About other record dimensions, please see also JIS S8502-1973 etc
|Comparative Table of Standards for 30cm LP|
|Item of Description||Standards||IEC98-1958||RIAA-1963||IEC98-1964*2||BS1928-1965||DIN45547-1981||IEC98-1987|
|Recorded Outer Diameter (Max)||292.1mm (11.5inch)||11 1/2"||292.6mm (11.52inch)||292.6mm (11.52inch)||292.6mm||292.6mm|
|Recorded Inner Diameter (Min)||120mm (4 3/4inch)*1||4 3/4"||Nil||Nil||115mm||Nil|
|Finishing Groove Diameter (concentric)||Nil*5||4 3/16" +/- 1/32"||106.4+/-0.8mm (4 3/16+/-1/32inch)||106.4+/-0.8mm (4 3/16+/-1/32inch)||106.4+/-0.8mm||106.4+/-0.8mm|
|Lead-out Pitch||6.35+/-3.18mm (1/4+/-1/8inch)||2 to 6 grooves/inch (4.2-12.7mm)||6.4+/-3.2mm (1/4+/-1/8inch)||6.4+/-3.2mm (1/4+/-1/8inch)||6.4+/-3.2mm||6.4+/-3.2mm|
|Lead-in Pitch||NIL||1/32"-1/16" (0.8-1.6mm)||0.8-1.6mm||0.8-1.6mm with NOTE: maximum 1.2mm for LP having a raised rim||0.8-1.0mm||1.2mm+/-0.4mm|
|Eccentricity of hole to groove spiral*3||0.2mm(0.008inch)||runout of recording grooves relative to center hole: 0.050" max. (1.27mm) See remark *7||0.2mm (0.008inch)||0.13mm (0.005in)||0.2mm||0.2mm|
|Eccentricity of hole to disk periphery*3||0.8mm (1/32inch)||0.8mm (1/32inch)||0.4mm (1/64inch)||Nil||Nil|
|Unbalance (allowable off-centre gravity)||Nil||Nil||Nil||11.1mm(7/16inch)*4||8mm||8mm|
|Diameter of Centre Hole||7.24 -0/+0.09mm (0.285-0.2885inch)||0.286" +0.001" -0.002"||7.24 -0/+0.09mm||7.24 -0/+0.09mm (0.285-0.2885inch)||7.24 -0/+0.09mm||7.24 -0/+0.09mm|
|VTA (Vertical Tracking Angle)||Nil||15 degrees||about 15 degrees||15 to 25 degrees*4||20+5/-0 degrees (VMA)*5||20+5/-0 degrees|
|Stylus Tip Radius (Spherical)||Monophonic: 0.020 to 0.026mm(0.8 to 1mil)||Stereophonic: desirable 0.5mil (0.013mm)||Stereophonic: 0.013 to 0.018mm(0.5 to 0.7mil)||with NOTE: "For both monophonic and stereophonic application, the preferred range of tip radius should be: 0.015 to 0.018mm (0.6 to 0.7mil)"*4||Nil||Nil|
|Monophonic: 0.013 to 0.025mm(0.5 to 1mil)|
|Included angle of spherical tip||40 to 50 degrees||Nil||40 to 55 degrees||40 to 55 degrees||Nil||less than 55 degrees|
|Groove Angle||88+/-5degrees||90/+ 5 degrees||90degrees||90+/-5degrees||90+/-0.7degrees||90+/-5degrees|
|Bottom Radius (Maximum)||7.5micron (0.0003")||(6.35micron) 0.00025"||4micron (0.00015")||4micron/(8micron)*4||8micron||8micron|
|Top Width of Groove (Monophonic)||>55micron(0.00215")||0.0022"-0.0032"||>51micron (0.002")||>51micron (0.002")||*6||Actual dimension: minimum 30micron (see my remark *6)|
|Top Width of Groove (Stereophonic)||Nil||Instantaneous 0.001" min||Nil||Nil (preferably not less than 25micron and average not less than 35micron)*4||Average more than 35micron Instantaneous more than 25micron|
|Figures in inch unit precede those in mm for IEC98-1958 & BS1928-1965.|
|*1||In the first edition of IEC98 (Section F5 Page 21) the "minimum diameter of recorded surface" is quoted for transcription recordings (Section F for broadcasting use) only. There is no corresponding description about minimum diameter for commercial disk records (Section E).|
|*2||I picked up the figures for IEC98-1964 from BS1928 as BS1928-1965 is based on 2nd edition of IEC(1964). Mirror documents with respective notes when BS differs from IEC descriptions.|
|*3||The permissible eccentricity of the centre hole relative to the groove spiral and to the disk periphery shall be as follows:|
|Eccentricity to groove spiral:||The eccentricity of the centre of the centre hole to the centre of the groove spiral.|
|Eccentricity to disk periphery:||The eccentricity of the centre of the centre hole to the centre of the disk periphery.|
|RIAA (Bulletin E4) commented on Runout of Recording Grooves Relative to Center Hole as follows: "This figure does not imply that a record having this degree of run-out would be acceptable from a quality standpoint. It does provide, for instance, a limit for the maximum sensitivity or a velocity trip when combined with the pitch of spirals between individual bands."|
find various types of eccentricity in hole and groove.
