treble rolloff (500 Hz and 2150 Hz in RIAA). This is the original flat portion of the recording curve around which the rest of the curve is built.
Above the low frequency cutoff point is the rumble shelf. This band of flat response (between 15 Hz and 50 Hz in RIAA) was inserted to keep from boosting rumble frequencies too much with the rest of the bass that is boosted in the next section. Not all records have rumble shelves.	The next part of the curve is the noise reducing treble roll-off (from 2150 Hz to 22 KHz in RIAA). This compensates for the treble boost in the recording curve. This is expressed in dB of reduction at 10K Hz (-13.7 dB for RIAA), and is usually a 6 dB/octave slope with more reduction at higher frequencies.
Next comes a section between the rumble shelf and the bass turnover frequency (50 Hz to 500 Hz in RIAA). In this section the bass is boosted at a 6 dB/octave slope, with the lower frequencies being stronger. This boost compensates for a roll-off in the bass during recording. This is done to allow more recording time on the record.	Finally comes the upper limit of the system's frequency response. Until recently, this was usually a function of the cutter head. The advent of the aborted CD-4 quadraphonic system forced a need for a standard cutoff frequency, which was set at 22 KHz in 1974.

The low and high frequency response limits are fixed at 15 Hz and 22 KHz. The other values are dependent on which recording curve is used. The curve is usually specified by three values, listed in this order:

The bass turnover frequency, in Hz.
• The values in Hz are: 200, 250, 300, 350, 400, 500, 630, and 800.
The rumble shelf plateau level, in dB above the flat midrange level. This is usually specified as a letter:
• The values in dB are: X = +12, C = +14, A = +16, B = +18, R = +20
• N = No rumble shelf used - the bass boost ends at the low-frequency limit.
• The treble roll-off, in dB at 10 KHz.
  • Usual values, in dB are: 0, -6, -8, -10, -10.5 -12, -12.7, -13.7, -16, -18.
  • A special value of D indicates a 3 dB/octave slope (instead of 6 dB/ octave) reaching -6 dB at 10 KHz.

The RIAA curve is identified as 500R-13.7, meaning a 500 Hz turnover, a 20 dB high rumble shelf, and a 13.7 dB rolloff at 10 KHz.

Other common curves:
500C-16 = Columbia LP curve 500B-16 = NAB transcription 400N-12 = AES	500C-10.5 = London LP curve 800N-12 = RCA 800N-8 = RCA 78	300N-16 = Columbia 78 250N-6 = American 78 250N-D = Decca FFRR 78

Use these table pages for the complete list of recording curves used, and which record companies used which curves:

四友

Tips to finding the correct playback equalization of a record of unknown vintage:

• Suggested equipment: variable speed turntable capable of the speeds needed, multi curve phono pre-amp, parametric EQ, and noise reduction device. An RIAA pre-amp and a 1/3 octave graphic equalizer can be substituted for the multi-curve pre-amp if needed.
• The phono cartridge should be wired in mono for 78s, with provision for reversing the phase and disconnecting either channel when needed.
• The proper styli are necessary for 78 RPM records. Attempting to use styli designed for stereo records on all 78s except Edison recordings can result in damage to both the stylus and the record.
• First find out the speed, groove size, and center hole size of the record. This can eliminate many combinations.
• If the stylus won't enter the playing grooves when placed at the edge of the record, the record may be cut outward. These records start at the center and end at the rim (Note: all CDs are center start).
• Look up the label (brand) in my label table. That may be enough for certain labels. Then take the curve name to the curve table for the details.
• Use the curve the table suggests, if one is available. But don't hesitate to modify the curve if the record sounds wrong.
• An excessive amount of hiss, or groove skipping without visible damage, can indicate the wrong stylus is in use. Hiss far in excess of the music can also indicate that the record is vertically cut.
• Shellac and Edison records need much less antiskating force than vinyl needs. Styrene usually needs more antiskate than vinyl.
• Individual records "imported" from another record company, or re-issued, might be recorded in the wrong curve.
• European records tended to have smaller amounts of treble boost and bass cut on them, compared to American records produced at the same time.
• For an unknown record, adjust the EQ in this order: treble roll-off, bass turnover, and rumble shelf. Keep the zone around 1 KHz at flat if using a graphic equalizer, unless an acoustic horn peak occurs in that region.
• Most records needing alternate EQ also have practically no usable information above 15 KHz or below 40 Hz. Roll off all frequencies outside these values.
• 78s made before 1937 usually have no usable frequencies above 10 KHz. Records made before 1926 usually have nothing but noise above 4 to 6 KHz and below 200 Hz.
• To find out if any usable material is in a frequency band, raise that band's slider on a graphic EQ.
• Because acoustic records have very little low bass response, special instruments were employed to replace bass drums, tubas, and string basses. The sounds of those instruments will not clean up as expected.
• If a noise reduction device is employed, the treble characteristic may have to be set to a lower amount of roll-off to allow the noise reduction device to act.
• Good noise reduction devices include DNR, noise gates, and expanders. These can be used with EQ. A sharp low pass filter with adjustable cutoff frequency is also useful.

EQ CURVES OF OLD RECORDSHere are the major recording curves used for producing records before 1964:

Code	NAME	SHELF UPPER-FREQ Hz	SHELF BOOST dB	BASS TURNOVER Hz	TREBLE ROLL-OFF dB	OTHER
800N-16	Acoustic	none	N - none	800	-16	Use variable hi-cut filter
800N-12	Acoustic	none	N - none	800	-12	Use variable hi-cut filter
630N-16	Acoustic	none	N - none	630	-16	Use variable hi-cut filter
630N-12	Acoustic	none	N - none	630	-12	Use variable hi-cut filter
200N-10	Acoustic	none	N - none	200	-10	Use variable hi-cut filter
400N-12	AES	none	N - none	400	-12	Audio Engineering Society
250N-6	American 78	none	N - none	250	-6	-
250N-8	American 78	none	N - none	250	-8	-
500N-8	Audiophile	none	N - none	500	-8	-
630N-16	Bartok	none	N - none	630	-16	-
400N-12.7	Capitol	none	N - none	400	-12.7	-
350N-10	CCIR 78	none	N - none	350	-10	-
300N-16	Columbia 78	none	N - none	300	-16	-
500C-16	Columbia LP	100	C +14	500	-16	Also called LP
500N-15	Cook	none	N - none	500	-15	Rolloff varies from -12 to -15 dB
250N-D	Decca 78	none	N - none	250	-D (-6 @ 3dB/octave)	Also ffrr 78
200N-0	Early 78	none	N - none	200	-0	Use variable hi-cut filter
250N-0	European 78	none	N - none	250	-0	Use variable hi-cut filter
250N-D	ffrr 78	none	N - none	250	-D (-6 @ 3dB/octave)	Also called Decca 78
500C-10.5	ffrr LP	100	C +14	500	-10.5	Also called London
500R-16	HMV LP	50	R +20	500	-16	EMI
500R-13.7	IEC	50	R +20	500	-13.7	Infrasonic 15 Hz, Ultrasonic 22 KHz
Code	NAME	SHELF UPPER-FREQ Hz	SHELF BOOST dB	BASS TURNOVER Hz	TREBLE ROLL-OFF dB	OTHER
800N-16	Kapp	none	N - none	800	-16	-
500C-10.5	London	100	C +14	500	-10.5	ffrr LP
500C-16	LP	100	C +14	500	-16	-
500N-12	MGM	none	N - none	500	-12	-
500C-6	Modern 78	100	C +14	500	-6	-
500C-8	Modern 78	100	C +14	500	-8	-
500B-16	NAB, NARTB	62.5	B +18	500	-16	National Association of Broadcasters
500R-13.7	New Orthophonic	50	R +20	500	-13.7	RCA also RIAA
500N-12.7	Old Orthophonic	none	N - none	500	-12.7	RCA
800N-8	Old RCA	none	N - none	800	-8	-
500C-12	Pacific Jazz	100	C +14	500	-12	-
400N-6	Philips	none	N - none	400	-6	-
250N-10	Poor 78	none	N - none	250	-10	Use variable hi-cut filter
500R-13.7	RIAA	50	R +20	500	-13.7	Recording Industry Assoc of America
500R-13.7	RCA New Orthophonic	50	R +20	500	-13.7	RCA also RIAA
500N-12.7	RCA Old Orthophonic 33	none	N - none	500	-12.7	RCA
800N-8	RCA, Old	none	N - none	800	-8	RCA made several changes
800N-12.7	RCA	none	N - none	800	-12.7	Release delays confused RCA curves
800N-12	Technichord	none	N - none	800	-12	-
400N-0	Telefunken 78	none	N - none	400	-0	Use variable hi-cut filter
350N-0	Universal 78	none	N - none	350	-0	Use variable hi-cut filter
350C-8	Worn 78	80	C +14	350	-8	Use variable hi-cut filter

EQUALIZING OLD RECORDS

四友

一个简单的制作

The RIAA EQ curve was established as the standard EQ for stereo and microgroove record cutting in 1955. Prior to that various EQ curves were used in cutting mono LPs and 78s that was why I built the Nardi monophono circuit from SP 16. This is a good design concept and uses my favorite tubes however I was not too sure about the split EQ time constants which may not be tracking each other accurately for a given curve. The direct coupled cathode follower also made it sound dark and a bit lifeless. I also found myself spending too much time fiddling with EQ rather than listening to music. Initially I was scouting eBay for a Fisher 50C but due to collector interest this unit is priced out of reach for mere mortals. I ruled out the McIntosh C8 and Scott 121 because they use negative feedback EQ. In my audio journey I try as hard as possible not to set design rules but so far any preamp or amp circuit that I encountered employing negative feedback always chokes the sound.