Moyer of RCA invented USP3,000,005（1961): Off-Center Indicator to check the concentricity of phonograph records and metal phonograph stampers, and said: "In producing a metal stamper, the center hole is obliterated during the plating process. It is necessary to punch a center hole in each metal stamper. If the punched hole is not substantially concentric with the recording spiral on the stamper, within permissible tolerances, the records produced from the stamper will exhibit the objectionable characteristics of wow."
|*4||As per Amendment Slip No. 1 published 26 January 1972 to BS1928-1965|
of concentric finishing groove 98.4mm was quoted for 45 rpm record.
Corresponding finishing groove radius for 33.3rpm record was under
consideration at the time. 106.4+/-0.8mm was quoted in DIN 45537(Monaural
Records 33.3rpm) & DIN 45547(Stereo Records 33.3rpm) both Nov. 1962.
DIN 45547 seems to define VMA (vertical modulated angle) for the nature of stereophonic groove.
|*6||DIN 45537 in 1962 (Monaural Records 33.3rpm) indicated top width: more than 55micron while bottom radius less than 4micron. By the way it is uncertain whether monophonic groove dimensions in stereo age/cutter were differing from monophonic groove dimensions in original monaural age/cutter or not. It may depend on the density of pitch (for example: original two sides recordings can be compressed to one side by the development of cutting engineering) or the cutting engineer's idea at the time. Since 1970 it was believed that the minimum top width of monophonic groove could be reduced to 30microns as indicated in IEC98-1987 though this standard has not clarified its application to monophonic groove. I think Amendment Slip No. 1 published 26 January 1972 to BS1928-1965 (where the tip radius 0.6-0.7mil can be commonly recommended for both monophonic and stereophonic application) is corresponding to this change of minimum top width for monophonic groove.|
|*7||RIAA Bulletin No. E4 made following Note : This figure does not imply that a record having this degree of run-out would be acceptable from a quality standpoint. It does provide, for instance, a limit for the maximum sensitivity or a velocity trip when combined with the pitch of spirals between individual bands.|
Centre hole diameter for both LP and SP was stipulated around 7.24mm(IEC) or 7.26mm(RIAA), but we find odd records which are beyond standards: not true round hole or burr around hole or bigger hole etc. Spindle diameter as per NAB was 0.283+0-0.0005inch (7.19-7.18mm), but I find various sizes of spindle diameter from 7.13 to 7.2mm according to turntables. I think that spindle diameter 7.2mm is too thick to receive various records without problem. IEC allowed 0.2mm eccentricity for record proper, but in our playing records actually the eccentricity often exceeds more than 0.5mm (=1mm as arm swinger) so that I can hear wow at the end of music sometimes. Some professional turntables have rather thinner spindle diameters since prompt change of records is their purpose: Specification sheet for EMT920=R80 in 1952 indicated spindle diameter 6.95±0.05mm in order to play various records including SP records. It seems that spindle diameter is not standardised as any international standard. Record stabilisers/clamps/weights have hole diameters around 7.3mm usually to fit in most turntable spindles.
Definition from IEC-98(1958):
C1. Commercial disk records (gramophone records, phonograph records). Processed recordings, usually pressings, made by usual commercial process and normally on sale to the public.
C2. Transcription recordings. Recordings made for programme interchange between broadcasting organizations and for other specialized purpose, not normally on sale to the public. Transcription recordings may be either "Direct Recordings" or "Pressings".
C3. Direct recordings. Recording made on disks (e.g. lacquer coated disks) which are suitable for direct reproduction without processing.
C4. Pressings. Copies of direct recordings obtained by a pressing operation similar to that used in normal commercial disk record manufacture.
C5. Commercial disk record playing unit. An assembly of a commercial disk record motor, turntable and pick-up on a common mounting plate.
C6. Commercial disk record changer. A commercial disk record playing unit with the addition of mechanism to enable series of records to be automatically played in sequence.
C7. Transcription turntable assembly. A reproducing turntable and its driving mechanism specially adapted for the reproduction of transcription recordings.