JEL mono preamp fitted with variable EQ

After going through my collection of vintage preamp schematics I built a monophonic preamp with passive EQ networks taken from the RCA SV1 preamp which is very similar to my stereo preamp that was based on the phono circuit found at the back of an RCA tube manual. I wanted to be period correct in this project and did away with Ni-mH battery biasing.

click to print

As shown in the schematic the standard RIAA/New Orthophonic, AES, Columbia LP and Old 78 passive EQ networks are inserted between the two triode halves of a 6SL7 and selected by mounting them on a 6 position double pole rotary switch. The "Old 78" EQ setting sounds and looks in the scope like it averages various American 78 EQ curves used from the late 30s until the mid 50s with a mild scratch filter that reduces shellac groove noise but still preserves enough top end to 10khz. This might not be compatible with European 78 pressings and do not have any to confirm. I have been enjoying American 78s from RCA, Columbia, Capitol and Decca using this EQ curve but might experiment with a couple more EQ networks from the table provided below since I have two more empty terminals in the switch.

The low impedance cathode follower above enables the circuit to drive a typical 50k- 100k line level load and can be handy for CD-R archiving projects. After trying several topologies in lowering the output Z of the RCA circuit, to my ears this capacitor coupled cathode follower introduces the least amount of sonic degradation. But for critical listening I still recommend the hi-Z output!

click to zoom or print

Pre-RIAA Equalizer designs for a 12AY7 circuit employing similar operating points. I scanned this page from "The Recording and Reproduction of Sound" by Oliver Read published by Howard W. Sams & Co., 1954. For information on EQ curves for records manufactured before 1955 click here.

Even if one uses a vintage tube preamp equipped with a comprehensive EQ selection it is almost impossible to determine exactly what EQ curve was used prior to RIAA standardization, thus the existence of tone controls in vintage units for the user to season to taste. One can get carried away with an EQ guide and dialing the right curve before playing a record but I would rather live with my four EQ settings sans tone controls and enjoy!

click to print

Line stage- 6J5 or 1/2 6SN7

The preamp can be built as a stand alone mono preamp with this line stage circuit using a 250k-500k log taper potentiometer for volume control. Cheap carbon track CTS sounds good but is noisier than the 250k Alps Blue Velvet.

click to print

smartpig

四友兄，请教一个问题，
唱放都标示MM或MC,到底有什么区别？是否只是增益方面的区别？
MC头+升压牛 进 MM放大，与MC头+升压牛 进MC放大，两种的区别只是在增益方面吗？
请指教，多谢！

无难

谢谢四友兄的资料，偶要慢慢学习一下，因为是外语，有点头疼。。。。

四友

原帖由 smartpig 于 2009-7-16 14:30 发表
四友兄，请教一个问题，
唱放都标示MM或MC,到底有什么区别？是否只是增益方面的区别？
MC头+升压牛 进 MM放大，与MC头+升压牛 进MC放大，两种的区别只是在增益方面吗？
请指教，多谢！

我前面文章有提过

唱头　　
在整个类比系统里，唱头对于声音的影响比例算是相当的高，区分上先由发
电方式区分为三种，第一是 MM 头，就是动磁头，线圈固定，针杆带动磁石
发电，这样的发电方式可以将线圈绕线数增加，以获得较高的输出电压，大
约在3~5mV 左右，输入到唱头放大即可得到类似 CD 输出的高电平；第二种
就是 MI形，也就是动铁型，厂商GRADO 大量生产这种方式的唱头，动作原
理类似于 MM，输出电压也相同，所以一般以 MM 头来看待；第三种 MC 头，针杆带动线圈切割磁力线来发
电，所以不可以带动太重的线圈，而导致输出电压偏低，一般介于0.15~0.5 mV 之间，输出时必须经过一个
升压变压器，将输出的电压升高，再经过唱头放大线路放大，也有厂商提供两用的唱头放大，同时接受 MM ,
MC 的输入，也有厂商生产高输出的 MC唱头，输出可以到 2.5~3.5mV 接近 MM 头的输出电压。不过目前高
输出MC唱头市面上已经很少见,由于近几年唱头放大在杂讯处理进步不少,所以为了音质的要求,中低输出的MC
唱头是目前市场主流. 大部分的廉价唱头都是 MM 头，所以导致认知上MM 的音质普遍不佳，但是也有一些厂
商提供优质的 MM 头，表现也相当好，MC 头几乎就是高价位唱头的代名词，几乎找不到一颗像是 MM 头的低
价；若是以音乐表现来说的话，MM 头可以将爵士音乐中活灵活现的气份表现的很好，而且相当便宜，缺点就
是细节少了一些，MC 头就来的细致一些，乐器的质感相当好，古典乐需要的质感可以完全表现出来，价钱也
高一些。上述看法只能算是一般认知,MM头或MC头都有表现很全面的,不可一概而论,重点在耳听为凭.

四友

即将测试的几只国产唱臂，现在国产品以非吴下阿蒙