Sizes of Transcription Records as specified in IEC98(1958):
|3 3/4in (95mm)||Minimum diameter of recorded surface for 78rpm coarse groove|
|7 1/2in (190mm)||Minimum diameter of recorded surface for 33 1/3rpm coarse groove|
|4 3/4in (120mm)||Minimum diameter of recorded surface for 33 1/3rpm fine groove|
|9 1/2in (241.3mm)||Outer diameter of recorded surface for 10inch (250mm) Direct recordings|
|9 1/2in (241.3mm)||Outer diameter of recorded surface for 12inch (300mm) Pressings|
|11 1/2in (292.1mm)||Outer diameter of recorded surface for 12inch (300mm) Direct recordings|
|11 1/2in (292.1mm)||Outer diameter of recorded surface for 13inch (330mm) Pressings|
|15 1/2in (393.7mm)||Outer diameter of recorded surface for 16inch (400mm) Direct recordings|
|15 1/2in (393.7mm)||Outer diameter of recorded surface for 17inch (430mm) Pressings|
|The recorded surface shall mean the modulated groove (not the plain/non-modulated groove)|
I don't know the reason why there was too much unrecorded margin for Pressings of Transcription Records (margin from the edge of records: around 3cm for 12in & around 1.8-1.9cm for others). There is a clause F3 mentioning as follows :The disk diameters of transcription recordings are under consideration. For pressings of direct recording disk the dimensions of Clause E3 (commercial disk diameters) apply.
7 1/2in (190mm) as minimum diameter of recorded surface for 33 1/3rpm coarse groove transcription is half of minimum diameter for normal 78rpm SP. I think this minimum diameter was decided in consideration of tracing loss of high frequency at reproduction. For example I simulated as under: stylus tip spherical radius 2.5mil(63.5micron) and recorded velocity 5cm/s peak lateral (constant velocity from 1kHz up). This loss in case of hill-and-dale modulation becomes greater than lateral so that IEC98-1958 does not refer to hill-and-dale transcription record.
The groove dimensions and reproducing stylus tip radius as specified in IEC98(1958): Recommendations for lateral-cut commercial and transcription disk recordings. My intention is to show the difference between commercial disk and transcription (broadcasting) disk.
Commercial disk records
|Minimum top width(*1)||0.006inch (0.15mm)||0.004inch (0.1mm)|
|Maximum bottom radius||0.001inch (0.025mm)||0.0015inch (0.038mm)|
|Included angle||88 degrees +/-5degrees||85 degrees +/-5degrees|
(*1): To obtain an extended playing time 78 rev/min coarse groove commercial records with top width of 0.004inch (0.1mm) are also used in some countries. For such a groove the tip radius of the reproducing stylus should be 0.0023inch (0.058mm)+/-0.0002inch(0.005mm).
|Reproducing stylus tip radius for coarse groove|
|Maximum(*2)||0.003inch (0.075mm)||0.0025inch (0.065mm)|
|Minimum||0.002inch (0.050mm)||0.002inch (0.050mm)|
(*2): A stylus with a tip radius not exceeding 0.0025inch(0.065mm) should generally be used with modern records, particularly with those having grooves with the minimum top width as specified.
Commercial disk records
|Minimum top width||0.00215inch (0.055mm)||0.002inch (0.05mm)|
|Maximum bottom radius||0.0003inch (0.0075mm)||0.0003inch (0.0075mm)|
|Included angle||88 degrees +/-5degrees||85 degrees +/-5degrees|
|Reproducing stylus tip radius for fine groove|
|Maximum||0.001inch (0.026mm)||0.001inch (0.026mm)|
|Minimum||0.0008inch (0.020mm)||0.0008inch (0.020mm)|
||Actual disk diameter||Notes|
|12 inch (300 mm)||11 7/8+/-1/32 in (301.6+/-0.8mm)||Most European disks lie within 11.8+/-0.1 in (300+/-2.5mm)|
|10 inch (250mm)||9 7/8+/-1/32 in (250.8+/-0.8mm)||Most European disks lie within 9.85+/-0.08 in (250+/-2mm)|
|7 inch (175 mm)||6 7/8+/-1/32 in (174.6+/-0.8mm)|
Personal Note on the application of the spherical tip on commercial LP records:
I read most significant passage in NAB(1964) as follows:
"In disc recording, it is the generally accepted practice to evaluate sound quality and musical balance of a disc on a reproducer which has a specified response (frequency characteristic)".
IMO: True Fidelity based on historical background is different from so-called Hi-Fidelity using most advanced equipment.
Often I hear unbalance (emphasis on high frequency band) at inner radius of record with using modern line contact styli on old records. Percy Wilson commented in his book "THE GRAMOPHONE HANDBOOK" (P.42-43: year 1957) about the reducing line speed toward inner radius of record: " This causes a progressive attenuation of treble from the outside to the inside of a record. To compensate for this some recording companies use a progressively increasing treble pre-emphasis as the stylus moves across the record. This is known as "radius correction"". In my estimation many recording companies since SP era had applied radius correction plus standard recording curve during recording process in order to make good sound balance across the records. When old records have been recorded in such way (pre-compensated suitably for reproduction by spherical tip), then advanced line contact stylus with reduced tracing loss would reproduce unbalance (emphasis on high frequency band) at inner groove radii of records. It is quite questionable whether modern records have been recorded or designed suitably for any special styli or not.
Hence I would prefer to use conventional spherical tip radius 0.6-0.7mil (15-18microns) for stereophonic and monaural LP records.
Some requirements in standards are changing by time.
In 1963 RIAA recommended to use spherical tip radius 0.5 mil (13microns) as desirable for stereophonic groove,
In 1964 IEC recommended to use spherical tip radius 13-18 microns for stereophonic groove,
In 1972 by amendment slip to BS1928 and 1975 by DIN45500 and in 1978 by IEC60581,
spherical tip 15-18microns was recommended for both mono & stereo application.
Note that LP production in most countries (USA/Japan/UK) reached the highest around 1975.
I don't know the reason (*) why the previous tip radius 13microns (0.5mil) was omitted from these recent standards.
Sometimes recent standards revert to the older standards because of finding certain inconvenience or unreality of the assumed advanced one. I find similar example in the description of maximum groove bottom radius in μm: 7.5(1958IEC), 6.35(1963RIAA), 4(1964IEC), 8(1972BS/1981DIN/1987IEC).
(*) I assume some reasons why the spherical tip radius 13microns (0.5mil) was omitted since 1972, around when discrete 4 channel (CD4) records appeared.
From the studies and experiments of CD4 era: Light VTF and large area of stylus contact were required for tracing the supersonic modulated groove.
When Static Vertical Tracking Force is fixed around 2 g, contact area of various tips in ascending order: spherical 13micron(0.5mil) eqv. to elliptic stylus < spherical 18micron (0.7mil) eqv. to Shibata & other line-contact styli - see details in stylus.xls including Walton's report(1961). Contact area and wear were focused in that time so that stylus for conventional monaural & stereophonic use was also refurbished as described in 1972 by amendment slip to BS1928-1965. In other words: the tracing/fundamental loss at high frequencies due to the dimension of stylus was focused at first as in case of 1963 RIAA recommendation, but in the next era (early 1970s) the translational loss due to the record elasticity and the stylus pressure was also taken into consideration.
Japanese patent paper 1984-33603 by Denon commented: "Up to now, smaller tip radius had been recommended in order to comply with high performance of record. Meanwhile its small contact area reduces the effective stiffness of record and shifts the high frequency resonance lower than 20kHz and also digs the groove wall deeply. In order to solve such problems, line contact stylus with larger contact area was applied. But the manufacturing process of such stylus is costly and complicated. Moreover after some time of use, the contact area of line contact stylus is increased by tip wear so that the life span of such stylus is relatively shorter." IMO: Micro Ridge （Shure V15VxMR 0.15x3mil）/Micro Linear (AT) etc seems to be based on USP 4521877(1985) by Namiki Precision & Jewel where the diamond ridge can be worn by time of use, but the effective radius of contact (=ridge width/2) remains unchanged so that its life span for use without deteriorating the characteristic is prolonged over 1000 hours of use. This Denon paper pointed out the high frequency resonance (between record elasticity and effective tip mass) around 20kHz - but many popular cartridges showed such peaks lower than 20kHz actually and most users are satisfied because they enjoy such as one of the characteristics of these cartridges. What's the problem? It looks simple: users would like to take their meals in their own dishes (something peculiar to them).
Conventional standards do not refer to any special form of stylus other than spherical stylus. The material of tip used can be either sapphire or diamond, both are still found in market (sapphire was used widely for SP pickups). Standards do no indicate any preference of course. I think that to use special form of stylus is similar to add salt or vinegar on cooked foods. To add or not to add flavour is up to the taste of users.
Considerations on the inclination of cutter needle and V groove.
1 F.L. Capps in his US patent 2187512-1940 (recording stylus) commented: "during a recording operation
the cutting face of the stylus is at an angle or 90 degrees to the surface of the blank being engraved or cut,
although the 90degree angle may be varied approximately 5 degrees forward or backward."
IEC & BS specified Groove Angle 90 degrees plus minus 5 degrees.
Their standards are practical when considering
I. the back-and-forth inclination of cutting stylus as mentioned by Capps
This change of groove angle is negligible: 90.22degrees instead of nominal 90degrees even when stylus inclined 5 degrees.
Equation for Formed Groove Angle = 2*DEGREES(ATAN(1/(COS(D*PI()/180))))
Condition: Nominal Groove Angle 90 degrees D: inclination angle in degree
II. the deformation of groove at recording master disk and pressing (heat and cool) process
2 Actually in addition to back-and-forth of cutting stylus
V groove itself is little inclined sidewise too due to the construction of cutter heads during modulations.
3 Under the above circumstances, the maximum curvature of "special" reproducing styli is kept not larger than 100 micron.